WorldWideScience

Sample records for geco galaxy evolution

  1. Dwarf spheroidal galaxies: Keystones of galaxy evolution

    Science.gov (United States)

    Gallagher, John S., III; Wyse, Rosemary F. G.

    1994-01-01

    Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark-matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

  2. Chemical evolution of galaxies

    CERN Document Server

    Matteucci, Francesca

    2012-01-01

    The term “chemical evolution of galaxies” refers to the evolution of abundances of chemical species in galaxies, which is due to nuclear processes occurring in stars and to gas flows into and out of galaxies. This book deals with the chemical evolution of galaxies of all morphological types (ellipticals, spirals and irregulars) and stresses the importance of the star formation histories in determining the properties of stellar populations in different galaxies. The topic is approached in a didactical and logical manner via galaxy evolution models which are compared with observational results obtained in the last two decades: The reader is given an introduction to the concept of chemical abundances and learns about the main stellar populations in our Galaxy as well as about the classification of galaxy types and their main observables. In the core of the book, the construction and solution of chemical evolution models are discussed in detail, followed by descriptions and interpretations of observations of ...

  3. GECO, un Gestor de Corpus colaborativo basado en web

    Directory of Open Access Journals (Sweden)

    Gerardo Sierra

    2017-12-01

    Full Text Available Este artículo presenta GEstor de COrpus (GECO, un software de gestión de corpus en línea que permite a los usuarios subir colecciones de documentos y volverlos corpus digitales. En el sistema, los corpus pueden ser procesados por otras aplicaciones, las cuales están implementadas como módulos integrados a la infraestructura de GECO. En este documento se describen a detalle sus características, así como la funcionalidad del generador de concordancias desarrollado en torno a él.

  4. Chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Vigroux, Laurent

    1979-01-01

    This research thesis addresses theories on the chemical evolution of galaxies which aim at explaining abundances of different elements in galaxies, and more particularly aims at improving the model by modifying hypotheses. After a description of the simple model and of its uncertainties, the author shows how it is possible to understand the evolution of the main elements. Predictions obtained with this model are then compared with the present knowledge on galaxies by considering them according to an increasing complexity: Sun's neighbourhood, our galaxy, other spiral galaxies, elliptical galaxies, and finally galaxy clusters. A specific attention is given to irregular galaxies which are the simplest systems [fr

  5. Spectral evolution of galaxies: current views

    International Nuclear Information System (INIS)

    Bruzual, A.G.

    1985-01-01

    A summary of current views on the interpretation of the various evolutionary tests aimed at detecting spectral evolution in galaxies is presented. It is concluded that the evolution taking place in known galaxy samples is a slow process (perhaps consistent with no evolution at all), and that the early phases of rapid spectral evolution in early-type galaxies have not yet been detected. (author)

  6. Galaxy formation and evolution

    CERN Document Server

    Mo, Houjun; White, Simon

    2010-01-01

    The rapidly expanding field of galaxy formation lies at the interface between astronomy, particle physics, and cosmology. Covering diverse topics from these disciplines, all of which are needed to understand how galaxies form and evolve, this book is ideal for researchers entering the field. Individual chapters explore the evolution of the Universe as a whole and its particle and radiation content; linear and nonlinear growth of cosmic structure; processes affecting the gaseous and dark matter components of galaxies and their stellar populations; the formation of spiral and elliptical galaxies; central supermassive black holes and the activity associated with them; galaxy interactions; and the intergalactic medium. Emphasizing both observational and theoretical aspects, this book provides a coherent introduction for astronomers, cosmologists, and astroparticle physicists to the broad range of science underlying the formation and evolution of galaxies.

  7. The chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Chiosi, Cesare

    1986-01-01

    The chemical evolution of galaxies is reviewed with particular attention to the theoretical interpretation of the distribution and abundances of elements in stars and the interstellar medium. The paper was presented to the conference on ''The early universe and its evolution'', Erice, Italy, 1986. The metallicity distribution of the solar vicinity, age metallicity relationship, abundance gradients in the galaxy, external galaxies, star formation and evolution, major sites of nucleosynthesis, yields of chemical elements, chemical models, and the galactic disk, are all discussed. (U.K.)

  8. Evolution of galaxies

    International Nuclear Information System (INIS)

    Palous, J.

    1987-01-01

    The proceedings contain 87 papers divided into 8 chapters. The chapter Bipolar outflows and star formations contains papers on optical and infrared observations of young bipolar outflow objects and the theory thereof, and on observations of cometary nebulae. The chapter Masers and early stellar evolution discusses molecular masers and star forming regions. The following chapter contains papers on initial mass function and star formation rates in galaxies. The chapter Clusters and star formation contains data on OB associations and open star clusters, their development and observations, CO and H 2 in our galaxy, the four vector model of radio emission and an atlas of the wavelength dependence of ultraviolet extinction in the Galaxy. The most voluminous is the chapter Evolution of galaxies. It contains papers on the theories of the physical and chemodynamic development of galaxies of different types, rotation research and rotation velocities of galaxies and their arms, and on mathematical and laboratory models of morphological development. Chapter seven contains papers dealing with active extragalactic objects, quasars and active galactic nuclei. The last chapter discusses cosmological models, the theory of the inflationary universe, and presents an interpretation of the central void and X-ray background. (M.D.). 299 figs., 48 tabs., 1651 refs

  9. Secular Evolution in Disk Galaxies

    Science.gov (United States)

    Kormendy, John

    2013-10-01

    Self-gravitating systems evolve toward the most tightly bound configuration that is reachable via the evolution processes that are available to them. They do this by spreading -- the inner parts shrink while the outer parts expand -- provided that some physical process efficiently transports energy or angular momentum outward. The reason is that self-gravitating systems have negative specific heats. As a result, the evolution of stars, star clusters, protostellar and protoplanetary disks, black hole accretion disks and galaxy disks are fundamentally similar. How evolution proceeds then depends on the evolution processes that are available to each kind of self-gravitating system. These processes and their consequences for galaxy disks are the subjects of my lectures and of this Canary Islands Winter School. I begin with a review of the formation, growth and death of bars. Then I review the slow (`secular') rearrangement of energy, angular momentum, and mass that results from interactions between stars or gas clouds and collective phenomena such as bars, oval disks, spiral structure and triaxial dark haloes. The `existence-proof' phase of this work is largely over: we have a good heuristic understanding of how nonaxisymmetric structures rearrange disk gas into outer rings, inner rings and stuff dumped onto the centre. The results of simulations correspond closely to the morphology of barred and oval galaxies. Gas that is transported to small radii reaches high densities. Observations confirm that many barred and oval galaxies have dense central concentrations of gas and star formation. The result is to grow, on timescales of a few Gyr, dense central components that are frequently mistaken for classical (elliptical-galaxy-like) bulges but that were grown slowly out of the disk (not made rapidly by major mergers). The resulting picture of secular galaxy evolution accounts for the richness observed in galaxy structure. We can distinguish between classical and pseudo

  10. Secular evolution of galaxies and galaxy clusters in decaying dark matter cosmology

    International Nuclear Information System (INIS)

    Ferrer, Francesc; Nipoti, Carlo; Ettori, Stefano

    2009-01-01

    If the dark matter sector in the Universe is composed by metastable particles, galaxies and galaxy clusters are expected to undergo significant secular evolution from high to low redshift. We show that the decay of dark matter, with a lifetime compatible with cosmological constraints, can be at the origin of the observed evolution of the Tully-Fisher relation of disk galaxies and alleviate the problem of the size evolution of elliptical galaxies, while being consistent with the current observational constraints on the gas fraction of clusters of galaxies.

  11. Dynamical evolution of galaxies in clusters

    International Nuclear Information System (INIS)

    Ostriker, J.P.

    1977-01-01

    In addition to the processes involved in the evolution of star clusters, there are three kinds of processes that are peculiar to, or far more important in, galaxy clusters than in star clusters: galaxy interactions with gas, high-velocity tidal interactions, and accretion and cannibalism. The latter is discussed at some length; analytical calculations for the apparent luminosity evolution of the first brightest galaxy and the apparent luminosity evolution of M 12 are described, along with the numerical simulation of cluster evolution. It appears that many of the notable features of centrally condensed clusters of galaxies, particularly the presence of very luminous but low-surface-brightness central cD systems, can be understood in terms of a straightforward dynamical theory of galactic cannibalism. It is possible to maintain the hypothesis that dynamical evolution gradually transforms Bautz--Morgan III clusters to type II systems or type I systems. 36 references, 5 figures

  12. Galaxy evolution in clusters since z=1

    Science.gov (United States)

    Aragón-Salamanca, A.

    2011-11-01

    It is now 30 years since Alan Dressler published his seminal paper onthe morphology-density relation. Although there is still much to learnon the effect of the environment on galaxy evolution, extensive progress has been made since then both observationally and theoretically.Galaxy clusters provide some of the most extreme environments in which galaxies evolve, making them excellent laboratories to study the age old question of "nature'' vs. "nurture'' in galaxy evolution. Here I review some of the key observational results obtained during the last decade on the evolution of the morphology, structure, dynamics, star-formation history and stellar populations of cluster galaxies since the time when the universe was half its present age.Many of the results presented here have been obtainedwithin the ESO Distant Cluster Survey (EDisCS) and Space Telescope A901/02 Galaxy Evolution Survey (STAGES) collaborations.

  13. Do Galaxies Follow Darwinian Evolution?

    Science.gov (United States)

    2006-12-01

    Using VIMOS on ESO's Very Large Telescope, a team of French and Italian astronomers have shown the strong influence the environment exerts on the way galaxies form and evolve. The scientists have for the first time charted remote parts of the Universe, showing that the distribution of galaxies has considerably evolved with time, depending on the galaxies' immediate surroundings. This surprising discovery poses new challenges for theories of the formation and evolution of galaxies. The 'nature versus nurture' debate is a hot topic in human psychology. But astronomers too face similar conundrums, in particular when trying to solve a problem that goes to the very heart of cosmological theories: are the galaxies we see today simply the product of the primordial conditions in which they formed, or did experiences in the past change the path of their evolution? ESO PR Photo 17/06 ESO PR Photo 45/06 Galaxy Distribution in Space In a large, three-year long survey carried out with VIMOS [1], the Visible Imager and Multi-Object Spectrograph on ESO's VLT, astronomers studied more than 6,500 galaxies over a wide range of distances to investigate how their properties vary over different timescales, in different environments and for varying galaxy luminosities [2]. They were able to build an atlas of the Universe in three dimensions, going back more than 9 billion years. This new census reveals a surprising result. The colour-density relation, that describes the relationship between the properties of a galaxy and its environment, was markedly different 7 billion years ago. The astronomers thus found that the galaxies' luminosity, their initial genetic properties, and the environments they reside in have a profound impact on their evolution. "Our results indicate that environment is a key player in galaxy evolution, but there's no simple answer to the 'nature versus nurture' problem in galaxy evolution," said Olivier Le Fèvre from the Laboratoire d'Astrophysique de Marseille

  14. Galaxy Evolution in Clusters Since z ~ 1

    Science.gov (United States)

    Aragón-Salamanca, A.

    Galaxy clusters provide some of the most extreme environments in which galaxies evolve, making them excellent laboratories to study the age old question of "nature" vs. "nurture" in galaxy evolution. Here I review some of the key observational results obtained during the last decade on the evolution of the morphology, structure, dynamics, star-formation history and stellar populations of cluster galaxies since the time when the Universe was half its present age. Many of the results presented here have been obtained within the ESO Distant Cluster Survey (EDisCS) and Space Telescope A901/02 Galaxy Evolution Survey (STAGES) collaborations.

  15. THE GALAXY OPTICAL LUMINOSITY FUNCTION FROM THE AGN AND GALAXY EVOLUTION SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Cool, Richard J. [The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Eisenstein, Daniel J. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Kochanek, Christopher S. [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Brown, Michael J. I. [School of Physics, Monash University, Clayton, Victoria 3800 (Australia); Caldwell, Nelson; Forman, William R.; Hickox, Ryan C.; Jones, Christine; Murray, Stephen S. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Dey, Arjun; Jannuzi, Buell T. [National Optical Astronomy Observatory, Tucson, AZ 85726 (United States); Moustakas, John [Center for Astrophysics and Space Science, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States)

    2012-03-20

    We present the galaxy optical luminosity function for the redshift range 0.05 < z < 0.75 from the AGN and Galaxy Evolution Survey, a spectroscopic survey of 7.6 deg{sup 2} in the Booetes field of the NOAO Deep Wide-Field Survey. Our statistical sample is composed of 12,473 galaxies with known redshifts down to I = 20.4 (AB). Our results at low redshift are consistent with those from Sloan Digital Sky Survey; at higher redshift, we find strong evidence for evolution in the luminosity function, including differential evolution between blue and red galaxies. We find that the luminosity density evolves as (1 + z){sup (0.54{+-}0.64)} for red galaxies and (1 + z){sup (1.64{+-}0.39)} for blue galaxies.

  16. Cosmic Collisions: Galaxy Mergers and Evolution

    Science.gov (United States)

    Trouille, Laura; Willett, Kyle; Masters, Karen; Lintott, Christopher; Whyte, Laura; Lynn, Stuart; Tremonti, Christina A.

    2014-08-01

    Over the years evidence has mounted for a significant mode of galaxy evolution via mergers. This process links gas-rich, spiral galaxies; starbursting galaxies; active galactic nuclei (AGN); post-starburst galaxies; and gas-poor, elliptical galaxies, as objects representing different phases of major galaxy mergers. The post-starburst phase is particularly interesting because nearly every galaxy that evolves from star-forming to quiescent must pass through it. In essence, this phase is a sort of galaxy evolution “bottleneck” that indicates that a galaxy is actively evolving through important physical transitions. In this talk I will present the results from the ‘Galaxy Zoo Quench’ project - using post-starburst galaxies to place observational constraints on the role of mergers and AGN activity in quenching star formation. `Quench’ is the first fully collaborative research project with Zooniverse citizen scientists online; engaging the public in all phases of research, from classification to data analysis and discussion to writing the article and submission to a refereed journal.

  17. Origin, structure and evolution of galaxies

    International Nuclear Information System (INIS)

    Zhi, F.L.

    1988-01-01

    Recent developments of the origin, structure and evolution of galaxies have been reviewed. The contents of this book are: Inflationary Universe; Cosmic String; Active Galaxies; Intergalactic Medium; Waves in Disk Galaxies; Dark Matter; Gas Dynamics in Disk Galaxies; Equilibrium and Stability of Spiral Galaxies

  18. Galaxy Zoo: Observing secular evolution through bars

    International Nuclear Information System (INIS)

    Cheung, Edmond; Faber, S. M.; Koo, David C.; Athanassoula, E.; Bosma, A.; Masters, Karen L.; Nichol, Robert C.; Melvin, Thomas; Bell, Eric F.; Lintott, Chris; Schawinski, Kevin; Skibba, Ramin A.; Willett, Kyle W.

    2013-01-01

    In this paper, we use the Galaxy Zoo 2 data set to study the behavior of bars in disk galaxies as a function of specific star formation rate (SSFR) and bulge prominence. Our sample consists of 13,295 disk galaxies, with an overall (strong) bar fraction of 23.6% ± 0.4%, of which 1154 barred galaxies also have bar length (BL) measurements. These samples are the largest ever used to study the role of bars in galaxy evolution. We find that the likelihood of a galaxy hosting a bar is anticorrelated with SSFR, regardless of stellar mass or bulge prominence. We find that the trends of bar likelihood and BL with bulge prominence are bimodal with SSFR. We interpret these observations using state-of-the-art simulations of bar evolution that include live halos and the effects of gas and star formation. We suggest our observed trends of bar likelihood with SSFR are driven by the gas fraction of the disks, a factor demonstrated to significantly retard both bar formation and evolution in models. We interpret the bimodal relationship between bulge prominence and bar properties as being due to the complicated effects of classical bulges and central mass concentrations on bar evolution and also to the growth of disky pseudobulges by bar evolution. These results represent empirical evidence for secular evolution driven by bars in disk galaxies. This work suggests that bars are not stagnant structures within disk galaxies but are a critical evolutionary driver of their host galaxies in the local universe (z < 1).

  19. The Evolution of Galaxies

    Czech Academy of Sciences Publication Activity Database

    Palouš, Jan

    2007-01-01

    Roč. 17, - (2007), s. 34-40 ISSN 1220-5168. [Heliospere and galaxy. Sinaia, 03.05.2007-05.05.2007] R&D Projects: GA MŠk(CZ) LC06014 Institutional research plan: CEZ:AV0Z10030501 Keywords : ISM structure * stars formation * evolution of galaxies Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  20. THE GALAXY OPTICAL LUMINOSITY FUNCTION FROM THE AGN AND GALAXY EVOLUTION SURVEY

    International Nuclear Information System (INIS)

    Cool, Richard J.; Eisenstein, Daniel J.; Kochanek, Christopher S.; Brown, Michael J. I.; Caldwell, Nelson; Forman, William R.; Hickox, Ryan C.; Jones, Christine; Murray, Stephen S.; Dey, Arjun; Jannuzi, Buell T.; Moustakas, John

    2012-01-01

    We present the galaxy optical luminosity function for the redshift range 0.05 2 in the Boötes field of the NOAO Deep Wide-Field Survey. Our statistical sample is composed of 12,473 galaxies with known redshifts down to I = 20.4 (AB). Our results at low redshift are consistent with those from Sloan Digital Sky Survey; at higher redshift, we find strong evidence for evolution in the luminosity function, including differential evolution between blue and red galaxies. We find that the luminosity density evolves as (1 + z) (0.54±0.64) for red galaxies and (1 + z) (1.64±0.39) for blue galaxies.

  1. Looking Wider and Further: The Evolution of Galaxies Inside Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yuanyuan [Univ. of Michigan, Ann Arbor, MI (United States)

    2016-01-01

    Galaxy clusters are rare objects in the universe, but on-going wide field optical surveys are identifying many thousands of them to redshift 1.0 and beyond. Using early data from the Dark Energy Survey (DES) and publicly released data from the Sloan Digital Sky Survey (SDSS), this dissertation explores the evolution of cluster galaxies in the redshift range from 0 to 1.0. As it is common for deep wide field sky surveys like DES to struggle with galaxy detection efficiency at cluster core, the first component of this dissertation describes an efficient package that helps resolving the issue. The second part focuses on the formation of cluster galaxies. The study quantifies the growth of cluster bright central galaxies (BCGs), and argues for the importance of merging and intra-cluster light production during BCG evolution. An analysis of cluster red sequence galaxy luminosity function is also performed, demonstrating that the abundance of these galaxies is mildly dependent on cluster mass and redshift. The last component of the dissertation characterizes the properties of galaxy filaments to help understanding cluster environments

  2. Glove-Enabled Computer Operations (GECO): Design and Testing of an Extravehicular Activity Glove Adapted for Human-Computer Interface

    Science.gov (United States)

    Adams, Richard J.; Olowin, Aaron; Krepkovich, Eileen; Hannaford, Blake; Lindsay, Jack I. C.; Homer, Peter; Patrie, James T.; Sands, O. Scott

    2013-01-01

    The Glove-Enabled Computer Operations (GECO) system enables an extravehicular activity (EVA) glove to be dual-purposed as a human-computer interface device. This paper describes the design and human participant testing of a right-handed GECO glove in a pressurized glove box. As part of an investigation into the usability of the GECO system for EVA data entry, twenty participants were asked to complete activities including (1) a Simon Says Games in which they attempted to duplicate random sequences of targeted finger strikes and (2) a Text Entry activity in which they used the GECO glove to enter target phrases in two different virtual keyboard modes. In a within-subjects design, both activities were performed both with and without vibrotactile feedback. Participants mean accuracies in correctly generating finger strikes with the pressurized glove were surprisingly high, both with and without the benefit of tactile feedback. Five of the subjects achieved mean accuracies exceeding 99 in both conditions. In Text Entry, tactile feedback provided a statistically significant performance benefit, quantified by characters entered per minute, as well as reduction in error rate. Secondary analyses of responses to a NASA Task Loader Index (TLX) subjective workload assessments reveal a benefit for tactile feedback in GECO glove use for data entry. This first-ever investigation of employment of a pressurized EVA glove for human-computer interface opens up a wide range of future applications, including text chat communications, manipulation of procedureschecklists, cataloguingannotating images, scientific note taking, human-robot interaction, and control of suit andor other EVA systems.

  3. Galaxy mergers and active nuclei. II. Cosmological evolution

    International Nuclear Information System (INIS)

    Roos, N.

    1985-01-01

    Galaxy mergers may produce active galactic nuclei (AGNs) by repopulating stellar loss-cone orbits around a central black hole. In the companion paper we derived a local bolometric luminosity function of AGNs based on this process. In this paper we interpret the observed cosmological evolution of the luminosity function of AGNs as due to evolution of the merging rate among galaxies after their formation at a redshift of approx.3. An important difference between our model and previous (empirical) models is that the evolution depends on galactic (stellar) luminosity instead of central nonthermal luminosity. The radio counts at 1.4 GHz and optical counts are reproduced by the model if the merging rate of the galaxies at the bright end of the galaxy luminosity function evolves considerably faster than the merging rate of the smaller galaxies. The theoretical and observed luminosity functions at high redshift have similar characteristics: (i) at high luminosity the evolution is best described by luminosity evolution, and (2) the luminosity function has a maximum at approx.10 3 Gpc -3 , which is the space density of the most massive galaxies. A large fraction of these galaxies are presumably formed in the precursors of rich clusters. Their merger rate is high initially and declines rapidly on a time scale of a few billion years. If the initial density fluctuation spectrum for protoclusters of mass M/sub cl/ has the form deltarho/rhoproportionalM/sup( -1+n//3)/2/sub cl/, then the steep evolution of the most luminous galaxies suggests nroughly-equal-1.3 at a redshift of approx.3, which is consistent with the observed clustering of galaxies

  4. Spectral evolution of galaxies

    International Nuclear Information System (INIS)

    Rocca-Volmerange, B.

    1989-01-01

    A recent striking event in Observational Cosmology is the discovery of a large population of galaxies at extreme cosmological distances (extended from spectral redshifts ≅ 1 to ≥ 3) corresponding to a lookback time of 80% of the Universe's age. However when galaxies are observed at such remote epochs, their appearances are affected by at least two simultaneous effects which are respectively a cosmological effect and the intrinsic evolution of their stellar populations which appear younger than in our nearby galaxies. The fundamental problem is first to disentangle the respective contributions of these two effects to apparent magnitudes and colors of distant galaxies. Other effects which are likely to modify the appearance of galaxies are amplification by gravitational lensing and interaction with environment will also be considered. (author)

  5. EVOLUTION OF GALAXY LUMINOSITY FUNCTION USING PHOTOMETRIC REDSHIFTS

    International Nuclear Information System (INIS)

    Ramos, B. H. F.; Pellegrini, P. S.; Da Costa, L. N.; Maia, M. A. G.; Ogando, R. L. C.; De Simoni, F.; Benoist, C.; Makler, M.; Mesquita, A. A.

    2011-01-01

    We examine the impact of using photometric redshifts for studying the evolution of both the global galaxy luminosity function (LF) and that for different galaxy types. To this end, we compare the LFs obtained using photometric redshifts from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) D1 field with those from the spectroscopic survey VIMOS VLT Deep Survey (VVDS) comprising ∼4800 galaxies. We find that for z ≤ 2.0, in the interval of magnitudes considered by this survey, the LFs obtained using photometric and spectroscopic redshifts show a remarkable agreement. This good agreement led us to use all four Deep fields of the CFHTLS comprising ∼386,000 galaxies to compute the LF of the combined fields and directly estimate the error in the parameters based on the field-to-field variation. We find that the characteristic absolute magnitude M* of Schechter fits fades by ∼0.7 mag from z ∼ 1.8 to z ∼ 0.3, while the characteristic density φ* increases by a factor of ∼4 in the same redshift interval. We use the galaxy classification provided by the template fitting program used to compute photometric redshifts and split the sample into galaxy types. We find that these Schechter parameters evolve differently for each galaxy type, an indication that their evolution is a combination of several effects: galaxy merging, star formation quenching, and mass assembly. All these results are compatible with those obtained by different spectroscopic surveys such as VVDS, DEEP2, and zCosmos, which reinforces the fact that photometric redshifts can be used to study galaxy evolution, at least for the redshift bins adopted so far. This is of great interest since future very large imaging surveys containing hundreds of millions of galaxies will allow us to obtain important precise measurements to constrain the evolution of the LF and to explore the dependence of this evolution on morphology and/or color helping constrain the mechanisms of galaxy evolution.

  6. Internal and environmental secular evolution of disk galaxies

    Science.gov (United States)

    Kormendy, John

    2015-03-01

    This Special Session is devoted to the secular evolution of disk galaxies. Here `secular' means `slow' i.e., evolution on time scales that are generally much longer than the galaxy crossing or rotation time. Internal and environmentally driven evolution both are covered. I am indebted to Albert Bosma for reminding me at the 2011 Canary Islands Winter School on Secular Evolution that our subject first appeared in print in a comment made by Ivan King (1977) in his introductory talk at the Yale University meeting on The Evolution of Galaxies and Stellar Populations: `John Kormendy would like us to consider the possibility that a galaxy can interact with itself.. . . I'm not at all convinced, but John can show you some interesting pictures.' Two of the earliest papers that followed were Kormendy (1979a, b); the first discusses the interaction of galaxy components with each other, and the second studies these phenomena in the context of a morphological survey of barred galaxies. The earliest modeling paper that we still use regularly is Combes & Sanders (1981), which introduces the now well known idea that box-shaped bulges in edge-on galaxies are side-on, vertically thickened bars. It is gratifying to see how this subject has grown since that time. Hundreds of papers have been written, and the topic features prominently at many meetings (e.g., Block et al. 2004; Falcoń-Barroso & Knapen 2012, and this Special Session). My talk here introduces both internal and environmental secular evolution; a brief abstract follows. My Canary Islands Winter School review covers both subjects in more detail (Kormendy 2012). Kormendy & Kennicutt (2004) is a comprehensive review of internal secular evolution, and Kormendy & Bender (2012) covers environmental evolution. Both of these subject make significant progress at this meeting. Secular evolution happens because self-gravitating systems evolve toward the most tightly bound configuration that is reachable by the evolution processes

  7. Island universes structure and evolution of disk galaxies

    CERN Document Server

    DE JONG, R. S

    2007-01-01

    This book contains an up-to-date review of the structure and evolution of disk galaxies from both the observational and theoretical point of view. The book is the proceedings of the "Island Universes" conference held at the island of Terschelling, The Netherlands in July 2005, which attracted about 130 experts and students in the field. The conference was organized as a tribute to Dr. Piet C. van der Kruit for receiving the honorary Jacobus C. Kapteyn Professorship in Astronomy. The eight topical themes discussed at the meeting are reflected in these proceedings: 1) Properties of Stellar Disks, 2) Kinematics and Dynamics of Disk Galaxies, 3) Bars, Spiral Structure, and Secular Evolution in Disk Galaxies, 4) The Outskirts and Environment of Disk Galaxies, 5) Interstellar Matter, 6) (Evolution of) Star Formation in Galactic Disks, 7) Disk Galaxies through Cosmic Time, and 8) Formation Models of Disk Galaxies. These proceedings are concluded with a conference summary reflecting on the most significant recent pro...

  8. Galaxy luminosity function: evolution at high redshift

    Science.gov (United States)

    Martinet, N.; Durret, F.; Guennou, L.; Adami, C.

    2014-12-01

    There are some disagreements about the abundance of faint galaxies in high redshift clusters. DAFT/FADA (Dark energy American French Team) is a medium redshift (0.4galaxy clusters ideal to tackle these problems. We present cluster galaxy luminosity functions (GLFs) based on photometric redshifts for 30 clusters in B, V, R and I restframe bands. We show that completeness is a key parameter to understand the different observed behaviors when fitting the GLFs. We also investigate the evolution of GLFs with redshift for red and blue galaxy populations separately. We find a drop of the faint end of red GLFs which is more important at higher redshift while the blue GLF faint end remains flat in our redshift range. These results can be interpreted in terms of galaxy quenching. Faint blue galaxies transform into red ones which enrich the red sequence from high to low redshifts in clusters while some blue galaxies are still accreted from the environment, compensating for this evolution so that the global GLF does not seem to evolve.

  9. Circumgalactic Matter Matters in Galaxy Evolution

    Science.gov (United States)

    Werk, Jessica

    2018-01-01

    The circumgalactic medium (CGM; non-ISM gas within a galaxy virial radius) regulates the gas flows that shape the assembly and evolution of galaxies. Owing to the vastly improved capabilities in space-based UV spectroscopy with the installation of HST/COS, observations and simulations of the CGM have emerged as the new frontier of galaxy evolution studies. In the last decade, we have learned that the CGM of Milky Way mass galaxies likely contains enough material to harbor most of the metals lost in galaxy winds and to sustain star-formation for billions of years. Remarkably, this implies that most of the heavy elements on earth cycled back and forth multiple times through the Milky Way’s own CGM before the formation of the solar system. In this talk, I will describe constraints we have placed on the origin and fate of this material by studying the gas kinematics, metallicity and ionization state. I will conclude by posing several unanswered questions about the CGM that will be addressed with future survey data and hydrodynamic simulations in a cosmological context.

  10. Gravitational instability, evolution of galaxies and star formation

    International Nuclear Information System (INIS)

    Palous, J.

    1979-01-01

    The gravitational collapse is the key to the theories of galaxy and star formation. The observations, showing intrinsic differences between elliptical and spiral galaxies, guide our fundamental conceptions on the formation and evolution of systems in question. Stars in elliptical galaxies and in spherical components of spiral galaxies were formed in a short period of time during early phases of protogalactic collapse, at a time of violent star formation. The disc-like components of spiral galaxies, however, were built gradually in the course of galactic evolution. Star formation in elliptical galaxies is described by the collision model of interstellar clouds, while star formation in discs is characterised by several processes: the expansion of HII regions, the expansion of supernovae remnants and the shock wave related to the presence of the spiral structure. (author)

  11. Galaxy Evolution Spectroscopic Explorer: Scientific Rationale

    Science.gov (United States)

    Heap, Sara; Ninkov, Zoran; Robberto, Massimo; Hull, Tony; Purves, Lloyd

    2016-01-01

    GESE is a mission concept consisting of a 1.5-m space telescope and UV multi-object slit spectrograph designed to help understand galaxy evolution in a critical era in the history of the universe, where the rate of star-formation stopped increasing and started to decline. To isolate and identify the various processes driving the evolution of these galaxies, GESE will obtain rest-frame far-UV spectra of 100,000 galaxies at redshifts, z approximately 1-2. To obtain such a large number of spectra, multiplexing over a wide field is an absolute necessity. A slit device such as a digital micro-mirror device (DMD) or a micro-shutter array (MSA) enables spectroscopy of a hundred or more sources in a single exposure while eliminating overlapping spectra of other sources and blocking unwanted background like zodiacal light. We find that a 1.5-m space telescope with a MSA slit device combined with a custom orbit enabling long, uninterrupted exposures (approximately 10 hr) are optimal for this spectroscopic survey. GESE will not be operating alone in this endeavor. Together with x-ray telescopes and optical/near-IR telescopes like Subaru/Prime Focus Spectrograph, GESE will detect "feedback" from young massive stars and massive black holes (AGN's), and other drivers of galaxy evolution.

  12. Chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Matteucci, F.; Consiglio Nazionale delle Ricerche, Frascati

    1989-01-01

    In principle, a good model of galactic chemical evolution should fulfil the majority of well established observational constraints. The goal of this paper is to review the observational data together with the existing chemical evolution models for the Milky Way (the disk), Blue Compact and Elliptical galaxies and to show how well the models can account for the observations. Some open problems and future prospects are also discussed. (author)

  13. Imprint of galaxy formation and evolution on globular cluster properties

    OpenAIRE

    Bekki, Kenji

    2006-01-01

    We discuss the origin of physical properties of globular cluster systems (GCSs) in galaxies in terms of galaxy formation and evolution processes. Based on numerical simulations of dynamical evolution of GCSs in galaxies, we particularly discuss (1) the origin of radial density profiles of GCSs, (2) kinematics of GCSs in elliptical galaxies, (3) transformation from nucleated dwarf galaxies into GCs (e.g., omega Centauri), and (4) the origin of GCSs in the Large Magellanic Cloud (LMC).

  14. The new galaxy evolution paradigm revealed by the Herschel surveys

    Science.gov (United States)

    Eales, Stephen; Smith, Dan; Bourne, Nathan; Loveday, Jon; Rowlands, Kate; van der Werf, Paul; Driver, Simon; Dunne, Loretta; Dye, Simon; Furlanetto, Cristina; Ivison, R. J.; Maddox, Steve; Robotham, Aaron; Smith, Matthew W. L.; Taylor, Edward N.; Valiante, Elisabetta; Wright, Angus; Cigan, Philip; De Zotti, Gianfranco; Jarvis, Matt J.; Marchetti, Lucia; Michałowski, Michał J.; Phillipps, Steven; Viaene, Sebastien; Vlahakis, Catherine

    2018-01-01

    The Herschel Space Observatory has revealed a very different galaxyscape from that shown by optical surveys which presents a challenge for galaxy-evolution models. The Herschel surveys reveal (1) that there was rapid galaxy evolution in the very recent past and (2) that galaxies lie on a single Galaxy Sequence (GS) rather than a star-forming 'main sequence' and a separate region of 'passive' or 'red-and-dead' galaxies. The form of the GS is now clearer because far-infrared surveys such as the Herschel ATLAS pick up a population of optically red star-forming galaxies that would have been classified as passive using most optical criteria. The space-density of this population is at least as high as the traditional star-forming population. By stacking spectra of H-ATLAS galaxies over the redshift range 0.001 high stellar masses, high star-formation rates but, even several billion years in the past, old stellar populations - they are thus likely to be relatively recent ancestors of early-type galaxies in the Universe today. The form of the GS is inconsistent with rapid quenching models and neither the analytic bathtub model nor the hydrodynamical EAGLE simulation can reproduce the rapid cosmic evolution. We propose a new gentler model of galaxy evolution that can explain the new Herschel results and other key properties of the galaxy population.

  15. COSMIC EVOLUTION OF DUST IN GALAXIES: METHODS AND PRELIMINARY RESULTS

    International Nuclear Information System (INIS)

    Bekki, Kenji

    2015-01-01

    We investigate the redshift (z) evolution of dust mass and abundance, their dependences on initial conditions of galaxy formation, and physical correlations between dust, gas, and stellar contents at different z based on our original chemodynamical simulations of galaxy formation with dust growth and destruction. In this preliminary investigation, we first determine the reasonable ranges of the most important two parameters for dust evolution, i.e., the timescales of dust growth and destruction, by comparing the observed and simulated dust mass and abundances and molecular hydrogen (H 2 ) content of the Galaxy. We then investigate the z-evolution of dust-to-gas ratios (D), H 2 gas fraction (f H 2 ), and gas-phase chemical abundances (e.g., A O = 12 + log (O/H)) in the simulated disk and dwarf galaxies. The principal results are as follows. Both D and f H 2 can rapidly increase during the early dissipative formation of galactic disks (z ∼ 2-3), and the z-evolution of these depends on initial mass densities, spin parameters, and masses of galaxies. The observed A O -D relation can be qualitatively reproduced, but the simulated dispersion of D at a given A O is smaller. The simulated galaxies with larger total dust masses show larger H 2 and stellar masses and higher f H 2 . Disk galaxies show negative radial gradients of D and the gradients are steeper for more massive galaxies. The observed evolution of dust masses and dust-to-stellar-mass ratios between z = 0 and 0.4 cannot be reproduced so well by the simulated disks. Very extended dusty gaseous halos can be formed during hierarchical buildup of disk galaxies. Dust-to-metal ratios (i.e., dust-depletion levels) are different within a single galaxy and between different galaxies at different z

  16. COSMIC EVOLUTION OF DUST IN GALAXIES: METHODS AND PRELIMINARY RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Bekki, Kenji [ICRAR, M468, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009 (Australia)

    2015-02-01

    We investigate the redshift (z) evolution of dust mass and abundance, their dependences on initial conditions of galaxy formation, and physical correlations between dust, gas, and stellar contents at different z based on our original chemodynamical simulations of galaxy formation with dust growth and destruction. In this preliminary investigation, we first determine the reasonable ranges of the most important two parameters for dust evolution, i.e., the timescales of dust growth and destruction, by comparing the observed and simulated dust mass and abundances and molecular hydrogen (H{sub 2}) content of the Galaxy. We then investigate the z-evolution of dust-to-gas ratios (D), H{sub 2} gas fraction (f{sub H{sub 2}}), and gas-phase chemical abundances (e.g., A {sub O} = 12 + log (O/H)) in the simulated disk and dwarf galaxies. The principal results are as follows. Both D and f{sub H{sub 2}} can rapidly increase during the early dissipative formation of galactic disks (z ∼ 2-3), and the z-evolution of these depends on initial mass densities, spin parameters, and masses of galaxies. The observed A {sub O}-D relation can be qualitatively reproduced, but the simulated dispersion of D at a given A {sub O} is smaller. The simulated galaxies with larger total dust masses show larger H{sub 2} and stellar masses and higher f{sub H{sub 2}}. Disk galaxies show negative radial gradients of D and the gradients are steeper for more massive galaxies. The observed evolution of dust masses and dust-to-stellar-mass ratios between z = 0 and 0.4 cannot be reproduced so well by the simulated disks. Very extended dusty gaseous halos can be formed during hierarchical buildup of disk galaxies. Dust-to-metal ratios (i.e., dust-depletion levels) are different within a single galaxy and between different galaxies at different z.

  17. Observing and Simulating Galaxy Evolution

    DEFF Research Database (Denmark)

    Olsen, Karen Pardos

    and temperature structure of these, with locally resolved radiation fields. In the first study, SÍGAME is combined with the radiative transfer code LIME to model the spectral line energy distribution (SLED) of CO. A CO SLED close to that of the Milky Way is found for normal star-forming massive galaxies at z _ 2......, but 50% smaller _CO factors, with the latter decreasing towards the center of each model galaxy. In a second study, SÍGAME is adapted to model the fine-structure line of singly ionized carbon, [CII] at 158 _m, the most powerful emission line of neutral ISM. Applying SÍGAME to the same type of galaxies......, and sheds light on the AGN-host co-evolution by connecting the fraction and luminosity of AGNs with galaxy properties. By analyzing a large survey in X-ray, AGNs of high and low X-ray luminosity are extracted among massive galaxies at z _ 2 via AGN classification methods, and stacking techniques of non...

  18. The evolution of galaxies at moderate redshift

    International Nuclear Information System (INIS)

    Lilly, S.J.

    1987-01-01

    Optical and infrared photometric data on 53 galaxies in five clusters at 0.38 < z < 0.58 are described and analysed to produce the rest-frame (U-V) and (V-H) colours. The 36 red galaxies form a homogeneous population in each cluster. The colours of the 17 blue galaxies clearly distinguish between the normal spirals and the peculiar 'A-type' galaxies found in these Butcher-Oemler clusters and suggest for the latter a substantial intermediate age 1-Gyr population as indicated by optical spectra. The average colours of the red elliptical galaxies at z ∼ 0.45 are systematically 0.12 mag bluer in the rest-frame (U-V), as expected from conventional evolutionary models, but are about 0.1 mag redder in (V-H), which is not predicted by the models. It is shown, however, that inclusion of the evolution of the upper Asymptotic Giant Branch, which is usually neglected, into a simple evolutionary model can explain the observed evolution vector in the (U-V)/(V-H) plane. (author)

  19. Galaxy Collisions, Gas Stripping and Star Formation in the Evolution of Galaxies

    Czech Academy of Sciences Publication Activity Database

    Palouš, Jan

    2006-01-01

    Roč. 18, - (2006), s. 125-146 ISSN 0941-1445. [From Cosmological Structures to the Milky Way. Praha, 20.09.2004-25.09.2004] Institutional research plan: CEZ:AV0Z10030501 Keywords : galaxies * evolution of galaxies * interstellar matter Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  20. Links between galaxy evolution, morphology and internal physical processes

    International Nuclear Information System (INIS)

    Kraljic, Katarina

    2014-01-01

    This thesis aims at making the link between galaxy evolution, morphology and internal physical processes, namely star formation as the outcome of the turbulent multiphase interstellar medium, using the cosmological zoom-in simulations, simulations of isolated and merging galaxies, and the analytic model of star formation. In Chapter 1, I explain the motivation for this thesis and briefly review the necessary background related to galaxy formation and modeling with the use of numerical simulations. I first explore the evolution of the morphology of Milky-Way-mass galaxies in a suite of zoom-in cosmological simulations through the analysis of bars. I analyze the evolution of the fraction of bars with redshift, its dependence on the stellar mass and accretion history of individual galaxies. I show in particular, that the fraction of bars declines with increasing redshift, in agreement with the observations. This work also shows that the obtained results suggest that the bar formation epoch corresponds to the transition between an early 'violent' phase of spiral galaxies formation at z > 1, during which they are often disturbed by major mergers or multiple minor mergers as well as violent disk instabilities, and a late 'secular' phase at z [fr

  1. Galaxy evolution in extreme environments: Molecular gas content star formation and AGN in isolated void galaxies

    Science.gov (United States)

    Das, Mousumi; Iono, Daisuke; Saito, Toshiki; Subramanian, Smitha

    Since the early redshift surveys of the large scale structure of our universe, it has become clear that galaxies cluster along walls, sheet and filaments leaving large, empty regions called voids between them. Although voids represent the most under dense parts of our universe, they do contain a sparse but significant population of isolated galaxies that are generally low luminosity, late type disk galaxies. Recent studies show that most void galaxies have ongoing star formation and are in an early stage of evolution. We present radio, optical studies of the molecular gas content and star formation in a sample of void galaxies. Using SDSS data, we find that AGN are rare in these systems and are found only in the Bootes void; their black hole masses and radio properties are similar to bright spirals galaxies. Our studies suggest that close galaxy interactions and gas accretion are the main drivers of galaxy evolution in these systems despite their location in the underdense environment of the voids.

  2. Monolithic View of Galaxy Formation and Evolution

    Directory of Open Access Journals (Sweden)

    Cesare Chiosi

    2014-07-01

    Full Text Available We review and critically discuss the current understanding of galaxy formation and evolution limited to Early Type Galaxies (ETGs as inferred from the observational data and briefly contrast the hierarchical and quasi-monolithic paradigms of formation and evolution. Since in Cold Dark Matter (CDM cosmogony small scale structures typically collapse early and form low-mass haloes that subsequently can merge to assembly larger haloes, galaxies formed in the gravitational potential well of a halo are also expected to merge thus assembling their mass hierarchically. Mergers should occur all over the Hubble time and large mass galaxies should be in place only recently. However, recent observations of high redshift galaxies tell a different story: massive ETGs are already in place at high redshift. To this aim, we propose here a revision of the quasi-monolithic scenario as an alternative to the hierarchical one, in which mass assembling should occur in early stages of a galaxy lifetime and present recent models of ETGs made of Dark and Baryonic Matter in a Λ-CDM Universe that obey the latter scheme. The galaxies are followed from the detachment from the linear regime and Hubble flow at z ≥ 20 down to the stage of nearly complete assembly of the stellar content (z ∼ 2 − 1 and beyond.  It is found that the total mass (Mh = MDM + MBM and/or initial over-density of the proto-galaxy drive the subsequent star formation histories (SFH. Massive galaxies (Mh ~ _1012M⊙ experience a single, intense burst of star formation (with rates ≥ 103M⊙/yr at early epochs, consistently with observations, with a weak dependence on the initial over-density; intermediate mass haloes (Mh~_ 1010 − 1011M⊙ have star formation histories that strongly depend on their initial over-density; finally, low mass haloes (Mh ~_ 109M⊙ always have erratic, burst-like star forming histories. The present-day properties (morphology, structure, chemistry and photometry of the

  3. RADIO SOURCE FEEDBACK IN GALAXY EVOLUTION

    International Nuclear Information System (INIS)

    Shabala, Stanislav; Alexander, Paul

    2009-01-01

    We present a galaxy evolution model which incorporates a physically motivated implementation of active galactic nucleus feedback. Intermittent jets inflate cocoons of radio plasma which then expand supersonically, shock heating the ambient gas. The model reproduces observed star formation histories to the highest redshifts for which reliable data exist, as well as the observed galaxy color bimodality. Intermittent radio source feedback also naturally provides a way of keeping the black hole and spheroid growth in step. We find possible evidence for a top-heavy initial mass function for z > 2, consistent with observations of element abundances, and submillimeter and Lyman break galaxy counts.

  4. Sharing Gravity's Microscope: Star Formation and Galaxy Evolution for Underserved Arizonans

    Science.gov (United States)

    Knierman, Karen A.; Monkiewicz, Jacqueline A.; Bowman, Catherine DD; Taylor, Wendy

    2016-01-01

    Learning science in a community is important for children of all levels and especially for many underserved populations. This project combines HST research of galaxy evolution using gravitationally lensed galaxies with hands-on activities and the Starlab portable planetarium to link astronomy with families, teachers, and students. To explore galaxy evolution, new activities were developed and evaluated using novel evaluation techniques. A new set of galaxy classification cards enable inquiry-based learning about galaxy ages, evolution, and gravitational lensing. Activities using new cylinder overlays for the Starlab transparent cylinder will enable the detailed examination of star formation and galaxy evolution as seen from the viewpoint inside of different types of galaxies. These activities were presented in several Arizona venues that enable family and student participation including ASU Earth and Space Open House, Arizona Museum of Natural History Homeschooling Events, on the Salt River Pima-Maricopa Indian Community, and inner city Phoenix schools serving mainly Hispanic populations. Additional events targeted underserved families at the Phoenix Zoo, in Navajo County, and for the Pascua Yaqui Tribe. After evaluation, the activities and materials will also be shared with local teachers and nationally.

  5. The post-infall evolution of a satellite galaxy

    OpenAIRE

    {Nichols} M.; {Revaz} Y.; {Jablonka} P.

    2015-01-01

    As galaxy simulations increase in resolution more attention is being paid towards the evolution of dwarf galaxies and how the simulations compare to observations. Despite this increasing resolution we are however, far away from resolving the interactions of satellite dwarf galaxies and the hot coronae which surround host galaxies. We describe a new method which focuses only on the local region surrounding an infalling dwarf in an effort to understand how the hot baryonic halo will alter the c...

  6. Chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Pagel, B.E.J.

    1979-01-01

    The chemical evolution of disk galaxies is discussed with special reference to results obtained from studies of the oxygen abundance in H II regions. Normal spirals (including our own) display the by now well known radial abundance gradient, which is discussed on the basis of the simple enrichment model and other models. The Magellanic Clouds, on the other hand, and the barred spiral NGC 1365, have been found to have little or no abundance gradient, implying a very different sort of evolution that may involve large-scale mixing. Finally, the simple model is tested against a number of results in H II regions where the ratio of total mass to mass of residual gas can be estimated. It turns out to fit adequately the Magellanic Clouds and a number of H II regions in the outer parts of spiral galaxies, but in more inner parts it fails, as do more sophisticated models involving infall during the formation of galactic disks that have proved very successful in other respects. (Auth.)

  7. ON THE SIZE AND COMOVING MASS DENSITY EVOLUTION OF EARLY-TYPE GALAXIES

    International Nuclear Information System (INIS)

    Van der Wel, Arjen; Bell, Eric F.; Van den Bosch, Frank C.; Gallazzi, Anna; Rix, Hans-Walter

    2009-01-01

    We present a simple, empirically motivated model that simultaneously predicts the evolution of the mean size and the comoving mass density of massive (>10 11 M sun ) early-type galaxies from z = 2 to the present. First, we demonstrate that some size evolution of the population can be expected simply due to the continuous emergence of early-type galaxies. The Sloan Digital Sky Survey (SDSS) data reveal that in the present-day universe more compact early-type galaxies with a given dynamical mass have older stellar populations. This implies that with increasing look-back time, the more extended galaxies will be more and more absent from the population. In contrast, at a given stellar velocity dispersion, SDSS data show that there is no relation between size and age, which implies that the velocity dispersion can be used to estimate the epoch at which galaxies stopped forming stars, turning into early-type galaxies. Based on this, we define an empirically motivated, redshift-dependent velocity dispersion threshold above which galaxies do not form stars at a significant rate, which we associate with the transformation into early-type galaxies. Applying this 'formation' criterion to a large sample of nearby early-type galaxies, we predict the redshift evolution in the size distribution and the comoving mass density. The resulting evolution in the mean size is roughly half of the observed evolution. Then we include a prescription for the merger histories of galaxies between the 'formation' redshift and the present, based on cosmological simulations of the assembly of dark matter halos. Such mergers after the transformation into an early-type galaxy are presumably dissipationless ('dry'), where the increase in size is expected to be approximately proportional to the increase in mass. This model successfully reproduces the observed evolution since z ∼ 2 in the mean size and in the comoving mass density of early-type galaxies with mass M > 10 11 M sun . We conclude that

  8. Exploring the cosmic evolution of habitability with galaxy merger trees

    Science.gov (United States)

    Stanway, E. R.; Hoskin, M. J.; Lane, M. A.; Brown, G. C.; Childs, H. J. T.; Greis, S. M. L.; Levan, A. J.

    2018-04-01

    We combine inferred galaxy properties from a semi-analytic galaxy evolution model incorporating dark matter halo merger trees with new estimates of supernova and gamma-ray burst rates as a function of metallicity from stellar population synthesis models incorporating binary interactions. We use these to explore the stellar-mass fraction of galaxies irradiated by energetic astrophysical transients and its evolution over cosmic time, and thus the fraction which is potentially habitable by life like our own. We find that 18 per cent of the stellar mass in the Universe is likely to have been irradiated within the last 260 Myr, with GRBs dominating that fraction. We do not see a strong dependence of irradiated stellar-mass fraction on stellar mass or richness of the galaxy environment. We consider a representative merger tree as a Local Group analogue, and find that there are galaxies at all masses which have retained a high habitable fraction (>40 per cent) over the last 6 Gyr, but also that there are galaxies at all masses where the merger history and associated star formation have rendered galaxies effectively uninhabitable. This illustrates the need to consider detailed merger trees when evaluating the cosmic evolution of habitability.

  9. Evolution of dwarf galaxies in the Centaurus A group

    OpenAIRE

    Makarova, L.; Makarov, D.

    2007-01-01

    We consider star formation properties of dwarf galaxies in Cen A group observed within our HST/ACS projects number 9771 and 10235. We model color-magnitude diagrams of the galaxies under consideration and measure star formation rate and metallicity dependence on time. We study environmental dependence of the galaxy evolution and probable origin of the dwarf galaxies in the group.

  10. GALAXY CLUSTERS AT HIGH REDSHIFT AND EVOLUTION OF BRIGHTEST CLUSTER GALAXIES

    International Nuclear Information System (INIS)

    Wen, Z. L.; Han, J. L.

    2011-01-01

    Identification of high-redshift clusters is important for studies of cosmology and cluster evolution. Using photometric redshifts of galaxies, we identify 631 clusters from the Canada-France-Hawaii Telescope (CFHT) wide field, 202 clusters from the CFHT deep field, 187 clusters from the Cosmic Evolution Survey (COSMOS) field, and 737 clusters from the Spitzer Wide-area InfraRed Extragalactic Survey (SWIRE) field. The redshifts of these clusters are in the range 0.1 ∼ + - m 3.6 μ m colors of the BCGs are consistent with a stellar population synthesis model in which the BCGs are formed at redshift z f ≥ 2 and evolved passively. The g' - z' and B - m 3.6μm colors of the BCGs at redshifts z > 0.8 are systematically bluer than the passive evolution model for galaxies formed at z f ∼ 2, indicating star formation in high-redshift BCGs.

  11. Stochastic star formation and the evolution of galaxies

    International Nuclear Information System (INIS)

    Seiden, P.E.; Schulman, L.S.; Gerola, H.

    1979-01-01

    The mechanism of stochastic self-propagating star formation has previously been invoked to explain the origin of spiral arms in galaxies. In this paper we extend the application of this mechanism to account for the diversity of morphological types and the evolution of galaxies. The new property that arises from consideration of this mechanism is that the rate of star formation exhibits the critical behavior of a phase transition. This is a general property of the system and is not strongly dependent on the details of the star--interstellar gas interaction. Examination of the properties of this phase transition provides a general scenario for the evolution of galaxies and the origin of the various morphological types

  12. Tracking Galaxy Evolution Through Low-Frequency Radio ...

    Indian Academy of Sciences (India)

    This justify focussing on transitional galaxies to find relic-evidences of the immediate past AGN-feedback which decide the future course of evolution of a galaxy. Relic radio lobes can be best detected in low frequency observations with the GMRT, LOFAR and in future SKA. The age of these relic radio plasma can be as old ...

  13. The Evolution of Galaxies in Cluster Environment; HI Perspective

    NARCIS (Netherlands)

    Fujita, A.; van Gorkom, J.; van Kampen, E.

    1999-01-01

    We investigate the degree to which the environment affects the evolution of galaxies in clusters. One way is to study the fate of gas in cluster galaxies by deep HI synthesis imaging. We are interested in the correlation between HI deficiency of galaxies and the dynamical states of clusters/the

  14. The Galaxy Evolution Probe

    Science.gov (United States)

    Glenn, Jason; Galaxy Evolution Probe Team

    2018-01-01

    The Galaxy Evolution Probe (GEP) is a concept for a far-infrared observatory to survey large regions of sky for star-forming galaxies from z = 0 to beyond z = 3. Our knowledge of galaxy formation is incomplete and requires uniform surveys over a large range of redshifts and environments to accurately describe mass assembly, star formation, supermassive black hole growth, interactions between these processes, and what led to their decline from z ~ 2 to the present day. Infrared observations are sensitive to dusty, star-forming galaxies, which have bright polycyclic aromatic hydrocarbon (PAH) emission features and warm dust continuum in the rest-frame mid infrared and cooler thermal dust emission in the far infrared. Unlike previous far-infrared continuum surveys, the GEP will measure photometric redshifts commensurate with galaxy detections from PAH emission and Si absorption features, without the need for obtaining spectroscopic redshifts of faint counterparts at other wavelengths.The GEP design includes a 2 m diameter telescope actively cooled to 4 K and two instruments: (1) An imager covering 10 to 300 um with 25 spectral resolution R ~ 8 bands (with lower R at the longest wavelengths) to detect star-forming galaxies and measure their redshifts photometrically. (2) A 23 – 190 um, R ~ 250 dispersive spectrometer for redshift confirmation and identification of obscured AGN using atomic fine-structure lines. Lines including [Ne V], [O IV], [O III], [O I], and [C II] will probe gas physical conditions, radiation field hardness, and metallicity. Notionally, the GEP will have a two-year mission: galaxy surveys with photometric redshifts in the first year and a second year devoted to follow-up spectroscopy. A comprehensive picture of star formation in galaxies over the last 10 billion years will be assembled from cosmologically relevant volumes, spanning environments from field galaxies and groups, to protoclusters, to dense galaxy clusters.Commissioned by NASA, the

  15. Estimating precise metallicity and stellar mass evolution of galaxies

    Science.gov (United States)

    Mosby, Gregory

    2018-01-01

    The evolution of galaxies can be conveniently broken down into the evolution of their contents. The changing dust, gas, and stellar content in addition to the changing dark matter potential and periodic feedback from a super-massive blackhole are some of the key ingredients. We focus on the stellar content that can be observed, as the stars reflect information about the galaxy when they were formed. We approximate the stellar content and star formation histories of unresolved galaxies using stellar population modeling. Though simplistic, this approach allows us to reconstruct the star formation histories of galaxies that can be used to test models of galaxy formation and evolution. These models, however, suffer from degeneracies at large lookback times (t > 1 Gyr) as red, low luminosity stars begin to dominate a galaxy’s spectrum. Additionally, degeneracies between stellar populations at different ages and metallicities often make stellar population modeling less precise. The machine learning technique diffusion k-means has been shown to increase the precision in stellar population modeling using a mono-metallicity basis set. However, as galaxies evolve, we expect the metallicity of stellar populations to vary. We use diffusion k-means to generate a multi-metallicity basis set to estimate the stellar mass and chemical evolution of unresolved galaxies. Two basis sets are formed from the Bruzual & Charlot 2003 and MILES stellar population models. We then compare the accuracy and precision of these models in recovering complete (stellar mass and metallicity) histories of mock data. Similarities in the groupings of stellar population spectra in the diffusion maps for each metallicity hint at fundamental age transitions common to both basis sets that can be used to identify stellar populations in a given age range.

  16. Multiwavelength Mapping of Galaxy Formation and Evolution

    CERN Document Server

    Renzini, Alvio; ESO Workshop

    2005-01-01

    The possibilities of astronomical observation have dramatically increased over the last decade. Major satellites, like the Hubble Space Telescope, Chandra and XMM Newton, are complemented by numerous large ground-based observatories, from 8m-10m optical telescopes to sub-mm and radio facilities. As a result, observational astronomy has access to virtually the whole electromagnetic spectrum of galaxies, even at high redshifts. Theoretical models of galaxy formation and cosmological evolution now face a serious challenge to match the plethora of observational data. In October 2003, over 170 astronomers from 15 countries met for a 4-day workshop to extensively illustrate and discuss all major observational projects and ongoing theoretical efforts to model galaxy formation and evolution. This volume contains the complete proceedings of this meeting and is therefore a unique and timely overview of the current state of research in this rapidly evolving field.

  17. Evolution of disk galaxies and the SO problem, revisited

    International Nuclear Information System (INIS)

    Bothun, G.D.

    1982-01-01

    We begin by summerizing the relevant properties of clusters of galaxies in relation to their ability to alter the course of galaxy evolution. Previous work on the effect of environment on the evolution of disk galaxies is also summerized and critiqued. The extensive data base of Bothun is then used to reexamine the issue of the role of the environment in motivating the evolution of disk galaxies. This data base consists of radio and optical observations of approx.350 galaxies in the clusters Peg I, Cancer, Pices, Coma, A1367, Z74--23, Hercules, A539, and A400. The data are portrayed in the color-gas content plane [log M/sub H//L/sub B/ vs. (B--V)/sup T/ 0 ], and theoretical evolutionary tracks have been constructed in that plane to serve as an adjunct to data interpretation. All analysis is done solely on the basis of the measurable quantities themselves, as opposed to morphological considerations. We find that spiral galaxies exhibit such a wide range in their integrated properties that attempting to force then into ''narrow'' morphological bins is neither practical or physically meaningful. With respect to the question of environmental modification of disk galaxies in clusters, we find the great majority of the data to mitigate strongly against any global environmental processes as having been important in determining the particular evolutionary history of cluster galaxies. Our basic conclusion is that initial conditions of formation and variations in star formation histories have been more important than environmental influences in determining the present-day character of spiral galaxies in clusters. The key parameter may well be the amount of neutral hydrogen remaining after star formation in the bulge component has ceased

  18. The Taxonomy of Blue Amorphous Galaxies. II. Structure and Evolution

    Science.gov (United States)

    Marlowe, Amanda T.; Meurer, Gerhardt R.; Heckman, Timothy M.

    1999-09-01

    Dwarf galaxies play an important role in our understanding of galaxy formation and evolution, and starbursts are believed to affect the structure and evolution of dwarf galaxies strongly. We have therefore embarked on a systematic study of 12 of the nearest dwarf galaxies thought to be undergoing bursts of star formation. These were selected primarily by their morphological type (blue ``amorphous'' galaxies). We show that these blue amorphous galaxies are not physically distinguishable from dwarfs selected as starbursting by other methods, such as blue compact dwarfs (BCDs) and H II galaxies. All these classes exhibit surface brightness profiles that are exponential in the outer regions (r>~1.5re) but often have a predominantly central blue excess, suggesting a young burst in an older, redder galaxy. Typically, the starbursting ``cores'' are young (~107-108 yr) events compared to the older (~109-1010 yr) underlying galaxy (the ``envelope''). The ratio of the core to envelope in blue light ranges from essentially zero to about 2. These starbursts are therefore modest events involving only a few percent of the stellar mass. The envelopes have surface brightnesses that are much higher than typical dwarf irregular (dI) galaxies, so it is unlikely that there is a straightforward evolutionary relation between typical dIs and dwarf starburst galaxies. Instead we suggest that amorphous galaxies may repeatedly cycle through starburst and quiescent phases, corresponding to the galaxies with strong and weak/absent cores, respectively. Once amorphous galaxies use up the available gas (either through star formation or galactic winds) so that star formation is shut off, the faded remnants would strongly resemble dwarf elliptical galaxies. However, in the current cosmological epoch, this is evidently a slow process that is the aftermath of a series of many weak, recurring bursts. Present-day dE's must have experienced more rapid and intense evolution than this in the distant past.

  19. The Evolution of the Stellar Hosts of Radio Galaxies

    International Nuclear Information System (INIS)

    Lacy, Mark; Bunker, Andrew J.; Ridgway, Susan E.

    2000-01-01

    We present new near-infrared images of z>0.8 radio galaxies from the flux-limited 7C-iii sample of radio sources for which we have recently obtained almost complete spectroscopic redshifts. The 7C objects have radio luminosities ≅20 times fainter than 3C radio galaxies at a given redshift. The absolute magnitudes of the underlying host galaxies and their scale sizes are only weakly dependent on radio luminosity. Radio galaxy hosts at z∼2 are significantly brighter than the hosts of radio-quiet quasars at similar redshifts and the recent model AGN hosts of Kauffmann and Haehnelt. There is no evidence for strong evolution in scale size, which shows a large scatter at all redshifts. The hosts brighten significantly with redshift, consistent with the passive evolution of a stellar population that formed at z(greater-or-similar sign)3. This scenario is consistent with studies of host galaxy morphology and submillimeter continuum emission, both of which show strong evolution at z(greater-or-similar sign)2.5. The lack of a strong ''redshift cutoff'' in the radio luminosity function to z>4 suggests that the formation epoch of the radio galaxy host population lasts (greater-or-similar sign)1 Gyr, from z(greater-or-similar sign)5 to z∼3. We suggest these facts are best explained by models in which the most massive galaxies and their associated AGN form early because of high baryon densities in the centers of their dark matter haloes. (c) 2000 The American Astronomical Society

  20. Evolution of galaxies clustering in the VIMOS-VLT Deep Survey

    International Nuclear Information System (INIS)

    Meneux, Baptiste

    2005-01-01

    The recent surveys of the Universe highlighted the presence of structures in the matter distribution, such as filaments and voids. To study the evolution of the galaxy spatial distribution, it is necessary to know their accurate position in a three dimensional space. This thesis took place within the framework of the VIMOS-VLT Deep Survey (VVDS). Its goal is to measure some 100000 redshifts to study the formation and evolution of the galaxies and large scale structures of the Universe up to z∼5. After having made a review of our knowledge of the galaxies distribution, then introduced the VVDS, I present the measurement and the evolution of the real-space two-point correlation function from the first epoch data of the VVDS, the largest sample of 10759 spectra ever acquired up to I_A_B = 24. I developed a whole set of programs made available to the VVDS consortium to easily measure the clustering length of galaxies in a given redshift range, with its associated errors, correcting the effects of the VVDS observing strategy. This tool enabled to measure the evolution of the real space correlation function of the global galaxies population up to z=2. I then extended this study dividing the full galaxies sample by spectral type and color. Finally, combining the GALEX data to the VVDS has allowed me to measure the clustering of an ultraviolet-selected sample of galaxies up to z∼1. This is the first time that such measurements are carried out on such a so long range of cosmic time. The results presented in this thesis are thus establishing a new reference in the field. (author) [fr

  1. The evolution of early-type galaxies in distant clusters

    International Nuclear Information System (INIS)

    Stanford, S.A.; Eisenhardt, P.R.; Dickinson, M.

    1998-01-01

    We present results from an optical-infrared photometric study of early-type (E+S0) galaxies in 19 galaxy clusters out to z=0.9. The galaxy sample is selected on the basis of morphologies determined from Hubble Space Telescope (HST) WFPC2 images and is photometrically defined in the K band in order to minimize redshift-dependent selection biases. Using new ground-based photometry in five optical and infrared bands for each cluster, we examine the evolution of the color-magnitude relation for early-type cluster galaxies, considering its slope, intercept, and color scatter around the mean relation. New multiwavelength photometry of galaxies in the Coma Cluster is used to provide a baseline sample at z∼0 with which to compare the distant clusters. The optical - IR colors of the early-type cluster galaxies become bluer with increasing redshift in a manner consistent with the passive evolution of an old stellar population formed at an early cosmic epoch. The degree of color evolution is similar for clusters at similar redshift and does not depend strongly on the optical richness or X-ray luminosity of the cluster, which suggests that the history of early-type galaxies is relatively insensitive to environment, at least above a certain density threshold. The slope of the color-magnitude relationship shows no significant change out to z=0.9, which provides evidence that it arises from a correlation between galaxy mass and metallicity, not age. Finally, the intrinsic scatter in the optical - IR colors of the galaxies is small and nearly constant with redshift, which indicates that the majority of giant, early-type galaxies in clusters share a common star formation history, with little perturbation due to uncorrelated episodes of later star formation. Taken together, our results are consistent with models in which most early-type galaxies in rich clusters are old, formed the majority of their stars at high redshift in a well-synchronized fashion, and evolved quiescently

  2. MID-INFRARED EVIDENCE FOR ACCELERATED EVOLUTION IN COMPACT GROUP GALAXIES

    International Nuclear Information System (INIS)

    Walker, Lisa May; Johnson, Kelsey E.; Gallagher, Sarah C.; Hibbard, John E.; Hornschemeier, Ann E.; Tzanavaris, Panayiotis; Charlton, Jane C.; Jarrett, Thomas H.

    2010-01-01

    Compact galaxy groups are at the extremes of the group environment, with high number densities and low velocity dispersions that likely affect member galaxy evolution. To explore the impact of this environment in detail, we examine the distribution in the mid-infrared (MIR) 3.6-8.0 μm color space of 42 galaxies from 12 Hickson compact groups (HCGs) in comparison with several control samples, including the LVL+SINGS galaxies, interacting galaxies, and galaxies from the Coma Cluster. We find that the HCG galaxies are strongly bimodal, with statistically significant evidence for a gap in their distribution. In contrast, none of the other samples show such a marked gap, and only galaxies in the Coma infall region have a distribution that is statistically consistent with the HCGs in this parameter space. To further investigate the cause of the HCG gap, we compare the galaxy morphologies of the HCG and LVL+SINGS galaxies, and also probe the specific star formation rate (SSFR) of the HCG galaxies. While galaxy morphology in HCG galaxies is strongly linked to position with MIR color space, the more fundamental property appears to be the SSFR, or star formation rate normalized by stellar mass. We conclude that the unusual MIR color distribution of HCG galaxies is a direct product of their environment, which is most similar to that of the Coma infall region. In both cases, galaxy densities are high, but gas has not been fully processed or stripped. We speculate that the compact group environment fosters accelerated evolution of galaxies from star-forming and neutral gas-rich to quiescent and neutral gas-poor, leaving few members in the MIR gap at any time.

  3. Galaxy evolution in dense environments: a concise HI perspective

    NARCIS (Netherlands)

    Verheijen, Marc A. W.; Diaferio, Antonaldo

    2004-01-01

    Observing the neutral hydrogen in galaxy clusters provides crucial insights in the physical processes that influence the evolution of gas-rich galaxies as they migrate from the lower-density filaments through the cluster outskirts into to the higher-density central regions. The morphology-density

  4. Co-evolution of elliptical galaxies and their central black holes

    International Nuclear Information System (INIS)

    Ciotti, I.

    2009-01-01

    After the discovery that supermassive black holes (SMBHs) are ubiquitous at the center of stellar spheroids and that their mass M BH , in the range 10 6 M-10 9 M, is tightly related to global properties of the host stellar system, the idea of the co-evolution of elliptical galaxies and of their SMBHs has become a central topic of modern astrophysics. Here, I summarize some consequences that can be derived from the galaxy Scaling Laws (SLs) and present a coherent scenario for the formation and evolution of elliptical galaxies and their central SMBHs, focusing in particular on the establishment and maintenance of their SLs. In particular, after a first observationally based part, the discussion focuses on the physical interpretation of the Fundamental Plane. Then, two important processes in principle able to destroy the galaxy and SMBH SLs, namely galaxy merging and cooling flows, are analyzed. Arguments supporting the necessity to clearly distinguish between the origin and maintenance of the different SLs, and the unavoidable occurrence of SMBH feedback on the galaxy ISM in the late stages of galaxy evolution (when elliptical galaxies are sometimes considered as dead, red objects), are then presented. At the end of the paper I will discuss some implications of the recent discovery of super-dense ellipticals in the distant Universe. In particular, I will argue that, if confirmed, these new observations would lead to the conclusion that at early epochs a relation between the stellar mass of the galaxy and the mass of the central SMBH should hold, consistent with the present day Magorrian relation, while the proportionality coefficient between M BH and the scale of velocity dispersion of the hosting spheroids should be significantly smaller than that at the present epoch

  5. Evolution of Late-type Galaxies in a Cluster Environment: Effects of High-speed Multiple Encounters with Early-type Galaxies

    Science.gov (United States)

    Hwang, Jeong-Sun; Park, Changbom; Banerjee, Arunima; Hwang, Ho Seong

    2018-04-01

    Late-type galaxies falling into a cluster would evolve being influenced by the interactions with both the cluster and the nearby cluster member galaxies. Most numerical studies, however, tend to focus on the effects of the former with little work done on those of the latter. We thus perform a numerical study on the evolution of a late-type galaxy interacting with neighboring early-type galaxies at high speed using hydrodynamic simulations. Based on the information obtained from the Coma cluster, we set up the simulations for the case where a Milky Way–like late-type galaxy experiences six consecutive collisions with twice as massive early-type galaxies having hot gas in their halos at the closest approach distances of 15–65 h ‑1 kpc at the relative velocities of 1500–1600 km s‑1. Our simulations show that the evolution of the late-type galaxy can be significantly affected by the accumulated effects of the high-speed multiple collisions with the early-type galaxies, such as on cold gas content and star formation activity of the late-type galaxy, particularly through the hydrodynamic interactions between cold disk and hot gas halos. We find that the late-type galaxy can lose most of its cold gas after the six collisions and have more star formation activity during the collisions. By comparing our simulation results with those of galaxy–cluster interactions, we claim that the role of the galaxy–galaxy interactions on the evolution of late-type galaxies in clusters could be comparable with that of the galaxy–cluster interactions, depending on the dynamical history.

  6. Predicting galaxy star formation rates via the co-evolution of galaxies and haloes

    Science.gov (United States)

    Watson, Douglas F.; Hearin, Andrew P.; Berlind, Andreas A.; Becker, Matthew R.; Behroozi, Peter S.; Skibba, Ramin A.; Reyes, Reinabelle; Zentner, Andrew R.; van den Bosch, Frank C.

    2015-01-01

    In this paper, we test the age matching hypothesis that the star formation rate (SFR) of a galaxy of fixed stellar mass is determined by its dark matter halo formation history, e.g. more quiescent galaxies reside in older haloes. We present new Sloan Digital Sky Survey measurements of the galaxy two-point correlation function and galaxy-galaxy lensing as a function of stellar mass and SFR, separated into quenched and star-forming galaxy samples to test this simple model. We find that our age matching model is in excellent agreement with these new measurements. We also find that our model is able to predict: (1) the relative SFRs of central and satellite galaxies, (2) the SFR dependence of the radial distribution of satellite galaxy populations within galaxy groups, rich groups, and clusters and their surrounding larger scale environments, and (3) the interesting feature that the satellite quenched fraction as a function of projected radial distance from the central galaxy exhibits an ˜r-.15 slope, independent of environment. These accurate predictions are intriguing given that we do not explicitly model satellite-specific processes after infall, and that in our model the virial radius does not mark a special transition region in the evolution of a satellite. The success of the model suggests that present-day galaxy SFR is strongly correlated with halo mass assembly history.

  7. Abundance gradients in disc galaxies and chemical evolution models

    International Nuclear Information System (INIS)

    Diaz, A.I.

    1989-01-01

    The present state of abundance gradients and chemical evolution models of spiral galaxies is reviewed. An up to date compilation of abundance data in the literature concerning HII regions over galactic discs is presented. From these data Oxygen and Nitrogen radial gradients are computed. The slope of the Oxygen gradient is shown to have a break at a radius between 1.5 and 1.75 times the value of the effective radius of the disc, i.e. the radius containing half of the light of the disc. The gradient is steeper in the central parts of the disc and becomes flatter in the outer parts. N/O gradients are shown to be rather different from galaxy to galaxy and only a weak trend of N/O with O/H is found. The existing chemical evolution models for spiral galaxies are reviewed with special emphasis in the interpretation of numerical models having a large number of parameters. (author)

  8. A UNIFIED EMPIRICAL MODEL FOR INFRARED GALAXY COUNTS BASED ON THE OBSERVED PHYSICAL EVOLUTION OF DISTANT GALAXIES

    International Nuclear Information System (INIS)

    Béthermin, Matthieu; Daddi, Emanuele; Sargent, Mark T.; Elbaz, David; Mullaney, James; Pannella, Maurilio; Magdis, Georgios; Hezaveh, Yashar; Le Borgne, Damien; Buat, Véronique; Charmandaris, Vassilis; Lagache, Guilaine; Scott, Douglas

    2012-01-01

    We reproduce the mid-infrared to radio galaxy counts with a new empirical model based on our current understanding of the evolution of main-sequence (MS) and starburst (SB) galaxies. We rely on a simple spectral energy distribution (SED) library based on Herschel observations: a single SED for the MS and another one for SB, getting warmer with redshift. Our model is able to reproduce recent measurements of galaxy counts performed with Herschel, including counts per redshift slice. This agreement demonstrates the power of our 2-Star-Formation Modes (2SFM) decomposition in describing the statistical properties of infrared sources and their evolution with cosmic time. We discuss the relative contribution of MS and SB galaxies to the number counts at various wavelengths and flux densities. We also show that MS galaxies are responsible for a bump in the 1.4 GHz radio counts around 50 μJy. Material of the model (predictions, SED library, mock catalogs, etc.) is available online.

  9. Simulating The Dynamical Evolution Of Galaxies In Group And Cluster Environments

    Science.gov (United States)

    Vijayaraghavan, Rukmani

    2015-07-01

    Galaxy clusters are harsh environments for their constituent galaxies. A variety of physical processes effective in these dense environments transform gas-rich, spiral, star-forming galaxies to elliptical or spheroidal galaxies with very little gas and therefore minimal star formation. The consequences of these processes are well understood observationally. Galaxies in progressively denser environments have systematically declining star formation rates and gas content. However, a theoretical understanding of of where, when, and how these processes act, and the interplay between the various galaxy transformation mechanisms in clusters remains elusive. In this dissertation, I use numerical simulations of cluster mergers as well as galaxies evolving in quiescent environments to develop a theoretical framework to understand some of the physics of galaxy transformation in cluster environments. Galaxies can be transformed in smaller groups before they are accreted by their eventual massive cluster environments, an effect termed `pre-processing'. Galaxy cluster mergers themselves can accelerate many galaxy transformation mechanisms, including tidal and ram pressure stripping of galaxies and galaxy-galaxy collisions and mergers that result in reassemblies of galaxies' stars and gas. Observationally, cluster mergers have distinct velocity and phase-space signatures depending on the observer's line of sight with respect to the merger direction. Using dark matter only as well as hydrodynamic simulations of cluster mergers with random ensembles of particles tagged with galaxy models, I quantify the effects of cluster mergers on galaxy evolution before, during, and after the mergers. Based on my theoretical predictions of the dynamical signatures of these mergers in combination with galaxy transformation signatures, one can observationally identify remnants of mergers and quantify the effect of the environment on galaxies in dense group and cluster environments. The presence of

  10. Molecules as tracers of galaxy evolution: an EMIR survey

    DEFF Research Database (Denmark)

    Costagliola, F.; Aalto, S.; I. Rodriguez, M.

    2011-01-01

    We investigate the molecular gas properties of a sample of 23 galaxies in order to find and test chemical signatures of galaxy evolution and to compare them to IR evolutionary tracers. Observation at 3 mm wavelengths were obtained with the EMIR broadband receiver, mounted on the IRAM 30 m telesco...

  11. Chemical Evolution and the Formation of Dwarf Galaxies in the Early Universe

    Science.gov (United States)

    Cote, Benoit; JINA-CEE, NuGrid, ChETEC

    2018-06-01

    Stellar abundances in local dwarf galaxies offer a unique window into the nature and nucleosynthesis of the first stars. They also contain clues regarding how galaxies formed and assembled in the early stages of the universe. In this talk, I will present our effort to connect nuclear astrophysics with the field of galaxy formation in order to define what can be learned about galaxy evolution using stellar abundances. In particular, I will describe the current state of our numerical chemical evolution pipeline which accounts for the mass assembly history of galaxies, present how we use high-redshift cosmological hydrodynamic simulations to calibrate our models and to learn about the formation of dwarf galaxies, and address the challenge of identifying the dominant r-process site(s) using stellar abundances.

  12. Iron abundance evolution in spiral and elliptical galaxies

    International Nuclear Information System (INIS)

    Matteucci, F.

    1987-01-01

    Chemical evolution models for the Galaxy and ellipticals, which take into account the most recent developments on theories of nucleosynthesis and supernova progenitors, are presented. The evolution of the abundance of iron in these systems, under the assumption that this element is mainly produced by type I SNe, originating from white dwarfs in binary systems, has been computed and the results have been compared with the observations. Overabundances of O, Si, Ne and Mg with respect to iron have been predicted for halo stars in their Galaxy. The existence of an Fe - total mass relation with a slope steeper than the corresponding relations for Mg and O has been predicted for ellipticals. The masses of Fe ejected by ellipticals of various masses into the intergalactic medium have also been computed in detail. The general agreement obtained between these theoretical models and the observations for galaxies of different morphological type supports the assumptions made about the origin of iron

  13. Deep CCD survey - galaxy luminosity and color evolution

    International Nuclear Information System (INIS)

    Tyson, J.A.

    1988-01-01

    Imaging and photometric observations of a statistically complete sample of galaxies in 12 high-latitude fields, obtained in the BJ (360-520 nm), R (580-720 nm) and I (780-1100 nm) bands using CCD detectors on the 4-m telescopes at CTIO and KPNO, are reported. The data are presented in extensive graphs and sample images and analyzed in detail with reference to theoretical models of galactic origin and evolution. The galaxy number-count slopes, d(log N)/dm, are found to be sub-Euclidean, varying from 0.34 in the I band to 0.45 in the BJ band, where the corrected counts appear to saturate at about 27 mag. The predictions of no-evolution models are shown to underpredict the counts at 25 mag (BJ) by a factor of 5-15 and the extragalactic background light from all galaxies (6.8 x 10 to the -6th erg/sq cm sec sr micron at 450 nm) by a factor greater than 2. 114 references

  14. On the Evolution of the Central Density of Quiescent Galaxies

    International Nuclear Information System (INIS)

    Tacchella, Sandro; Carollo, C. Marcella; Woo, Joanna; Faber, S. M.; Koo, David C.; Cibinel, Anna; Dekel, Avishai; Renzini, Alvio

    2017-01-01

    We investigate the origin of the evolution of the population-averaged central stellar mass density (Σ_1) of quiescent galaxies (QGs) by probing the relation between stellar age and Σ_1 at z ∼ 0. We use the Zurich ENvironmental Study (ZENS), which is a survey of galaxy groups with a large fraction of satellite galaxies. QGs shape a narrow locus in the Σ_1– M _⋆ plane, which we refer to as Σ_1 ridgeline. Colors of ( B − I ) and ( I − J ) are used to divide QGs into three age categories: young ( 4 Gyr). At fixed stellar mass, old QGs on the Σ_1 ridgeline have higher Σ_1 than young QGs. This shows that galaxies landing on the Σ_1 ridgeline at later epochs arrive with lower Σ_1, which drives the zeropoint of the ridgeline down with time. We compare the present-day zeropoint of the oldest population at z = 0 with the zeropoint of the quiescent population 4 Gyr back in time, at z = 0.37. These zeropoints are identical, showing that the intrinsic evolution of individual galaxies after they arrive on the Σ_1 ridgeline must be negligible, or must evolve parallel to the ridgeline during this interval. The observed evolution of the global zeropoint of 0.07 dex over the last 4 Gyr is thus largely due to the continuous addition of newly quenched galaxies with lower Σ_1 at later times (“progenitor bias”). While these results refer to the satellite-rich ZENS sample as a whole, our work suggests a similar age–Σ_1 trend for central galaxies.

  15. Evolution of Hot Gas in Elliptical Galaxies

    Science.gov (United States)

    Mathews, William G.

    2004-01-01

    This theory grant was awarded to study the curious nature, origin and evolution of hot gas in elliptical galaxies and their surrounding groups. Understanding the properties of this X-ray emitting gas has profound implications over the broad landscape of modern astrophysics: cosmology, galaxy formation, star formation, cosmic metal enrichment, galactic structure and dynamics, and the physics of hot gases containing dust and magnetic fields. One of our principal specific objectives was to interpret the marvelous new observations from the XMM and Chandru satellite X-ray telescopes.

  16. CHEMICAL EVOLUTION LIBRARY FOR GALAXY FORMATION SIMULATION

    International Nuclear Information System (INIS)

    Saitoh, Takayuki R.

    2017-01-01

    We have developed a software library for chemical evolution simulations of galaxy formation under the simple stellar population (SSP) approximation. In this library, all of the necessary components concerning chemical evolution, such as initial mass functions, stellar lifetimes, yields from Type II and Type Ia supernovae, asymptotic giant branch stars, and neutron star mergers, are compiled from the literature. Various models are pre-implemented in this library so that users can choose their favorite combination of models. Subroutines of this library return released energy and masses of individual elements depending on a given event type. Since the redistribution manner of these quantities depends on the implementation of users’ simulation codes, this library leaves it up to the simulation code. As demonstrations, we carry out both one-zone, closed-box simulations and 3D simulations of a collapsing gas and dark matter system using this library. In these simulations, we can easily compare the impact of individual models on the chemical evolution of galaxies, just by changing the control flags and parameters of the library. Since this library only deals with the part of chemical evolution under the SSP approximation, any simulation codes that use the SSP approximation—namely, particle-base and mesh codes, as well as semianalytical models—can use it. This library is named “CELib” after the term “Chemical Evolution Library” and is made available to the community.

  17. CHEMICAL EVOLUTION LIBRARY FOR GALAXY FORMATION SIMULATION

    Energy Technology Data Exchange (ETDEWEB)

    Saitoh, Takayuki R., E-mail: saitoh@elsi.jp [Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro, Tokyo, 152-8551 (Japan)

    2017-02-01

    We have developed a software library for chemical evolution simulations of galaxy formation under the simple stellar population (SSP) approximation. In this library, all of the necessary components concerning chemical evolution, such as initial mass functions, stellar lifetimes, yields from Type II and Type Ia supernovae, asymptotic giant branch stars, and neutron star mergers, are compiled from the literature. Various models are pre-implemented in this library so that users can choose their favorite combination of models. Subroutines of this library return released energy and masses of individual elements depending on a given event type. Since the redistribution manner of these quantities depends on the implementation of users’ simulation codes, this library leaves it up to the simulation code. As demonstrations, we carry out both one-zone, closed-box simulations and 3D simulations of a collapsing gas and dark matter system using this library. In these simulations, we can easily compare the impact of individual models on the chemical evolution of galaxies, just by changing the control flags and parameters of the library. Since this library only deals with the part of chemical evolution under the SSP approximation, any simulation codes that use the SSP approximation—namely, particle-base and mesh codes, as well as semianalytical models—can use it. This library is named “CELib” after the term “Chemical Evolution Library” and is made available to the community.

  18. On the Evolution of the Central Density of Quiescent Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Tacchella, Sandro; Carollo, C. Marcella; Woo, Joanna [Department of Physics, Institute for Astronomy, ETH Zurich, CH-8093 Zurich (Switzerland); Faber, S. M.; Koo, David C. [Department of Astronomy and Astrophysics, University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA (United States); Cibinel, Anna [Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH (United Kingdom); Dekel, Avishai [Center for Astrophysics and Planetary Science, Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Renzini, Alvio, E-mail: sandro.tacchella@phys.ethz.ch [INAF Osservatorio Astronomico di Padova, vicolo dellOsservatorio 5, I-35122 Padova (Italy)

    2017-07-20

    We investigate the origin of the evolution of the population-averaged central stellar mass density (Σ{sub 1}) of quiescent galaxies (QGs) by probing the relation between stellar age and Σ{sub 1} at z ∼ 0. We use the Zurich ENvironmental Study (ZENS), which is a survey of galaxy groups with a large fraction of satellite galaxies. QGs shape a narrow locus in the Σ{sub 1}– M {sub ⋆} plane, which we refer to as Σ{sub 1} ridgeline. Colors of ( B − I ) and ( I − J ) are used to divide QGs into three age categories: young (<2 Gyr), intermediate (2–4 Gyr), and old (>4 Gyr). At fixed stellar mass, old QGs on the Σ{sub 1} ridgeline have higher Σ{sub 1} than young QGs. This shows that galaxies landing on the Σ{sub 1} ridgeline at later epochs arrive with lower Σ{sub 1}, which drives the zeropoint of the ridgeline down with time. We compare the present-day zeropoint of the oldest population at z = 0 with the zeropoint of the quiescent population 4 Gyr back in time, at z = 0.37. These zeropoints are identical, showing that the intrinsic evolution of individual galaxies after they arrive on the Σ{sub 1} ridgeline must be negligible, or must evolve parallel to the ridgeline during this interval. The observed evolution of the global zeropoint of 0.07 dex over the last 4 Gyr is thus largely due to the continuous addition of newly quenched galaxies with lower Σ{sub 1} at later times (“progenitor bias”). While these results refer to the satellite-rich ZENS sample as a whole, our work suggests a similar age–Σ{sub 1} trend for central galaxies.

  19. Evolution of disk galaxies and the origin of SO galaxies

    International Nuclear Information System (INIS)

    Larson, R.B.; Tinsley, B.M.; Caldwell, C.N.

    1980-01-01

    We reconsider the relation between spiral and SO galaxies in the light of recent data on the colors and morphology of disk systems, and on the content of clusters at different redshifts. Star formation will strongly deplete the gas in most spirals in a fraction of the Hubble time, so we suggest that the gas in spirals has been replenished by infall from residual envelopes, probably including gas-rich companions and tidal debris. SO's may then be disk systems that lost their gas-rich envelopes at an early stage and consumed their remaining gas by star formation. This picture is consistent with the color of SO's if most of their star formation stopped at least a few gigayears ago, and it is consistent with their small disk-to-bulge ratios relative to spirals, since this is a direct result of the early truncation of star formation. Numerical simulations show that the gas envelopes of disk galaxies in clusters are largely stripped away when the clusters collapse, but star formation can continue in the spirals for several gigayears while their remaining disk gas is consumed. These results can explain the blue galaxies observed by Butcher and Oemler in two condensed clusters at zapprox.0.4: these clusters are seen just before most of their galaxies run out of gas, so that star formation is still occurring in them but will soon die out, causing the spirals to evolve into SO's with normal present colors. A rapid evolution of the galaxy content of condensed clusters is predicted at moderate redshifts, ranging from a large fraction of blue galaxies at zapprox.0.4 to very few at zapprox.0

  20. Evolution of the clustering of photometrically selected SDSS galaxies

    OpenAIRE

    Ross, Ashley; Percival, Will; Brunner, R.

    2010-01-01

    We measure the angular auto-correlation functions, ω(θ), of Sloan Digital Sky Survey (SDSS) galaxies selected to have photometric redshifts 0.1 < z < 0.4 and absolute r-band magnitudes Mr < −21.2. We split these galaxies into five overlapping redshift shells of width 0.1 and measure ω(θ) in each subsample in order to investigate the evolution of SDSS galaxies. We find that the bias increases substantially with redshift – much more so than one would expect for a passively evolving sample. We u...

  1. Multiparameter imaging of calcium and abscisic acid and high-resolution quantitative calcium measurements using R-GECO1-mTurquoise in Arabidopsis.

    Science.gov (United States)

    Waadt, Rainer; Krebs, Melanie; Kudla, Jörg; Schumacher, Karin

    2017-10-01

    Calcium signals occur in specific spatio-temporal patterns in response to various stimuli and are coordinated with, for example, hormonal signals, for physiological and developmental adaptations. Quantification of calcium together with other signalling molecules is required for correlative analyses and to decipher downstream calcium-decoding mechanisms. Simultaneous in vivo imaging of calcium and abscisic acid has been performed here to investigate the interdependence of the respective signalling processes in Arabidopsis thaliana roots. Advanced ratiometric genetically encoded calcium indicators have been generated and in vivo calcium calibration protocols were established to determine absolute calcium concentration changes in response to auxin and ATP. In roots, abscisic acid induced long-term basal calcium concentration increases, while auxin triggered rapid signals in the elongation zone. The advanced ratiometric calcium indicator R-GECO1-mTurquoise exhibited an increased calcium signal resolution compared to commonly used Förster resonance energy transfer-based indicators. Quantitative calcium measurements in Arabidopsis root tips using R-GECO1-mTurquoise revealed detailed maps of absolute calcium concentration changes in response to auxin and ATP. Calcium calibration protocols using R-GECO1-mTurquoise enabled high-resolution quantitative imaging of resting cytosolic calcium concentrations and their dynamic changes that revealed distinct hormonal and ATP responses in roots. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  2. Very deep IRAS survey - constraints on the evolution of starburst galaxies

    International Nuclear Information System (INIS)

    Hacking, P.; Houck, J.R.; Condon, J.J.; National Radio Astronomy Observatory, Charlottesville, VA)

    1987-01-01

    Counts of sources (primarily starburst galaxies) from a deep 60 microns IRAS survey published by Hacking and Houck (1987) are compared with four evolutionary models. The counts below 100 mJy are higher than expected if no evolution has taken place out to a redshift of approximately 0.2. Redshift measurements of the survey sources should be able to distinguish between luminosity-evolution and density-evolution models and detect as little as a 20 percent brightening or increase in density of infrared sources per billion years ago (H/0/ = 100 km/s per Mpc). Starburst galaxies cannot account for the reported 100 microns background without extreme evolution at high redshifts. 21 references

  3. ZFOURGE/CANDELS: ON THE EVOLUTION OF M* GALAXY PROGENITORS FROM z = 3 TO 0.5

    International Nuclear Information System (INIS)

    Papovich, C.; Quadri, R.; Tilvi, V.; Tran, K.-V.; Labbé, I.; Straatman, C. M. S.; Behroozi, P.; Ferguson, H. C.; Bell, E. F.; Glazebrook, K.; Kacprzak, G. G.; Spitler, L.; Cowley, M.; Davé, R.; Dekel, A.; Dickinson, M.; Inami, H.; Finkelstein, S. L.; Gawiser, E.; Faber, S. M.

    2015-01-01

    Galaxies with stellar masses near M* contain the majority of stellar mass in the universe, and are therefore of special interest in the study of galaxy evolution. The Milky Way (MW) and Andromeda (M31) have present-day stellar masses near M*, at 5 × 10 10 M ☉ (defined here to be MW-mass) and 10 11 M ☉ (defined to be M31-mass). We study the typical progenitors of these galaxies using the FOURSTAR Galaxy Evolution Survey (ZFOURGE). ZFOURGE is a deep medium-band near-IR imaging survey, which is sensitive to the progenitors of these galaxies out to z ∼ 3. We use abundance-matching techniques to identify the main progenitors of these galaxies at higher redshifts. We measure the evolution in the stellar mass, rest-frame colors, morphologies, far-IR luminosities, and star formation rates, combining our deep multiwavelength imaging with near-IR Hubble Space Telescope imaging from Cosmic Near-IR Deep Extragalactic Legacy Survey (CANDELS), and Spitzer and Herschel far-IR imaging from Great Observatories Origins Deep Survey-Herschel and CANDELS-Herschel. The typical MW-mass and M31-mass progenitors passed through the same evolution stages, evolving from blue, star-forming disk galaxies at the earliest stages to redder dust-obscured IR-luminous galaxies in intermediate stages and to red, more quiescent galaxies at their latest stages. The progenitors of the MW-mass galaxies reached each evolutionary stage at later times (lower redshifts) and with stellar masses that are a factor of two to three lower than the progenitors of the M31-mass galaxies. The process driving this evolution, including the suppression of star formation in present-day M* galaxies, requires an evolving stellar-mass/halo-mass ratio and/or evolving halo-mass threshold for quiescent galaxies. The effective size and SFRs imply that the baryonic cold-gas fractions drop as galaxies evolve from high redshift to z ∼ 0 and are strongly anticorrelated with an increase in the Sérsic index. Therefore, the

  4. ZFOURGE/CANDELS: On the Evolution of M* Galaxy Progenitors from z = 3 to 0.5

    Science.gov (United States)

    Papovich, C.; Labbé, I.; Quadri, R.; Tilvi, V.; Behroozi, P.; Bell, E. F.; Glazebrook, K.; Spitler, L.; Straatman, C. M. S.; Tran, K.-V.; Cowley, M.; Davé, R.; Dekel, A.; Dickinson, M.; Ferguson, H. C.; Finkelstein, S. L.; Gawiser, E.; Inami, H.; Faber, S. M.; Kacprzak, G. G.; Kawinwanichakij, L.; Kocevski, D.; Koekemoer, A.; Koo, D. C.; Kurczynski, P.; Lotz, J. M.; Lu, Y.; Lucas, R. A.; McIntosh, D.; Mehrtens, N.; Mobasher, B.; Monson, A.; Morrison, G.; Nanayakkara, T.; Persson, S. E.; Salmon, B.; Simons, R.; Tomczak, A.; van Dokkum, P.; Weiner, B.; Willner, S. P.

    2015-04-01

    Galaxies with stellar masses near M* contain the majority of stellar mass in the universe, and are therefore of special interest in the study of galaxy evolution. The Milky Way (MW) and Andromeda (M31) have present-day stellar masses near M*, at 5 × 1010 M ⊙ (defined here to be MW-mass) and 1011 M ⊙ (defined to be M31-mass). We study the typical progenitors of these galaxies using the FOURSTAR Galaxy Evolution Survey (ZFOURGE). ZFOURGE is a deep medium-band near-IR imaging survey, which is sensitive to the progenitors of these galaxies out to z ~ 3. We use abundance-matching techniques to identify the main progenitors of these galaxies at higher redshifts. We measure the evolution in the stellar mass, rest-frame colors, morphologies, far-IR luminosities, and star formation rates, combining our deep multiwavelength imaging with near-IR Hubble Space Telescope imaging from Cosmic Near-IR Deep Extragalactic Legacy Survey (CANDELS), and Spitzer and Herschel far-IR imaging from Great Observatories Origins Deep Survey-Herschel and CANDELS-Herschel. The typical MW-mass and M31-mass progenitors passed through the same evolution stages, evolving from blue, star-forming disk galaxies at the earliest stages to redder dust-obscured IR-luminous galaxies in intermediate stages and to red, more quiescent galaxies at their latest stages. The progenitors of the MW-mass galaxies reached each evolutionary stage at later times (lower redshifts) and with stellar masses that are a factor of two to three lower than the progenitors of the M31-mass galaxies. The process driving this evolution, including the suppression of star formation in present-day M* galaxies, requires an evolving stellar-mass/halo-mass ratio and/or evolving halo-mass threshold for quiescent galaxies. The effective size and SFRs imply that the baryonic cold-gas fractions drop as galaxies evolve from high redshift to z ~ 0 and are strongly anticorrelated with an increase in the Sérsic index. Therefore, the growth

  5. COSMIC EVOLUTION OF SIZE AND VELOCITY DISPERSION FOR EARLY-TYPE GALAXIES

    International Nuclear Information System (INIS)

    Fan, L.; Lapi, A.; Bressan, A.; De Zotti, G.; Danese, L.; Bernardi, M.

    2010-01-01

    Massive (stellar mass M * ∼> 3 x 10 10 M sun ), passively evolving galaxies at redshifts z ∼> 1 exhibit on average physical sizes smaller, by factors ∼3, than local early-type galaxies (ETGs) endowed with the same stellar mass. Small sizes are in fact expected on theoretical grounds, if dissipative collapse occurs. Recent results show that the size evolution at z ∼ 1, where both compact and already extended galaxies are observed and the scatter in size is remarkably larger than it is locally. The presence at high redshift of a significant number of ETGs with the same size as their local counterparts, as well as ETGs with quite small size (∼ H (z). We demonstrate that the projected mass of compact, high-redshift galaxies and that of local ETGs within the same physical radius, the nominal half-luminosity radius of high-redshift ETGs, differ substantially in that the high-redshift ETGs are on average significantly denser. This result suggests that the physical mechanism responsible for the size increase should also remove mass from central galaxy regions (r ∼ 1, we predict the local velocity dispersion distribution function. On comparing it to the observed one, we show that velocity dispersion evolution of massive ETGs is fully compatible with the observed average evolution in size at constant stellar mass. Less massive ETGs (with stellar masses M * ∼ 10 M sun ) are expected to evolve less both in size and in velocity dispersion, because their evolution is essentially determined by supernova feedback, which cannot yield winds as powerful as those triggered by quasars. The differential evolution is expected to leave imprints in the size versus luminosity/mass, velocity dispersion versus luminosity/mass, and central black hole mass versus velocity dispersion relationships, as observed in local ETGs.

  6. AGES: THE AGN AND GALAXY EVOLUTION SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Kochanek, C. S. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Eisenstein, D. J.; Caldwell, N.; Jones, C.; Murray, S. S.; Forman, W. R.; Green, P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Cool, R. J. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544 (United States); Assef, R. J.; Eisenhardt, P.; Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Jannuzi, B. T.; Dey, A. [NOAO, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Brown, M. J. I. [School of Physics, Monash University, Clayton, Victoria 3800 (Australia); Gonzalez, A. H. [Department of Astronomy, Bryant Space Science Center, University of Florida, Gainesville, FL 32611 (United States)

    2012-05-01

    The AGN and Galaxy Evolution Survey (AGES) is a redshift survey covering, in its standard fields, 7.7 deg{sup 2} of the Booetes field of the NOAO Deep Wide-Field Survey. The final sample consists of 23,745 redshifts. There are well-defined galaxy samples in 10 bands (the B{sub W} , R, I, J, K, IRAC 3.6, 4.5, 5.8, and 8.0 {mu}m, and MIPS 24 {mu}m bands) to a limiting magnitude of I < 20 mag for spectroscopy. For these galaxies, we obtained 18,163 redshifts from a sample of 35,200 galaxies, where random sparse sampling was used to define statistically complete sub-samples in all 10 photometric bands. The median galaxy redshift is 0.31, and 90% of the redshifts are in the range 0.085 < z < 0.66. Active galactic nuclei (AGNs) were selected as radio, X-ray, IRAC mid-IR, and MIPS 24 {mu}m sources to fainter limiting magnitudes (I < 22.5 mag for point sources). Redshifts were obtained for 4764 quasars and galaxies with AGN signatures, with 2926, 1718, 605, 119, and 13 above redshifts of 0.5, 1, 2, 3, and 4, respectively. We detail all the AGES selection procedures and present the complete spectroscopic redshift catalogs and spectral energy distribution decompositions. Photometric redshift estimates are provided for all sources in the AGES samples.

  7. THE REDSHIFT EVOLUTION OF THE RELATION BETWEEN STELLAR MASS, STAR FORMATION RATE, AND GAS METALLICITY OF GALAXIES

    International Nuclear Information System (INIS)

    Niino, Yuu

    2012-01-01

    We investigate the relation between stellar mass (M * ), star formation rate (SFR), and metallicity (Z) of galaxies, the so-called fundamental metallicity relation, in the galaxy sample of the Sloan Digital Sky Survey Data Release 7. We separate the galaxies into narrow redshift bins and compare the relation at different redshifts and find statistically significant (>99%) evolution. We test various observational effects that might cause seeming Z evolution and find it difficult to explain the evolution of the relation only by the observational effects. In the current sample of low-redshift galaxies, galaxies with different M * and SFR are sampled from different redshifts, and there is degeneracy between M * /SFR and redshift. Hence, it is not straightforward to distinguish a relation between Z and SFR from a relation between Z and redshift. The separation of the intrinsic relation from the redshift evolution effect is a crucial issue in the understanding of the evolution of galaxies.

  8. Quantifying the Effects of Gas-Rich Flyby Encounters on Galaxy Evolution

    Science.gov (United States)

    Dumas, Julie; Holley-Bockelmann, Kelly; Lang, Meagan

    2017-01-01

    Recent work has shown that flyby encounters may be a common event in a galaxy's lifetime. Galaxy flybys are a one-time encounter when two halos interpenetrate, but unlike a galaxy merger, the two halos later detach. Relatively little work has been done to assess how flybys affect galaxy evolution. We present preliminary results of a suite of high-resolution hydrodynamical + N-body simulations of gas-rich flyby encounters, concentrating on Milky Way-like primaries. We track the bulk changes in structure, star formation history, kinematics, and morphology over a broad span of flyby encounters.

  9. Co-evolution of Massive Black Holes and Their Host Galaxies

    Science.gov (United States)

    Chen, Y. M.

    2010-07-01

    A scenario of co-evolution of supermassive black holes (SMBHs) and galaxies has been clearly conducted by the important evidence from observational results of quasar host galaxies and the relation between spheroid and SMBH mass. There are a plenty of unresolved problems and questions, some being basic, to be addressed in this scenario. The main goal of the present thesis is focusing on the mysterious scenario including growth of primordial black holes, cosmological evolution of spins and duty cycle of SMBHs, and interaction between the SMBH activity and star formation in galaxies from low to high redshifts. We review the main progress of this field over the past decade since the discovery of Magorrian relation and present comments on some questions in light of our view of points. The key questions to be addressed in this thesis work are: (1) how does the fast growth of primordial black holes influence their evolution? (2) what is the equation to describe the co-evolution of SMBHs and galaxies? (3) what is the mechanism to control the co-evolution? (4) how to transport the fueling gas from kpc scale to the center? It has been suggested that fast growth of primordial black holes via super-Eddington accretion is a promising way to form SMBHs in high redshift universe. Neutrino cooling has been employed and expedites the growth. We consider the Compton heating of the surroundings of the primordial black holes. We find that the realistic accretion rate is only a few percent of the Eddington rate, and the accretion is episodic. It implies that the fast growth via super-Eddington is not feasible. These conclusions have been confirmed by the detailed numerical simulations of Milosavljevic et al. (2008). The difficulties of the fast growth via accretion of baryon particles make the formation of SMBHs elusive in high redshift universe. We developed a new formulation to calculate the duty cycle of SMBHs based on the Soltan argument. We show it can be expressed by the mass

  10. THE EFFECTS OF THE IONIZING RADIATION BACKGROUND ON GALAXY EVOLUTION

    International Nuclear Information System (INIS)

    Hambrick, D. Clay; Ostriker, Jeremiah P.; Naab, Thorsten; Johansson, Peter H.

    2009-01-01

    We find that the amount and nature of the assumed ionizing background can strongly affect galaxy formation and evolution. Galaxy evolution simulations typically incorporate an ultraviolet background which falls off rapidly above z = 3; e.g., that of Haardt and Madau. However, this decline may be too steep to fit the Wilkinson Microwave Anistropy Probe constraints on electron scattering optical depth or observations of intermediate redshift (z ∼ 2-4) Lyα forest transmission. As an alternative, we present simulations of the cosmological formation of individual galaxies with UV backgrounds that decline more slowly at high redshift: both a simple intensity rescaling and the background recently derived by Faucher-Giguere, which softens the spectrum at higher redshifts. We also test an approximation of the X-ray background with a similar z dependence. We find for the test galaxies that an increase in either the intensity or hardness of ionizing radiation generically pushes star formation toward lower redshifts: although overall star formation in the simulation boxes is reduced by 10%-25%, the galaxies show a factor of ∼2 increase in the fraction of stars within a 30 kpc radius that are formed after z = 1. Other effects include late gas inflows enhanced up to 30 times, stellar half-mass radii decreased by up to 30%, central velocity dispersions increased up to 40%, and a strong reduction in substructure. The magnitude of the effects depends on the environmental/accretion properties of the particular galaxy.

  11. EVOLUTION OF GALAXY GROUPS IN THE ILLUSTRIS SIMULATION

    Energy Technology Data Exchange (ETDEWEB)

    Raouf, Mojtaba; Khosroshahi, Habib G. [School of Astronomy, Institute for Research in Fundamental Sciences (IPM), Tehran, 19395-5746 (Iran, Islamic Republic of); Dariush, A., E-mail: m.raouf@ipm.ir [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)

    2016-06-20

    We present the first study of the evolution of galaxy groups in the Illustris simulation. We focus on dynamically relaxed and unrelaxed galaxy groups representing dynamically evolved and evolving galaxy systems, respectively. The evolutionary state of a group is probed from its luminosity gap and separation between the brightest group galaxy and the center of mass of the group members. We find that the Illustris simulation overproduces galaxy systems with a large luminosity gap, known as fossil systems, in comparison to observations and the probed semi-analytical predictions. However, this simulation is just as successful as the probed semi-analytic model in recovering the correlation between luminosity gap and offset of the luminosity centroid. We find evolutionary tracks based on luminosity gap that indicate that a group with a large luminosity gap is rooted in one with a small luminosity gap, regardless of the position of the brightest group galaxy within the halo. This simulation helps to explore, for the first time, the black hole mass and its accretion rate in galaxy groups. For a given stellar mass of the brightest group galaxies, the black hole mass is larger in dynamically relaxed groups with a lower rate of mass accretion. We find this to be consistent with the latest observational studies of radio activity in the brightest group galaxies in fossil groups. We also find that the intragalactic medium in dynamically evolved groups is hotter for a given halo mass than that in evolving groups, again consistent with earlier observational studies.

  12. The Dramatic Size and Kinematic Evolution of Massive Early-type Galaxies

    Science.gov (United States)

    Lapi, A.; Pantoni, L.; Zanisi, L.; Shi, J.; Mancuso, C.; Massardi, M.; Shankar, F.; Bressan, A.; Danese, L.

    2018-04-01

    We aim to provide a holistic view on the typical size and kinematic evolution of massive early-type galaxies (ETGs) that encompasses their high-z star-forming progenitors, their high-z quiescent counterparts, and their configurations in the local Universe. Our investigation covers the main processes playing a relevant role in the cosmic evolution of ETGs. Specifically, their early fast evolution comprises biased collapse of the low angular momentum gaseous baryons located in the inner regions of the host dark matter halo; cooling, fragmentation, and infall of the gas down to the radius set by the centrifugal barrier; further rapid compaction via clump/gas migration toward the galaxy center, where strong heavily dust-enshrouded star formation takes place and most of the stellar mass is accumulated; and ejection of substantial gas amount from the inner regions by feedback processes, which causes a dramatic puffing-up of the stellar component. In the late slow evolution, passive aging of stellar populations and mass additions by dry merger events occur. We describe these processes relying on prescriptions inspired by basic physical arguments and by numerical simulations to derive new analytical estimates of the relevant sizes, timescales, and kinematic properties for individual galaxies along their evolution. Then we obtain quantitative results as a function of galaxy mass and redshift, and compare them to recent observational constraints on half-light size R e , on the ratio v/σ between rotation velocity and velocity dispersion (for gas and stars) and on the specific angular momentum j ⋆ of the stellar component; we find good consistency with the available multiband data in average values and dispersion, both for local ETGs and for their z ∼ 1–2 star-forming and quiescent progenitors. The outcomes of our analysis can provide hints to gauge sub-grid recipes implemented in simulations, to tune numerical experiments focused on specific processes, and to plan

  13. Redshift evolution of the dynamical properties of massive galaxies from SDSS-III/BOSS

    International Nuclear Information System (INIS)

    Beifiori, Alessandra; Saglia, Roberto P.; Bender, Ralf; Senger, Robert; Thomas, Daniel; Maraston, Claudia; Steele, Oliver; Masters, Karen L.; Pforr, Janine; Tojeiro, Rita; Johansson, Jonas; Nichol, Robert C.; Chen, Yan-Mei; Wake, David; Bolton, Adam; Brownstein, Joel R.; Leauthaud, Alexie; Schneider, Donald P.; Skibba, Ramin; Pan, Kaike

    2014-01-01

    We study the redshift evolution of the dynamical properties of ∼180, 000 massive galaxies from SDSS-III/BOSS combined with a local early-type galaxy sample from SDSS-II in the redshift range 0.1 ≤ z ≤ 0.6. The typical stellar mass of this sample is M * ∼2 × 10 11 M ☉ . We analyze the evolution of the galaxy parameters effective radius, stellar velocity dispersion, and the dynamical to stellar mass ratio with redshift. As the effective radii of BOSS galaxies at these redshifts are not well resolved in the Sloan Digital Sky Survey (SDSS) imaging we calibrate the SDSS size measurements with Hubble Space Telescope/COSMOS photometry for a sub-sample of galaxies. We further apply a correction for progenitor bias to build a sample which consists of a coeval, passively evolving population. Systematic errors due to size correction and the calculation of dynamical mass are assessed through Monte Carlo simulations. At fixed stellar or dynamical mass, we find moderate evolution in galaxy size and stellar velocity dispersion, in agreement with previous studies. We show that this results in a decrease of the dynamical to stellar mass ratio with redshift at >2σ significance. By combining our sample with high-redshift literature data, we find that this evolution of the dynamical to stellar mass ratio continues beyond z ∼ 0.7 up to z > 2 as M dyn /M * ∼(1 + z) –0.30±0.12 , further strengthening the evidence for an increase of M dyn /M * with cosmic time. This result is in line with recent predictions from galaxy formation simulations based on minor merger driven mass growth, in which the dark matter fraction within the half-light radius increases with cosmic time.

  14. Redshift evolution of the dynamical properties of massive galaxies from SDSS-III/BOSS

    Energy Technology Data Exchange (ETDEWEB)

    Beifiori, Alessandra; Saglia, Roberto P.; Bender, Ralf; Senger, Robert [Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, D-85748 Garching (Germany); Thomas, Daniel; Maraston, Claudia; Steele, Oliver; Masters, Karen L.; Pforr, Janine; Tojeiro, Rita; Johansson, Jonas; Nichol, Robert C. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom); Chen, Yan-Mei; Wake, David [Department of Astronomy, University of Wisconsin-Madison, 475 N. Charter Street, Madison, WI 53706 (United States); Bolton, Adam; Brownstein, Joel R. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Leauthaud, Alexie [Institute for the Physics and Mathematics of the Universe (IPMU), The University of Tokyo, Chiba 277-8582 (Japan); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Skibba, Ramin [Department of Physics, Center for Astrophysics and Space Sciences, University of California, 9500 Gilman Drive, San Diego, CA 92093 (United States); Pan, Kaike, E-mail: beifiori@mpe.mpg.de [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); and others

    2014-07-10

    We study the redshift evolution of the dynamical properties of ∼180, 000 massive galaxies from SDSS-III/BOSS combined with a local early-type galaxy sample from SDSS-II in the redshift range 0.1 ≤ z ≤ 0.6. The typical stellar mass of this sample is M{sub *} ∼2 × 10{sup 11} M{sub ☉}. We analyze the evolution of the galaxy parameters effective radius, stellar velocity dispersion, and the dynamical to stellar mass ratio with redshift. As the effective radii of BOSS galaxies at these redshifts are not well resolved in the Sloan Digital Sky Survey (SDSS) imaging we calibrate the SDSS size measurements with Hubble Space Telescope/COSMOS photometry for a sub-sample of galaxies. We further apply a correction for progenitor bias to build a sample which consists of a coeval, passively evolving population. Systematic errors due to size correction and the calculation of dynamical mass are assessed through Monte Carlo simulations. At fixed stellar or dynamical mass, we find moderate evolution in galaxy size and stellar velocity dispersion, in agreement with previous studies. We show that this results in a decrease of the dynamical to stellar mass ratio with redshift at >2σ significance. By combining our sample with high-redshift literature data, we find that this evolution of the dynamical to stellar mass ratio continues beyond z ∼ 0.7 up to z > 2 as M{sub dyn}/M{sub *} ∼(1 + z){sup –0.30±0.12}, further strengthening the evidence for an increase of M{sub dyn}/M{sub *} with cosmic time. This result is in line with recent predictions from galaxy formation simulations based on minor merger driven mass growth, in which the dark matter fraction within the half-light radius increases with cosmic time.

  15. Abundances as tracers of the formation and evolution of (Dwarf) galaxies

    NARCIS (Netherlands)

    Tolstoy, E.; Randich, S; Pasquini, L

    2006-01-01

    This aims to be an overview of what detailed observations of individual stars in nearby dwarf galaxies may teach us about galaxy evolution. This includes some early results from the DART (Dwarf Abundances and Radial velocity Team) Large Programme at ESO. This project has used 2.2m/WFI and VLT/FLAMES

  16. Abundances as Tracers of the Formation and Evolution of (Dwarf) Galaxies

    OpenAIRE

    Tolstoy, Eline

    2004-01-01

    This aims to be an overview of what detailed observations of individual stars in nearby dwarf galaxies may teach us about galaxy evolution. This includes some early results from the DART (Dwarf Abundances and Radial velocity Team) Large Programme at ESO. This project has used 2.2m/WFI and VLT/FLAMES to obtain spectra of large samples of individual stars in nearby dwarf spheroidal galaxies and determine accurate abundances and kinematics. These results can be used to trace the formation and ev...

  17. The ALHAMBRA survey: evolution of galaxy clustering since z ˜ 1

    Science.gov (United States)

    Arnalte-Mur, P.; Martínez, V. J.; Norberg, P.; Fernández-Soto, A.; Ascaso, B.; Merson, A. I.; Aguerri, J. A. L.; Castander, F. J.; Hurtado-Gil, L.; López-Sanjuan, C.; Molino, A.; Montero-Dorta, A. D.; Stefanon, M.; Alfaro, E.; Aparicio-Villegas, T.; Benítez, N.; Broadhurst, T.; Cabrera-Caño, J.; Cepa, J.; Cerviño, M.; Cristóbal-Hornillos, D.; del Olmo, A.; González Delgado, R. M.; Husillos, C.; Infante, L.; Márquez, I.; Masegosa, J.; Moles, M.; Perea, J.; Pović, M.; Prada, F.; Quintana, J. M.

    2014-06-01

    We study the clustering of galaxies as function of luminosity and redshift in the range 0.35 work cover 2.38 deg2 in seven independent fields, after applying a detailed angular selection mask, with accurate photometric redshifts, σz ≲ 0.014(1 + z), down to IAB accounting for photometric redshifts uncertainties. We infer the galaxy bias, and study its evolution with luminosity. We study the effect of sample variance, and confirm earlier results that the Cosmic Evolution Survey (COSMOS) and European Large Area ISO Survey North 1 (ELAIS-N1) fields are dominated by the presence of large structures. For the intermediate and bright samples, Lmed ≳ 0.6L*, we obtain a strong dependence of bias on luminosity, in agreement with previous results at similar redshift. We are able to extend this study to fainter luminosities, where we obtain an almost flat relation, similar to that observed at low redshift. Regarding the evolution of bias with redshift, our results suggest that the different galaxy populations studied reside in haloes covering a range in mass between log10[Mh/( h-1 M⊙)] ≳ 11.5 for samples with Lmed ≃ 0.3L* and log10[Mh/( h-1 M⊙)] ≳ 13.0 for samples with Lmed ≃ 2L*, with typical occupation numbers in the range of ˜1-3 galaxies per halo.

  18. EVOLUTION OF THE GALAXY-DARK MATTER CONNECTION AND THE ASSEMBLY OF GALAXIES IN DARK MATTER HALOS

    Energy Technology Data Exchange (ETDEWEB)

    Yang Xiaohu; Zhang Youcai; Han Jiaxin [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030 (China); Mo, H. J. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States); Van den Bosch, Frank C., E-mail: xhyang@shao.ac.cn [Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)

    2012-06-10

    halo; the ratio M{sub *,c}/M initially increases rapidly with time until the halo mass reaches {approx}10{sup 12} h{sup -1} M{sub Sun }, at which point M{sub *,c}/M {approx} 0.03. Once M {approx}> 10{sup 12} h{sup -1} M{sub Sun }, there is little growth in M{sub *,c}, causing the ratio M{sub *,c}/M to decline. In Milky Way (MW)-sized halos more than half of the central stellar mass is assembled at z {approx}< 0.5. (5) In low-mass halos, the accretion of satellite galaxies contributes little to the formation of their central galaxies, indicating that most of their stars must have formed in situ. In massive halos more than half of the stellar mass of the central galaxy has to be formed in situ, and the accretion of satellites can only become significant at z {approx}< 2. (6) The total mass in halo stars is more than twice that of the central galaxy in massive halos, but less than 10% of M{sub *,c} in MW-sized halos. (7) The 2PCFs of galaxies on small scales hold important information regarding the evolution of satellite galaxies, which at high-z is predicted to be much steeper than at low-z, especially for more massive galaxies. We discuss various implications of our findings regarding the formation and evolution of galaxies in a {Lambda}CDM cosmology.

  19. General constraints on the effect of gas flows in the chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Edmunds, M.G.

    1990-01-01

    The basic equations for the chemical evolution of galaxies in which the 'simple' closed box model is modified to allow any form of inflow or outflow are examined. It is found that there are quite general limiting constraints on the effects that such flows can have. Some implications for the actual chemical evolution of galaxies are discussed, and the constraints should also be useful in understanding the behaviour of detailed numerical models of galactic chemical evolution involving gas flows. (author)

  20. Inhomogeneous Chemical Evolution of the Galaxy in the Solar ...

    Indian Academy of Sciences (India)

    The evolution of the galaxy is simulated by considering discrete .... The discrete nature of the simulations along with the high temporal resolution of 1 Myr ...... be revived again even if a major homogenizing event occurs over spatial dimensions.

  1. Chemical evolution of two-component galaxies. II

    International Nuclear Information System (INIS)

    Caimmi, R.

    1978-01-01

    In order to confirm and refine the results obtained in a previous paper the chemical evolution of two-component (spheroid + disk) galaxies is derived rejecting the instantaneous recycling approximation, by means of numerical computations, accounting for (i) the collapse phase of the gas, assumed to be uniform in density and composition, and (ii) a birth-rate stellar function. Computations are performed relatively to the solar neighbourhood and to model galaxies which closely resemble the real morphological sequence: in both cases, numerical results are compared with analytical ones. The numerical models of this paper constitute a first-order approximation, while higher order approximations could be made by rejecting the hypothesis of uniform density and composition, and making use of detailed dynamical models. (Auth.)

  2. THE SIZE EVOLUTION OF PASSIVE GALAXIES: OBSERVATIONS FROM THE WIDE-FIELD CAMERA 3 EARLY RELEASE SCIENCE PROGRAM

    International Nuclear Information System (INIS)

    Ryan, R. E. Jr.; McCarthy, P. J.; Cohen, S. H.; Rutkowski, M. J.; Mechtley, M. R.; Windhorst, R. A.; Yan, H.; Hathi, N. P.; Koekemoer, A. M.; Bond, H. E.; Bushouse, H.; O'Connell, R. W.; Balick, B.; Calzetti, D.; Crockett, R. M.; Disney, M.; Dopita, M. A.; Frogel, J. A.; Hall, D. N. B.; Holtzman, J. A.

    2012-01-01

    We present the size evolution of passively evolving galaxies at z ∼ 2 identified in Wide-Field Camera 3 imaging from the Early Release Science program. Our sample was constructed using an analog to the passive BzK galaxy selection criterion, which isolates galaxies with little or no ongoing star formation at z ∼> 1.5. We identify 30 galaxies in ∼40 arcmin 2 to H obs ∼ * ∼ 10 11 M ☉ ) undergo the strongest evolution from z ∼ 2 to the present. Parameterizing the size evolution as (1 + z) –α , we find a tentative scaling of α ≈ (– 0.6 ± 0.7) + (0.9 ± 0.4)log (M * /10 9 M ☉ ), where the relatively large uncertainties reflect the poor sampling in stellar mass due to the low numbers of high-redshift systems. We discuss the implications of this result for the redshift evolution of the M * -R e relation for red galaxies.

  3. The formation and evolution of galaxies in an expanding universe

    Science.gov (United States)

    Ceverino-Rodriguez, Daniel

    with few hundred km s -1 and occasionally 1000 - 2000 kms - 1 . The gas has high metallicity, which may exceed the solar metallicity. The temperature of the gas in the outflows and in chimneys can be very high: T = 10 7 - 10^8 K. The density profile of dark matter is still consistent with a cuspy profile. The simulations reproduce this picture only if the resolution is very high: better than 50 pc, which is 10 times better than the typical resolution in previous cosmological simulations. Our simulations of galaxy formation reach a resolution of 35 pc. At the time in which most of the mass is assembled into a galaxy, a big fraction of the gas in the galactic disk has already been converted into stars. Therefore, we can assume that the remaining gas does not affect the evolution of the stellar distribution. In this approximation, all gasdynamical processes are neglected and we treat a galaxy as a pure collisionless system. Then we use N-body-only models to study the long-term evolution of an already formed stellar disk. During this evolution, the disk develops a bar at the center through disk instabilities. We find dynamical resonances between the bar and disk or halo material. These resonances can capture stars near certain resonant orbits. As a result, resonances prevent the evolution of the stars trapped around these orbits.

  4. Thermal design and test verification of GALAXY evolution explorer (GALEX)

    Science.gov (United States)

    Wu, P. S.; Lee, S. -C.

    2002-01-01

    This paper describes the thermal control design of GALEX, an ultraviolet telescope that investigates the UV properties of local galaxies, history of star formation, and global causes of star formation and evolution.

  5. THE CLUSTERING OF GALAXIES IN THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: LUMINOSITY AND COLOR DEPENDENCE AND REDSHIFT EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Guo Hong; Zehavi, Idit [Department of Astronomy, Case Western Reserve University, OH 44106 (United States); Zheng Zheng [Department of Physics and Astronomy, University of Utah, UT 84112 (United States); Weinberg, David H. [Department of Astronomy and CCAPP, Ohio State University, Columbus, OH 43210 (United States); Berlind, Andreas A. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Blanton, Michael [Center for Cosmology and Particle Physics, New York University, New York, NY 10003 (United States); Chen Yanmei [Department of Astronomy, Nanjing University, Nanjing 210093 (China); Eisenstein, Daniel J.; McBride, Cameron K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Ho, Shirley; Ross, Nicholas P. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Kazin, Eyal [Center for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122 (Australia); Manera, Marc; Maraston, Claudia; Percival, Will J.; Ross, Ashley J.; Samushia, Lado [Institute of Cosmology and Gravitation, Dennis Sciama Building, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom); Nuza, Sebastian E. [Leibniz-Institut fuer Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Padmanabhan, Nikhil; Parejko, John K. [Department of Physics, Yale University, 260 Whitney Ave, New Haven, CT 06520 (United States); and others

    2013-04-20

    We measure the luminosity and color dependence and the redshift evolution of galaxy clustering in the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey Ninth Data Release. We focus on the projected two-point correlation function (2PCF) of subsets of its CMASS sample, which includes about 260,000 galaxies over {approx}3300 deg{sup 2} in the redshift range 0.43 < z < 0.7. To minimize the selection effect on galaxy clustering, we construct well-defined luminosity and color subsamples by carefully accounting for the CMASS galaxy selection cuts. The 2PCF of the whole CMASS sample, if approximated by a power-law, has a correlation length of r{sub 0} = 7.93 {+-} 0.06 h {sup -1} Mpc and an index of {gamma} = 1.85 {+-} 0.01. Clear dependences on galaxy luminosity and color are found for the projected 2PCF in all redshift bins, with more luminous and redder galaxies generally exhibiting stronger clustering and steeper 2PCF. The color dependence is also clearly seen for galaxies within the red sequence, consistent with the behavior of SDSS-II main sample galaxies at lower redshifts. At a given luminosity (k + e corrected), no significant evolution of the projected 2PCFs with redshift is detected for red sequence galaxies. We also construct galaxy samples of fixed number density at different redshifts, using redshift-dependent magnitude thresholds. The clustering of these galaxies in the CMASS redshift range is found to be consistent with that predicted by passive evolution. Our measurements of the luminosity and color dependence and redshift evolution of galaxy clustering will allow for detailed modeling of the relation between galaxies and dark matter halos and new constraints on galaxy formation and evolution.

  6. Strong Stellar-driven Outflows Shape the Evolution of Galaxies at Cosmic Dawn

    Energy Technology Data Exchange (ETDEWEB)

    Fontanot, Fabio; De Lucia, Gabriella [INAF—Astronomical Observatory of Trieste, via G.B. Tiepolo 11, I-34143 Trieste (Italy); Hirschmann, Michaela [Sorbonne Universités, UPMC-CNRS, UMR7095, Institut d’Astrophysique de Paris, F-75014 Paris (France)

    2017-06-20

    We study galaxy mass assembly and cosmic star formation rate (SFR) at high redshift (z ≳ 4), by comparing data from multiwavelength surveys with predictions from the GAlaxy Evolution and Assembly (gaea) model. gaea implements a stellar feedback scheme partially based on cosmological hydrodynamical simulations, which features strong stellar-driven outflows and mass-dependent timescales for the re-accretion of ejected gas. In previous work, we have shown that this scheme is able to correctly reproduce the evolution of the galaxy stellar mass function (GSMF) up to z ∼ 3. We contrast model predictions with both rest-frame ultraviolet (UV) and optical luminosity functions (LFs), which are mostly sensitive to the SFR and stellar mass, respectively. We show that gaea is able to reproduce the shape and redshift evolution of both sets of LFs. We study the impact of dust on the predicted LFs, and we find that the required level of dust attenuation is in qualitative agreement with recent estimates based on the UV continuum slope. The consistency between data and model predictions holds for the redshift evolution of the physical quantities well beyond the redshift range considered for the calibration of the original model. In particular, we show that gaea is able to recover the evolution of the GSMF up to z ∼ 7 and the cosmic SFR density up to z ∼ 10.

  7. Strong Stellar-driven Outflows Shape the Evolution of Galaxies at Cosmic Dawn

    International Nuclear Information System (INIS)

    Fontanot, Fabio; De Lucia, Gabriella; Hirschmann, Michaela

    2017-01-01

    We study galaxy mass assembly and cosmic star formation rate (SFR) at high redshift (z ≳ 4), by comparing data from multiwavelength surveys with predictions from the GAlaxy Evolution and Assembly (gaea) model. gaea implements a stellar feedback scheme partially based on cosmological hydrodynamical simulations, which features strong stellar-driven outflows and mass-dependent timescales for the re-accretion of ejected gas. In previous work, we have shown that this scheme is able to correctly reproduce the evolution of the galaxy stellar mass function (GSMF) up to z ∼ 3. We contrast model predictions with both rest-frame ultraviolet (UV) and optical luminosity functions (LFs), which are mostly sensitive to the SFR and stellar mass, respectively. We show that gaea is able to reproduce the shape and redshift evolution of both sets of LFs. We study the impact of dust on the predicted LFs, and we find that the required level of dust attenuation is in qualitative agreement with recent estimates based on the UV continuum slope. The consistency between data and model predictions holds for the redshift evolution of the physical quantities well beyond the redshift range considered for the calibration of the original model. In particular, we show that gaea is able to recover the evolution of the GSMF up to z ∼ 7 and the cosmic SFR density up to z ∼ 10.

  8. The next generation of galaxy evolution models: A symbiosis of stellar populations and chemical abundances

    Science.gov (United States)

    Kotulla, Ralf

    2012-10-01

    Over its lifespan Hubble has invested significant effort into detailed observations of galaxies both in the local and distant universe. To extract the physical information from the observed {spectro-}photometry requires detailed and accurate models. Stellar population synthesis models are frequently used to obtain stellar masses, star formation rate, galaxy ages and star formation histories. Chemical evolution models offer another valuable and complementary approach to gain insight into many of the same aspects, yet these two methods have rarely been used in combination.Our proposed next generation of galaxy evolution models will help us improve our understanding of how galaxies form and evolve. Building on GALEV evolutionary synthesis models we incorporate state-of-the-art input physics for stellar evolution of binaries and rotating stars as well as new spectral libraries well matched to the modern observational capabilities. Our improved chemical evolution model allows us to self-consistently trace abundances of individual elements, fully accounting for the increasing initial abundances of successive stellar generations. GALEV will support variable Initial Mass Functions {IMF}, enabling us to test recent observational findings of a non-universal IMF by predicting chemical properties and integrated spectra in an integrated and consistent manner.HST is the perfect instrument for testing this approach. Its wide wavelength coverage from UV to NIR enables precise SED fitting, and with its spatial resolution we can compare the inferred chemical evolution to studies of star clusters and resolved stellar populations in nearby galaxies.

  9. Morphological survey of bar, lens, and ring components in galaxies: Secular evolution in galaxy structure

    International Nuclear Information System (INIS)

    Kormendy, J.

    1979-01-01

    A morphological survey of barred galaxies is made to investigate the frequency of occurrence, nature, and size distributions of bars, lenses, inner and outer rings, and global spiral structure. The 121 brightest available barred galaxies are examined on Sky Survey copy plates, and on deeper and larger-scale plates, with the following main results.1. Lenses and inner rings are components of major importance in barred galaxies, occurring, respectively, in 54% of SBO--SBa, and 76% of SBab--SBc galaxies. Few early-type galaxies have rings; almost no late-type ones have lenses.2. There is an intimate connection between bars and lenses: in 17 of 20 galaxies with both components, the bar exactly fills the lens in one dimension.3. We suggest that lenses originate as bars, through an unknown process which makes some bars evolve away to a nearly axisymmetric state. Several properties of the proposed process are deduced. We emphasize the possible importance of internal processes of secular evolution in galaxy structure.4. Several galaxies, notably NGC 3945, seem to have strongly triaxial bulge components.5. Inner rings are round. Lenses tend to be slightly triaxial, flattened ellipsoids, with a preferred equatorial axis ratio of approx.0.9 +- 0.05. Most outer rings are prolate, the shortest dimension being the one filled by the bar.6. The sizes of bars, rings, and lenses are well correlated with the absolute magnitude of the galaxy, such that the mean surface brightness is constant for each morphological type. The form of the correlation M/sub B/+5 log D= constant is such that these diameters cannot be used as distance indicators. We show that the galaxy mass determines the bar size uniquely.7. Spiral structure in SB galaxies is distorted to resemble inner and outer rings, showing that the arms feel the potential of the bar. Also, of 61 survey galaxies with spiral structure, 55 have global patterns usually interpreted as density waves

  10. The Formation and Evolution of Star Clusters in Interacting Galaxies

    Science.gov (United States)

    Maji, Moupiya; Zhu, Qirong; Li, Yuexing; Charlton, Jane; Hernquist, Lars; Knebe, Alexander

    2017-08-01

    Observations of globular clusters show that they have universal lognormal mass functions with a characteristic peak at ˜ 2× {10}5 {M}⊙ , but the origin of this peaked distribution is highly debated. Here we investigate the formation and evolution of star clusters (SCs) in interacting galaxies using high-resolution hydrodynamical simulations performed with two different codes in order to mitigate numerical artifacts. We find that massive SCs in the range of ˜ {10}5.5{--}{10}7.5 {M}⊙ form preferentially in the highly shocked regions produced by galaxy interactions. The nascent cluster-forming clouds have high gas pressures in the range of P/k˜ {10}8{--}{10}12 {{K}} {{cm}}-3, which is ˜ {10}4{--}{10}8 times higher than the typical pressure of the interstellar medium but consistent with recent observations of a pre-super-SC cloud in the Antennae Galaxies. Furthermore, these massive SCs have quasi-lognormal initial mass functions with a peak around ˜ {10}6 {M}⊙ . The number of clusters declines with time due to destructive processes, but the shape and the peak of the mass functions do not change significantly during the course of galaxy collisions. Our results suggest that gas-rich galaxy mergers may provide a favorable environment for the formation of massive SCs such as globular clusters, and that the lognormal mass functions and the unique peak may originate from the extreme high-pressure conditions of the birth clouds and may survive the dynamical evolution.

  11. Automata network models of galaxy evolution

    Science.gov (United States)

    Chappell, David; Scalo, John

    1993-01-01

    Two ideas appear frequently in theories of star formation and galaxy evolution: (1) star formation is nonlocally excitatory, stimulating star formation in neighboring regions by propagation of a dense fragmenting shell or the compression of preexisting clouds; and (2) star formation is nonlocally inhibitory, making H2 regions and explosions which can create low-density and/or high temperature regions and increase the macroscopic velocity dispersion of the cloudy gas. Since it is not possible, given the present state of hydrodynamic modeling, to estimate whether one of these effects greatly dominates the other, it is of interest to investigate the predicted spatial pattern of star formation and its temporal behavior in simple models which incorporate both effects in a controlled manner. The present work presents preliminary results of such a study which is based on lattice galaxy models with various types of nonlocal inhibitory and excitatory couplings of the local SFR to the gas density, temperature, and velocity field meant to model a number of theoretical suggestions.

  12. Black hole-galaxy co-evolution in the Mufasa simulations

    Science.gov (United States)

    Dave, Romeel; Angles-Alcazar, Daniel

    2017-08-01

    The Mufasa simulations are large-scale cosmological and zoom simulations of galaxy formation that employ novel state of the art modules for star formation and feedback physics, resulting in very good agreement with many key galaxy observables over most of cosmic time. We have recently included black hole growth and feedback using the torque-limited accretion model, which has several advantages over the commonly-used Bondi accretion. We also include AGN feedback using a BAL mode at high Eddington rates and low black hole masses, and a jet mode at low Eddington rates that successfully quenches galaxies. In this talk I will describe preliminary results of the AGN population and its evolution over cosmic time within our new simulations, including cosmological simulations of the general black hole population as well as zoom simulations targeting massive galaxies, with a focus on understanding the co-growth of black holes and galaxies as a function of mass, environment, and cosmic epoch. I will also discuss multi-wavelength approaches to testing and constraining our black hole model in particular using upcoming X-ray and radio facilities such as Lynx and the SKA.

  13. Interpreting the evolution of galaxy colours from z = 8 to 5

    Science.gov (United States)

    Mancini, Mattia; Schneider, Raffaella; Graziani, Luca; Valiante, Rosa; Dayal, Pratika; Maio, Umberto; Ciardi, Benedetta

    2016-11-01

    We attempt to interpret existing data on the evolution of the UV luminosity function and UV colours, β, of galaxies at 5 ≤ z ≤ 8, to improve our understanding of their dust content and interstellar medium properties. To this aim, we post-process the results of a cosmological hydrodynamical simulation with a chemical evolution model, which includes dust formation by supernovae and intermediate-mass stars, dust destruction in supernova shocks, and grain growth by accretion of gas-phase elements in dense gas. We find that observations require a steep, Small Magellanic Cloud-like extinction curve and a clumpy dust distribution, where stellar populations younger than 15 Myr are still embedded in their dusty natal clouds. Investigating the scatter in the colour distribution and stellar mass, we find that the observed trends can be explained by the presence of two populations: younger, less massive galaxies where dust enrichment is mainly due to stellar sources, and massive, more chemically evolved ones, where efficient grain growth provides the dominant contribution to the total dust mass. Computing the IR-excess-UV colour relation, we find that all but the dustiest model galaxies follow a relation shallower than the Meurer et al. one, usually adopted to correct the observed UV luminosities of high-z galaxies for the effects of dust extinction. As a result, their total star formation rates might have been overestimated. Our study illustrates the importance to incorporate a proper treatment of dust in simulations of high-z galaxies, and that massive, dusty, UV-faint galaxies might have already appeared at z ≲ 7.

  14. THE SIZE EVOLUTION OF PASSIVE GALAXIES: OBSERVATIONS FROM THE WIDE-FIELD CAMERA 3 EARLY RELEASE SCIENCE PROGRAM

    Energy Technology Data Exchange (ETDEWEB)

    Ryan, R. E. Jr. [Physics Department, University of California, Davis, CA 95616 (United States); McCarthy, P. J. [Observatories of the Carnegie Institute of Washington, Pasadena, CA 91101 (United States); Cohen, S. H.; Rutkowski, M. J.; Mechtley, M. R.; Windhorst, R. A. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Yan, H. [Center for Cosmology and Astroparticle Physics, Ohio State University, Columbus, OH 43210 (United States); Hathi, N. P. [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Koekemoer, A. M.; Bond, H. E.; Bushouse, H. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); O' Connell, R. W. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Balick, B. [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Calzetti, D. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Crockett, R. M. [Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom); Disney, M. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom); Dopita, M. A. [Research School of Astronomy and Astrophysics, The Australian National University, Weston Creek, ACT 2611 (Australia); Frogel, J. A. [Galaxies Unlimited, Lutherville, MD 21093 (United States); Hall, D. N. B. [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Holtzman, J. A., E-mail: rryan@physics.ucdavis.edu [Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States); and others

    2012-04-10

    We present the size evolution of passively evolving galaxies at z {approx} 2 identified in Wide-Field Camera 3 imaging from the Early Release Science program. Our sample was constructed using an analog to the passive BzK galaxy selection criterion, which isolates galaxies with little or no ongoing star formation at z {approx}> 1.5. We identify 30 galaxies in {approx}40 arcmin{sup 2} to H < 25 mag. By fitting the 10-band Hubble Space Telescope photometry from 0.22 {mu}m {approx}< {lambda}{sub obs} {approx}< 1.6 {mu}m with stellar population synthesis models, we simultaneously determine photometric redshift, stellar mass, and a bevy of other population parameters. Based on the six galaxies with published spectroscopic redshifts, we estimate a typical redshift uncertainty of {approx}0.033(1 + z). We determine effective radii from Sersic profile fits to the H-band image using an empirical point-spread function. By supplementing our data with published samples, we propose a mass-dependent size evolution model for passively evolving galaxies, where the most massive galaxies (M{sub *} {approx} 10{sup 11} M{sub Sun }) undergo the strongest evolution from z {approx} 2 to the present. Parameterizing the size evolution as (1 + z){sup -{alpha}}, we find a tentative scaling of {alpha} Almost-Equal-To (- 0.6 {+-} 0.7) + (0.9 {+-} 0.4)log (M{sub *}/10{sup 9} M{sub Sun }), where the relatively large uncertainties reflect the poor sampling in stellar mass due to the low numbers of high-redshift systems. We discuss the implications of this result for the redshift evolution of the M{sub *}-R{sub e} relation for red galaxies.

  15. Angular momentum transport and evolution of lopsided galaxies

    Science.gov (United States)

    Saha, Kanak; Jog, Chanda J.

    2014-10-01

    The surface brightness distribution in the majority of stellar galactic discs falls off exponentially. Often what lies beyond such a stellar disc is the neutral hydrogen gas whose distribution also follows a nearly exponential profile at least for a number of nearby disc galaxies. Both the stars and gas are commonly known to host lopsided asymmetry especially in the outer parts of a galaxy. The role of such asymmetry in the dynamical evolution of a galaxy has not been explored so far. Following Lindblad's original idea of kinematic density waves, we show that the outer part of an exponential disc is ideally suitable for hosting lopsided asymmetry. Further, we compute the transport of angular momentum in the combined stars and gas disc embedded in a dark matter halo. We show that in a pure star and gas disc, there is a transition point where the free precession frequency of a lopsided mode, Ω - κ, changes from retrograde to prograde and this in turn reverses the direction of angular momentum flow in the disc leading to an unphysical behaviour. We show that this problem is overcome in the presence of a dark matter halo, which sets the angular momentum flow outwards as required for disc evolution, provided the lopsidedness is leading in nature. This, plus the well-known angular momentum transport in the inner parts due to spiral arms, can facilitate an inflow of gas from outside perhaps through the cosmic filaments.

  16. A multi-wavelength study of the evolution of early-type galaxies in groups: the ultraviolet view

    Science.gov (United States)

    Rampazzo, R.; Mazzei, P.; Marino, A.; Bianchi, L.; Plana, H.; Trinchieri, G.; Uslenghi, M.; Wolter, A.

    2018-04-01

    The ultraviolet-optical colour magnitude diagram of rich galaxy groups is characterised by a well developed Red Sequence, a Blue Cloud and the so-called Green Valley. Loose, less evolved groups of galaxies which are probably not virialised yet may lack a well defined Red Sequence. This is actually explained in the framework of galaxy evolution. We are focussing on understanding galaxy migration towards the Red Sequence, checking for signatures of such a transition in their photometric and morphological properties. We report on the ultraviolet properties of a sample of early-type (ellipticals+S0s) galaxies inhabiting the Red Sequence. The analysis of their structures, as derived by fitting a Sérsic law to their ultraviolet luminosity profiles, suggests the presence of an underlying disk. This is the hallmark of dissipation processes that still must have a role to play in the evolution of this class of galaxies. Smooth particle hydrodynamic simulations with chemo-photometric implementations able to match the global properties of our targets are used to derive their evolutionary paths through ultraviolet-optical colour magnitude diagrams, providing some fundamental information such as the crossing time through the Green Valley, which depends on their luminosity. The transition from the Blue Cloud to the Red Sequence takes several Gyrs, being about 3-5 Gyr for the brightest galaxies and longer for fainter ones, if occurring. The photometric study of nearby galaxy structures in the ultraviolet is seriously hampered by either the limited field of view of the cameras (e.g., in Hubble Space Telescope) or by the low spatial resolution of the images (e.g., in the Galaxy Evolution Explorer). Current missions equipped with telescopes and cameras sensitive to ultraviolet wavelengths, such as Swift- UVOT and Astrosat-UVIT, provide a relatively large field of view and a better resolution than the Galaxy Evolution Explorer. More powerful ultraviolet instruments (size, resolution

  17. Generative Models in Deep Learning: Constraints for Galaxy Evolution

    Science.gov (United States)

    Turp, Maximilian Dennis; Schawinski, Kevin; Zhang, Ce; Weigel, Anna K.

    2018-01-01

    New techniques are essential to make advances in the field of galaxy evolution. Recent developments in the field of artificial intelligence and machine learning have proven that these tools can be applied to problems far more complex than simple image recognition. We use these purely data driven approaches to investigate the process of star formation quenching. We show that Variational Autoencoders provide a powerful method to forward model the process of galaxy quenching. Our results imply that simple changes in specific star formation rate and bulge to disk ratio cannot fully describe the properties of the quenched population.

  18. SEMI-ANALYTIC GALAXY EVOLUTION (SAGE): MODEL CALIBRATION AND BASIC RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Croton, Darren J.; Stevens, Adam R. H.; Tonini, Chiara; Garel, Thibault; Bernyk, Maksym; Bibiano, Antonio; Hodkinson, Luke; Mutch, Simon J.; Poole, Gregory B.; Shattow, Genevieve M. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122 (Australia)

    2016-02-15

    This paper describes a new publicly available codebase for modeling galaxy formation in a cosmological context, the “Semi-Analytic Galaxy Evolution” model, or sage for short.{sup 5} sage is a significant update to the 2006 model of Croton et al. and has been rebuilt to be modular and customizable. The model will run on any N-body simulation whose trees are organized in a supported format and contain a minimum set of basic halo properties. In this work, we present the baryonic prescriptions implemented in sage to describe the formation and evolution of galaxies, and their calibration for three N-body simulations: Millennium, Bolshoi, and GiggleZ. Updated physics include the following: gas accretion, ejection due to feedback, and reincorporation via the galactic fountain; a new gas cooling–radio mode active galactic nucleus (AGN) heating cycle; AGN feedback in the quasar mode; a new treatment of gas in satellite galaxies; and galaxy mergers, disruption, and the build-up of intra-cluster stars. Throughout, we show the results of a common default parameterization on each simulation, with a focus on the local galaxy population.

  19. SEMI-ANALYTIC GALAXY EVOLUTION (SAGE): MODEL CALIBRATION AND BASIC RESULTS

    International Nuclear Information System (INIS)

    Croton, Darren J.; Stevens, Adam R. H.; Tonini, Chiara; Garel, Thibault; Bernyk, Maksym; Bibiano, Antonio; Hodkinson, Luke; Mutch, Simon J.; Poole, Gregory B.; Shattow, Genevieve M.

    2016-01-01

    This paper describes a new publicly available codebase for modeling galaxy formation in a cosmological context, the “Semi-Analytic Galaxy Evolution” model, or sage for short. 5 sage is a significant update to the 2006 model of Croton et al. and has been rebuilt to be modular and customizable. The model will run on any N-body simulation whose trees are organized in a supported format and contain a minimum set of basic halo properties. In this work, we present the baryonic prescriptions implemented in sage to describe the formation and evolution of galaxies, and their calibration for three N-body simulations: Millennium, Bolshoi, and GiggleZ. Updated physics include the following: gas accretion, ejection due to feedback, and reincorporation via the galactic fountain; a new gas cooling–radio mode active galactic nucleus (AGN) heating cycle; AGN feedback in the quasar mode; a new treatment of gas in satellite galaxies; and galaxy mergers, disruption, and the build-up of intra-cluster stars. Throughout, we show the results of a common default parameterization on each simulation, with a focus on the local galaxy population

  20. Evolution of Extragalactic Radio Sources and Quasar/Galaxy Unification

    Science.gov (United States)

    Onah, C. I.; Ubachukwu, A. A.; Odo, F. C.; Onuchukwu, C. C.

    2018-04-01

    We use a large sample of radio sources to investigate the effects of evolution, luminosity selection and radio source orientation in explaining the apparent deviation of observed angular size - redshift (θ - z) relation of extragalactic radio sources (EGRSs) from the standard model. We have fitted the observed θ - z data with standard cosmological models based on a flat universe (Ω0 = 1). The size evolution of EGRSs has been described as luminosity, temporal and orientation-dependent in the form DP,z,Φ ≍ P±q(1 + z)-m sinΦ, with q=0.3, Φ=59°, m=-0.26 for radio galaxies and q=-0.5, Φ=33°, m=3.1 for radio quasars respectively. Critical points of luminosity, logPcrit=26.33 WHz-1 and logDc=2.51 kpc (316.23 kpc) of the present sample of radio sources were also observed. All the results were found to be consistent with the popular quasar/galaxy unification scheme.

  1. ATLAS Probe: Exploring Frontiers in Galaxy Evolution, Cosmology, and Milky Way Science

    Science.gov (United States)

    Wang, Yun; Robberto, Massimo; Dickinson, Mark; Ferguson, Henry C.; Hillenbrand, Lynne; Hirata, Christopher M.; Cimatti, Andrea; Bartlett, James; Barkhouser, Robert; Benjamin, Robert A.; Brinchmann, Jarle; Chary, Ranga-Ram; Conroy, Charlie; Daddi, Emanuele; Donahue, Megan; Dore, Olivier; Eisenhardt, Peter; Fraser, Wesley C.; Helou, George; Kirkpatrick, J. Davy; Malhotra, Sangeeta; Moscardini, Lauro; Ninkov, Zoran; Ressler, Michael; Rhoads, James; Rhodes, Jason; Shapley, Alice; Smee, Stephen; ATLAS Probe Team

    2018-01-01

    ATLAS (Astrophysics Telescope for Large Area Spectroscopy) Probe is a concept for a NASA probe-class space mission that leverages WFIRST imaging for targeted spectroscopy. ATLAS Probe will obtain spectra of 90% of all galaxies imaged by the WFIRST High Latitude Survey at z > 0.5, with slit spectra of 300 million galaxies to z = 7. ATLAS Probe and WFIRST together will produce a 3D map of the Universe with Mpc resolution over 2200 sq deg, the definitive data sets for studying galaxy evolution, probing dark matter, dark energy and modification of general relativity, and quantifying the 3D structure and stellar content of the Milky Way.ATLAS Probe science spans four broad categories: (1) Revolutionize galaxy evolution studies by tracing the relation between galaxies and dark matter from the local group to cosmic voids and filaments, from the epoch of reionization through the peak era of galaxy assembly. (2) Open a new window into the Universe by mapping the dark matter filaments using 3D weak lensing with spectroscopic redshifts to unveil the nature of the dark Universe, and obtaining definitive measurements of dark energy and possible modification of general relativity using cosmic large-scale structure. (3) Probe the Milky Way's dust-shrouded regions, reaching the far side of our Galaxy. (4) Characterize asteroids and comets in the outer Solar System.ATLAS Probe is a 1.5m telescope with a field of view (FoV) of 0.4 sq deg, and uses Digital Micromirror Devices (DMDs) as slit selectors. It has a spectroscopic resolution of R = 600, and a wavelength range of 1-4μm. The lack of slit spectroscopy from space over a wide FoV is the obvious gap in current and planned future space missions; ATLAS fills this big gap with an unprecedented spectroscopic capability (with an estimated spectroscopic multiplex factor of 5000-10000). It has an estimated cost under $1B, with a single instrument, a telescope aperture that allows for a lighter launch vehicle, and mature technology

  2. Collateral Damage: the Implications of Utrecht Star Cluster Astrophysics for Galaxy Evolution

    Science.gov (United States)

    Kruijssen, J. M. D.

    2013-01-01

    Until the early 2000s, the research portfolio of the Astronomical Institute in Utrecht (SIU) did not include galaxy evolution. Somewhat serendipitously, this changed with the advent of the star cluster group. In only a few years, a simple framework was developed to describe and quantify the properties of dynamically evolving star cluster populations. Since then, the ‘Utrecht cluster disruption model’ has shown that the galactic environment plays an important role in setting the evolution of stellar clusters. From this simple result, it follows that cluster populations bear some imprint of the characteristics and histories of their host galaxies, and that star clusters can be used to trace galaxy evolution—an aim for which the Utrecht star cluster models were never designed, but which they are well-capable of fulfilling. I review some of the work in this direction, with a strong emphasis on the contributions from the SIU.

  3. Infrared galaxies evolution. From cosmological observations with ISO to a mid-infrared to sub-millimetric modeling

    International Nuclear Information System (INIS)

    Dole, Herve

    2000-01-01

    This thesis deals with the analysis of the FIRBACK deep survey performed in the far infrared at λ=170 μm with the Infrared Space Observatory whose aim is the study of the galaxies contributing to the Cosmic Infrared Background, and with the modelling of galaxy evolution in the mid-infrared to submillimeter range. The FIRBACK survey covers 3. 89 Sq. Deg. in 3 high galactic latitude and low foreground emission fields (2 of which are in the northern sky). I first present the techniques of reduction, processing and calibration of the ISOPHOT cosmological data. I show that there is a good agreement between PHOT and DIRBE on extended emission, thanks to the derivation of the PHOT footprint. Final maps are created, and the survey is confusion limited at σc=45 mJy. I present then the techniques of source extraction and the simulations for photometry needed to build the final catalog of 106 sources between 180 mJy (4σ) and 2.4 Jy. The complementary catalog is made of 90 sources between 135 and 180 mJy. Galaxy counts show a large excess with respect to local counts or models (with and without evolution), only compatible with strong evolution scenarios. The Cosmic Infrared Background (CIB) is resolved at 4 % at 170 μm. The identifications of the sources at other wavelengths suggest that most of the sources are local, but a non-negligible part lies above redshift 1. I have developed a phenomenological model of galaxy evolution in order to constrain galaxy evolution in the infrared and to have a better understanding of what the FIRBACK sources are. Using the local Luminosity Function (LF), and template spectra of starburst galaxies, it is possible to constrain the evolution of the LF using all the available data: deep source counts at 15, 170 and 850 μm and the CIB spectrum. I show that galaxy evolution is dominated by a high infrared luminosity population, peaking at L=2.0*10"1"1 Redshift distributions are in agreement with available observations. Predictions are

  4. THE EVOLUTION OF ACTIVE GALACTIC NUCLEI IN CLUSTERS OF GALAXIES TO REDSHIFT 1.3

    International Nuclear Information System (INIS)

    Martini, Paul; Sivakoff, Gregory R.; Mulchaey, John S.

    2009-01-01

    We have measured the luminous active galactic nucleus (AGN) population in a large sample of clusters of galaxies and find evidence for a substantial increase in the cluster AGN population from z ∼ 0.05 to z ∼ 1.3. The present sample now includes 32 clusters of galaxies, including 15 clusters above z = 0.4, which corresponds to a three-fold increase compared to our previous work at high redshift. At z R R (z) + 1 that host AGNs with rest-frame, hard X-ray [2-10 keV] luminosities L X,H ≥ 10 43 erg s -1 . The AGN fraction increases from f A = 0.134 +0.18 -0.087 % at a median z = 0.19 to f A = 1.00 +0.29 -0.23 % at a median z = 0.72. Our best estimate of the evolution is a factor of 8 increase to z = 1 and the statistical significance of the increase is 3.8σ. This dramatic evolution is qualitatively similar to the evolution of the star-forming galaxy population in clusters known as the Butcher-Oemler effect. We discuss the implications of this result for the coevolution of black holes and galaxies in clusters, the evolution of AGN feedback, searches for clusters with the Sunyaev-Zel'dovich effect, and the possible detection of environment-dependent downsizing.

  5. EVOLUTION OF THE MASS-METALLICITY RELATIONS IN PASSIVE AND STAR-FORMING GALAXIES FROM SPH-COSMOLOGICAL SIMULATIONS

    International Nuclear Information System (INIS)

    Romeo Velonà, A. D.; Gavignaud, I.; Meza, A.; Sommer-Larsen, J.; Napolitano, N. R.; Antonuccio-Delogu, V.; Cielo, S.

    2013-01-01

    We present results from SPH-cosmological simulations, including self-consistent modeling of supernova feedback and chemical evolution, of galaxies belonging to two clusters and 12 groups. We reproduce the mass-metallicity (ZM) relation of galaxies classified in two samples according to their star-forming (SF) activity, as parameterized by their specific star formation rate (sSFR), across a redshift range up to z = 2. The overall ZM relation for the composite population evolves according to a redshift-dependent quadratic functional form that is consistent with other empirical estimates, provided that the highest mass bin of the brightest central galaxies is excluded. Its slope shows irrelevant evolution in the passive sample, being steeper in groups than in clusters. However, the subsample of high-mass passive galaxies only is characterized by a steep increase of the slope with redshift, from which it can be inferred that the bulk of the slope evolution of the ZM relation is driven by the more massive passive objects. The scatter of the passive sample is dominated by low-mass galaxies at all redshifts and keeps constant over cosmic times. The mean metallicity is highest in cluster cores and lowest in normal groups, following the same environmental sequence as that previously found in the red sequence building. The ZM relation for the SF sample reveals an increasing scatter with redshift, indicating that it is still being built at early epochs. The SF galaxies make up a tight sequence in the SFR-M * plane at high redshift, whose scatter increases with time alongside the consolidation of the passive sequence. We also confirm the anti-correlation between sSFR and stellar mass, pointing at a key role of the former in determining the galaxy downsizing, as the most significant means of diagnostics of the star formation efficiency. Likewise, an anti-correlation between sSFR and metallicity can be established for the SF galaxies, while on the contrary more active galaxies

  6. MUFASA: the strength and evolution of galaxy conformity in various tracers

    Science.gov (United States)

    Rafieferantsoa, Mika; Davé, Romeel

    2018-03-01

    We investigate galaxy conformity using the MUFASA cosmological hydrodynamical simulation. We show a bimodal distribution in galaxy colour with radius, albeit with too many low-mass quenched satellite galaxies compared to observations. MUFASA produces conformity in observed properties such as colour, specific star formation rate (sSFR), and H I content, i.e. neighbouring galaxies have similar properties. We see analogous trends in other properties such as in environment, stellar age, H2 content, and metallicity. We introduce quantifying conformity using S(R), measuring the relative difference in upper and lower quartile properties of the neighbours. We show that low-mass and non-quenched haloes have weak conformity (S(R)≲ 0.5) extending to large projected radii R in all properties, while high-mass and quenched haloes have strong conformity (S(R)˜ 1) that diminishes rapidly with R and disappears at R ≳ 1 Mpc. S(R) is strongest for environment in low-mass haloes, and sSFR (or colour) in high-mass haloes, and is dominated by one-halo conformity with the exception of H I in small haloes. Metallicity shows a curious anticonformity in massive haloes. Tracking the evolution of conformity for z = 0 galaxies back in time shows that conformity broadly emerges as a late-time (z ≲ 1) phenomenon. However, for fixed halo mass bins, conformity is fairly constant with redshift out to z ≳ 2. These trends are consistent with the idea that strong conformity only emerges once haloes grow above MUFASA's quenching mass scale of ˜1012 M⊙. A quantitative measure of conformity in various properties, along with its evolution, thus represents a new and stringent test of the impact of quenching on environment within current galaxy formation models.

  7. Chemical evolution of the Galaxy at the initial rapid-collapse phase

    Energy Technology Data Exchange (ETDEWEB)

    Caimmi, R [Padua Univ. (Italy). Istituto di Astronomia

    1978-04-01

    Equations for the chemical evolution of the Galaxy are derived, accounting for (i) the dynamical evolution of the Galaxy (i.e. the collapse of the proto-galaxy) and (ii) either a variable mass-spectrum in the birth-rate stellar function of the type B(m,t) = psi(t)phi(m,t), or a constant mass-spectrum with variable lower mass limit for star birth: msub(mf) = msub(mf)(Z). Simple equations are adopted for the collapse of the proto-galaxy, accounting for the experimental data (i.e. axial ratio and major semi-axis) relative to the halo and to the disk, and best fitted for a rapid collapse; gas density is assumed to be always uniform. Numerical computations of several cases show that there is qualitative agreement with the experimental data relative to the Z(t) function when: (i) the mass-spectrum is nearly constant in time: phi(m,t) approximately phi(m) = msup(-2.35); (ii) the efficiency phi(t) proportional to rhosup(..cap alpha..) is sufficiently high; moreover, the super metallic effect (SME) takes place for ..cap alpha.. greater than a given value (..cap alpha.. > approximately 1.5); (iii) the shorter the collapse time Tsub(c), the more rapid is the initial increase of metallicity, the asymptotic value being left nearly unaltered. The theoretical results are not in complete agreement with the observed data bearing on the Nsub(n)(Z) function (Nsub(n) is the number of stars whose Main-Sequence lifetime is not less than the age of the Galaxy), while a hypothesis of star formation with different efficiencies in different zones of the Galaxy, and successive stellar mixing from zone to zone, is not inconsistent with such data.

  8. Chemical evolution of the Galaxy at the initial rapid-collapse phase

    International Nuclear Information System (INIS)

    Caimmi, R.

    1978-01-01

    Equations for the chemical evolution of the Galaxy are derived, accounting for (i) the dynamical evolution of the Galaxy (i.e. the collapse of the proto-galaxy) and (ii) either a variable mass-spectrum in the birth-rate stellar function of the type B(m,t) = psi(t)phi(m,t), or a constant mass-spectrum with variable lower mass limit for star birth: msub(mf) = msub(mf)(Z). Simple equations are adopted for the collapse of the proto-galaxy, accounting for the experimental data (i.e. axial ratio and major semi-axis) relative to the halo and to the disk, and best fitted for a rapid collapse; gas density is assumed to be always uniform. Numerical computations of several cases show that there is qualitative agreement with the experimental data relative to the Z(t) function when: (i) the mass-spectrum is nearly constant in time: phi(m,t) approximately phi(m) = msup(-2.35); (ii) the efficiency phi(t) proportional to rhosup(α) is sufficiently high; moreover, the super metallic effect (SME) takes place for α greater than a given value (α > approximately 1.5); (iii) the shorter the collapse time Tsub(c), the more rapid is the initial increase of metallicity, the asymptotic value being left nearly unaltered. The theoretical results are not in complete agreement with the observed data bearing on the Nsub(n)(Z) function (Nsub(n) is the number of stars whose Main-Sequence lifetime is not less than the age of the Galaxy), while a hypothesis of star formation with different efficiencies in different zones of the Galaxy, and successive stellar mixing from zone to zone, is not inconsistent with such data. (Auth.)

  9. TRACING THE EVOLUTION OF HIGH-REDSHIFT GALAXIES USING STELLAR ABUNDANCES

    Energy Technology Data Exchange (ETDEWEB)

    Crosby, Brian D.; O’Shea, Brian W. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Beers, Timothy C. [Department of Physics and JINA—Center for the Evolution of the Elements, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Tumlinson, Jason, E-mail: crosby.bd@gmail.com [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2016-03-20

    This paper presents the first results from a model for chemical evolution that can be applied to N-body cosmological simulations and quantitatively compared to measured stellar abundances from large astronomical surveys. This model convolves the chemical yield sets from a range of stellar nucleosynthesis calculations (including asymptotic giant branch stars, Type Ia and II supernovae, and stellar wind models) with a user-specified stellar initial mass function (IMF) and metallicity to calculate the time-dependent chemical evolution model for a “simple stellar population” (SSP) of uniform metallicity and formation time. These SSP models are combined with a semianalytic model for galaxy formation and evolution that uses merger trees from N-body cosmological simulations to track several α- and iron-peak elements for the stellar and multiphase interstellar medium components of several thousand galaxies in the early (z ≥ 6) universe. The simulated galaxy population is then quantitatively compared to two complementary data sets of abundances in the Milky Way stellar halo and is capable of reproducing many of the observed abundance trends. The observed abundance ratio distributions are best reproduced with a Chabrier IMF, a chemically enriched star formation efficiency of 0.2, and a redshift of reionization of 7. Many abundances are qualitatively well matched by our model, but our model consistently overpredicts the carbon-enhanced fraction of stars at low metallicities, likely owing to incomplete coverage of Population III stellar yields and supernova models and the lack of dust as a component of our model.

  10. The role of major mergers in (obscured) black hole growth and galaxy evolution

    Science.gov (United States)

    Treister, E.; Privon, G.; Ricci, C.; Bauer, F.; Schawinski, K.; MODA Collaboration

    2017-10-01

    A clear picture is emerging in which rapid supermassive black hole (SMBH) growth episodes (luminous AGN) are directly linked to major galaxy mergers. Here, we present the first results from our MODA program aimed to obtain optical and near-IR Integral Field Unit (IFU) spectroscopy and mm/sub-mm ALMA maps for a sample of confirmed nearby dual AGN (separation 10 kpc), including the archetypical galaxy NGC6240. Specifically, we will focus here on Mrk 463, a very rich system of two galaxies separated by 3.8 kpc hosting two SMBH growing simultaneously. Clear evidence for complex morphologies and kinematics, outflows and feedback effects can be seen in this system, evidencing the deep connection between major galaxy mergers, SMBH growth and galaxy evolution.

  11. Topics in Galaxy Evolution: Early Star Formation and Quenching

    Science.gov (United States)

    Goncalves, Thiago Signorini

    In this thesis, we present three projects designed to shed light on yet unanswered questions on galaxy formation and evolution. The first two concern a sample of UV-bright starburst galaxies in the local universe (z ˜0.2). These objects are remarkably similar to star-forming galaxies that were abundant at high redshifts (2 manipulating our observations to mimic our objects at greater distances, we show how low resolution and signal-to-noise ratios can lead to erroneous conclusions, in particular when attempting to diagnose mergers as the origin of the starburst. Then, we present results from a pilot survey to study the cold, molecular gas reservoir in such objects. Again, we show that the observed properties are analogous to those observed at high redshift, in particular with respect to baryonic gas fractions in the galaxy, higher than normally found in low-extinction objects in the local universe. Furthermore, we show how gas surface density and star-formation surface density follow the same relation as local galaxies, albeit at much higher values. Finally, we discuss an observational project designed to measure the mass flux density from the blue sequence to the red sequence across the so-called green valley. We obtain the deepest spectra ever observed of green valley galaxies at intermediate redshifts (z˜0.8) in order to measure spectral features from which we can measure the star formation histories of individual galaxies. We measure a mass flux ratio that is higher than observed in the local universe, indicating the red sequence was growing faster when the universe was half its present age than today.

  12. Non-instantaneous gas recycling and chemical evolution in N-body disk galaxies

    Czech Academy of Sciences Publication Activity Database

    Jungwiert, Bruno; Carraro, G.; Dalla Vecchia, C.

    2004-01-01

    Roč. 289, 3-4 (2004), s. 441-444 ISSN 0004-640X. [From observations to self-consistent modelling of the ISM in galaxies. Porto, 03.09.2002-05.09.2002] R&D Projects: GA ČR GP202/01/D075 Institutional research plan: CEZ:AV0Z1003909 Keywords : N-body simulations * galaxy evolution * gas recycling Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.597, year: 2004

  13. THE REDSHIFT EVOLUTION OF OXYGEN AND NITROGEN ABUNDANCES IN EMISSION-LINE SDSS GALAXIES

    International Nuclear Information System (INIS)

    Thuan, Trinh X.; Pilyugin, Leonid S.; Zinchenko, Igor A.

    2010-01-01

    The oxygen and nitrogen abundance evolutions with redshift and galaxy stellar mass in emission-line galaxies from the Sloan Digital Sky Survey (SDSS) are investigated. This is the first such study for nitrogen abundances, and it provides an additional constraint for the study of the chemical evolution of galaxies. We have devised a criterion to recognize and exclude from consideration active galactic nuclei and star-forming galaxies with large errors in the line flux measurements. To select star-forming galaxies with accurate line fluxes measurements, we require that, for each galaxy, the nitrogen abundances derived with various calibrations based on different emission lines agree. Using this selection criterion, subsamples of star-forming SDSS galaxies have been extracted from catalogs of the Max-Planck-Institute for Astrophysics/Johns Hopkins University group. We found that the galaxies of highest masses, those with masses ∼>10 11.2 M sun , have not been enriched in both oxygen and nitrogen over the last ∼3 Gyr: they have formed their stars in the so distant past that these have returned their nucleosynthesis products to the interstellar medium before z = 0.25. The galaxies in the mass range from ∼10 11.0 M sun to ∼10 11.2 M sun do not show an appreciable enrichment in oxygen, but do show some enrichment in nitrogen: they also formed their stars before z = 0.25 but later in comparison to the galaxies of highest masses; these stars have not returned nitrogen to the interstellar medium before z = 0.25 because they have not had enough time to evolve. This suggests that stars with lifetimes of 2-3 Gyr, in the 1.5-2 M sun mass range, contribute to the nitrogen production. Finally, galaxies with masses ∼ 11 M sun show enrichment in both oxygen and nitrogen during the last 3 Gyr: they have undergone appreciable star formation and have converted up to ∼20% of their mass into stars over this period. Both oxygen and nitrogen enrichments increase with decreasing

  14. E+A Galaxy Properties and Post-Starburst Galaxy Evolution Data through SDSS-IV MaNGA and Illustris: A Co-Analysis

    Science.gov (United States)

    Ojanen, Winonah; Dudley, Raymond; Edwards, Kay; Gonzalez, Andrea; Johnson, Amalya; Kerrison, Nicole; Marinelli, Mariarosa; Melchert, Nancy; Liu, Charles; Sloan Collaboration, SDSS-IV MaNGA

    2018-01-01

    E+A galaxies (Elliptical + A-type stars) are post-starburst galaxies that have experienced a sudden quenching phase. Using previous research methods, 39 candidates out of 2,812 galaxies observed, or 1.4%, were selected from the SDSS-IV MaNGA survey. We then identified morphological characteristics of the 39 galaxies including stellar kinematics, Gini coefficient, gas density and distribution and stellar ages. To study the origin of how E+A galaxies evolved to their present state, galaxy simulation data from the Illustris simulation was utilized to identify similar quenched post-starburst candidates. Seven post-starburst candidates were identified through star formation rate histories of Illustris simulated galaxies. The evolution of these galaxies is studied from 0 to 13.8 billion years ago to identify what caused the starburst and quenching of the Illustris candidates. Similar morphological characteristics of Illustris post-starburst candidates are pulled from before, during, and post-starburst and compared to the same morphological characteristics of the E+A galaxies from SDSS-IV MaNGA. The characteristics and properties of the Illustris galaxies are used to identify the possible evolutionary histories of the observed E+A galaxies. This work was supported by grants AST-1460860 from the National Science Foundation and SDSS FAST/SSP-483 from the Alfred P. Sloan Foundation to the CUNY College of Staten Island.

  15. Dwarf galaxies in the coma cluster: Star formation properties and evolution

    Science.gov (United States)

    Hammer, Derek M.

    The infall regions of galaxy clusters are unique laboratories for studying the impact of environment on galaxy evolution. This intermediate region links the low-density field environment and the dense core of the cluster, and is thought to host recently accreted galaxies whose star formation is being quenched by external processes associated with the cluster. In this dissertation, we measure the star formation properties of galaxies at the infall region of the nearby rich cluster of galaxies, Coma. We rely primarily on Ultraviolet (UV) data owing to its sensitivity to recent star formation and we place more emphasis on the properties of dwarf galaxies. Dwarf galaxies are good tracers of external processes in clusters but their evolution is poorly constrained as they are intrinsically faint and hence more challenging to detect. We make use of deep GALEX far-UV and near-UV observations at the infall region of the Coma cluster. This area of the cluster has supporting photometric coverage at optical and IR wavelengths in addition to optical spectroscopic data that includes deep redshift coverage of dwarf galaxies in Coma. Our GALEX observations were the deepest exposures taken for a local galaxy cluster. The depth of these images required alternative data analysis techniques to overcome systematic effects that limit the default GALEX pipeline analysis. Specifically, we used a deblending method that improved detection efficiency by a factor of ˜2 and allowed reliable photometry a few magnitudes deeper than the pipeline catalog. We performed deep measurements of the total UV galaxy counts in our field that were used to measure the source confusion limit for crowded GALEX fields. The star formation properties of Coma members were studied for galaxies that span from starbursts to passive galaxies. Star-forming galaxies in Coma tend to have lower specific star formation rates, on average, as compared to field galaxies. We show that the majority of these galaxies are likely

  16. THE METALLICITY BIMODALITY OF GLOBULAR CLUSTER SYSTEMS: A TEST OF GALAXY ASSEMBLY AND OF THE EVOLUTION OF THE GALAXY MASS-METALLICITY RELATION

    International Nuclear Information System (INIS)

    Tonini, Chiara

    2013-01-01

    We build a theoretical model to study the origin of the globular cluster metallicity bimodality in the hierarchical galaxy assembly scenario. The model is based on empirical relations such as the galaxy mass-metallicity relation [O/H]-M star as a function of redshift, and on the observed galaxy stellar mass function up to redshift z ∼ 4. We make use of the theoretical merger rates as a function of mass and redshift from the Millennium simulation to build galaxy merger trees. We derive a new galaxy [Fe/H]-M star relation as a function of redshift, and by assuming that globular clusters share the metallicity of their original parent galaxy at the time of their formation, we populate the merger tree with globular clusters. We perform a series of Monte Carlo simulations of the galaxy hierarchical assembly, and study the properties of the final globular cluster population as a function of galaxy mass, assembly and star formation history, and under different assumptions for the evolution of the galaxy mass-metallicity relation. The main results and predictions of the model are the following. (1) The hierarchical clustering scenario naturally predicts a metallicity bimodality in the galaxy globular cluster population, where the metal-rich subpopulation is composed of globular clusters formed in the galaxy main progenitor around redshift z ∼ 2, and the metal-poor subpopulation is composed of clusters accreted from satellites, and formed at redshifts z ∼ 3-4. (2) The model reproduces the observed relations by Peng et al. for the metallicities of the metal-rich and metal-poor globular cluster subpopulations as a function of galaxy mass; the positions of the metal-poor and metal-rich peaks depend exclusively on the evolution of the galaxy mass-metallicity relation and the [O/Fe], both of which can be constrained by this method. In particular, we find that the galaxy [O/Fe] evolves linearly with redshift from a value of ∼0.5 at redshift z ∼ 4 to a value of ∼0.1 at

  17. DYNAMICAL EVOLUTION OF AGN HOST GALAXIES-GAS IN/OUT-FLOW RATES IN SEVEN NUGA GALAXIES

    International Nuclear Information System (INIS)

    Haan, Sebastian; Schinnerer, Eva; Rix, Hans-Walter; Emsellem, Eric; GarcIa-Burillo, Santiago; Combes, Francoise; Mundell, Carole G.

    2009-01-01

    To examine the role of the host galaxy structure in fueling nuclear activity, we estimated gas flow rates from several kpc down to the inner few 10 pc for seven nearby spiral galaxies, selected from the NUclei of GAlaxies sample. We calculated gravitational torques from near-infrared images and determined gas in/out-flow rates as a function of radius and location within the galactic disks, based on high angular resolution interferometric observations of molecular (CO using Plateau de Bure interferometer) and atomic (H I using the Very Large Array) gas. The results are compared with kinematic evidence for radial gas flows and the dynamical state of the galaxies (via resonances) derived from several different methods. We show that gravitational torques are very efficient at transporting gas from the outer disk all the way into the galaxies centers at ∼100 pc; previously assumed dynamical barriers to gas transport, such as the corotation resonance of stellar bars, seem to be overcome by gravitational torque induced gas flows from other nonaxisymmetric structures. The resulting rates of gas mass inflow range from 0.01 to 50 M sun yr -1 and are larger for the galaxy center than for the outer disk. Our gas flow maps show the action of nested bars within larger bars for three galaxies. Noncircular streaming motions found in the kinematic maps are larger in the center than in the outer disk and appear to correlate only loosely with the in/out-flow rates as a function of radius. We demonstrate that spiral gas disks are very dynamic systems that undergo strong radial evolution on timescales of a few rotation periods (e.g., 5 x 10 8 yrs at a radius of 5 kpc), due to the effectiveness of gravitational torques in redistributing the cold galactic gas.

  18. The origin of nitrogen and the chemical evolution of spiral galaxies

    OpenAIRE

    Díaz, Angeles I.; Tosi, M.

    1986-01-01

    This is an electronic version of an article published in Astronomy and Astrophysics. Diaz, A.I. and M. Tosi. The origin of nitrogen and the chemical evolution of spiral galaxies. Astronomy and Astrophysics 158 (1986): 60-66

  19. Low-ionization galaxies and evolution in a pilot survey up to z = 1

    International Nuclear Information System (INIS)

    Giraud, Edmond; Gu Qiusheng; Melnick, Jorge; Selman, Fernando; Quintana, Hernan; Toledo, Ignacio; Zelaya, Paula

    2011-01-01

    We present galactic spectroscopic data from a pencil beam of 10.75' x 7.5' centered on the X-ray cluster RXJ0054.0-2823 at z = 0.29. We study the spectral evolution of galaxies from z = 1 down to the cluster redshift in a magnitude-limited sample at R ≤ 23, for which the statistical properties of the sample are well understood. We divide emission-line galaxies into star-forming galaxies, Low Ionization Nuclear Emission line Regions (LINERs), and Seyferts by using emission-line ratios of [OII], Hβ, and [OIII], and derive stellar fractions from population synthesis models. We focus our analysis on absorption and low-ionization galaxies. For absorption-line galaxies, we recover the well-known result that these galaxies have had no detectable evolution since z ∼ 0.6 - 0.7, but we also find that in the range z = 0.65 - 1, at least 50% of the stars in bright absorption systems are younger than 2.5 Gyr Faint absorption-line galaxies in the cluster at z = 0.29 also had significant star formation during the previous 2 - 3 Gyr, but their brighter counterparts seem to be only composed of old stars. At z ∼ 0.8, our dynamically young cluster had a truncated red-sequence. This result seems to be consistent with a scenario where the final assembly of E/S0 took place at z < 1. In the volume-limited range 0.35 ≤ z ≤ 0.65, we find that 23% of the early-type galaxies have LINER-like spectra with Hβ in absorption and have a significant component of A stars. The vast majority of LINERs in our sample have significant populations of young and intermediate-aged stars and are thus not related to AGNs, but to the population of 'retired galaxies' recently identified by Cid Fernandes et al. in the Sloan Digital Sky Survey (SDSS). Early-type LINERs with various fractions of A stars and E+A galaxies appear to play an important role in the formation of the red sequence.

  20. Galactic chemical evolution in hierarchical formation models - I. Early-type galaxies in the local Universe

    NARCIS (Netherlands)

    Arrigoni, Matías; Trager, Scott C.; Somerville, Rachel S.; Gibson, Brad K.

    We study the metallicities and abundance ratios of early-type galaxies in cosmological semi-analytic models (SAMs) within the hierarchical galaxy formation paradigm. To achieve this we implemented a detailed galactic chemical evolution model and can now predict abundances of individual elements for

  1. Galactic chemical evolution in hierarchical formation models : I. Early-type galaxies in the local Universe

    NARCIS (Netherlands)

    Arrigoni, Matias; Trager, Scott C.; Somerville, Rachel S.; Gibson, Brad K.

    2010-01-01

    We study the metallicities and abundance ratios of early-type galaxies in cosmological semi-analytic models (SAMs) within the hierarchical galaxy formation paradigm. To achieve this we implemented a detailed galactic chemical evolution model and can now predict abundances of individual elements for

  2. Measuring size evolution of distant, faint galaxies in the radio regime

    Science.gov (United States)

    Lindroos, L.; Knudsen, K. K.; Stanley, F.; Muxlow, T. W. B.; Beswick, R. J.; Conway, J.; Radcliffe, J. F.; Wrigley, N.

    2018-05-01

    We measure the evolution of sizes for star-forming galaxies as seen in 1.4 GHz continuum radio for z = 0-3. The measurements are based on combined VLA+MERLIN data of the Hubble Deep Field, and using a uv-stacking algorithm combined with model fitting to estimate the average sizes of galaxies. A sample of ˜1000 star-forming galaxies is selected from optical and near-infrared catalogues, with stellar masses M⊙ ≈ 1010-1011 M⊙ and photometric redshifts 0-3. The median sizes are parametrized for stellar mass M* = 5 × 1010 M⊙ as R_e = A× {}(H(z)/H(1.5))^{α _z}. We find that the median radio sizes evolve towards larger sizes at later times with αz = -1.1 ± 0.6, and A (the median size at z ≈ 1.5) is found to be 0.26^'' ± 0.07^'' or 2.3±0.6 kpc. The measured radio sizes are typically a factor of 2 smaller than those measure in the optical, and are also smaller than the typical H α sizes in the literature. This indicates that star formation, as traced by the radio continuum, is typically concentrated towards the centre of galaxies, for the sampled redshift range. Furthermore, the discrepancy of measured sizes from different tracers of star formation, indicates the need for models of size evolution to adopt a multiwavelength approach in the measurement of the sizes star-forming regions.

  3. Early-type Galaxy Spin Evolution in the Horizon-AGN Simulation

    Science.gov (United States)

    Choi, Hoseung; Yi, Sukyoung K.; Dubois, Yohan; Kimm, Taysun; Devriendt, Julien. E. G.; Pichon, Christophe

    2018-04-01

    Using the Horizon-AGN simulation data, we study the relative role of mergers and environmental effects in shaping the spin of early-type galaxies (ETGs) after z ≃ 1. We follow the spin evolution of 10,037 color-selected ETGs more massive than {10}10 {M}ȯ that are divided into four groups: cluster centrals (3%), cluster satellites (33%), group centrals (5%), and field ETGs (59%). We find a strong mass dependence of the slow rotator fraction, f SR, and the mean spin of massive ETGs. Although we do not find a clear environmental dependence of f SR, a weak trend is seen in the mean value of the spin parameter driven by the satellite ETGs as they gradually lose their spin as their environment becomes denser. Galaxy mergers appear to be the main cause of total spin changes in 94% of the central ETGs of halos with {M}vir}> {10}12.5 {M}ȯ , but only 22% of satellite and field ETGs. We find that non-merger-induced tidal perturbations better correlate with the galaxy spin down in satellite ETGs than in mergers. Given that the majority of ETGs are not central in dense environments, we conclude that non-merger tidal perturbation effects played a key role in the spin evolution of ETGs observed in the local (z < 1) universe.

  4. Dynamical effects in the formation and evolution of galaxies and clusters

    International Nuclear Information System (INIS)

    White, S.D.M.

    1977-01-01

    The development of computer programs capable of simulating the self-consistent evolution of systems of a thousand or more self-gravitating particles has opened to experiment many aspects of problems concerning the dissipationless formation of galaxies and galaxy clusters which could previously only be treated at the cost of extreme oversimplification. As a result of experiments now being carried out, the range of validity, the inadequacies and the mistaken emphasis of many previous analyses are becoming evident. The applications of numerical experiments are discussed and illustrated. (U.K.)

  5. Evolution of the degree of substructures in simulated galaxy clusters

    Science.gov (United States)

    De Boni, Cristiano; Böhringer, Hans; Chon, Gayoung; Dolag, Klaus

    2018-05-01

    We study the evolution of substructure in the mass distribution with mass, redshift and radius in a sample of simulated galaxy clusters. The sample, containing 1226 objects, spans the mass range M200 = 1014 - 1.74 × 1015 M⊙ h-1 in six redshift bins from z = 0 to z = 1.179. We consider three different diagnostics: 1) subhalos identified with SUBFIND; 2) overdense regions localized by dividing the cluster into octants; 3) offset between the potential minimum and the center of mass. The octant analysis is a new method that we introduce in this work. We find that none of the diagnostics indicate a correlation between the mass of the cluster and the fraction of substructures. On the other hand, all the diagnostics suggest an evolution of substructures with redshift. For SUBFIND halos, the mass fraction is constant with redshift at Rvir, but shows a mild evolution at R200 and R500. Also, the fraction of clusters with at least a subhalo more massive than one thirtieth of the total mass is less than 20%. Our new method based on the octants returns a mass fraction in substructures which has a strong evolution with redshift at all radii. The offsets also evolve strongly with redshift. We also find a strong correlation for individual clusters between the offset and the fraction of substructures identified with the octant analysis. Our work puts strong constraints on the amount of substructures we expect to find in galaxy clusters and on their evolution with redshift.

  6. Formation and evolution of star clusters and their host galaxies

    NARCIS (Netherlands)

    Kruijssen, J.M.D.

    2011-01-01

    The vast majority of galaxies contains large populations of stellar clusters, which are bound groups of a few tens to millions of stars. A cluster is formed from a single giant molecular cloud and therefore its stars share the same age and chemical composition. The formation and evolution of star

  7. Evolution of N/O ratios in galaxies from cosmological hydrodynamical simulations

    Science.gov (United States)

    Vincenzo, Fiorenzo; Kobayashi, Chiaki

    2018-04-01

    We study the redshift evolution of the gas-phase O/H and N/O abundances, both (i) for individual ISM regions within single spatially-resolved galaxies and (ii) when dealing with average abundances in the whole ISM of many unresolved galaxies. We make use of a cosmological hydrodynamical simulation including detailed chemical enrichment, which properly takes into account the variety of different stellar nucleosynthetic sources of O and N in galaxies. We identify 33 galaxies in the simulation, lying within dark matter halos with virial mass in the range 1011 ≤ MDM ≤ 1013 M⊙ and reconstruct how they evolved with redshift. For the local and global measurements, the observed increasing trend of N/O at high O/H can be explained, respectively, (i) as the consequence of metallicity gradients which have settled in the galaxy interstellar medium, where the innermost galactic regions have the highest O/H abundances and the highest N/O ratios, and (ii) as the consequence of an underlying average mass-metallicity relation that galaxies obey as they evolve across cosmic epochs, where - at any redshift - less massive galaxies have lower average O/H and N/O ratios than the more massive ones. We do not find a strong dependence on the environment. For both local and global relations, the predicted N/O-O/H relation is due to the mostly secondary origin of N in stars. We also predict that the O/H and N/O gradients in the galaxy interstellar medium gradually flatten as functions of redshift, with the average N/O ratios being strictly coupled with the galaxy star formation history. Because N production strongly depends on O abundances, we obtain a universal relation for the N/O-O/H abundance diagram whether we consider average abundances of many unresolved galaxies put together or many abundance measurements within a single spatially-resolved galaxy.

  8. The evolution of magnetic fields in clusters of galaxies

    International Nuclear Information System (INIS)

    Stoeckl, J.

    2011-01-01

    Although the observational knowledge base about the properties of magnetic fields in clusters of galaxies has significantly improved in recent years, our understanding of the evolution and influence of the magnetic fields is still limited. We present results from our study on the influence of cluster scale magnetic fields on the structure formation of clusters of galaxies and the evolution of the intra-cluster medium (ICM). The high-resolution simulations employ a self-consistent numerical setup, which includes gravity, cosmology, magnetohydrodynamics and radiative cooling. We find that during structure formation cosmological magnetic seed fields of the order of 10 -1 1 to 10 -9 G are amplified by up to six orders of magnitude, which is in good agreement with observations. Furthermore we find that merger shocks during the cluster formation can have a dispersive effect on the magnetic field in the cluster center, and the outgoing shock waves can lead to magnetic fields of the order of [mu]G even at distances of more than 1 Mpc from the center. We highlight this as a possible explanation for the faint or undetectable radio halos that can be observed together with strong radio relics. (author) [de

  9. The E-MOSAICS project: simulating the formation and co-evolution of galaxies and their star cluster populations

    Science.gov (United States)

    Pfeffer, Joel; Kruijssen, J. M. Diederik; Crain, Robert A.; Bastian, Nate

    2018-04-01

    We introduce the MOdelling Star cluster population Assembly In Cosmological Simulations within EAGLE (E-MOSAICS) project. E-MOSAICS incorporates models describing the formation, evolution, and disruption of star clusters into the EAGLE galaxy formation simulations, enabling the examination of the co-evolution of star clusters and their host galaxies in a fully cosmological context. A fraction of the star formation rate of dense gas is assumed to yield a cluster population; this fraction and the population's initial properties are governed by the physical properties of the natal gas. The subsequent evolution and disruption of the entire cluster population are followed accounting for two-body relaxation, stellar evolution, and gravitational shocks induced by the local tidal field. This introductory paper presents a detailed description of the model and initial results from a suite of 10 simulations of ˜L⋆ galaxies with disc-like morphologies at z = 0. The simulations broadly reproduce key observed characteristics of young star clusters and globular clusters (GCs), without invoking separate formation mechanisms for each population. The simulated GCs are the surviving population of massive clusters formed at early epochs (z ≳ 1-2), when the characteristic pressures and surface densities of star-forming gas were significantly higher than observed in local galaxies. We examine the influence of the star formation and assembly histories of galaxies on their cluster populations, finding that (at similar present-day mass) earlier-forming galaxies foster a more massive and disruption-resilient cluster population, while galaxies with late mergers are capable of forming massive clusters even at late cosmic epochs. We find that the phenomenological treatment of interstellar gas in EAGLE precludes the accurate modelling of cluster disruption in low-density environments, but infer that simulations incorporating an explicitly modelled cold interstellar gas phase will overcome

  10. The Metallicity Evolution of Low Mass Galaxies: New Contraints at Intermediate Redshift

    Science.gov (United States)

    Henry, Alaina; Martin, Crystal L.; Finlator, Kristian; Dressler, Alan

    2013-01-01

    We present abundance measurements from 26 emission-line-selected galaxies at z approx. 0.6-0.7. By reaching stellar masses as low as 10(exp 8) M stellar mass, these observations provide the first measurement of the intermediate-redshift mass-metallicity (MZ) relation below 10(exp 9)M stellar mass. For the portion of our sample above M is greater than 10(exp 9)M (8/26 galaxies), we find good agreement with previous measurements of the intermediate-redshift MZ relation. Compared to the local relation, we measure an evolution that corresponds to a 0.12 dex decrease in oxygen abundances at intermediate redshifts. This result confirms the trend that metallicity evolution becomes more significant toward lower stellar masses, in keeping with a downsizing scenario where low-mass galaxies evolve onto the local MZ relation at later cosmic times. We show that these galaxies follow the local fundamental metallicity relation, where objects with higher specific (mass-normalized) star formation rates (SFRs) have lower metallicities. Furthermore, we show that the galaxies in our sample lie on an extrapolation of the SFR-M* relation (the star-forming main sequence). Leveraging the MZ relation and star-forming main sequence (and combining our data with higher-mass measurements from the literature), we test models that assume an equilibrium between mass inflow, outflow, and star formation.We find that outflows are required to describe the data. By comparing different outflow prescriptions, we show that momentum, driven winds can describe the MZ relation; however, this model underpredicts the amount of star formation in low-mass galaxies. This disagreement may indicate that preventive feedback from gas heating has been overestimated, or it may signify a more fundamental deviation from the equilibrium assumption.

  11. STELLAR POPULATIONS AND EVOLUTION OF EARLY-TYPE CLUSTER GALAXIES: CONSTRAINTS FROM OPTICAL IMAGING AND SPECTROSCOPY OF z = 0.5–0.9 GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Jørgensen, Inger; Chiboucas, Kristin

    2013-01-01

    We present an analysis of stellar populations and evolutionary history of galaxies in three similarly rich galaxy clusters MS0451.6–0305 (z = 0.54), RXJ0152.7–1357 (z = 0.83), and RXJ1226.9+3332 (z = 0.89). Our analysis is based on high signal-to-noise ground-based optical spectroscopy and Hubble Space Telescope imaging for a total of 17-34 members in each cluster. Using the dynamical masses together with the effective radii and the velocity dispersions, we find no indication of evolution of sizes or velocity dispersions with redshift at a given galaxy mass. We establish the Fundamental Plane (FP) and scaling relations between absorption line indices and velocity dispersions. We confirm that the FP is steeper at z ≈ 0.86 compared to the low-redshift FP, indicating that under the assumption of passive evolution the formation redshift, z form , depends on the galaxy velocity dispersion (or alternatively mass). At a velocity dispersion of σ = 125 km s –1 (Mass = 10 10.55 M ☉ ) we find z form = 1.24 ± 0.05, while at σ = 225 km s –1 (Mass = 10 11.36 M ☉ ) the formation redshift is z form = 1.95 +0.3 –0.2 , for a Salpeter initial mass function. The three clusters follow similar scaling relations between absorption line indices and velocity dispersions as those found for low-redshift galaxies. The zero point offsets for the Balmer lines depend on cluster redshifts. However, the offsets indicate a slower evolution, and therefore higher formation redshift, than the zero point differences found from the FP, if interpreting the data using a passive evolution model. Specifically, the strength of the higher order Balmer lines Hδ and Hγ implies z form > 2.8. The scaling relations for the metal indices in general show small and in some cases insignificant zero point offsets, favoring high formation redshifts for a passive evolution model. Based on the absorption line indices and recent stellar population models from Thomas et al., we find that MS0451.6–0305

  12. Galaxy Evolution Insights from Spectral Modeling of Large Data Sets from the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    Hoversten, Erik A. [Johns Hopkins Univ., Baltimore, MD (United States)

    2007-10-01

    This thesis centers on the use of spectral modeling techniques on data from the Sloan Digital Sky Survey (SDSS) to gain new insights into current questions in galaxy evolution. The SDSS provides a large, uniform, high quality data set which can be exploited in a number of ways. One avenue pursued here is to use the large sample size to measure precisely the mean properties of galaxies of increasingly narrow parameter ranges. The other route taken is to look for rare objects which open up for exploration new areas in galaxy parameter space. The crux of this thesis is revisiting the classical Kennicutt method for inferring the stellar initial mass function (IMF) from the integrated light properties of galaxies. A large data set (~ 105 galaxies) from the SDSS DR4 is combined with more in-depth modeling and quantitative statistical analysis to search for systematic IMF variations as a function of galaxy luminosity. Galaxy Hα equivalent widths are compared to a broadband color index to constrain the IMF. It is found that for the sample as a whole the best fitting IMF power law slope above 0.5 M is Γ = 1.5 ± 0.1 with the error dominated by systematics. Galaxies brighter than around Mr,0.1 = -20 (including galaxies like the Milky Way which has Mr,0.1 ~ -21) are well fit by a universal Γ ~ 1.4 IMF, similar to the classical Salpeter slope, and smooth, exponential star formation histories (SFH). Fainter galaxies prefer steeper IMFs and the quality of the fits reveal that for these galaxies a universal IMF with smooth SFHs is actually a poor assumption. Related projects are also pursued. A targeted photometric search is conducted for strongly lensed Lyman break galaxies (LBG) similar to MS1512-cB58. The evolution of the photometric selection technique is described as are the results of spectroscopic follow-up of the best targets. The serendipitous discovery of two interesting blue compact dwarf galaxies is reported. These

  13. Synthetic nebular emission from massive galaxies - I: origin of the cosmic evolution of optical emission-line ratios

    Science.gov (United States)

    Hirschmann, Michaela; Charlot, Stephane; Feltre, Anna; Naab, Thorsten; Choi, Ena; Ostriker, Jeremiah P.; Somerville, Rachel S.

    2017-12-01

    Galaxies occupy different regions of the [O III]λ5007/H β-versus-[N II]λ6584/H α emission-line ratio diagram in the distant and local Universe. We investigate the origin of this intriguing result by modelling self-consistently, for the first time, nebular emission from young stars, accreting black holes (BHs) and older, post-asymptotic giant branch (post-AGB) stellar populations in galaxy formation simulations in a full cosmological context. In post-processing, we couple new-generation nebular-emission models with high-resolution, cosmological zoom-in simulations of massive galaxies to explore which galaxy physical properties drive the redshift evolution of the optical-line ratios [O III]λ5007/H β, [N II]λ6584/H α, [S II]λλ6717, 6731/H α and [O I]λ6300/H α. The line ratios of simulated galaxies agree well with observations of both star-forming and active local Sloan Digital Sky Survey galaxies. Towards higher redshifts, at fixed galaxy stellar mass, the average [O III]/H β is predicted to increase and [N II]/H α, [S II]/H α and [O I]/H α to decrease - widely consistent with observations. At fixed stellar mass, we identify star formation history, which controls nebular emission from young stars via the ionization parameter, as the primary driver of the cosmic evolution of [O III]/H β and [N II]/H α. For [S II]/H α and [O I]/H α, this applies only to redshifts greater than z = 1.5, the evolution at lower redshift being driven in roughly equal parts by nebular emission from active galactic nuclei and post-AGB stellar populations. Instead, changes in the hardness of ionizing radiation, ionized-gas density, the prevalence of BH accretion relative to star formation and the dust-to-metal mass ratio (whose impact on the gas-phase N/O ratio we model at fixed O/H) play at most a minor role in the cosmic evolution of simulated galaxy line ratios.

  14. THE PROPAGATION OF UNCERTAINTIES IN STELLAR POPULATION SYNTHESIS MODELING. II. THE CHALLENGE OF COMPARING GALAXY EVOLUTION MODELS TO OBSERVATIONS

    International Nuclear Information System (INIS)

    Conroy, Charlie; Gunn, James E.; White, Martin

    2010-01-01

    Models for the formation and evolution of galaxies readily predict physical properties such as star formation rates, metal-enrichment histories, and, increasingly, gas and dust content of synthetic galaxies. Such predictions are frequently compared to the spectral energy distributions of observed galaxies via the stellar population synthesis (SPS) technique. Substantial uncertainties in SPS exist, and yet their relevance to the task of comparing galaxy evolution models to observations has received little attention. In the present work, we begin to address this issue by investigating the importance of uncertainties in stellar evolution, the initial stellar mass function (IMF), and dust and interstellar medium (ISM) properties on the translation from models to observations. We demonstrate that these uncertainties translate into substantial uncertainties in the ultraviolet, optical, and near-infrared colors of synthetic galaxies. Aspects that carry significant uncertainties include the logarithmic slope of the IMF above 1 M sun , dust attenuation law, molecular cloud disruption timescale, clumpiness of the ISM, fraction of unobscured starlight, and treatment of advanced stages of stellar evolution including blue stragglers, the horizontal branch, and the thermally pulsating asymptotic giant branch. The interpretation of the resulting uncertainties in the derived colors is highly non-trivial because many of the uncertainties are likely systematic, and possibly correlated with the physical properties of galaxies. We therefore urge caution when comparing models to observations.

  15. Chemical evolution of Local Group dwarf galaxies in a cosmological context - I. A new modelling approach and its application to the Sculptor dwarf spheroidal galaxy

    Science.gov (United States)

    Romano, Donatella; Starkenburg, Else

    2013-09-01

    We present a new approach for chemical evolution modelling, specifically designed to investigate the chemical properties of dwarf galaxies in a full cosmological framework. In particular, we focus on the Sculptor dwarf spheroidal galaxy, for which a wealth of observational data exists, as a test bed for our model. We select four candidate Sculptor-like galaxies from the satellite galaxy catalogue generated by implementation of a version of the Munich semi-analytic model for galaxy formation on the level 2 Aquarius dark matter simulations and use the mass assembly and star formation histories predicted for these four systems as an input for the chemical evolution code. We follow explicitly the evolution of several chemical elements, both in the cold gas out of which the stars form and in the hot medium residing in the halo. We take into account in detail the lifetimes of stars of different initial masses, the distribution of the delay times for Type Ia supernova explosions and the dependence of the stellar yields from the initial metallicity of the stars. We allow large fractions of metals to be deposited into the hot phase, either directly as stars die or through reheated gas flows powered by supernova explosions. We find that, in order to reproduce both the observed metallicity distribution function and the observed abundance ratios of long-lived stars of Sculptor, large fractions of the reheated metals must never re-enter regions of active star formation. With this prescription, all the four analogues to the Sculptor dwarf spheroidal galaxy extracted from the simulated satellites catalogue on the basis of luminosity and stellar population ages are found to reasonably match the detailed chemical properties of real Sculptor stars. However, all model galaxies do severely underestimate the fraction of very metal poor stars observed in Sculptor. Our analysis thus sets further constraints on the semi-analytical models and, at large, on possible metal enrichment

  16. Further constraints on the evolution of K-s-selected galaxies in the GOODS/CDFS field

    NARCIS (Netherlands)

    Caputi, KI; McLure, RJ; Dunlop, JS; Cirasuolo, M; Schael, AM

    2006-01-01

    We have selected and analysed the properties of a sample of 2905 K-s <21.5 galaxies in similar to 131 arcmin(2) of the Great Observatories Origins Deep Survey (GOODS) Chandra Deep Field South (CDFS), to obtain further constraints on the evolution of K-s-selected galaxies with respect to the results

  17. MINOR MERGERS AND THE SIZE EVOLUTION OF ELLIPTICAL GALAXIES

    International Nuclear Information System (INIS)

    Naab, Thorsten; Johansson, Peter H.; Ostriker, Jeremiah P.

    2009-01-01

    Using a high-resolution hydrodynamical cosmological simulation of the formation of a massive spheroidal galaxy we show that elliptical galaxies can be very compact and massive at high redshift in agreement with recent observations. Accretion of stripped infalling stellar material increases the size of the system with time and the central concentration is reduced by dynamical friction of the surviving stellar cores. In a specific case of a spheroidal galaxy with a final stellar mass of 1.5 x 10 11 M sun we find that the effective radius r e increases from 0.7 ± 0.2 kpc at z = 3 to r e = 2.4 ± 0.4 kpc at z = 0 with a concomitant decrease in the effective density of an order of magnitude and a decrease of the central velocity dispersion by approximately 20% over this time interval. A simple argument based on the virial theorem shows that during the accretion of weakly bound material (minor mergers) the radius can increase as the square of the mass in contrast to the usual linear rate of increase for major mergers. By undergoing minor mergers compact high-redshift spheroids can evolve into present-day systems with sizes and concentrations similar to observed local ellipticals. This indicates that minor mergers may be the main driver for the late evolution of sizes and densities of early-type galaxies.

  18. Galaxy evolution. Black hole feedback in the luminous quasar PDS 456.

    Science.gov (United States)

    Nardini, E; Reeves, J N; Gofford, J; Harrison, F A; Risaliti, G; Braito, V; Costa, M T; Matzeu, G A; Walton, D J; Behar, E; Boggs, S E; Christensen, F E; Craig, W W; Hailey, C J; Matt, G; Miller, J M; O'Brien, P T; Stern, D; Turner, T J; Ward, M J

    2015-02-20

    The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow's kinetic power larger than 10(46) ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution. Copyright © 2015, American Association for the Advancement of Science.

  19. Quenching or Bursting: Star Formation Acceleration—A New Methodology for Tracing Galaxy Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Martin, D. Christopher; Darvish, Behnam; Seibert, Mark [California Institute of Technology, MC 405-47, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Gonçalves, Thiago S. [Observatorio do Valongo, Universidade Federal do Rio de Janeiro, Ladeira Pedro Antonio, 43, Saude, Rio de Janeiro-RJ 20080-090 (Brazil); Schiminovich, David [Department of Astronomy, Columbia University, New York, NY 10027 (United States)

    2017-06-10

    We introduce a new methodology for the direct extraction of galaxy physical parameters from multiwavelength photometry and spectroscopy. We use semianalytic models that describe galaxy evolution in the context of large-scale cosmological simulation to provide a catalog of galaxies, star formation histories, and physical parameters. We then apply models of stellar population synthesis and a simple extinction model to calculate the observable broadband fluxes and spectral indices for these galaxies. We use a linear regression analysis to relate physical parameters to observed colors and spectral indices. The result is a set of coefficients that can be used to translate observed colors and indices into stellar mass, star formation rate, and many other parameters, including the instantaneous time derivative of the star formation rate, which we denote the Star Formation Acceleration (SFA), We apply the method to a test sample of galaxies with GALEX photometry and SDSS spectroscopy, deriving relationships between stellar mass, specific star formation rate, and SFA. We find evidence for a mass-dependent SFA in the green valley, with low-mass galaxies showing greater quenching and higher-mass galaxies greater bursting. We also find evidence for an increase in average quenching in galaxies hosting an active galactic nucleus. A simple scenario in which lower-mass galaxies accrete and become satellite galaxies, having their star-forming gas tidally and/or ram-pressure stripped, while higher-mass galaxies receive this gas and react with new star formation, can qualitatively explain our results.

  20. Quenching or Bursting: Star Formation Acceleration—A New Methodology for Tracing Galaxy Evolution

    Science.gov (United States)

    Martin, D. Christopher; Gonçalves, Thiago S.; Darvish, Behnam; Seibert, Mark; Schiminovich, David

    2017-06-01

    We introduce a new methodology for the direct extraction of galaxy physical parameters from multiwavelength photometry and spectroscopy. We use semianalytic models that describe galaxy evolution in the context of large-scale cosmological simulation to provide a catalog of galaxies, star formation histories, and physical parameters. We then apply models of stellar population synthesis and a simple extinction model to calculate the observable broadband fluxes and spectral indices for these galaxies. We use a linear regression analysis to relate physical parameters to observed colors and spectral indices. The result is a set of coefficients that can be used to translate observed colors and indices into stellar mass, star formation rate, and many other parameters, including the instantaneous time derivative of the star formation rate, which we denote the Star Formation Acceleration (SFA), We apply the method to a test sample of galaxies with GALEX photometry and SDSS spectroscopy, deriving relationships between stellar mass, specific star formation rate, and SFA. We find evidence for a mass-dependent SFA in the green valley, with low-mass galaxies showing greater quenching and higher-mass galaxies greater bursting. We also find evidence for an increase in average quenching in galaxies hosting an active galactic nucleus. A simple scenario in which lower-mass galaxies accrete and become satellite galaxies, having their star-forming gas tidally and/or ram-pressure stripped, while higher-mass galaxies receive this gas and react with new star formation, can qualitatively explain our results.

  1. Quenching or Bursting: Star Formation Acceleration—A New Methodology for Tracing Galaxy Evolution

    International Nuclear Information System (INIS)

    Martin, D. Christopher; Darvish, Behnam; Seibert, Mark; Gonçalves, Thiago S.; Schiminovich, David

    2017-01-01

    We introduce a new methodology for the direct extraction of galaxy physical parameters from multiwavelength photometry and spectroscopy. We use semianalytic models that describe galaxy evolution in the context of large-scale cosmological simulation to provide a catalog of galaxies, star formation histories, and physical parameters. We then apply models of stellar population synthesis and a simple extinction model to calculate the observable broadband fluxes and spectral indices for these galaxies. We use a linear regression analysis to relate physical parameters to observed colors and spectral indices. The result is a set of coefficients that can be used to translate observed colors and indices into stellar mass, star formation rate, and many other parameters, including the instantaneous time derivative of the star formation rate, which we denote the Star Formation Acceleration (SFA), We apply the method to a test sample of galaxies with GALEX photometry and SDSS spectroscopy, deriving relationships between stellar mass, specific star formation rate, and SFA. We find evidence for a mass-dependent SFA in the green valley, with low-mass galaxies showing greater quenching and higher-mass galaxies greater bursting. We also find evidence for an increase in average quenching in galaxies hosting an active galactic nucleus. A simple scenario in which lower-mass galaxies accrete and become satellite galaxies, having their star-forming gas tidally and/or ram-pressure stripped, while higher-mass galaxies receive this gas and react with new star formation, can qualitatively explain our results.

  2. Nearby Galaxies: Templates for Galaxies Across Cosmic Time

    OpenAIRE

    Lockman, F. J.; Ott, J.

    2009-01-01

    Studies of nearby galaxies including the Milky Way have provided fundamental information on the evolution of structure in the Universe, the existence and nature of dark matter, the origin and evolution of galaxies, and the global features of star formation. Yet despite decades of work, many of the most basic aspects of galaxies and their environments remain a mystery. In this paper we describe some outstanding problems in this area and the ways in which large radio facilities will contribute ...

  3. Evolution of Gas Across Spiral Arms in the Whirlpool Galaxy

    Science.gov (United States)

    Louie, Melissa Nicole

    To investigate the dynamic evolution of gas across spiral arms, we conducted a detailed study of the gas and star formation along the spiral arms in the Whirlpool Galaxy, M51. This nearby, face-on spiral galaxy provides a unique laboratory to study the relationship between gas dynamics and star formation. The textbook picture of interstellar medium (ISM) evolution is rapidly changing. Molecular gas was once believed to form along spiral arms from the diffuse atomic gas in the inter-arm regions. Star formation occurs within giant molecular clouds during spiral arm passage. Lastly, the molecular gas is photo-dissociated back into atomic gas by massive stars on the downstream side of the spiral arm. Recent evidence, however, is revealing a new picture of the interstellar medium and the process of star formation. We seek development of a new picture by studying the development and evolution of molecular gas and the role of large scale galactic dynamics in organizing the interstellar medium. This thesis begins by presenting work measuring the geometrical offsets between interstellar gas and recent star formation. Interstellar gas is traced by atomic hydrogen and carbon monoxide (CO). Star formation is traced by ionized hydrogen recombination lines and infrared emission from dust warmed by young bright stars. Measuring these offsets can help determine the underlying large scale galactic dynamics. Along the spiral arms in M51, offsets between CO and the star formation tracers suggest that gas is flowing through the spiral arms, but the offsets do not show the expected signature of a single pattern speed and imply a more complicated pattern. This thesis also examines the intermediate stages of gas evolution, by studying a denser component of the ISM closer to which stars will form. Only a small percent of the bulk molecular gas will become dense enough to form stars. HCN and HCO+ probe densities ˜104 cm-3, where as the bulk gas is 500 cm-3. This thesis looks at HCN and

  4. The evolution of the intergalactic medium and the origin of the galaxy luminosity function

    Science.gov (United States)

    Valls-Gabaud, David; Blanchard, Alain; Mamon, Gary

    1993-01-01

    The coupling of the Press and Schechter prescription with the CDM scenario and the Hoyle-Rees-Ostriker cooling criterion leads to a galaxy formation scenario in which galaxies are overproduced by a large factor. Although star formation might be suppressed in the smaller halos, a large amount of energy per galactic mass is needed to account for the present number density of galaxies. The evolution of the intergalactic medium (IGM) provides a simple criterion to prevent galaxy formation without requiring feedback, since halos with small virial temperatures are not able to retain the infalling hot gas of the IGM. If the ionizing background has decreased since z is approximately 1 - 2, then this criterion explains the slope of the luminosity function at the faint end. In addition, this scenario predicts two populations of dwarf galaxies, well differentiated in age, gas content, stellar populations, and clustering properties, which can be identified with dE and dIm galaxies.

  5. On the Evolution of Helium in Blue Compact Galaxies

    International Nuclear Information System (INIS)

    Fields, B.D.; Olive, K.A.

    1998-01-01

    We discuss the chemical evolution of dwarf irregular and blue compact galaxies in light of recent data, new stellar yields, and chemical evolution models. We examine the abundance data for evidence of H ii region self-enrichment effects, which would lead to correlations in the scatter of helium, nitrogen, and oxygen abundances around their mean trends. The observed helium abundance trends show no such correlations, although the nitrogen-oxygen trend does show strong evidence for real scatter beyond observational error. We construct simple models for the chemical evolution of these galaxies, using the most recent yields of 4 He, C, N, and O in intermediate- and high-mass stars. The effects of galactic outflows, which can arise both from bulk heating and evaporation of the interstellar medium and from the partial escape of enriched supernova ejecta are included. In agreement with other studies, we find that supernova-enriched outflows can roughly reproduce the observed He, C, N, and O trends; however, in models that fit N versus O, the slopes ΔY/ΔO and ΔY/ΔN consistently fall more than 2 σ below the fit to observations. We discuss the role of the models and their uncertainties in the extrapolation of primordial helium from the data. We also explore the model dependence arising from nucleosynthesis uncertainties associated with nitrogen yields in intermediate-mass stars, the fate of 8 endash 11 M circle-dot stars, and massive star winds. copyright copyright 1998. The American Astronomical Society

  6. Evolution of galaxies in clusters. V. A study of populations since zapprox.0.5

    International Nuclear Information System (INIS)

    Butcher, H.; Oemler, A. Jr.

    1984-01-01

    In this paper we analyze photometry of 33 clusters of galaxies, with redshifts between 0.003 (the Virgo Cluster) and 0.54 (Cl 0016+16) to search for evolution of the colors of cluster populations. In each cluster we select these galaxies brighter than M/sub V/ = -20 which are within the circular area containing the inner 30% of the total Jupiter population. From the distribution of these galaxies in the color-magnitude plane, we determine the fraction of galaxies whose rest-frame B-V colors are at least 0.2 mag bluer than the ridge line of the early type galaxies at that magnitude. We define this to be the blue galaxy population, f/sub B/, and find it to have the following characteristics in compact, concentrated clusters: (1) For z or approx. =0.1 f/sub B/ increases with redshift reaching f/sub B/approx.0.25 at z = 0.5. (3) The values of f/sub B/ seen in clusters at a particular redshift are mostly consistent with clusters being random samples of one homogeneous galaxy population, but there is some evidence that processes within individual clusters may also affect the galaxy content

  7. Flight Calibration of the Galaxy Evolution Explorer (GALEX)

    Science.gov (United States)

    Morrissey, Patrick; GALEX Science Team

    2006-12-01

    We present current performance results for the Galaxy Evolution Explorer (GALEX), a NASA mission that is performing a survey of the sky in two ultraviolet bands. The GALEX instrument comprises a 50 cm diameter modified Ritchey-Chretien telescope with imaging and objective-grism spectroscopic modes that feed a pair of large-format microchannel-plate-intensified, delay-line readout detectors. Simultaneous 2-color imaging of the large 1.2 degree field is achieved with an innovative optical system including a thin-film multilayer dichroic beamsplitter, which complements the bandpass-defining characteristics of a Lyman-alpha blocking filter and CsI cathode in the 23 nm-wide FUV band centered at 154 nm, in parallel with a red-blocking filter and CsTe cathode in the 80 nm-wide NUV band centered at 230 nm. Flight calibration based on three years of observations has significantly improved the instrument performance, especially in the areas of astrometric accuracy, photometric precision and image resolution. GALEX continues to meet its requirements for resolution, efficiency, astrometry, bandpass definition and survey sensitivity. Hardware issues with the FUV detector are being managed successfully with impacts to mission efficiency but not data quality. We describe recent results as they pertain to the GR2 and GR3 public data releases and outline plans for further improvement. GALEX (Galaxy Evolution Explorer) is a NASA Small Explorer, launched in April 2003. We gratefully acknowledge NASA's support for construction, operation, and science analysis for the GALEX mission.

  8. Evolution in the Colors of Lyman Break Galaxies from z~4 to z~3

    Science.gov (United States)

    Papovich, Casey; Dickinson, Mark; Ferguson, Henry C.; Giavalisco, Mauro; Lotz, Jennifer; Madau, Piero; Idzi, Rafal; Kretchmer, Claudia; Moustakas, Leonidas A.; de Mello, Duilia F.; Gardner, Jonathan P.; Rieke, Marcia J.; Somerville, Rachel S.; Stern, Daniel

    2004-01-01

    The integrated colors of distant galaxies provide a means for interpreting the properties of their stellar content. Here we use rest-frame UV-to-optical colors to constrain the spectral energy distributions and stellar populations of color-selected, B-dropout galaxies at z~4 in the Great Observatories Origins Deep Survey (GOODS). We combine the Advanced Camera for Surveys data with ground-based near-infrared images, which extend the coverage of galaxies at z~4 to the rest-frame B band. We observe a color-magnitude trend in the rest-frame m(UV)-B versus B diagram for the z~4 galaxies that has a fairly well-defined ``blue envelope,'' and is strikingly similar to that of color-selected, U-dropout galaxies at z~3. We also find that although the co-moving luminosity density at rest-frame UV wavelengths (1600 Å) is roughly comparable at z~3 and ~4, the luminosity density at rest-frame optical wavelengths increases by about one-third from z~4 to ~3. Although the star formation histories of individual galaxies may involve complex and stochastic events, the evolution in the global luminosity density of the UV-bright galaxy population corresponds to an average star formation history with a star formation rate that is constant or increasing over these redshifts. This suggests that the evolution in the luminosity density corresponds to an increase in the stellar mass density of >~33%. Based on observations taken with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555, and based on observations collected at the European Southern Observatory, Chile (ESO programs 168.A-0485, 64.O-0643, 66.A-0572, and 68.A-0544).

  9. The Evolution of Dwarf-Irregular Galaxy NGC 1569: A Kinematic Study of the Stars and Gas

    Science.gov (United States)

    Johnson, Megan C.

    2011-12-01

    The evolution and formation of dwarf galaxies has great importance to our knowledge of cosmological history from the Big Bang through the present day structure we observe in our local universe. Dwarf galaxies are believed to be the "building blocks" of larger galaxies, which implies that interactions and mergers of these small systems must have occurred frequently in the early universe. There is a population of starburst dwarf irregular (dIm) galaxies that seem to have characteristics indicative of interactions or mergers. One of these dIm galaxies is the nearby post-starburst NGC 1569. This dissertation project explores the stellar and gas kinematics of NGC 1569 as well as examines a deep neutral Hydrogen (HI) map made using the Robert C. Byrd Green Bank Telescope (GBT). From these observations, this dissertation analyzes the evolution of NGC 1569 by understanding the three-dimensional shape of this dIm system for the first time. The structure of dIm galaxies is an important fundamental, physical property necessary to understand the evolution and formation of these common systems. However, the intrinsic shape of dIm galaxies remains controversial. Projected minor-to-major axis ratios provide insufficient data to determine the shapes of dIm galaxies. Fortunately, there is another method by which accurate structures can be measured. The stellar velocity dispersion, coupled with the maximum rotational velocity derived from HI observations, gives a measure of how kinematically hot a system is, and, therefore, indicates its structure. In this dissertation, we present the stellar kinematics, including the stellar velocity dispersion, of NGC 1569 obtained using the Kitt Peak National Observatory (KPNO) Mayall 4-m+Echelle spectrograph. These data are combined with an in depth analysis of high resolution HI data and a discussion of the nature of this starburst dwarf system. The dissertation concludes with a deep HI map of NGC 1569 and three of its nearest neighbors in the

  10. Galaxies and gamma-ray astronomy

    International Nuclear Information System (INIS)

    Bignami, G.F.; Fichtel, C.E.; Hartman, R.C.; Thompson, D.J.

    1979-01-01

    Comparisons between the recently measured X-ray spectra of active galaxies, the intensity upper limits to the γ-ray emission above 35 MeV from the same objects obtained from data from SAS 2, and other γ-ray data are used to address the nature of the high-energy spectra of several types of active galaxies, their contribution to the measured diffuse γ-ray emission between 1 and 150 MeV, and constraints which may be placed on cosmological evolutionary factors. It is found that a substantial increase in slope of the photon energy spectrum must occur in the low-energy γ-ray region for Seyfert galaxies, BL Lac objects, and emission line galaxies. A spectral steepening is also seen for 3C 273 and Cen A, the only quasar and radio galaxy for which accurate X-ray spectra are presently available above 20 keV. A cosmological integration shows that Seyfert galaxies, BL Lac objects, and quasars may account for most of the 1--150 MeV diffuse background, even without significant evolution. Sharp emission line galaxies and radio galaxies made a much smaller contribution under the same assumptions. The observed isotropic γ-radiation limits the γ-ray evolution possible for Seyfert galaxies, BL Lac objects, and quasars. The high-latitude galactic radiation limits the γ-ray evolution of normal field galaxies. The integrated emission of normal field galaxies with evolution back to z=4 cannot exceed about 10 times the integrated emission assuming no evolution

  11. Can cluster environment modify the dynamical evolution of spiral galaxies?

    Science.gov (United States)

    Amram, P.; Balkowski, C.; Cayatte, V.; Marcelin, M.; Sullivan, W. T., III

    1993-01-01

    Over the past decade many effects of the cluster environment on member galaxies have been established. These effects are manifest in the amount and distribution of gas in cluster spirals, the luminosity and light distributions within galaxies, and the segregation of morphological types. All these effects could indicate a specific dynamical evolution for galaxies in clusters. Nevertheless, a more direct evidence, such as a different mass distribution for spiral galaxies in clusters and in the field, is not yet clearly established. Indeed, Rubin, Whitmore, and Ford (1988) and Whitmore, Forbes, and Rubin (1988) (referred to as RWF) presented evidence that inner cluster spirals have falling rotation curves, unlike those of outer cluster spirals or the great majority of field spirals. If falling rotation curves exist in centers of clusters, as argued by RWF, it would suggest that dark matter halos were absent from cluster spirals, either because the halos had become stripped by interactions with other galaxies or with an intracluster medium, or because the halos had never formed in the first place. Even if they didn't disagree with RWF, other researchers pointed out that the behaviour of the slope of the rotation curves of spiral galaxies (in Virgo) is not so clear. Amram, using a different sample of spiral galaxies in clusters, found only 10% of declining rotation curves (2 declining vs 17 flat or rising) in opposition to RWF who find about 40% of declining rotation curves in their sample (6 declining vs 10 flat or rising), we will hereafter briefly discuss the Amram data paper and compare it to the results of RWF. We have measured the rotation curves for a sample of 21 spiral galaxies in 5 nearby clusters. These rotation curves have been constructed from detailed two-dimensional maps of each galaxy's velocity field as traced by emission from the Ha line. This complete mapping, combined with the sensitivity of our CFHT 3.60 m. + Perot-Fabry + CCD observations, allows

  12. Inferring the photometric and size evolution of galaxies from image simulations. I. Method

    Science.gov (United States)

    Carassou, Sébastien; de Lapparent, Valérie; Bertin, Emmanuel; Le Borgne, Damien

    2017-09-01

    Context. Current constraints on models of galaxy evolution rely on morphometric catalogs extracted from multi-band photometric surveys. However, these catalogs are altered by selection effects that are difficult to model, that correlate in non trivial ways, and that can lead to contradictory predictions if not taken into account carefully. Aims: To address this issue, we have developed a new approach combining parametric Bayesian indirect likelihood (pBIL) techniques and empirical modeling with realistic image simulations that reproduce a large fraction of these selection effects. This allows us to perform a direct comparison between observed and simulated images and to infer robust constraints on model parameters. Methods: We use a semi-empirical forward model to generate a distribution of mock galaxies from a set of physical parameters. These galaxies are passed through an image simulator reproducing the instrumental characteristics of any survey and are then extracted in the same way as the observed data. The discrepancy between the simulated and observed data is quantified, and minimized with a custom sampling process based on adaptive Markov chain Monte Carlo methods. Results: Using synthetic data matching most of the properties of a Canada-France-Hawaii Telescope Legacy Survey Deep field, we demonstrate the robustness and internal consistency of our approach by inferring the parameters governing the size and luminosity functions and their evolutions for different realistic populations of galaxies. We also compare the results of our approach with those obtained from the classical spectral energy distribution fitting and photometric redshift approach. Conclusions: Our pipeline infers efficiently the luminosity and size distribution and evolution parameters with a very limited number of observables (three photometric bands). When compared to SED fitting based on the same set of observables, our method yields results that are more accurate and free from

  13. DUAL SUPERMASSIVE BLACK HOLE CANDIDATES IN THE AGN AND GALAXY EVOLUTION SURVEY

    International Nuclear Information System (INIS)

    Comerford, Julia M.; Schluns, Kyle; Greene, Jenny E.; Cool, Richard J.

    2013-01-01

    Dual supermassive black holes (SMBHs) with kiloparsec-scale separations in merger-remnant galaxies are informative tracers of galaxy evolution, but the avenue for identifying them in large numbers for such studies is not yet clear. One promising approach is to target spectroscopic signatures of systems where both SMBHs are fueled as dual active galactic nuclei (AGNs), or where one SMBH is fueled as an offset AGN. Dual AGNs may produce double-peaked narrow AGN emission lines, while offset AGNs may produce single-peaked narrow AGN emission lines with line-of-sight velocity offsets relative to the host galaxy. We search for such dual and offset systems among 173 Type 2 AGNs at z +3.6 -1.9 % to 18 +5 -5 %). This may be associated with the rise in the galaxy merger fraction over the same cosmic time. As further evidence for a link with galaxy mergers, the AGES offset and dual AGN candidates are tentatively ∼3 times more likely than the overall AGN population to reside in a host galaxy that has a companion galaxy (from 16/173 to 2/7, or 9 +3 -2 % to 29 -19 +26 %). Follow-up observations of the seven offset and dual AGN candidates in AGES will definitively distinguish velocity offsets produced by dual SMBHs from those produced by narrow-line region kinematics, and will help sharpen our observational approach to detecting dual SMBHs

  14. Exploring the luminosity evolution and stellar mass assembly of 2SLAQ luminous red galaxies between redshifts 0.4 and 0.8

    Science.gov (United States)

    Banerji, Manda; Ferreras, Ignacio; Abdalla, Filipe B.; Hewett, Paul; Lahav, Ofer

    2010-03-01

    We present an analysis of the evolution of 8625 luminous red galaxies (LRGs) between z = 0.4 and 0.8 in the 2dF and Sloan Digital Sky Survey LRG and QSO (2SLAQ) survey. The LRGs are split into redshift bins and the evolution of both the luminosity and stellar mass function with redshift is considered and compared to the assumptions of a passive evolution scenario. We draw attention to several sources of systematic error that could bias the evolutionary predictions made in this paper. While the inferred evolution is found to be relatively unaffected by the exact choice of spectral evolution model used to compute K + e corrections, we conclude that photometric errors could be a source of significant bias in colour-selected samples such as this, in particular when using parametric maximum likelihood based estimators. We find that the evolution of the most massive LRGs is consistent with the assumptions of passive evolution and that the stellar mass assembly of the LRGs is largely complete by z ~ 0.8. Our findings suggest that massive galaxies with stellar masses above 1011Msolar must have undergone merging and star formation processes at a very early stage (z >~ 1). This supports the emerging picture of downsizing in both the star formation as well as the mass assembly of early-type galaxies. Given that our spectroscopic sample covers an unprecedentedly large volume and probes the most massive end of the galaxy mass function, we find that these observational results present a significant challenge for many current models of galaxy formation.

  15. EVOLUTION OF QUIESCENT AND STAR-FORMING GALAXIES SINCE z ∼ 1.5 AS A FUNCTION OF THEIR VELOCITY DISPERSIONS

    International Nuclear Information System (INIS)

    Bezanson, Rachel; Van Dokkum, Pieter; Franx, Marijn

    2012-01-01

    We measure stellar masses and structural parameters for 5500 quiescent and 20,000 star-forming galaxies at 0.3 < z ≤ 1.5 in the Newfirm Medium Band Survey COSMOS and UKIDSS UDS fields. We combine these measurements to infer velocity dispersions and determine how the number density of galaxies at fixed inferred dispersion, or the velocity dispersion function (VDF), evolves with time for each population. We show that the number of galaxies with high velocity dispersions appears to be surprisingly stable with time, regardless of their star formation history. Furthermore, the overall VDF for star-forming galaxies is constant with redshift, extending down to the lowest velocity dispersions probed by this study. The only galaxy population showing strong evolution are quiescent galaxies with low inferred dispersions, whose number density increases by a factor of ∼4 since z = 1.5. This buildup leads to an evolution in the quiescent fraction of galaxies such that the threshold dispersion above which quiescent galaxies dominate the counts moves to lower velocity dispersion with time. We show that our results are qualitatively consistent with a simple model in which star-forming galaxies quench and are added to the quiescent population. In order to compensate for the migration into the quiescent population, the velocity dispersions of star-forming galaxies must increase, with a rate that increases with dispersion.

  16. Evolution of the UV upturn in cluster galaxies: Abell 1689

    Science.gov (United States)

    Ali, S. S.; Bremer, M. N.; Phillipps, S.; De Propris, R.

    2018-05-01

    We have measured the strength of the UV upturn for red sequence galaxies in the Abell 1689 cluster at z = 0.18, reaching to or below the L* level and therefore probing the general evolution of the upturn phenomenon. We find that the range of UV upturn strengths in the population as a whole has not declined over the past 2.2 Gyrs. This is consistent with a model where hot horizontal branch stars, produced by a Helium-enriched population, provide the required UV flux. Based on local counterparts, this interpretation of the result implies Helium abundances of at least 1.5 times the primordial value for this HB population, along with high formation and assembly redshifts for the galaxies and at least a subset of their stellar populations.

  17. Evolution of the Stellar Mass–Metallicity Relation. I. Galaxies in the z ∼ 0.4 Cluster Cl0024

    Science.gov (United States)

    Leethochawalit, Nicha; Kirby, Evan N.; Moran, Sean M.; Ellis, Richard S.; Treu, Tommaso

    2018-03-01

    We present the stellar mass–stellar metallicity relationship (MZR) in the galaxy cluster Cl0024+1654 at z ∼ 0.4 using full-spectrum stellar population synthesis modeling of individual quiescent galaxies. The lower limit of our stellar mass range is M * = 109.7 M ⊙, the lowest galaxy mass at which individual stellar metallicity has been measured beyond the local universe. We report a detection of an evolution of the stellar MZR with observed redshift at 0.037 ± 0.007 dex per Gyr, consistent with the predictions from hydrodynamical simulations. Additionally, we find that the evolution of the stellar MZR with observed redshift can be explained by an evolution of the stellar MZR with the formation time of galaxies, i.e., when the single stellar population (SSP)-equivalent ages of galaxies are taken into account. This behavior is consistent with stars forming out of gas that also has an MZR with a normalization that decreases with redshift. Lastly, we find that over the observed mass range, the MZR can be described by a linear function with a shallow slope ([{Fe}/{{H}}]\\propto (0.16+/- 0.03){log}{M}* ). The slope suggests that galaxy feedback, in terms of mass-loading factor, might be mass-independent over the observed mass and redshift range.

  18. Molecules as tracers of galaxy evolution : an EMIR survey I. Presentation of the data and first results

    NARCIS (Netherlands)

    Costagliola, F.; Aalto, S.; Rodriguez, M. I.; Muller, S.; Spoon, H. W. W.; Martin, S.; Perez-Torres, M. A.; Alberdi, A.; Lindberg, J. E.; Batejat, F.; Juette, E.; Lahuis, F.; van der Werf, Paul P.

    Aims. We investigate the molecular gas properties of a sample of 23 galaxies in order to find and test chemical signatures of galaxy evolution and to compare them to IR evolutionary tracers. Methods. Observation at 3 mm wavelengths were obtained with the EMIR broadband receiver, mounted on the IRAM

  19. Comparing Simulations and Observations of Galaxy Evolution: Methods for Constraining the Nature of Stellar Feedback

    Science.gov (United States)

    Hummels, Cameron

    Computational hydrodynamical simulations are a very useful tool for understanding how galaxies form and evolve over cosmological timescales not easily revealed through observations. However, they are only useful if they reproduce the sorts of galaxies that we see in the real universe. One of the ways in which simulations of this sort tend to fail is in the prescription of stellar feedback, the process by which nascent stars return material and energy to their immediate environments. Careful treatment of this interaction in subgrid models, so-called because they operate on scales below the resolution of the simulation, is crucial for the development of realistic galaxy models. Equally important is developing effective methods for comparing simulation data against observations to ensure galaxy models which mimic reality and inform us about natural phenomena. This thesis examines the formation and evolution of galaxies and the observable characteristics of the resulting systems. We employ extensive use of cosmological hydrodynamical simulations in order to simulate and interpret the evolution of massive spiral galaxies like our own Milky Way. First, we create a method for producing synthetic photometric images of grid-based hydrodynamical models for use in a direct comparison against observations in a variety of filter bands. We apply this method to a simulation of a cluster of galaxies to investigate the nature of the red-sequence/blue-cloud dichotomy in the galaxy color-magnitude diagram. Second, we implement several subgrid models governing the complex behavior of gas and stars on small scales in our galaxy models. Several numerical simulations are conducted with similar initial conditions, where we systematically vary the subgrid models, afterward assessing their efficacy through comparisons of their internal kinematics with observed systems. Third, we generate an additional method to compare observations with simulations, focusing on the tenuous circumgalactic

  20. THE CFHTLS-DEEP CATALOG OF INTERACTING GALAXIES. I. MERGER RATE EVOLUTION TO z = 1.2

    International Nuclear Information System (INIS)

    Bridge, C. R.; Carlberg, R. G.; Sullivan, M.

    2010-01-01

    We present the rest-frame optical galaxy merger fraction between 0.2 vega ≤ 22.2 (∼27,000 galaxies) over 2 square degrees, we have compiled the CFHTLS-Deep Catalog of Interacting Galaxies, with ∼ 1600 merging galaxies. We find the merger fraction to be 4.3% ± 0.3% at z ∼ 0.3 and 19.0% ± 2.5% at z ∼ 1, implying evolution of the merger fraction going as (1 + z) m , with m = 2.25 ± 0.24. This result is inconsistent with a mild or non-evolving (m 4σ level of confidence. A mild trend, where by massive galaxies with M * >10 10.7 M sun are undergoing fewer mergers than less massive systems (M * ∼ 10 10 M sun ), consistent with the expectations of galaxy assembly downsizing is observed. Our results also show that interacting galaxies have on average SFRs double that found in non-interacting field galaxies. We conclude that (1) the optical galaxy merger fraction does evolve with redshift, (2) the merger fraction depends mildly on stellar mass, with lower mass galaxies having higher merger fractions at z < 1, and (3) star formation is triggered at all phases of a merger, with larger enhancements at later stages, consistent with N-body simulations.

  1. Active galactic nuclei and their role in galaxy evolution : The infrared perspective

    NARCIS (Netherlands)

    Caputi, K. I.

    The remarkable progress made in infrared (IR) astronomical instruments over the last 10-15 years has radically changed our vision of the extragalactic IR sky, and overall understanding of galaxy evolution. In particular, this has been the case for the study of active galactic nuclei (AGN), for which

  2. RADIAL DISTRIBUTION OF STARS, GAS, AND DUST IN SINGS GALAXIES. III. MODELING THE EVOLUTION OF THE STELLAR COMPONENT IN GALAXY DISKS

    International Nuclear Information System (INIS)

    Munoz-Mateos, J. C.; Boissier, S.; Gil de Paz, A.; Zamorano, J.; Gallego, J.; Kennicutt, R. C. Jr; Moustakas, J.; Prantzos, N.

    2011-01-01

    We analyze the evolution of 42 spiral galaxies in the Spitzer Infrared Nearby Galaxies Survey. We make use of ultraviolet (UV), optical, and near-infrared radial profiles, corrected for internal extinction using the total-infrared to UV ratio, to probe the emission of stellar populations of different ages as a function of galactocentric distance. We fit these radial profiles with models that describe the chemical and spectro-photometric evolution of spiral disks within a self-consistent framework. These backward evolutionary models successfully reproduce the multi-wavelength profiles of our galaxies, except for the UV profiles of some early-type disks for which the models seem to retain too much gas. From the model fitting we infer the maximum circular velocity of the rotation curve V C and the dimensionless spin parameter λ. The values of V C are in good agreement with the velocities measured in H I rotation curves. Even though our sample is not volume limited, the resulting distribution of λ is close to the lognormal function obtained in cosmological N-body simulations, peaking at λ ∼ 0.03 regardless of the total halo mass. We do not find any evident trend between λ and Hubble type, besides an increase in the scatter for the latest types. According to the model, galaxies evolve along a roughly constant mass-size relation, increasing their scale lengths as they become more massive. The radial scale length of most disks in our sample seems to have increased at a rate of 0.05-0.06 kpc Gyr -1 , although the same cannot be said of a volume-limited sample. In relative terms, the scale length has grown by 20%-25% since z = 1 and, unlike the former figure, we argue that this relative growth rate can be indeed representative of a complete galaxy sample.

  3. Radial Distribution of Stars, Gas, and Dust in SINGS Galaxies. III. Modeling the Evolution of the Stellar Component in Galaxy Disks

    Science.gov (United States)

    Muñoz-Mateos, J. C.; Boissier, S.; Gil de Paz, A.; Zamorano, J.; Kennicutt, R. C., Jr.; Moustakas, J.; Prantzos, N.; Gallego, J.

    2011-04-01

    We analyze the evolution of 42 spiral galaxies in the Spitzer Infrared Nearby Galaxies Survey. We make use of ultraviolet (UV), optical, and near-infrared radial profiles, corrected for internal extinction using the total-infrared to UV ratio, to probe the emission of stellar populations of different ages as a function of galactocentric distance. We fit these radial profiles with models that describe the chemical and spectro-photometric evolution of spiral disks within a self-consistent framework. These backward evolutionary models successfully reproduce the multi-wavelength profiles of our galaxies, except for the UV profiles of some early-type disks for which the models seem to retain too much gas. From the model fitting we infer the maximum circular velocity of the rotation curve V C and the dimensionless spin parameter λ. The values of V C are in good agreement with the velocities measured in H I rotation curves. Even though our sample is not volume limited, the resulting distribution of λ is close to the lognormal function obtained in cosmological N-body simulations, peaking at λ ~ 0.03 regardless of the total halo mass. We do not find any evident trend between λ and Hubble type, besides an increase in the scatter for the latest types. According to the model, galaxies evolve along a roughly constant mass-size relation, increasing their scale lengths as they become more massive. The radial scale length of most disks in our sample seems to have increased at a rate of 0.05-0.06 kpc Gyr-1, although the same cannot be said of a volume-limited sample. In relative terms, the scale length has grown by 20%-25% since z = 1 and, unlike the former figure, we argue that this relative growth rate can be indeed representative of a complete galaxy sample.

  4. The effects of the initial mass function on the chemical evolution of elliptical galaxies

    Science.gov (United States)

    De Masi, Carlo; Matteucci, F.; Vincenzo, F.

    2018-03-01

    We describe the use of our chemical evolution model to reproduce the abundance patterns observed in a catalogue of elliptical galaxies from the Sloan Digital Sky Survey Data Release 4. The model assumes ellipticals form by fast gas accretion, and suffer a strong burst of star formation followed by a galactic wind, which quenches star formation. Models with fixed initial mass function (IMF) failed in simultaneously reproducing the observed trends with the galactic mass. So, we tested a varying IMF; contrary to the diffused claim that the IMF should become bottom heavier in more massive galaxies, we find a better agreement with data by assuming an inverse trend, where the IMF goes from being bottom heavy in less massive galaxies to top heavy in more massive ones. This naturally produces a downsizing in star formation, favouring massive stars in largest galaxies. Finally, we tested the use of the integrated Galactic IMF, obtained by averaging the canonical IMF over the mass distribution function of the clusters where star formation is assumed to take place. We combined two prescriptions, valid for different SFR regimes, to obtain the Integrated Initial Mass Function values along the whole evolution of the galaxies in our models. Predicted abundance trends reproduce the observed slopes, but they have an offset relative to the data. We conclude that bottom-heavier IMFs do not reproduce the properties of the most massive ellipticals, at variance with previous suggestions. On the other hand, an IMF varying with galactic mass from bottom heavier to top heavier should be preferred.

  5. The Metallicity of Void Dwarf Galaxies

    Science.gov (United States)

    Kreckel, K.; Croxall, K.; Groves, B.; van de Weygaert, R.; Pogge, R. W.

    2015-01-01

    The current ΛCDM cosmological model predicts that galaxy evolution proceeds more slowly in lower density environments, suggesting that voids are a prime location to search for relatively pristine galaxies that are representative of the building blocks of early massive galaxies. To test the assumption that void galaxies are more pristine, we compare the evolutionary properties of a sample of dwarf galaxies selected specifically to lie in voids with a sample of similar isolated dwarf galaxies in average density environments. We measure gas-phase oxygen abundances and gas fractions for eight dwarf galaxies (Mr > -16.2), carefully selected to reside within the lowest density environments of seven voids, and apply the same calibrations to existing samples of isolated dwarf galaxies. We find no significant difference between these void dwarf galaxies and the isolated dwarf galaxies, suggesting that dwarf galaxy chemical evolution proceeds independent of the large-scale environment. While this sample is too small to draw strong conclusions, it suggests that external gas accretion is playing a limited role in the chemical evolution of these systems, and that this evolution is instead dominated mainly by the internal secular processes that are linking the simultaneous growth and enrichment of these galaxies.

  6. THE POTENTIAL IMPORTANCE OF BINARY EVOLUTION IN ULTRAVIOLET-OPTICAL SPECTRAL FITTING OF EARLY-TYPE GALAXIES

    International Nuclear Information System (INIS)

    Li, Zhongmu; Mao, Caiyan; Chen, Li; Zhang, Qian; Li, Maocai

    2013-01-01

    Most galaxies possibly contain some binaries, and more than half of Galactic hot subdwarf stars, which are thought to be a possible origin of the UV-upturn of old stellar populations, are found in binaries. However, the effect of binary evolution has not been taken into account in most works on the spectral fitting of galaxies. This paper studies the role of binary evolution in the spectral fitting of early-type galaxies, via a stellar population synthesis model including both single and binary star populations. Spectra from ultraviolet to optical bands are fitted to determine a few galaxy parameters. The results show that the inclusion of binaries in stellar population models may lead to obvious change in the determination of some parameters of early-type galaxies and therefore it is potentially important for spectral studies. In particular, the ages of young components of composite stellar populations become much older when using binary star population models instead of single star population models. This implies that binary star population models will measure significantly different star formation histories for early-type galaxies compared to single star population models. In addition, stellar population models with binary interactions on average measure larger dust extinctions than single star population models. This suggests that when binary star population models are used, negative extinctions are possibly no longer necessary in the spectral fitting of galaxies (see previous works, e.g., Cid Fernandes et al. for comparison). Furthermore, it is shown that optical spectra have strong constraints on stellar age while UV spectra have strong constraints on binary fraction. Finally, our results suggest that binary star population models can provide new insight into the stellar properties of globular clusters

  7. Evolution of star systems supplied by external stars: a model for Galaxy nuclei

    International Nuclear Information System (INIS)

    Dokuchaev, V.I.; Ozernoj, L.M.; AN SSSR, Moscow. Inst. Yadernykh Issledovanij)

    1985-01-01

    Extended rarefied environments around the core of a non-isothermic galaxy nucleus can supply the core by both energies and masses of external stars due to relaxation mechanisms. These factors can influence considerably the secular evolution of the core when competing with usual star evaporation from it. Conditions are found under which external environments influence the core evolution much more than star evaporation. This results in expansion of the core instead of its collapse

  8. The Munich Near-Infrared Cluster Survey - IX. Galaxy evolution to z ~ 2 from optically selected catalogues†‡

    Science.gov (United States)

    Feulner, Georg; Goranova, Yuliana; Hopp, Ulrich; Gabasch, Armin; Bender, Ralf; Botzler, Christine S.; Drory, Niv

    2007-06-01

    We present B-, R- and I-band-selected galaxy catalogues based on the Munich Near-Infrared Cluster Survey (MUNICS) which, together with the previously used K-selected sample, serve as an important probe of galaxy evolution in the redshift range 0 Karl-Schwarzschild Strasse 2, D-85748, Garching bei München, Germany.

  9. Star formation and galactic evolution. I. General expressions and applications to our galaxy

    International Nuclear Information System (INIS)

    Kaufman, M.

    1979-01-01

    The study of galactic evolution involves three mechanisms for triggering star formation in interstellar clouds: (i) star formation triggered by a galactic spiral density wave, (ii) star formation triggered by shock waves from supernovae, and (iii) star formation triggered by an expanding H II region. Useful analytic approximations to the birthrate per unit mass are obtained by treating the efficiencies of these various mechanisms as time independent. In situations where shock waves from high-mass stars (either expanding H II regions or supernova explosions) are the only important star-forming mechanisms, the birthrate is exponential in time. This case is appropriate for the past evolution of an elliptical galaxy, nuclear bulge, or galactic halo. In the disk of a spiral galaxy where all three mechanisms operate, the birthrate consists of an exponential term plus a time-independent term. In both situations, the value of the time constant T in the exponential term is directly related to the efficiency of the shock waves from massive stars in initiating star formation.For our Galaxy, this simplified model is used to compute the radial distributions of young objects and low-mass stars in the disk, and the past and present birthrates in the solar-neighborhood shell

  10. Tidal interaction of galaxies

    International Nuclear Information System (INIS)

    Kozlov, N.N.; Syunyaev, R.A.; Ehneev, T.M.

    1974-01-01

    One of the hypotheses explaining the occurrence of anomalous details in interacting galaxies has been investigated. Pairs of galaxies with 'tails' oppositely directed or neighbouring galaxies with cofferdams 'bridges', as if connecting the galaxies, are called interacting galaxies. The hypothesis connects the origin of cofferdams and 'tails' of interacting galaxies with tidal effects ; the action of power gravitational forces in the intergalactic space. A source of such forces may be neighbouring stellar systems or invisible bodies, for instance, 'dead' quasars after a gravitational collapse. The effect of large masses of matter on the galaxy evolution has been investigated in the Institute of Applied Mathematics of the Academy of Sciences of the USSSR in 1971-1972 by numerical simulation of the process on a digital computer with the subsequent data transmission on a display. Different versions of a massive body flight relative to a galaxy disk are considered. Photographs of a display screen at different moments of time are presented. As a result of mathematical simulation of galaxies gravitational interactions effects are discovered which resemble real structures in photographs of galaxies. It seems to be premature to state that namely these mechanisms cause the formation of 'tails' and cofferdams between galaxies. However, even now it is clear that the gravitational interaction strongly affects the dynamics of the stellar system evolution. Further studies should ascertain a true scale of this effect and its genuine role in galaxy evolution

  11. Evolution of Galaxy Luminosity and Stellar-Mass Functions since $z=1$ with the Dark Energy Survey Science Verification Data

    Energy Technology Data Exchange (ETDEWEB)

    Capozzi, D.; et al.

    2017-07-27

    We present the first study of the evolution of the galaxy luminosity and stellar-mass functions (GLF and GSMF) carried out by the Dark Energy Survey (DES). We describe the COMMODORE galaxy catalogue selected from Science Verification images. This catalogue is made of $\\sim 4\\times 10^{6}$ galaxies at $0galaxy catalogues and they enable us to study the evolution of GLF and GSMF at $0galaxies build up their masses over cosmic time. We find that both the ${\\it i}$-band galaxy luminosity and stellar mass functions are characterised by a double-Schechter shape at $z<0.2$. Both functions agree well with those based on spectroscopic redshifts. The DES GSMF agrees especially with those measured for the GAlaxy Mass Assembly and the PRism MUlti-object Survey out to $z\\sim1$. At $0.2galaxies have less stellar mass, their luminosities do not change substantially because of their younger and brighter stellar populations. Finally, we also find evidence for a top-down mass-dependent evolution of the GSMF.

  12. CANDELS: THE EVOLUTION OF GALAXY REST-FRAME ULTRAVIOLET COLORS FROM z = 8 TO 4

    International Nuclear Information System (INIS)

    Finkelstein, Steven L.; Papovich, Casey; Salmon, Brett; Bassett, Robert; Finlator, Kristian; Dickinson, Mark; Ferguson, Henry C.; Koekemoer, Anton M.; Grogin, Norman A.; Giavalisco, Mauro; Reddy, Naveen A.; Mobasher, Bahram; Conselice, Christopher J.; Dunlop, James S.; McLure, Ross J.; Faber, S. M.; Kocevski, Dale D.; Lai, Kamson; Hathi, Nimish P.; Lee, Kyoung-Soo

    2012-01-01

    We study the evolution of galaxy rest-frame ultraviolet (UV) colors in the epoch 4 ∼ 3.5, including 113 at z ≅ 7-8. We fit the observed spectral energy distribution to a suite of synthetic stellar population models and measure the value of the UV spectral slope (β) from the best-fit model spectrum. We run simulations to show that this measurement technique results in a smaller scatter on β than other methods, as well as a reduced number of galaxies with catastrophically incorrect β measurements (i.e., Δβ > 1). We find that the median value of β evolves significantly from –1.82 +0.00 –0.04 at z = 4 to –2.37 +0.26 –0.06 at z = 7. Additionally, we find that faint galaxies at z = 7 have β –2.68 +0.39 –0.24 (∼ –2.4 after correcting for observational bias); this is redder than previous claims in the literature and does not require 'exotic' stellar populations (e.g., very low metallicities or top-heavy initial mass functions) to explain their colors. This evolution can be explained by an increase in dust extinction, from low amounts at z = 7 to A V ∼ 0.5 mag at z = 4. The timescale for this increase is consistent with low-mass asymptotic giant branch stars forming the bulk of the dust. We find no significant ( UV when measuring M UV at a consistent rest-frame wavelength of 1500 Å. This is particularly true at bright magnitudes, though our results do show evidence for a weak correlation at faint magnitudes when galaxies in the HUDF are considered separately, hinting that dynamic range in sample luminosities may play a role. We do find a strong correlation between β and the stellar mass at all redshifts, in that more massive galaxies exhibit redder colors. The most massive galaxies in our sample have similarly red colors at each redshift, implying that dust can build up quickly in massive galaxies and that feedback is likely removing dust from low-mass galaxies at z ≥ 7. Thus, the stellar-mass—metallicity relation, previously observed up

  13. A PHYSICAL MODEL FOR THE 0 {approx}< z {approx}< 8 REDSHIFT EVOLUTION OF THE GALAXY ULTRAVIOLET LUMINOSITY AND STELLAR MASS FUNCTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Tacchella, Sandro; Carollo, C. Marcella [Department of Physics, Institute for Astronomy, ETH Zurich, CH-8093 Zurich (Switzerland); Trenti, Michele, E-mail: tasandro@phys.ethz.ch [Kavli Institute for Cosmology and Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom)

    2013-05-10

    We present a model to understand the redshift evolution of the UV luminosity and stellar mass functions of Lyman break galaxies. Our approach is based on the assumption that the luminosity and stellar mass of a galaxy is related to its dark-matter (DM) halo assembly and gas infall rate. Specifically, galaxies experience a burst of star formation at the halo assembly time, followed by a constant star formation rate, representing a secular star formation activity sustained by steady gas accretion. Star formation from steady gas accretion is the dominant contribution to the galaxy UV luminosity at all redshifts. The model is calibrated by constructing a galaxy luminosity versus halo mass relation at z = 4 via abundance matching. After this luminosity calibration, the model naturally fits the z = 4 stellar mass function, and correctly predicts the evolution of both luminosity and stellar mass functions from z = 0 to z = 8. While the details of star formation efficiency and feedback are hidden within our calibrated luminosity versus halo mass relation, our study highlights that the primary driver of galaxy evolution across cosmic time is the buildup of DM halos, without the need to invoke a redshift-dependent efficiency in converting gas into stars.

  14. Colors and the evolution of amorphous galaxies

    International Nuclear Information System (INIS)

    Gallagher, J.S. III; Hunter, D.A.

    1987-01-01

    UBVRI and H-alpha photometric observations are presented for 16 amorphous galaxies and a comparison sample of Magellanic irregular (Im) and Sc spiral galaxies. These data are analyzed in terms of star-formation rates and histories in amorphous galaxies. Amorphous galaxies have mean global colors and star-formation rates per unit area that are similar to those in giant Im systems, despite differences in spatial distributions of star-forming centers in these two galactic structural classes. Amorphous galaxies differ from giant Im systems in having somewhat wider scatter in relationships between B - V and U - B colors, and between U - B and L(H-alpha)/L(B). This scatter is interpreted as resulting from rapid variations in star-formation rates during the recent past, which could be a natural consequence of the concentration of star-forming activity into centrally located, supergiant young stellar complexes in many amorphous galaxies. While the unusual spatial distribution and intensity of star formation in some amorphous galaxies is due to interactions with other galaxies, several amorphous galaxies are relatively isolated and thus the processes must be internal. The ultimate evolutionary fate of rapidly evolving amorphous galaxies remains unknown. 77 references

  15. An integral constraint for the evolution of the galaxy two-point correlation function

    International Nuclear Information System (INIS)

    Peebles, P.J.E.; Groth, E.J.

    1976-01-01

    Under some conditions an integral over the galaxy two-point correlation function, xi(x,t), evolves with the expansion of the universe in a simple manner easily computed from linear perturbation theory.This provides a useful constraint on the possible evolution of xi(x,t) itself. We test the integral constraint with both an analytic model and numerical N-body simulations for the evolution of irregularities in an expanding universe. Some applications are discussed. (orig.) [de

  16. Cosmic Star Formation History and Evolution of the Galaxy UV Luminosity Function for z < 1

    Science.gov (United States)

    Zhang, Keming; Schiminovich, David

    2018-01-01

    We present the latest constraints on the evolution of the far-ultraviolet luminosity function of galaxies (1500 Å, UVLF hereafter) for 0 NSA, GAMA, VIPERS, and COSMOS photo-z. Our final sample consists of ~170000 galaxies, which represents the largest sample used in such studies. By integrating wide NSA and GAMA data and deep VIPERS and COSMOS photo-z data, we have been able to constrain both the bright end and the faint end of the luminosity function with high accuracy over the entire redshift range. We fit a Schechter function to our measurements of the UVLF, both to parameterize its evolution, and to integrate for SFR densities. From z~1 to z~0, the characteristic absolute magnitude of the UVLF increases linearly by ~1.5 magnitudes, while the faint end slope remains shallow (alpha < 1.5). However, the Schechter function fit exhibits an excess of galaxies at the bright end, which is accounted for by contributions from AGN. We also describe our methodology, which can be applied more generally to any combination of wide-shallow and deep-narrow surveys.

  17. THE EVOLUTION OF THE STAR FORMATION RATE OF GALAXIES AT 0.0 ≤ z ≤ 1.2

    International Nuclear Information System (INIS)

    Rujopakarn, Wiphu; Eisenstein, Daniel J.; Rieke, George H.; Rieke, Marcia J.; Papovich, Casey; Cool, Richard J.; Moustakas, John; Jannuzi, Buell T.; Dey, Arjun; Kochanek, Christopher S.; Eisenhardt, Peter; Murray, Steve S.; Brown, Michael J. I.; Le Floc'h, Emeric

    2010-01-01

    We present the 24 μm rest-frame luminosity function (LF) of star-forming galaxies in the redshift range 0.0 ≤ z ≤ 0.6 constructed from 4047 spectroscopic redshifts from the AGN and Galaxy Evolution Survey of 24 μm selected sources in the Booetes field of the NOAO Deep Wide-Field Survey. This sample provides the best available combination of large area (9 deg 2 ), depth, and statistically complete spectroscopic observations, allowing us to probe the evolution of the 24 μm LF of galaxies at low and intermediate redshifts while minimizing the effects of cosmic variance. In order to use the observed 24 μm luminosity as a tracer for star formation, active galactic nuclei (AGNs) that could contribute significantly at 24 μm are identified and excluded from our star-forming galaxy sample based on their mid-IR spectral energy distributions or the detection of X-ray emission. Optical emission line diagnostics are considered for AGN identification, but we find that 24 μm emission from optically selected AGNs is usually from star-forming activity and therefore should not be excluded. The evolution of the 24 μm LF of star-forming galaxies for redshifts of z ≤ 0.65 is consistent with a pure luminosity evolution where the characteristic 24 μm luminosity evolves as (1 + z) 3.8±0.3 . We extend our evolutionary study to encompass 0.0 ≤ z ≤ 1.2 by combining our data with that of the Far-Infrared Deep Extragalactic Legacy Survey. Over this entire redshift range, the evolution of the characteristic 24 μm luminosity is described by a slightly shallower power law of (1 + z) 3.4±0.2 . We find a local star formation rate density of (1.09 ± 0.21) x 10 -2 M sun yr -1 Mpc -3 , and that it evolves as (1 + z) 3.5±0.2 over 0.0 ≤ z ≤ 1.2. These estimates are in good agreement with the rates using optical and UV fluxes corrected for the effects of intrinsic extinction in the observed sources. This agreement confirms that star formation at z ∼< 1.2 is robustly traced by

  18. THE STAR FORMATION HISTORY AND CHEMICAL EVOLUTION OF STAR-FORMING GALAXIES IN THE NEARBY UNIVERSE

    International Nuclear Information System (INIS)

    Torres-Papaqui, J. P.; Coziol, R.; Ortega-Minakata, R. A.; Neri-Larios, D. M.

    2012-01-01

    We have determined the metallicity (O/H) and nitrogen abundance (N/O) of a sample of 122,751 star-forming galaxies (SFGs) from the Data Release 7 of the Sloan Digital Sky Survey. For all these galaxies we have also determined their morphology and obtained a comprehensive picture of their star formation history (SFH) using the spectral synthesis code STARLIGHT. The comparison of the chemical abundance with the SFH allows us to describe the chemical evolution of the SFGs in the nearby universe (z ≤ 0.25) in a manner consistent with the formation of their stellar populations and morphologies. A high fraction (45%) of the SFGs in our sample show an excess abundance of nitrogen relative to their metallicity. We also find this excess to be accompanied by a deficiency of oxygen, which suggests that this could be the result of effective starburst winds. However, we find no difference in the mode of star formation of the nitrogen-rich and nitrogen-poor SFGs. Our analysis suggests that they all form their stars through a succession of bursts of star formation extended over a period of few Gyr. What produces the chemical differences between these galaxies seems therefore to be the intensity of the bursts: the galaxies with an excess of nitrogen are those that are presently experiencing more intense bursts or have experienced more intense bursts in their past. We also find evidence relating the chemical evolution process to the formation of the galaxies: the galaxies with an excess of nitrogen are more massive, and have more massive bulges and earlier morphologies than those showing no excess. Contrary to expectation, we find no evidence that the starburst wind efficiency decreases with the mass of the galaxies. As a possible explanation we propose that the loss of metals consistent with starburst winds took place during the formation of the galaxies, when their potential wells were still building up, and consequently were weaker than today, making starburst winds more

  19. Quasar Host Galaxies/Neptune Rotation/Galaxy Building Blocks/Hubble Deep Field/Saturn Storm

    Science.gov (United States)

    2001-01-01

    Computerized animations simulate a quasar erupting in the core of a normal spiral galaxy, the collision of two interacting galaxies, and the evolution of the universe. Hubble Space Telescope (HST) images show six quasars' host galaxies (including spirals, ellipticals, and colliding galaxies) and six clumps of galaxies approximately 11 billion light years away. A false color time lapse movie of Neptune displays the planet's 16-hour rotation, and the evolution of a storm on Saturn is seen though a video of the planet's rotation. A zoom sequence starts with a ground-based image of the constellation Ursa major and ends with the Hubble Deep Field through progressively narrower and deeper views.

  20. Combining Galaxy-Galaxy Lensing and Galaxy Clustering

    Energy Technology Data Exchange (ETDEWEB)

    Park, Youngsoo [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Krause, Elisabeth [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Dodelson, Scott [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Jain, Bhuvnesh [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Amara, Adam [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Becker, Matt [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Bridle, Sarah [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Clampitt, Joseph [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Crocce, Martin [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Honscheid, Klaus [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Gaztanaga, Enrique [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Sanchez, Carles [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Wechsler, Risa [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2015-01-01

    Combining galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth rate of large scale structure, a quantity that will shed light on the mechanism driving the acceleration of the Universe. The Dark Energy Survey (DES) is a prime candidate for such an analysis, with its measurements of both the distribution of galaxies on the sky and the tangential shears of background galaxies induced by these foreground lenses. By constructing an end-to-end analysis that combines large-scale galaxy clustering and small-scale galaxy-galaxy lensing, we also forecast the potential of a combined probes analysis on DES datasets. In particular, we develop a practical approach to a DES combined probes analysis by jointly modeling the assumptions and systematics affecting the different components of the data vector, employing a shared halo model, HOD parametrization, photometric redshift errors, and shear measurement errors. Furthermore, we study the effect of external priors on different subsets of these parameters. We conclude that DES data will provide powerful constraints on the evolution of structure growth in the universe, conservatively/ optimistically constraining the growth function to 8%/4.9% with its first-year data covering 1000 square degrees, and to 4%/2.3% with its full five-year data covering 5000 square degrees.

  1. Observational tests for the evolution of massive stars in nearby galaxies

    International Nuclear Information System (INIS)

    Leitherer, C.

    1990-01-01

    Population synthesis calculations applicable to the massive stellar content in nearby galaxies are presented. Stellar evolution calculations are combined with mass loss, model atmospheres with line blanketing, and a spectral type calibration to compute observable parameters of massive stars as a function of the star formation rate and the initial mass function slope. The number of O stars of given spectral types, the number of W-R stars, supernova rates, and fluxes of ionizing photons are predicted. Important constraints for the theories of stellar atmospheres and stellar evolution can be derived from observations if stellar number counts and ionizing flux data are available. 94 refs

  2. Evolution of the mass-metallicity relations in passive and star-forming galaxies from SPH-cosmological simulations

    DEFF Research Database (Denmark)

    Velonà, A. D Romeo; Sommer-Larsen, J.; Napolitano, N. R.

    2013-01-01

    at high redshift, whose scatter increases with time alongside the consolidation of the passive sequence. We also confirm the anti-correlation between sSFR and stellar mass, pointing at a key role of the former in determining the galaxy downsizing, as the most significant means of diagnostics of the star...... formation efficiency. Likewise, an anti-correlation between sSFR and metallicity can be established for the SF galaxies, while on the contrary more active galaxies in terms of simple SFR are also metal-richer. Finally, the [O/Fe] abundance ratio is presented too: we report a strong increasing evolution...

  3. RED NUGGETS AT HIGH REDSHIFT: STRUCTURAL EVOLUTION OF QUIESCENT GALAXIES OVER 10 Gyr OF COSMIC HISTORY

    International Nuclear Information System (INIS)

    Damjanov, Ivana; Abraham, Roberto G.; Carlberg, Raymond G.; Mentuch, Erin; Glazebrook, Karl; Caris, Evelyn; Green, Andrew W.; McCarthy, Patrick J.; Chen, Hsiao-Wen; Crampton, David; Murowinski, Richard; Joergensen, Inger; Roth, Kathy; Juneau, Stephanie; Le Borgne, Damien; Marzke, Ronald O.; Savaglio, Sandra; Yan Haojing

    2011-01-01

    We present an analysis of the size growth seen in early-type galaxies over 10 Gyr of cosmic time. Our analysis is based on a homogeneous synthesis of published data from 16 spectroscopic surveys observed at similar spatial resolution, augmented by new measurements for galaxies in the Gemini Deep Deep Survey. In total, our sample contains structural data for 465 galaxies (mainly early-type) in the redshift range 0.2 e ∝(1 + z) -1.62±0.34 . Surprisingly, this power law seems to be in good agreement with the recently reported continuous size evolution of UV-bright galaxies in the redshift range z ∼ 0.5-3.5. It is also in accordance with the predictions from recent theoretical models.

  4. Dust Evolution in Galaxy Cluster Simulations

    Science.gov (United States)

    Gjergo, Eda; Granato, Gian Luigi; Murante, Giuseppe; Ragone-Figueroa, Cinthia; Tornatore, Luca; Borgani, Stefano

    2018-06-01

    We implement a state-of-the-art treatment of the processes affecting the production and Interstellar Medium (ISM) evolution of carbonaceous and silicate dust grains within SPH simulations. We trace the dust grain size distribution by means of a two-size approximation. We test our method on zoom-in simulations of four massive (M200 ≥ 3 × 1014M⊙) galaxy clusters. We predict that during the early stages of assembly of the cluster at z ≳ 3, where the star formation activity is at its maximum in our simulations, the proto-cluster regions are rich in dusty gas. Compared to the case in which only dust production in stellar ejecta is active, if we include processes occurring in the cold ISM,the dust content is enhanced by a factor 2 - 3. However, the dust properties in this stage turn out to be significantly different from those observationally derived for the average Milky Way dust, and commonly adopted in calculations of dust reprocessing. We show that these differences may have a strong impact on the predicted spectral energy distributions. At low redshift in star forming regions our model reproduces reasonably well the trend of dust abundances over metallicity as observed in local galaxies. However we under-produce by a factor of 2 to 3 the total dust content of clusters estimated observationally at low redshift, z ≲ 0.5 using IRAS, Planck and Herschel satellites data. This discrepancy does not subsist by assuming a lower sputtering efficiency, which erodes dust grains in the hot Intracluster Medium (ICM).

  5. Evolution of the major merger galaxy pair fraction at z < 1

    Energy Technology Data Exchange (ETDEWEB)

    Keenan, R. C.; Hsieh, B. C.; Lin, L.; Chou, R. C. Y.; Huang, S.; Lin, J. H.; Chang, K. H. [Academia Sinica Institute for Astronomy and Astrophysics, Taipei, Taiwan (China); Foucaud, S. [Shanghai Jiao Tong University, Shanghai (China); De Propris, R. [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Turku (Finland)

    2014-11-10

    We present a study of the largest available sample of near-infrared selected (i.e., stellar mass selected) dynamically close pairs of galaxies at low redshifts (z < 0.3). We combine this sample with new estimates of the major merger pair fraction for stellar mass selected galaxies at z < 0.8, from the Red Sequence Cluster Survey (RCS1). We construct our low-redshift K-band selected sample using photometry from the UKIRT Infrared Deep Sky Survey and the Two Micron All Sky Survey (2MASS) in the K band (∼2.2 μm). Combined with all available spectroscopy, our K-band selected sample contains ∼250, 000 galaxies and is >90% spectroscopically complete. The depth and large volume of this sample allow us to investigate the low-redshift pair fraction and merger rate of galaxies over a wide range in K-band luminosity. We find the major merger pair fraction to be flat at ∼2% as a function of K-band luminosity for galaxies in the range 10{sup 8}-10{sup 12} L {sub ☉}, in contrast to recent results from studies in the local group that find a substantially higher low-mass pair fraction. This low-redshift major merger pair fraction is ∼40%-50% higher than previous estimates drawn from K-band samples, which were based on 2MASS photometry alone. Combining with the RCS1 sample, we find a much flatter evolution (m = 0.7 ± 0.1) in the relation f {sub pair}∝(1 + z) {sup m} than indicated in many previous studies. These results indicate that a typical L ∼ L* galaxy has undergone ∼0.2-0.8 major mergers since z = 1 (depending on the assumptions of merger timescale and percentage of pairs that actually merge).

  6. Evolution of the major merger galaxy pair fraction at z < 1

    International Nuclear Information System (INIS)

    Keenan, R. C.; Hsieh, B. C.; Lin, L.; Chou, R. C. Y.; Huang, S.; Lin, J. H.; Chang, K. H.; Foucaud, S.; De Propris, R.

    2014-01-01

    We present a study of the largest available sample of near-infrared selected (i.e., stellar mass selected) dynamically close pairs of galaxies at low redshifts (z < 0.3). We combine this sample with new estimates of the major merger pair fraction for stellar mass selected galaxies at z < 0.8, from the Red Sequence Cluster Survey (RCS1). We construct our low-redshift K-band selected sample using photometry from the UKIRT Infrared Deep Sky Survey and the Two Micron All Sky Survey (2MASS) in the K band (∼2.2 μm). Combined with all available spectroscopy, our K-band selected sample contains ∼250, 000 galaxies and is >90% spectroscopically complete. The depth and large volume of this sample allow us to investigate the low-redshift pair fraction and merger rate of galaxies over a wide range in K-band luminosity. We find the major merger pair fraction to be flat at ∼2% as a function of K-band luminosity for galaxies in the range 10 8 -10 12 L ☉ , in contrast to recent results from studies in the local group that find a substantially higher low-mass pair fraction. This low-redshift major merger pair fraction is ∼40%-50% higher than previous estimates drawn from K-band samples, which were based on 2MASS photometry alone. Combining with the RCS1 sample, we find a much flatter evolution (m = 0.7 ± 0.1) in the relation f pair ∝(1 + z) m than indicated in many previous studies. These results indicate that a typical L ∼ L* galaxy has undergone ∼0.2-0.8 major mergers since z = 1 (depending on the assumptions of merger timescale and percentage of pairs that actually merge).

  7. MAJOR-MERGER GALAXY PAIRS IN THE COSMOS FIELD—MASS-DEPENDENT MERGER RATE EVOLUTION SINCE z = 1

    International Nuclear Information System (INIS)

    Xu, C. Kevin; Zhao, Yinghe; Gao, Y.; Scoville, N.; Capak, P.; Drory, N.

    2012-01-01

    We present results of a statistical study of the cosmic evolution of the mass-dependent major-merger rate since z = 1. A stellar mass limited sample of close major-merger pairs (the CPAIR sample) was selected from the archive of the COSMOS survey. Pair fractions at different redshifts derived using the CPAIR sample and a local K-band-selected pair sample show no significant variations with stellar mass. The pair fraction exhibits moderately strong cosmic evolution, with the best-fitting function of f pair = 10 –1.88(±0.03) (1 + z) 2.2(±0.2) . The best-fitting function for the merger rate is R mg (Gyr –1 ) = 0.053 × (M star /10 10.7 M ☉ ) 0.3 (1 + z) 2.2 /(1 + z/8). This rate implies that galaxies of M star ∼ 10 10 -10 11.5 M ☉ have undergone ∼0.5-1.5 major mergers since z = 1. Our results show that, for massive galaxies (M star ≥ 10 10.5 M ☉ ) at z ≤ 1, major mergers involving star-forming galaxies (i.e., wet and mixed mergers) can account for the formation of both ellipticals and red quiescent galaxies (RQGs). On the other hand, major mergers cannot be responsible for the formation of most low mass ellipticals and RQGs of M star ∼ 10.3 M ☉ . Our quantitative estimates indicate that major mergers have significant impact on the stellar mass assembly of the most massive galaxies (M star ≥ 10 11.3 M ☉ ), but for less massive galaxies the stellar mass assembly is dominated by the star formation. Comparison with the mass-dependent (ultra)luminous infrared galaxies ((U)LIRG) rates suggests that the frequency of major-merger events is comparable to or higher than that of (U)LIRGs.

  8. VizieR Online Data Catalog: VANDELS High-Redshift Galaxy Evolution (McLure+, 2017)

    Science.gov (United States)

    McLure, R.; Pentericci, L.; Vandels Team

    2017-11-01

    This is the first data release (DR1) of the VANDELS survey, an ESO public spectroscopy survey targeting the high-redshift Universe. The VANDELS survey uses the VIMOS spectrograph on ESO's VLT to obtain ultra-deep, medium resolution, optical spectra of galaxies within the UKIDSS Ultra Deep Survey (UDS) and Chandra Deep Field South (CDFS) survey fields (0.2 sq. degree total area). Using robust photometric redshift pre-selection, VANDELS is targeting ~2100 galaxies in the redshift interval 1.0=3. In addition, VANDELS is targeting a substantial number of passive galaxies in the redshift interval 1.0filter, which covers the wavelength range 4800-10000Å at a dispersion of 2.5Å/pix and a spectral resolution of R~600. Each galaxy receives between a minimum of 20-hours and a maximum of 80-hours of on-source integration time. The fundamental aim of the survey is to provide the high signal-to-noise spectra necessary to measure key physical properties such as stellar population ages, metallicities and outflow velocities from detailed absorption-line studies. By targeting two extra-galactic survey fields with superb multi-wavelength imaging data, VANDELS is designed to produce a unique legacy dataset for exploring the physics underpinning high-redshift galaxy evolution. (2 data files).

  9. Connecting traces of galaxy evolution: the missing core mass-morphological fine structure relation

    Science.gov (United States)

    Bonfini, P.; Bitsakis, T.; Zezas, A.; Duc, P.-A.; Iodice, E.; González-Martín, O.; Bruzual, G.; González Sanoja, A. J.

    2018-01-01

    Deep exposure imaging of early-type galaxies (ETGs) are revealing the second-order complexity of these objects, which have been long considered uniform, dispersion-supported spheroidals. `Fine structure' features (e.g. ripples, plumes, tidal tails, rings) as well as depleted stellar cores (i.e. central light deficits) characterize a number of massive ETG galaxies, and can be interpreted as the result of galaxy-galaxy interactions. We discuss how the time-scale for the evolution of cores and fine structures are comparable, and hence it is expected that they develop in parallel after the major interaction event which shaped the ETG. Using archival data, we compare the `depleted stellar mass' (i.e. the mass missing from the depleted stellar core) against the prominence of the fine structure features, and observe that they correlate inversely. This result confirms our expectation that, while the supermassive black hole (SMBH) binary (constituted by the SMBHs of the merger progenitors) excavates the core via three-body interactions, the gravitational potential of the newborn galaxy relaxes, and the fine structures fade below detection levels. We expect the inverse correlation to hold at least within the first Gyr from the merger which created the SMBH binary; after then, the fine structure evolves independently.

  10. The dwarf galaxy population of nearby galaxy clusters

    NARCIS (Netherlands)

    Lisker, Thorsten; Wittmann, Carolin; Pak, Mina; Janz, Joachim; Bialas, Daniel; Peletier, Reynier; Grebel, Eva; Falcon Barroso, Jesus; Toloba, Elisa; Smakced Collaboration, Focus Collaboration

    The Fornax, Virgo, Ursa Major and Perseus galaxy clusters all have very different characteristics, in terms of their density, mass, and large-scale environment. We can regard these clusters as laboratories for studying environmental influence on galaxy evolution, using the sensitive low-mass

  11. Conventional outlooks on the origin and evolution of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Dallaporta, N; Secco, L [Padua Univ. (Italy) Ist. di Astronomia

    1982-01-01

    As not many extended summaries have been in the past undertaken, we have thought it could be of some utility to make a kind of summary on the conventional views concerning the origin and the evolution of galaxies, with the main aim of stressing both their shortcomings or their partial successes and bridging, as far as possible, the gaps of understanding or of linking between the different chronological phases of the whole process and the different theoretical emphasis concerning the physical factors of importance for the interpretation of the observational field. As a starting point for our work, let us formulate the whole problem according to two different questions, the tentative answer to which constitute the main streams of research in this field of science: 1) Why do galaxies exist. and 2) Why, as they exist in fact, are they as we observe they are. These two questions are the basic starting points to the understanding of the already mentioned B) cosmological phase and C) astrophysical phase. Our summary will be successively concerned with these two stages.

  12. Faint galaxies - Bounds on the epoch of galaxy formation and the cosmological deceleration parameter

    International Nuclear Information System (INIS)

    Yoshii, Yuzuru; Peterson, B.A.

    1991-01-01

    Models of galaxy luminosity evolution are used to interpret the observed color distributions, redshift distributions, and number counts of faint galaxies. It is found from the color distributions that the redshift corresponding to the epoch of galaxy formation must be greater than three, and that the number counts of faint galaxies, which are sensitive to the slope of the faint end of the luminosity function, are incompatible with q0 = 1/2 and indicate a smaller value. The models assume that the sequence of galaxy types is due to different star-formation rates, that the period of galaxy formation can be characterized by a single epoch, and that after formation, galaxies change in luminosity by star formation and stellar evolution, maintaining a constant comoving space density. 40 refs

  13. THE EVOLUTION OF DUSTY STAR FORMATION IN GALAXY CLUSTERS TO z = 1: SPITZER INFRARED OBSERVATIONS OF THE FIRST RED-SEQUENCE CLUSTER SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Webb, T. M. A.; O' Donnell, D.; Coppin, Kristen; Faloon, Ashley; Geach, James E.; Noble, Allison [McGill University, 3600 rue University, Montreal, QC, H3A 2T8 (Canada); Yee, H. K. C. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George St., Toronto, ON, M5S 3H4 (Canada); Gilbank, David [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Ellingson, Erica [Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, Boulder, CO 80309 (United States); Gladders, Mike [Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 (United States); Muzzin, Adam [Leiden Observatory, University of Leiden, Niels Bohrweg 2, NL-2333 CA, Leiden (Netherlands); Wilson, Gillian [Department of Physics and Astronomy, University of California at Riverside, 900 University Avenue, Riverside, CA 92521 (United States); Yan, Renbin [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States)

    2013-10-01

    We present the results of an infrared (IR) study of high-redshift galaxy clusters with the MIPS camera on board the Spitzer Space Telescope. We have assembled a sample of 42 clusters from the Red-Sequence Cluster Survey-1 over the redshift range 0.3 < z < 1.0 and spanning an approximate range in mass of 10{sup 14-15} M {sub ☉}. We statistically measure the number of IR-luminous galaxies in clusters above a fixed inferred IR luminosity of 2 × 10{sup 11} M {sub ☉}, assuming a star forming galaxy template, per unit cluster mass and find it increases to higher redshift. Fitting a simple power-law we measure evolution of (1 + z){sup 5.1±1.9} over the range 0.3 < z < 1.0. These results are tied to the adoption of a single star forming galaxy template; the presence of active galactic nuclei, and an evolution in their relative contribution to the mid-IR galaxy emission, will alter the overall number counts per cluster and their rate of evolution. Under the star formation assumption we infer the approximate total star formation rate per unit cluster mass (ΣSFR/M {sub cluster}). The evolution is similar, with ΣSFR/M {sub cluster} ∼ (1 + z){sup 5.4±1.9}. We show that this can be accounted for by the evolution of the IR-bright field population over the same redshift range; that is, the evolution can be attributed entirely to the change in the in-falling field galaxy population. We show that the ΣSFR/M {sub cluster} (binned over all redshift) decreases with increasing cluster mass with a slope (ΣSFR/M{sub cluster}∼M{sub cluster}{sup -1.5±0.4}) consistent with the dependence of the stellar-to-total mass per unit cluster mass seen locally. The inferred star formation seen here could produce ∼5%-10% of the total stellar mass in massive clusters at z = 0, but we cannot constrain the descendant population, nor how rapidly the star-formation must shut-down once the galaxies have entered the cluster environment. Finally, we show a clear decrease in the number of IR

  14. THE BARYON CYCLE AT HIGH REDSHIFTS: EFFECTS OF GALACTIC WINDS ON GALAXY EVOLUTION IN OVERDENSE AND AVERAGE REGIONS

    Energy Technology Data Exchange (ETDEWEB)

    Sadoun, Raphael [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112-0830 (United States); Shlosman, Isaac; Choi, Jun-Hwan; Romano-Díaz, Emilio, E-mail: raphael.sadoun@utah.edu [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055 (United States)

    2016-10-01

    We employ high-resolution cosmological zoom-in simulations focusing on a high-sigma peak and an average cosmological field at z ∼ 6–12 in order to investigate the influence of environment and baryonic feedback on galaxy evolution in the reionization epoch. Strong feedback, e.g., galactic winds, caused by elevated star formation rates (SFRs) is expected to play an important role in this evolution. We compare different outflow prescriptions: (i) constant wind velocity (CW), (ii) variable wind scaling with galaxy properties (VW), and (iii) no outflows (NW). The overdensity leads to accelerated evolution of dark matter and baryonic structures, absent from the “normal” region, and to shallow galaxy stellar mass functions at the low-mass end. Although CW shows little dependence on the environment, the more physically motivated VW model does exhibit this effect. In addition, VW can reproduce the observed specific SFR (sSFR) and the sSFR–stellar mass relation, which CW and NW fail to satisfy simultaneously. Winds also differ substantially in affecting the state of the intergalactic medium (IGM). The difference lies in the volume-filling factor of hot, high-metallicity gas, which is near unity for CW, while such gas remains confined in massive filaments for VW, and locked up in galaxies for NW. Such gas is nearly absent from the normal region. Although all wind models suffer from deficiencies, the VW model seems to be promising in correlating the outflow properties with those of host galaxies. Further constraints on the state of the IGM at high z are needed to separate different wind models.

  15. The role of AGN feedback in galaxy evolution at high-redshift

    International Nuclear Information System (INIS)

    Collet, Cedric

    2014-01-01

    There is growing evidence that supermassive black holes may play a crucial role for galaxy evolution, in particular during the formation of massive galaxies at high redshift (z ≅ 2 - 3). Our work focuses on quantifying the effects of jets of radiogalaxies and of large bolometric luminosities of quasars on the interstellar gas in their host galaxies. To this end, we studied the kinematics of the ionized gas in 12 moderately powerful radio galaxies and 11 quasars (6 radio-loud and 5 radio-quiet) at high redshifts with rest-frame optical imaging spectroscopy obtained at the VLT with SINFONI. We searched for outflows and other signatures of feedback from the supermassive black holes in the centers of these galaxies to evaluate if the AGN may plausibly quench star formation. In our sample of moderately powerful radiogalaxies, we observe velocity dispersions nearly as large as those observed in the most powerful ones (with FWHM ≅ 1000 km/s), but the quantity of ionized gas is decreased by one order of magnitude (M-ion gas ≅ 10"8 - 10"9 M-sun) and velocity gradients tend to be less dramatic (Δv ≤ 400 km/s), when they are observed. In our sample of quasars, we had to carefully subtract the broad spectral component of emission lines to have access to its narrow, and spatially extended, component. We detect truly extended emission line regions in 4/6 sources of our radio-loud sub-sample and in 1/5 source of our radio-quiet sub-sample. We estimate that masses of ionized gas in these sources are smaller than in our sample of high-redshift radiogalaxies (with Mion gas ≅ 10"7 - 10"8 Msun) and kinematics tend to be more quiescent, akin to what is observed in local quasars. Finally, detailed observations of two outliers among our sample of high-redshift radiogalaxies revealed that one of them is closely surrounded by 14 companions galaxies, hence lying in an over density. We therefore interpret the presence and morphology of ionized gas around these galaxies as evidence

  16. The evolution of the cluster optical galaxy luminosity function between z = 0.4 and 0.9 in the DAFT/FADA survey

    Science.gov (United States)

    Martinet, Nicolas; Durret, Florence; Guennou, Loïc; Adami, Christophe; Biviano, Andrea; Ulmer, Melville P.; Clowe, Douglas; Halliday, Claire; Ilbert, Olivier; Márquez, Isabel; Schirmer, Mischa

    2015-03-01

    Context. There is some disagreement about the abundance of faint galaxies in high-redshift clusters, with contradictory results in the literature arising from studies of the optical galaxy luminosity function (GLF) for small cluster samples. Aims: We compute GLFs for one of the largest medium-to-high-redshift (0.4 ≤ z DAFT/FADA survey in the B,V,R, and I rest-frame bands. We used photometric redshifts computed from BVRIZJ images to constrain galaxy cluster membership. We carried out a detailed estimate of the completeness of our data. We distinguished the red-sequence and blue galaxies using a V - I versus I colour-magnitude diagram. We studied the evolution of these two populations with redshift. We fitted Schechter functions to our stacked GLFs to determine average cluster characteristics. Results: We find that the shapes of our GLFs are similar for the B,V,R, and I bands with a drop at the red GLF faint ends that is more pronounced at high redshift: αred ~ -0.5 at 0.40 ≤ z 0.1 at 0.65 ≤ z < 0.90. The blue GLFs have a steeper faint end (αblue ~ -1.6) than the red GLFs, which appears to be independent of redshift. For the full cluster sample, blue and red GLFs meet at MV = -20, MR = -20.5, and MI = -20.3. A study of how galaxy types evolve with redshift shows that late-type galaxies appear to become early types between z ~ 0.9 and today. Finally, the faint ends of the red GLFs of more massive clusters appear to be richer than less massive clusters, which is more typical of the lower redshift behaviour. Conclusions: Our results indicate that these clusters form at redshifts higher than z = 0.9 from galaxy structures that already have an established red sequence. Late-type galaxies then appear to evolve into early types, enriching the red sequence between this redshift and today. This effect is consistent with the evolution of the faint-end slope of the red sequence and the galaxy type evolution that we find. Finally, faint galaxies accreted from the field

  17. THE CONTRIBUTION OF X-RAY BINARIES TO THE EVOLUTION OF LATE-TYPE GALAXIES: EVOLUTIONARY POPULATION SYNTHESIS SIMULATIONS

    International Nuclear Information System (INIS)

    Zuo Zhaoyu; Li Xiangdong

    2011-01-01

    X-ray studies of normal late-type galaxies have shown that non-nuclear X-ray emission is typically dominated by X-ray binaries and provides a useful measure of star formation activity. We have modeled the X-ray evolution of late-type galaxies over the ∼14 Gyr of cosmic history, with an evolutionary population synthesis code developed by Hurley et al. Our calculations reveal a decrease in the X-ray luminosity-to-mass ratio L X /M with time, in agreement with observations. We show that this decrease is a natural consequence of stellar and binary evolution and the mass accumulating process in galaxies. The X-ray-to-optical luminosity ratio L X /L B is found to be fairly constant (around ∼10 30 erg s -1 L -1 B,sun ) and insensitive to the star formation history in the galaxies. The nearly constant value of L X /L B is in conflict with the observed increase in L X /L B from z = 0 to 1.4. The discrepancy may be caused by intense obscured star formation activity that leads to a nonlinear relationship between X-ray and B-band emission.

  18. Significance of Environmental Density in Shocked Poststarburst Galaxy Evolution

    Science.gov (United States)

    Jaliff, Laura

    2018-01-01

    The Shocked POstarbusrt Galaxy Survey (SPOGS) comprises 1,066 galaxies undergoing the transformation from blue cloud late-type spirals to red sequence non-star-forming early-type ellipticals and lenticulars. They are selected via spectral analysis of ionized gas line ratios, which indicate shocked objects, and Balmer H-δ equivalent width, which select recently formed stars, but not active star formation. E+A galaxies (Zabludoff et al. 1996), like SPOGs, contain young stars but, unlike SPOGs, no emission lines consistent with star formation. They differ in that the quality used to discern SPOGs, their shocks, produces H-α lines that prevent them from being found via the same criteria as E+As. Thus, SPOGs can be found before being entirely stripped of their gas, and, while E+As are largely red and dead, found leaving the green valley, SPOGS are mostly entering it. The environmental density data for SPOGs was retrieved via the NASA Extragalactic Database (NED) radial velocity constrained cone tool, which provides counts and densities within spheres of radii 1, 5, and 10 Mpc from the center of search as well as relative positions and redshifts of objects. The kinematic morphology-density relation (Cappellari et al. 2011) is employed as a point of comparison for how SPOGs’ environmental densities might relate to morphological and spectroscopic factors, including tidal features, asymmetry, and color, in order to fully understand the role of environmental factors in SPOGS object evolution.

  19. Effect of a Brans--Dicke cosmology upon stellar evolution and the evolution of galaxies

    International Nuclear Information System (INIS)

    Prather, M.J.

    1976-01-01

    The effect which a variable G cosmology, such as Brans-Dicke, will have on the evolution of individual stars and of galaxies composed of these stars is examined in the hope that present day observation of globular clusters or giant elliptical galaxies will provide a test for the Brans--Dicke theory. The higher value of the gravitational coupling coefficient G in the past history of various Brans--Dicke universes is studied in detail. A low density, open universe is selected for study: fractional closure density = 0.2, present Hubble constant = km/s/Mpc, stellar formation at a red-shift of 5, and the Brans--Dicke parameter omega = 6. In this universe a set of stellar evolutionary tracks is computed from the Zero-Age Main Sequence through the Giant Branch to the Horizontal Branch for approximately solar composition, (Y,Z) = (0.25, 0.02). When compared at equivalent evolutionary phases, the luminosity of individual stars is found to increase greatly with G from the ZAMS to the HB. The higher G greatly speeds up the evolutionary time scale for the main sequence, and it decreases the core mass at the helium flash, leaving the luminosity of the tip of the GB and the HB unchanged. The net effect of a higher G on a cluster of stars is to increase the apparent mass at the turn-off and to reduce the lifetimes of all the evolutionary phases from the ZAMS to the HB by the same factor. Thus, the relative number density of stars in the major phases of stellar evolution is unchanged

  20. Galaxy mergers

    International Nuclear Information System (INIS)

    Roos, N.

    1981-01-01

    This thesis contains a series of four papers dealing with the effects of interactions among galaxies during the epoch of cluster formation. Galaxy interactions are investigated and the results incorporated in numerical simulations of the formation of groups and clusters of galaxies. The role of galaxy interactions is analysed in the more general context of simulations of an expanding universe. The evolution of galaxies in rich clusters is discussed. The results of the investigations are presented and their relation to other work done in the field are briefly reviewed and an attempt is made to link galaxy mergers to the occurrence of activity in galactic nuclei. (Auth.)

  1. HI-Selected Galaxies in Hierarchical Models of Galaxy Formation and Evolution

    Science.gov (United States)

    Zoldan, Anna

    2017-07-01

    This poster presents the main results of a statistical study of HI-selected galaxies based on six different semi-analytic models, all run on the same cosmological N-body simulation. One of these models includes an explicit treatment for the partition of cold gas into atomic and molecular hydrogen. All models considered agree nicely with the measured HI mass function in the local Universe and with the measured scaling relations between HI and galaxy stellar mass. Most models also reproduce the observed 2-point correlation function for HI rich galaxies, with the exception of one model that predicts very little HI associated with galaxies in haloes above 10^12 Msun. We investigated the influence of satellite treatment on the final HI content and found that it introduces large uncertainties at low HI masses. We found that the assumption of instantaneous stripping of hot gas in satellites does not translate necessarily in lower HI masses. We demonstrate that the assumed stellar feedback, combined with star formation, also affect significantly the gas content of satellite galaxies. Finally, we also analyse the origin of the correlation between HI content of model galaxies and the spin of the parent haloes. Zoldan et al., 2016, MNRAS, 465, 2236

  2. Our aging galaxy

    International Nuclear Information System (INIS)

    Lyngaa, G.

    1980-01-01

    The origin and evolution of the galaxies is described, according to the presently prevailing theories. The various types of galaxy and their structures are described, and also the formation of stars from the gas clouds. The spiral structure and the evolution of the disc are discussed. Finally the future development on the time scale of thousands of millions of years is briefly discussed. (JIW)

  3. Properties of Galaxies and Groups: Nature versus Nurture

    Science.gov (United States)

    Niemi, Sami-Matias

    2011-09-01

    Due to the inherently nonlinear nature of gravity cosmological N-body simulations have become an invaluable tool when the growth of structure is being studied and modelled closer to the present epoch. Large simulations with high dynamical range have made it possible to model the formation and growth of cosmic structure with unprecedented accuracy. Moreover, galaxies, the basic building blocks of the Universe, can also be modelled in cosmological context. However, despite all the simulations and successes in recent decades, there are still many unanswered questions in the field of galaxy formation and evolution. One of the longest standing issue being the significance of the formation place and thus initial conditions to a galaxy's evolution in respect to environment, often formulated simply as "nature versus nurture" like in human development and psychology. Unfortunately, our understanding of galaxy evolution in different environments is still limited, albeit, for example, the morphology-density relation has shown that the density of the galaxy's local environment can affect its properties. Consequently, the environment should play a role in galaxy evolution, however despite the efforts, the exact role of the galaxy's local environment to its evolution remains open. This thesis introduction discusses briefly the background cosmology, cosmological N-body simulations and semi-analytical models. The second part is reserved for groups of galaxies, whether they are gravitationally bound, and what this may imply for galaxy evolution. The third part of the thesis concentrates on describing results of a case study of isolated field elliptical galaxies. The final chapter discusses another case study of luminous infra-red galaxies.

  4. CANDELS: THE EVOLUTION OF GALAXY REST-FRAME ULTRAVIOLET COLORS FROM z = 8 TO 4

    Energy Technology Data Exchange (ETDEWEB)

    Finkelstein, Steven L. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Papovich, Casey; Salmon, Brett; Bassett, Robert [George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Finlator, Kristian [Physics Department, University of California, Santa Barbara, CA 93106 (United States); Dickinson, Mark [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Ferguson, Henry C.; Koekemoer, Anton M.; Grogin, Norman A. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Giavalisco, Mauro [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Reddy, Naveen A.; Mobasher, Bahram [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Conselice, Christopher J. [School of Physics and Astronomy, University of Nottingham, Nottingham (United Kingdom); Dunlop, James S.; McLure, Ross J. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh (United Kingdom); Faber, S. M.; Kocevski, Dale D.; Lai, Kamson [University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States); Hathi, Nimish P. [Carnegie Observatories, Pasadena, CA 91101 (United States); Lee, Kyoung-Soo, E-mail: stevenf@astro.as.utexas.edu [Yale Center for Astronomy and Astrophysics, Departments of Physics and Astronomy, Yale University, New Haven, CT 06520 (United States); and others

    2012-09-10

    We study the evolution of galaxy rest-frame ultraviolet (UV) colors in the epoch 4 {approx}< z {approx}< 8. We use new wide-field near-infrared data in the Great Observatories Origins Deep Survey-South field from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, Hubble Ultra Deep Field (HUDF) 2009, and Early Release Science programs to select galaxies via photometric redshift measurements. Our sample consists of 2812 candidate galaxies at z {approx}> 3.5, including 113 at z {approx_equal} 7-8. We fit the observed spectral energy distribution to a suite of synthetic stellar population models and measure the value of the UV spectral slope ({beta}) from the best-fit model spectrum. We run simulations to show that this measurement technique results in a smaller scatter on {beta} than other methods, as well as a reduced number of galaxies with catastrophically incorrect {beta} measurements (i.e., {Delta}{beta} > 1). We find that the median value of {beta} evolves significantly from -1.82{sup +0.00}{sub -0.04} at z = 4 to -2.37{sup +0.26}{sub -0.06} at z = 7. Additionally, we find that faint galaxies at z = 7 have {beta} -2.68{sup +0.39}{sub -0.24} ({approx} -2.4 after correcting for observational bias); this is redder than previous claims in the literature and does not require 'exotic' stellar populations (e.g., very low metallicities or top-heavy initial mass functions) to explain their colors. This evolution can be explained by an increase in dust extinction, from low amounts at z = 7 to A{sub V} {approx} 0.5 mag at z = 4. The timescale for this increase is consistent with low-mass asymptotic giant branch stars forming the bulk of the dust. We find no significant (<2{sigma}) correlation between {beta} and M{sub UV} when measuring M{sub UV} at a consistent rest-frame wavelength of 1500 A. This is particularly true at bright magnitudes, though our results do show evidence for a weak correlation at faint magnitudes when galaxies in the HUDF

  5. Is the non-isothermal double β-model incompatible with no time evolution of galaxy cluster gas mass fraction?

    Science.gov (United States)

    Holanda, R. F. L.

    2018-05-01

    In this paper, we propose a new method to obtain the depletion factor γ(z), the ratio by which the measured baryon fraction in galaxy clusters is depleted with respect to the universal mean. We use exclusively galaxy cluster data, namely, X-ray gas mass fraction (fgas) and angular diameter distance measurements from Sunyaev-Zel'dovich effect plus X-ray observations. The galaxy clusters are the same in both data set and the non-isothermal spherical double β-model was used to describe their electron density and temperature profiles. In order to compare our results with those from recent cosmological hydrodynamical simulations, we suppose a possible time evolution for γ(z), such as, γ(z) =γ0(1 +γ1 z) . As main conclusions we found that: the γ0 value is in full agreement with the simulations. On the other hand, although the γ1 value found in our analysis is compatible with γ1 = 0 within 2σ c.l., our results show a non-negligible time evolution for the depletion factor, unlike the results of the simulations. However, we also put constraints on γ(z) by using the fgas measurements and angular diameter distances obtained from the flat ΛCDM model (Planck results) and from a sample of galaxy clusters described by an elliptical profile. For these cases no significant time evolution for γ(z) was found. Then, if a constant depletion factor is an inherent characteristic of these structures, our results show that the spherical double β-model used to describe the galaxy clusters considered does not affect the quality of their fgas measurements.

  6. ON THE REDSHIFT EVOLUTION OF THE Lyα ESCAPE FRACTION AND THE DUST CONTENT OF GALAXIES

    International Nuclear Information System (INIS)

    Hayes, Matthew; Schaerer, Daniel; Oestlin, Goeran; Mas-Hesse, J. Miguel; Atek, Hakim; Kunth, Daniel

    2011-01-01

    The Lyα emission line has been proven to be a powerful tool for studying evolving galaxies at the highest redshift. However, in order to use Lyα as a physical probe of galaxies, it becomes vital to know the Lyα escape fraction (f Lyα esc ). Unfortunately, due to the resonant nature of Lyα, f Lyα esc may vary unpredictably and requires empirical measurement. Here, we compile Lyα luminosity functions (LFs) between redshifts z = 0 and 8 and, combined with Hα and ultraviolet data, assess how f Lyα esc evolves with redshift. We find a strong upward evolution in f Lyα esc over the range z = 0.3-6, which is well fit by the power law f Lyα esc ∝(1 + z) ξ with ξ = (2.57 +0.19 -0.12 ). This predicts that f Lyα esc should reach unity at z = 11.1. By comparing f Lyα esc and E B-V in individual galaxies we derive an empirical relationship between f Lyα esc and E B-V , which includes resonance scattering and can explain the redshift evolution of f Lyα esc between z = 0 and 6 purely as a function of the evolution in the dust content of galaxies. Beyond z ∼ 6.5, f Lyα esc drops more substantially, an effect attributed to either ionizing photon leakage, or an increase in the neutral gas fraction of the intergalactic medium. While distinguishing between these two scenarios may be extremely challenging, by framing the problem this way we remove the uncertainty of the halo mass from Lyα-based tests of reionization. We finally derive a new method by which to estimate the dust content of galaxies, based purely upon the observed Lyα and UV LFs. These data are characterized by an exponential with an e-folding scale of z EBV ∼ 3.4.

  7. The galaxy ancestor problem

    Science.gov (United States)

    Disney, M. J.; Lang, R. H.

    2012-11-01

    The Hubble Space Telescope (HST) findsgalaxies whose Tolman dimming exceeds 10 mag. Could evolution alone explain these as our ancestor galaxies or could they be representatives of quite a different dynasty whose descendants are no longer prominent today? We explore the latter hypothesis and argue that surface brightness selection effects naturally bring into focus quite different dynasties from different redshifts. Thus, the HST z = 7 galaxies could be examples of galaxies whose descendants are both too small and too choked with dust to be recognizable in our neighbourhood easily today. Conversely, the ancestors of the Milky Way and its obvious neighbours would have completely sunk below the sky at z > 1.2, unless they were more luminous in the past, although their diffused light could account for the missing re-ionization flux. This Succeeding Prominent Dynasties Hypothesis (SPDH) fits the existing observations both naturally and well even without evolution, including the bizarre distributions of galaxy surface brightness found in deep fields, the angular size ˜(1 + z)-1 law, 'downsizing' which turns out to be an 'illusion' in the sense that it does not imply evolution, 'infant mortality', that is, the discrepancy between stars born and stars seen, the existence of 'red nuggets', and finally the recently discovered and unexpected excess of quasar absorption line damped Lyα systems at high redshift. If galaxies were not significantly brighter in the past and the SPDH were true, then a large proportion of galaxies could remain sunk from sight, possibly at all redshifts, and these sunken galaxies could supply the missing re-ionization flux. We show that fishing these sunken galaxies out of the sky by their optical emissions alone is practically impossible, even when they are nearby. More ingenious methods are needed to detect them. It follows that disentangling galaxy evolution through studying ever higher redshift galaxies may be a forlorn hope because one could

  8. Galaxy formation

    International Nuclear Information System (INIS)

    Gribbin, J.

    1979-01-01

    The current debate on the origin and evolution of galaxies is reviewed and evidence to support the so-called 'isothermal' and 'adiabatic' fluctuation models considered. It is shown that new theories have to explain the formation of both spiral and elliptical galaxies and the reason for their differences. It is stated that of the most recent models the best indicates that rotating spiral galaxies are formed naturally when gas concentrates in the centre of a great halo and forms stars while ellipticals are explained by later interactions between spiral galaxies and merging, which can cancel out the rotation while producing an elliptical galaxy in which the stars, coming from two original galaxies, follow very elliptical, anisotropic orbits. (UK)

  9. THE RISE AND FALL OF PASSIVE DISK GALAXIES: MORPHOLOGICAL EVOLUTION ALONG THE RED SEQUENCE REVEALED BY COSMOS

    International Nuclear Information System (INIS)

    Bundy, Kevin; Hopkins, Philip; Ma, Chung-Pei; Scarlata, Claudia; Capak, Peter; Carollo, C. M.; Oesch, Pascal; Ellis, Richard S.; Salvato, Mara; Scoville, Nick; Drory, Niv; Leauthaud, Alexie; Koekemoer, Anton M.; Murray, Norman; Ilbert, Olivier; Pozzetti, Lucia

    2010-01-01

    The increasing abundance of passive 'red-sequence' galaxies since z ∼ 1-2 is mirrored by a coincident rise in the number of galaxies with spheroidal morphologies. In this paper, however, we show in detail, that, the correspondence between galaxy morphology and color is not perfect, providing insight into the physical origin of this evolution. Using the COSMOS survey, we study a significant population of red-sequence galaxies with disk-like morphologies. These passive disks typically have Sa-Sb morphological types with large bulges, but they are not confined to dense environments. They represent nearly one-half of all red-sequence galaxies and dominate at lower masses (∼ 10 M sun ) where they are increasingly disk-dominated. As a function of time, the abundance of passive disks with M * ∼ 11 M sun increases, but not as fast as red-sequence spheroidals in the same mass range. At higher mass, the passive disk population has declined since z ∼ 1, likely because they transform into spheroidals. Based on these trends, we estimate that as much as 60% of galaxies transitioning onto the red sequence evolve through a passive disk phase. The origin of passive disks therefore has broad implications for our understanding of how star formation shuts down. Because passive disks tend to be more bulge-dominated than their star-forming counterparts, a simple fading of blue disks does not fully explain their origin. We explore the strengths and weaknesses of several more sophisticated explanations, including environmental effects, internal stabilization, and disk regrowth during gas-rich mergers. While previous work has sought to explain color and morphological transformations with a single process, these observations open the way to new insight by highlighting the fact that galaxy evolution may actually proceed through several separate stages.

  10. GALAXY DOWNSIZING AND THE REDSHIFT EVOLUTION OF OXYGEN AND NITROGEN ABUNDANCES: ORIGIN OF THE SCATTER IN THE N/H-O/H DIAGRAM

    International Nuclear Information System (INIS)

    Pilyugin, Leonid S.; Thuan, Trinh X.

    2011-01-01

    The oxygen and nitrogen abundance evolutions with redshift of emission-line galaxies in the Sloan Digital Sky Survey are considered for four intervals of galaxy stellar masses, ranging from 10 11.3 M sun to 10 10.2 M sun . We have measured their line fluxes and derived the O and N abundances using recent calibrations. The evolution of O and N abundances with redshift clearly shows the galaxy downsizing effect, where enrichment (and hence star formation) ceases in high-mass galaxies at earlier times and shifts to lower-mass galaxies at later epochs. The origin of the scatter in the N/H-O/H diagram has been examined. The most massive galaxies, where O and N enrichment and star formation have already stopped, occupy a narrow band in the N/H-O/H diagram, defining an upper envelope. The less massive galaxies which are still undergoing star formation at the current epoch are shifted downward, toward lower N/H values in the N/H-O/H diagram. This downward shift is caused by the time delay between N and O enrichment. This time delay together with the different star formation histories in galaxies is responsible for the large scatter in the N/H-O/H diagram.

  11. Smooth-arm spiral galaxies: their properties and significance to cluster-galaxy evolution

    International Nuclear Information System (INIS)

    Wilkerson, M.S.

    1979-01-01

    In this dissertation a number of galaxies with optical appearances between those of normal, actively-star-forming spirals and SO galaxies have been examined. These so-called smooth-arm spiral galaxies exhibit spiral arms without any of the spiral tracers - H II regions, O-B star associations, dust - indicative of current star formation. Tests were made to find if, perhaps, these smooth-arm spirals could have, at one time, been normal, actively-star-forming spirals whose gas had been somehow removed; and that are currently transforming into SO galaxies. This scenario proceeds as (1) removal of gas, (2) gradual dying of disk density wave, (3) emergence of SO galaxy. If the dominant method of gas removal is ram-pressure stripping by a hot, intracluster medium, then smooth-arm spirals should occur primarily in x-ray clusters. Some major findings of this dissertation are as follows: (1) Smooth-arm spirals are redder than normal spirals of the same morphological type. Most smooth-arm spirals cannot be distinguished by color from SO galaxies. (2) A weak trend exists for smooth-arm spirals with stronger arms to be bluer than those with weaker arms; thus implying that the interval since gas removal has been shorter for the galaxies with stronger arms. (3) Smooth-arm spirals are deficient in neutral hydrogen - sometimes by an order of magnitude or, possibly, more

  12. Tidal interaction, star formation and chemical evolution in blue compact dwarf galaxy Mrk 22

    Science.gov (United States)

    Paswan, A.; Omar, A.; Jaiswal, S.

    2018-02-01

    The optical spectroscopic and radio interferometric H I 21 cm-line observations of the blue compact dwarf galaxy Mrk 22 are presented. The Wolf-Rayet (WR) emission-line features corresponding to high ionization lines of He II λ4686 and C IV λ5808 from young massive stars are detected. The ages of two prominent star-forming regions in the galaxy are estimated as ∼10 and ∼ 4 Myr. The galaxy has non-thermal radio deficiency, which also indicates a young starburst and lack of supernovae events from the current star formation activities, consistent with the detection of WR emission-line features. A significant N/O enrichment is seen in the fainter star-forming region. The gas-phase metallicities [12 + log(O/H)] for the bright and faint regions are estimated as 7.98±0.07 and 7.46±0.09, respectively. The galaxy has a large diffuse H I envelop. The H I images reveal disturbed gas kinematics and H I clouds outside the optical extent of the galaxy, indicating recent tidal interaction or merger in the system. The results strongly indicate that Mrk 22 is undergoing a chemical and morphological evolution due to ongoing star formation, most likely triggered by a merger.

  13. A Chemical Evolution Model for the Fornax Dwarf Spheroidal Galaxy

    Directory of Open Access Journals (Sweden)

    Yuan Zhen

    2016-01-01

    Full Text Available Fornax is the brightest Milky Way (MW dwarf spheroidal galaxy and its star formation history (SFH has been derived from observations. We estimate the time evolution of its gas mass and net inflow and outflow rates from the SFH usinga simple star formation law that relates the star formation rate to the gas mass. We present a chemical evolution model on a 2D mass grid with supernovae (SNe as sources of metal enrichment. We find that a key parameter controlling the enrichment is the mass Mx of the gas to mix with the ejecta from each SN. The choice of Mx depends on the evolution of SN remnants and on the global gas dynamics. It differs between the two types of SNe involved and between the periods before and after Fornax became an MW satellite at time t = tsat. Our results indicate that due to the global gas outflow at t > tsat, part of the ejecta from each SN may directly escape from Fornax. Sample results from our model are presented and compared with data.

  14. The Co-evolution of QSOs and Galaxies

    Science.gov (United States)

    Coziol, R.; Torres-Papaqui, J. P.; Andernach, H.

    2015-07-01

    Using two large samples of QSOs detected in the mid-infrared (MIR) with WISE, we find that the change of W2-W3 colors with redshift suggests that star formation in their host galaxies increases by a factor of 3 from z = 0 to 2.7, then stays constant up to z = 4, and decreases above z=4. This behavior is slightly different from the best fits for the star formation history of field galaxies as deduced from the Optical-UV and IR, but is consistent with what is observed for sub-mm galaxies at high z. Our results constitute the clearest evidence, so far, that QSO host galaxies form their stars before field galaxies, and are in good agreement with the hierarchical biased structure formation paradigm.

  15. Mass and environment as drivers of galaxy evolution. III. The constancy of the faint-end slope and the merging of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Ying-jie; Lilly, Simon J.; Carollo, Marcella [Institute of Astronomy, ETH Zurich, 8093 Zurich (Switzerland); Renzini, Alvio [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy)

    2014-08-01

    Using our continuity approach, we explore the underlying connections between the evolution of the faint-end slope α{sub s} of the stellar mass function of star-forming galaxies, the logarithmic slope β of the specific star formation rate (sSFR)-mass relation, and the merging of galaxies. We derive analytically the consequences of the observed constancy of α{sub s} since redshifts of at least z ∼ 2. If the logarithmic slope β of the sSFR-mass relation is negative, then the faint-end slope α{sub s} should quickly diverge due to the differential mass increase of galaxies on the star-forming main sequence, and this will also quickly destroy the Schechter form of the mass function. This problem can be solved by removing low-mass galaxies by merging them into more massive galaxies. We quantify this process by introducing the specific merger mass rate (sMMR) as the specific rate of mass added to a given galaxy through mergers. For a modest negative value of β ∼ –0.1, an average sMMR ∼ 0.1 sSFR across the population is required to keep α{sub s} constant with epoch, as observed. This in turn implies a merger rate of ∼0.2 sSFR for major mergers, which is consistent with the available observational estimates. More negative values of β require higher sMMR and higher merger rates, and the steepening of the mass function becomes impossible to control for β < –(α{sub s} + 2). The close link that is required between the in situ sSFR and the sMMR probably arises because both are closely linked to the buildup of dark matter halos. These new findings further develop the formalism for the evolving galaxy population that we introduced earlier and show how striking symmetries in the galaxy population can emerge as the result of deep links between the physical processes involved.

  16. Euroconference on the appropriate modellings of galaxy evolution from their cosmological formation to their presently observable structures

    CERN Document Server

    Stasińska, Grażyna; Harfst, Stefan; Kroupa, Pavel; Theis, Christian; THE EVOLUTION OF GALAXIES

    2003-01-01

    Galaxies have a history This has become clear from recent sky surveys which have shown that distant galaxies, formed early in the life of the Universe, differ from the nearby ones New observational windows at ultraviolet, infrared and millimetric wavelengths (provided by ROSAT, IRAM, IUE, IRAS, ISO) have revealed that galaxies contain a wealth of components very hot gas, atomic hydrogen, molecules, dust, dark matter A significant advance is expected from the results of new instruments (VLT, FIRST, XMM) which will allow one to explore the most distant Universe Three Euroconferences were planned to punctuate this new epoch in galactic research, bringing together specialists in various fields of Astronomy This book contains the proceedings of the third conference and presents the actual state-of-the-art of modelling galaxy evolution

  17. Galaxy formation: internal mechanisms and cosmological processes

    International Nuclear Information System (INIS)

    Martig, Marie

    2010-01-01

    This thesis is devoted to galaxy formation and evolution in a cosmological context. Cosmological simulations have unveiled two main modes of galaxy growth: hierarchical growth by mergers and accretion of cold gas from cosmic filaments. However, these simulations rarely take into account small scale mechanisms, that govern internal evolution and that are a key ingredient to understand galaxy formation and evolution. Thanks to a new simulation technique that I have developed, I first studied the colors of galaxies, and in particular the reddening of elliptical galaxies. I showed that the gas disk in an elliptical galaxy could be stabilized against star formation because of the galaxy's stellar component being within a spheroid instead of a disk. This mechanism can explain the red colors of some elliptical galaxies that contain a gas disk. I also studied the formation of spiral galaxies: most cosmological simulations cannot explain the formation of Milky Way-like galaxies, i.e. with a large disk and a small bulge. I showed that this issue could be partly solved by taking into account in the simulations the mass loss from evolved stars through stellar winds, planetary nebulae and supernovae explosions. (author) [fr

  18. Diverse Formation Mechanisms for Compact Galaxies

    Science.gov (United States)

    Kim, Jin-Ah; Paudel, Sanjaya; Yoon, Suk-Jin

    2018-01-01

    Compact, quenched galaxies such as M32 are unusual ones located off the mass - size scaling relation defined by normal galaxies. Still, their formation mechanisms remain unsolved. Here we investigate the evolution of ~100 compact, quenched galaxies at z = 0 identified in the Illustris cosmological simulation. We identify three ways for a galaxy to become a compact one and, often, multiple mechanisms operate in a combined manner. First, stripping is responsible for making about a third of compact galaxies. Stripping removes stars from galaxies, usually while keeping their sizes intact. About one third are galaxies that cease their growth early on after entering into more massive, gigantic halos. Finally, about half of compact galaxies, ~ 35 % of which turn out to undergo stripping, experience the compaction due to the highly centrally concentrated star formation. We discuss the evolutionary path of compact galaxies on the mass – size plane for each mechanism in a broader context of dwarf galaxy formation and evolution.

  19. Cooking a `Sausage': the impact of merger shocks in cluster gas and galaxy evolution

    Science.gov (United States)

    Stroe, Andra; Sobral, David; Harwood, Jeremy; Van Weeren, Reinout J.; Rumsey, Clare; Intema, Huib; Röttgering, Huub; Brüggen, Marcus; Saunders, Richard; Hardcastle, Martin; Hoeft, Matthias

    2015-01-01

    Galaxy clusters mainly grow through mergers with other clusters and groups. Major mergers give rise to important astrophysical phenomena such as the segregation of dark and luminous matter and the formation of cluster-wide traveling shocks and also drive galaxy evolution. The observable effects of shock waves can be seen at radio wavelengths as relics: elongated, diffuse synchrotron emitting areas located at the periphery of merging clusters. Despite the great interest in relics, candidates with simple geometry, undisturbed morphology and high surface brightness are scarce. The `Sausage' cluster hosts an extraordinary Mpc-wide relic, which enables us to study to study particle acceleration and the effects of shocks on cluster galaxies. We use a unique combination of facilities (INT, WHT, Keck, Subaru, CFHT, GMRT, WSRT, AMI) to obtain the first cluster-wide, multi-wavelength, multi-method analysis aimed at giving a complete picture of a merging cluster with relics. Using the radio data, we derive shock properties and the magnetic field structure for the relic. Using spectral modeling, we test acceleration and electron energy-loss mechanisms and resolve the discrepancy between the Mach number calculated from the radio and X-rays. Our results indicate that particles are shock-accelerated, but turbulent re-acceleration or unusually efficient transport of particles in the downstream area and line-of-sight mixing are important effects. We demonstrate the feasibility of high-frequency observations of radio relics, by presenting a 16 GHz detection of the `Sausage' relic. The radio analysis is complemented by Hα mapping of the cluster volume, aimed at providing the first direct test as to whether the shock drives or prohibits star formation. We find numerous Hα emitting galaxies in close proximity to the radio relic which are extremely massive, metal-rich, mostly star-forming with evidence for gas mass loss though outflows. We speculate that the complex interaction

  20. On the evolution of the star formation rate function of massive galaxies: constraints at 0.4 MUSIC catalogue

    Science.gov (United States)

    Fontanot, Fabio; Cristiani, Stefano; Santini, Paola; Fontana, Adriano; Grazian, Andrea; Somerville, Rachel S.

    2012-03-01

    We study the evolution of the star formation rate function (SFRF) of massive (M★ > 1010 M⊙) galaxies over the 0.4 MUSIC) catalogue, which provides a suitable coverage of the spectral region from 0.3 to 24 ?m and either spectroscopic or photometric redshifts for each object. Individual SFRs have been obtained by combining ultraviolet and 24-?m observations, when the latter were available. For all other sources a 'spectral energy distribution (SED) fitting' SFR estimate has been considered. We then define a stellar mass limited sample, complete in the M★ > 1010 M⊙ range and determine the SFRF using the 1/Vmax algorithm. We thus define simulated galaxy catalogues based on the predictions of three different state-of-the-art semi-analytical models (SAMs) of galaxy formation and evolution, and compare them with the observed SFRF. We show that the theoretical SFRFs are well described by a double power law functional form and its redshift evolution is approximated with high accuracy by a pure evolution of the typical SFR (SFR★). We find good agreement between model predictions and the high-SFR end of the SFRF, when the observational errors on the SFR are taken into account. However, the observational SFRF is characterized by a double-peaked structure, which is absent in its theoretical counterparts. At z > 1.0 the observed SFRF shows a relevant density evolution, which is not reproduced by SAMs, due to the well-known overprediction of intermediate-mass galaxies at z˜ 2. SAMs are thus able to reproduce the most intense SFR events observed in the GOODS-MUSIC sample and their redshift distribution. At the same time, the agreement at the low-SFR end is poor: all models overpredict the space density of SFR ˜ 1 M⊙ yr-1 and no model reproduces the double-peaked shape of the observational SFRF. If confirmed by deeper infrared observations, this discrepancy will provide a key constraint on theoretical modelling of star formation and stellar feedback.

  1. Elliptical and lenticular galaxies evolution

    International Nuclear Information System (INIS)

    Vigroux, L.

    1981-01-01

    Different evolutionnary models for elliptical and lenticular galaxies are discussed. In the first part, we show that, at least some peculiar early types galaxies exhibit some activity. Then we describe the observationnal constraints: the color-magnitude diagram, the color gradient and the high metallicity of intraclusters gas. Among the different models, only the dissipation collapse followed by a hot wind driven by supernovae explosion explain in a natural way these constraints. Finally, the origin of SO is briefly discussed [fr

  2. Galaxy Formation

    DEFF Research Database (Denmark)

    Sparre, Martin

    Galaxy formation is an enormously complex discipline due to the many physical processes that play a role in shaping galaxies. The objective of this thesis is to study galaxy formation with two different approaches: First, numerical simulations are used to study the structure of dark matter and how...... galaxies form stars throughout the history of the Universe, and secondly it is shown that observations of gamma-ray bursts (GRBs) can be used to probe galaxies with active star formation in the early Universe. A conclusion from the hydrodynamical simulations is that the galaxies from the stateof...... is important, since it helps constraining chemical evolution models at high redshift. A new project studying how the population of galaxies hosting GRBs relate to other galaxy population is outlined in the conclusion of this thesis. The core of this project will be to quantify how the stellar mass function...

  3. Predicting Galaxy Star Formation Rates via the Co-evolution of Galaxies and Halos

    OpenAIRE

    Watson, Douglas F.; Hearin, Andrew P.; Berlind, Andreas A.; Becker, Matthew R.; Behroozi, Peter S.; Skibba, Ramin A.; Reyes, Reinabelle; Zentner, Andrew R.; Bosch, Frank C. van den

    2014-01-01

    In this paper, we test the age matching hypothesis that the star formation rate (SFR) of a galaxy of fixed stellar mass is determined by its dark matter halo formation history, and as such, that more quiescent galaxies reside in older halos. This simple model has been remarkably successful at predicting color-based galaxy statistics at low redshift as measured in the Sloan Digital Sky Survey (SDSS). To further test this method with observations, we present new SDSS measurements of the galaxy ...

  4. Evolution of the plasma universe: I. Double radio galaxies, quasars, and extragalactic jets

    International Nuclear Information System (INIS)

    Peratt, A.L.

    1986-01-01

    Cosmic plasma physics and our concept of the universe is in a state of rapid revision. This change started with in-situ measurements of plasmas in Earth's ionosphere, cometary atmospheres, and planetary magnetospheres; the translation of knowledge from laboratory experiments to astrophysical phenomena; discoveries of helical and filamentary plasma structures in the Galaxy and double radio sources; and the particle simulation of plasmas not accessible to in-situ measurement. Because of these, Birkeland (field-aligned) currents, double layers, and magnetic-field-aligned electric fields are now known to be far more important to the evolution of space plasma, including the acceleration of charged particles to high energies, than previously thought. This paper and its sequel investigate the observational evidence for a plasma universe threaded by Birkeland currents or filaments. This model of the universe was inspired by the advent of three-dimensional fully electromagnetic particle simulations and their application to the study of laboratory z pinches. This study resulted in totally unexpected phenomena in the data post-processed from the simulation particle, field, and history dumps. In particular, when the simulation parameters were scaled to galactic dimensions, the interaction between pinched filaments led to synchrotron radiation whose emission properties were found to share the following characteristics with double radio galaxies and quasars: power magnitude, isophotal morphology, spectra, brightness along source, polarization, and jets. The evolution of these pinched synchrotron emitting plasmas to elliptical, peculiar, and spiral galaxies by continuing the simulation run is addressed in a sequel paper

  5. The Metallicity Evolution of Blue Compact Dwarf Galaxies from the Intermediate Redshift to the Local Universe

    Science.gov (United States)

    Lian, Jianhui; Hu, Ning; Fang, Guanwen; Ye, Chengyun; Kong, Xu

    2016-03-01

    We present oxygen abundance measurements for 74 blue compact dwarf (BCD) galaxies in the redshift range of [0.2, 0.5] using the strong-line method. The spectra of these objects are taken using Hectospec on the Multiple Mirror Telescope. More than half of these BCDs had dust attenuation corrected using the Balmer decrement method. For comparison, we also selected a sample of 2023 local BCDs from the Sloan Digital Sky Survey (SDSS) database. Based on the local and intermediate-z BCD samples, we investigated the cosmic evolution of the metallicity, star formation rate (SFR), and Dn(4000) index. Compared with local BCDs, the intermediate-z BCDs had a systematically higher R23 ratio but a similar O32 ratio. Interestingly, no significant deviation in the mass-metallicity (MZ) relation was found between the intermediate-z and local BCDs. Besides the metallicity, the intermediate-z BCDs also exhibited an SFR distribution that was consistent with local BCDs, suggesting a weak dependence on redshift. The intermediate-z BCDs seemed to be younger than the local BCDs with lower Dn(4000) index values. The insignificant deviation in the mass-metallicity and mass-SFR relations between intermediate-z and local BCDs indicates that the relations between the global parameters of low-mass compact galaxies may be universal. These results from low-mass compact galaxies could be used to place important observational constraints on galaxy formation and evolution models.

  6. THE METALLICITY EVOLUTION OF BLUE COMPACT DWARF GALAXIES FROM THE INTERMEDIATE REDSHIFT TO THE LOCAL UNIVERSE

    International Nuclear Information System (INIS)

    Lian, Jianhui; Hu, Ning; Ye, Chengyun; Kong, Xu; Fang, Guanwen

    2016-01-01

    We present oxygen abundance measurements for 74 blue compact dwarf (BCD) galaxies in the redshift range of [0.2, 0.5] using the strong-line method. The spectra of these objects are taken using Hectospec on the Multiple Mirror Telescope. More than half of these BCDs had dust attenuation corrected using the Balmer decrement method. For comparison, we also selected a sample of 2023 local BCDs from the Sloan Digital Sky Survey (SDSS) database. Based on the local and intermediate-z BCD samples, we investigated the cosmic evolution of the metallicity, star formation rate (SFR), and D n (4000) index. Compared with local BCDs, the intermediate-z BCDs had a systematically higher R23 ratio but a similar O32 ratio. Interestingly, no significant deviation in the mass–metallicity (MZ) relation was found between the intermediate-z and local BCDs. Besides the metallicity, the intermediate-z BCDs also exhibited an SFR distribution that was consistent with local BCDs, suggesting a weak dependence on redshift. The intermediate-z BCDs seemed to be younger than the local BCDs with lower D n (4000) index values. The insignificant deviation in the mass–metallicity and mass–SFR relations between intermediate-z and local BCDs indicates that the relations between the global parameters of low-mass compact galaxies may be universal. These results from low-mass compact galaxies could be used to place important observational constraints on galaxy formation and evolution models

  7. THE METALLICITY EVOLUTION OF BLUE COMPACT DWARF GALAXIES FROM THE INTERMEDIATE REDSHIFT TO THE LOCAL UNIVERSE

    Energy Technology Data Exchange (ETDEWEB)

    Lian, Jianhui; Hu, Ning; Ye, Chengyun; Kong, Xu [CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China); Fang, Guanwen, E-mail: ljhhw@mail.ustc.edu.cn, E-mail: xkong@ustc.edu.cn [Institute for Astronomy and History of Science and Technology, Dali University, Dali 671003 (China)

    2016-03-01

    We present oxygen abundance measurements for 74 blue compact dwarf (BCD) galaxies in the redshift range of [0.2, 0.5] using the strong-line method. The spectra of these objects are taken using Hectospec on the Multiple Mirror Telescope. More than half of these BCDs had dust attenuation corrected using the Balmer decrement method. For comparison, we also selected a sample of 2023 local BCDs from the Sloan Digital Sky Survey (SDSS) database. Based on the local and intermediate-z BCD samples, we investigated the cosmic evolution of the metallicity, star formation rate (SFR), and D{sub n}(4000) index. Compared with local BCDs, the intermediate-z BCDs had a systematically higher R23 ratio but a similar O32 ratio. Interestingly, no significant deviation in the mass–metallicity (MZ) relation was found between the intermediate-z and local BCDs. Besides the metallicity, the intermediate-z BCDs also exhibited an SFR distribution that was consistent with local BCDs, suggesting a weak dependence on redshift. The intermediate-z BCDs seemed to be younger than the local BCDs with lower D{sub n}(4000) index values. The insignificant deviation in the mass–metallicity and mass–SFR relations between intermediate-z and local BCDs indicates that the relations between the global parameters of low-mass compact galaxies may be universal. These results from low-mass compact galaxies could be used to place important observational constraints on galaxy formation and evolution models.

  8. Globular cluster formation and evolution in the context of cosmological galaxy assembly: open questions

    Science.gov (United States)

    Forbes, Duncan A.; Bastian, Nate; Gieles, Mark; Crain, Robert A.; Kruijssen, J. M. Diederik; Larsen, Søren S.; Ploeckinger, Sylvia; Agertz, Oscar; Trenti, Michele; Ferguson, Annette M. N.; Pfeffer, Joel; Gnedin, Oleg Y.

    2018-02-01

    We discuss some of the key open questions regarding the formation and evolution of globular clusters (GCs) during galaxy formation and assembly within a cosmological framework. The current state of the art for both observations and simulations is described, and we briefly mention directions for future research. The oldest GCs have ages greater than or equal to 12.5 Gyr and formed around the time of reionization. Resolved colour-magnitude diagrams of Milky Way GCs and direct imaging of lensed proto-GCs at z˜6 with the James Webb Space Telescope (JWST) promise further insight. GCs are known to host multiple populations of stars with variations in their chemical abundances. Recently, such multiple populations have been detected in ˜2 Gyr old compact, massive star clusters. This suggests a common, single pathway for the formation of GCs at high and low redshift. The shape of the initial mass function for GCs remains unknown; however, for massive galaxies a power-law mass function is favoured. Significant progress has been made recently modelling GC formation in the context of galaxy formation, with success in reproducing many of the observed GC-galaxy scaling relations.

  9. The dynamics of aggregates of galaxies as related to their main galaxies

    International Nuclear Information System (INIS)

    Einasto, J.; Joeveer, M.; Kaasik, A.; Vennik, J.

    1976-01-01

    The dynamics of the aggregates of galaxies is compared with the dynamics of their member galaxies. It is demonstrated that within a factor 1.5-2 the dispersion of relative line-of-sight velocities is constant from the nuclei of main galaxies to the periphery of an aggregate. This isothermality of aggregates of galaxies is observed in all aggregates studied so far, from poor groups to rich clusters. The fact that the velocity dispersion of stars in galaxies is equal to that of galaxies in aggregates applies only to main galaxies. The stars in all companion galaxies have a smaller velocity dispersion of stars. The dynamical evolution of both galaxies and aggregates of galaxies is very slow. Thus the above data suggest that galaxies and their aggregates were formed together. (orig.) [de

  10. Gas Removal in the Ursa Minor Galaxy: Linking Hydrodynamics and Chemical Evolution Models

    Energy Technology Data Exchange (ETDEWEB)

    Caproni, Anderson; Lanfranchi, Gustavo Amaral; Baio, Gabriel Henrique Campos; Kowal, Grzegorz [Núcleo de Astrofísica Teórica, Universidade Cruzeiro do Sul, R. Galvão Bueno 868, Liberdade, 01506-000, São Paulo, SP (Brazil); Falceta-Gonçalves, Diego, E-mail: anderson.caproni@cruzeirodosul.edu.br [Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, Rua Arlindo Bettio 1000, CEP 03828-000 São Paulo (Brazil)

    2017-04-01

    We present results from a non-cosmological, three-dimensional hydrodynamical simulation of the gas in the dwarf spheroidal galaxy Ursa Minor. Assuming an initial baryonic-to-dark-matter ratio derived from the cosmic microwave background radiation, we evolved the galactic gas distribution over 3 Gyr, taking into account the effects of the types Ia and II supernovae. For the first time, we used in our simulation the instantaneous supernovae rates derived from a chemical evolution model applied to spectroscopic observational data of Ursa Minor. We show that the amount of gas that is lost in this process is variable with time and radius, being the highest rates observed during the initial 600 Myr in our simulation. Our results indicate that types Ia and II supernovae must be essential drivers of the gas loss in Ursa Minor galaxy (and probably in other similar dwarf galaxies), but it is ultimately the combination of galactic winds powered by these supernovae and environmental effects (e.g., ram-pressure stripping) that results in the complete removal of the gas content.

  11. KINEMATIC PROPERTIES AS PROBES OF THE EVOLUTION OF DWARF GALAXIES IN THE VIRGO CLUSTER

    International Nuclear Information System (INIS)

    Toloba, E.; Gorgas, J.; De Paz, A. Gil; Boselli, A.; Peletier, R. F.; Yildiz, U.; Cenarro, A. J.; Gadotti, D. A.; Pedraz, S.

    2009-01-01

    We present new observational results on the kinematical, morphological, and stellar population properties of a sample of 21 dEs located both in the Virgo Cluster and in the field, which show that 52% of the dEs (1) are rotationally supported, (2) exhibit structural signs of typical rotating systems such as disks, bars, or spiral arms, (3) are younger (∼3 Gyr) than non-rotating dEs, and (4) are preferentially located either in the outskirts of Virgo or in the field. This evidence is consistent with the idea that rotationally supported dwarfs are late-type spirals or irregulars that recently entered the cluster and lost their gas through a ram pressure stripping event, quenching their star formation and becoming dEs through passive evolution. We also find that all, but one, galaxies without photometric hints for hosting disks are pressure supported and are all situated in the inner regions of the cluster. This suggests a different evolution from the rotationally supported systems. Three different scenarios for these non-rotating galaxies are discussed (in situ formation, harassment, and ram pressure stripping).

  12. Magnetic field evolution in dwarf and Magellanic-type galaxies

    Science.gov (United States)

    Siejkowski, H.; Soida, M.; Chyży, K. T.

    2018-03-01

    Aims: Low-mass galaxies radio observations show in many cases surprisingly high levels of magnetic field. The mass and kinematics of such objects do not favour the development of effective large-scale dynamo action. We attempted to check if the cosmic-ray-driven dynamo can be responsible for measured magnetization in this class of poorly investigated objects. We investigated how starburst events on the whole, as well as when part of the galactic disk, influence the magnetic field evolution. Methods: We created a model of a dwarf/Magellanic-type galaxy described by gravitational potential constituted from two components: the stars and the dark-matter halo. The model is evolved by solving a three-dimensional (3D) magnetohydrodynamic equation with an additional cosmic-ray component, which is approximated as a fluid. The turbulence is generated in the system via supernova explosions manifested by the injection of cosmic-rays. Results: The cosmic-ray-driven dynamo works efficiently enough to amplify the magnetic field even in low-mass dwarf/Magellanic-type galaxies. The e-folding times of magnetic energy growth are 0.50 and 0.25 Gyr for the slow (50 km s-1) and fast (100 km s-1) rotators, respectively. The amplification is being suppressed as the system reaches the equipartition level between kinetic, magnetic, and cosmic-ray energies. An episode of star formation burst amplifies the magnetic field but only for a short time while increased star formation activity holds. We find that a substantial amount of gas is expelled from the galactic disk, and that the starburst events increase the efficiency of this process.

  13. What drives the evolution of Luminous Compact Blue Galaxies in Clusters vs. the Field?

    Science.gov (United States)

    Wirth, Gregory D.; Bershady, Matthew A.; Crawford, Steven M.; Hunt, Lucas; Pisano, Daniel J.; Randriamampandry, Solohery M.

    2018-06-01

    Low-mass dwarf ellipticals are the most numerous members of present-day galaxy clusters, but the progenitors of this dominant population remain unclear. A prime candidate is the class of objects known as Luminous Compact Blue Galaxies (LCBGs), common in intermediate-redshift clusters but virtually extinct today. Recent cosmological simulations suggest that present-day dwarf galaxies begin as irregular field galaxies, undergo an environmentally-driven starburst phase as they enter the cluster, and stop forming stars earlier than their counterparts in the field. This model predicts that cluster dwarfs should have lower stellar mass per unit dynamical mass than their counterparts in the field. We are undertaking a two-pronged archival research program to test this key prediction using the combination of precision photometry from space and high-quality spectroscopy. First, we are combining optical HST/ACS imaging of five z=0.55 clusters (including two HST Frontier Fields) with Spitzer IR imaging and publicly-released Keck/DEIMOS spectroscopy to measure stellar-to-dynamical-mass ratios for a large sample of cluster LCBGs. Second, we are exploiting a new catalog of LCBGs in the COSMOS field to gather corresponding data for a significant sample of field LCBGs. By comparing mass ratios from these datasets, we aim to test theoretical predictions and determine the primary physical driver of cluster dwarf-galaxy evolution.

  14. THE EVOLUTION OF DUSTY STAR FORMATION IN GALAXY CLUSTERS TO z = 1: SPITZER INFRARED OBSERVATIONS OF THE FIRST RED-SEQUENCE CLUSTER SURVEY

    International Nuclear Information System (INIS)

    Webb, T. M. A.; O'Donnell, D.; Coppin, Kristen; Faloon, Ashley; Geach, James E.; Noble, Allison; Yee, H. K. C.; Gilbank, David; Ellingson, Erica; Gladders, Mike; Muzzin, Adam; Wilson, Gillian; Yan, Renbin

    2013-01-01

    We present the results of an infrared (IR) study of high-redshift galaxy clusters with the MIPS camera on board the Spitzer Space Telescope. We have assembled a sample of 42 clusters from the Red-Sequence Cluster Survey-1 over the redshift range 0.3 14-15 M ☉ . We statistically measure the number of IR-luminous galaxies in clusters above a fixed inferred IR luminosity of 2 × 10 11 M ☉ , assuming a star forming galaxy template, per unit cluster mass and find it increases to higher redshift. Fitting a simple power-law we measure evolution of (1 + z) 5.1±1.9 over the range 0.3 cluster ). The evolution is similar, with ΣSFR/M cluster ∼ (1 + z) 5.4±1.9 . We show that this can be accounted for by the evolution of the IR-bright field population over the same redshift range; that is, the evolution can be attributed entirely to the change in the in-falling field galaxy population. We show that the ΣSFR/M cluster (binned over all redshift) decreases with increasing cluster mass with a slope (ΣSFR/M cluster ∼M cluster -1.5±0.4 ) consistent with the dependence of the stellar-to-total mass per unit cluster mass seen locally. The inferred star formation seen here could produce ∼5%-10% of the total stellar mass in massive clusters at z = 0, but we cannot constrain the descendant population, nor how rapidly the star-formation must shut-down once the galaxies have entered the cluster environment. Finally, we show a clear decrease in the number of IR-bright galaxies per unit optical galaxy in the cluster cores, confirming star formation continues to avoid the highest density regions of the universe at z ∼ 0.75 (the average redshift of the high-redshift clusters). While several previous studies appear to show enhanced star formation in high-redshift clusters relative to the field we note that these papers have not accounted for the overall increase in galaxy or dark matter density at the location of clusters. Once this is done, clusters at z ∼ 0.75 have the same

  15. Kelvin-Helmholtz evolution in subsonic cold streams feeding galaxies

    Science.gov (United States)

    Angulo, Adrianna; Coffing, S.; Kuranz, C.; Drake, R. P.; Klein, S.; Trantham, M.; Malamud, G.

    2017-10-01

    The most prolific star formers in cosmological history lie in a regime where dense filament structures carried substantial mass into the galaxy to sustain star formation without producing a shock. However, hydrodynamic instabilities present on the filament surface limit the ability of such structures to deliver dense matter deeply enough to sustain star formation. Simulations lack the finite resolution necessary to allow fair treatment of the instabilities present at the stream boundary. Using the Omega EP laser, we simulate this mode of galaxy formation with a cold, dense, filament structure within a hotter, subsonic flow and observe the interface evolution. Machined surface perturbations stimulate the development of the Kelvin-Helmholtz (KH) instability due to the resultant shear between the two media. A spherical crystal imaging system produces high-resolution radiographs of the KH structures along the filament surface. The results from the first experiments of this kind, using a rod with single-mode, long-wavelength modulations, will be discussed. This work is funded by the U.S. Department of Energy, through the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, Grant Number DE-NA0002956, and the National Laser User Facility Program, Grant Number DE-NA0002719, and through.

  16. Gradients of stellar population properties and evolution clues in a nearby galaxy M101

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Lin; Kong, Xu; Lin, Xuanbin; Mao, Yewei; Cheng, Fuzhen [Center for Astrophysics, University of Science and Technology of China, Hefei 230026 (China); Zou, Hu; Jiang, Zhaoji; Zhou, Xu, E-mail: linlin@mail.ustc.edu.cn, E-mail: xkong@ustc.edu.cn, E-mail: zouhu@nao.cas.cn [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2013-06-01

    Multiband photometric images from ultraviolet and optical to infrared are collected to derive spatially resolved properties of the nearby Scd-type galaxy M101. With evolutionary stellar population synthesis models, two-dimensional distributions and radial profiles of age, metallicity, dust attenuation, and star formation timescale in the form of the Sandage star formation history are obtained. When fitting with the models, we use the IRX-A {sub FUV} relation, found to depend on a second parameter of birth rate b (ratio of present- and past-averaged star formation rates), to constrain the dust attenuation. There are obvious parameter gradients in the disk of M101, which supports the theory of an 'inside-out' disk growth scenario. Two distinct disk regions with different gradients of age and color are discovered, similar to another late-type galaxy, NGC 628. The metallicity gradient of the stellar content is flatter than that of H II regions. The stellar disk is optically thicker inside than outside and the global dust attenuation of this galaxy is lower compared with galaxies of similar and earlier morphological type. We note that a variational star formation timescale describes the real star formation history of a galaxy. The timescale increases steadily from the center to the outskirt. We also confirm that the bulge in this galaxy is a disk-like pseudobulge, whose evolution is likely to be induced by some secular processes of the small bar which is relatively young, metal-rich, and contains much dust.

  17. Ultrafaint dwarfs—star formation and chemical evolution in the smallest galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Webster, David; Bland-Hawthorn, Joss [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Sutherland, Ralph, E-mail: d.webster@physics.usyd.edu.au [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston, ACT 2611 (Australia)

    2014-11-20

    In earlier work, we showed that a dark matter halo with a virial mass of 10{sup 7} M {sub ☉} can retain a major part of its baryons in the face of the pre-ionization phase and supernova (SN) explosion from a 25 M {sub ☉} star. Here, we expand on the results of that work, investigating the star formation and chemical evolution of the system beyond the first SN. In a galaxy with a mass M {sub vir} = 10{sup 7} M {sub ☉}, sufficient gas is retained by the potential for a second period of star formation to occur. The impact of a central explosion is found to be much stronger than that of an off-center explosion both in blowing out the gas and in enriching it, as in the off-center case most of the SN energy and metals escape into the intergalactic medium. We model the star formation and metallicity, given the assumption that stars form for 100, 200, 400, and 600 Myr, and discuss the results in the context of recent observations of very low-mass galaxies. We show that we can account for most features of the observed relationship between [α/Fe] and [Fe/H] in ultra-faint dwarf galaxies with the assumption that the systems formed at a low mass, rather than being remnants of much larger systems.

  18. The Evolution of Neutral Hydrogen in Galaxy Groups

    Science.gov (United States)

    Sanderson, Kelly Nicole; Wilcots, Eric; Hess, Kelley M.

    2018-01-01

    The Illustris suite of simulations is held as the standard of large scale gravitational and hydro-dynamical simulations and allows us to make a better comparisons with physical processes at the gaseous level by providing a higher mass resolution than previously available through the Millenium-II simulation. We present a comparison of an analysis on the HI content and distribution of galaxies in groups as a function of their group dark matter halo to the results of a large scale cosmological simulation. From the simulation we select optical group members above a Mr=-18 r-band magnitude and HI group members with HI above 109.5M⊙. We find that 74% of the HI detected galaxies are in groups or clusters and 84% of the optically detected galaxies are in groups or clusters. In the Hess & Wilcots (2013) paper it was found that as group membership, or group dark matter halo mass, increased, the fraction of galaxies detected in HI decreased and the spatial distribution of galaxies in these groups increased. We show the spatial distributions of galaxies, HI and optically detected, in order to reproduce these results. We find that Illustris qualitatively reproduces these trends, however, the simulation seems to be overestimating the mass of HI gas in all of its galaxies as well as the number of galaxies above the 109.5M⊙ limit.

  19. The Properties of Faint Field Galaxies

    Science.gov (United States)

    Driver, Simon. P.

    1994-12-01

    One of the current drawbacks of Charge Coupled Devices (CCDs) is their restrictive fields of view. The Hitchhiker CCD camera overcomes this limitation by operating in parallel with existing instrumentation and is able to cover a large area as well as large volumes. Hitchhiker is mounted on the 4.2m William Herschel Telescope and has been operating for two years. The first use of the Hitchhiker data set has been to study the general properties of faint galaxies. The observed trend of how the differential numbers of galaxies vary with magnitude agrees extremely well with those of other groups and covers, for the first time, all four major optical bandpasses. This multi-band capability has also allowed the study of how the colors of galaxies change with magnitude and how the correlation of galaxies on the sky varies between the optical bandpasses. A dwarf dominated model has been developed to explain these observations and challenges our knowledge of the space-density of dwarf galaxies. The model demonstrates that a simple upward turn in the luminosity distribution of galaxies, similar to that observed in clusters, would remain undetected by the field surveys yet can explain many of the observations without recourse to non-passive galaxy evolution. The conclusion is that the field luminosity distribution is not constrained at faint absolute magnitudes. A combination of a high density of dwarf galaxies and mild evolution could explain all the observations. Continuing work with HST and the Medium Deep Survey Team now reveals the morphological mix of galaxies down to mI ~ 24.0. The results confirm that ellipticals and early-type spirals are well fitted by standard no-evolution models whilst the late-type spirals can only be fitted by strong evolution and/or a significant turn-up in the local field LF.

  20. The evolution of C/O in dwarf galaxies from Hubble Space Telescope FOS observations

    Science.gov (United States)

    Garnett, D. R.; Skillman, E. D.; Dufour, R. J.; Peimbert, M.; Torres-Peimbert, S.; Terlevich, R.; Terlevich, E.; Shields, G. A.

    1995-01-01

    We present UV observations of seven H II regions in low-luminosity dwarf irregular galaxies and the Magellanic Clouds obtained with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) in order to measure the C/O abundance ratio in the interstellar medium (ISM) of those galaxies. We measure both O III 1666 A and C III 1909 A in our spectra, enabling us to determine C(+2)/O(+2) with relatively small uncertainties. The results from our HST observations show a continuous increase in C/O with increasing O/H, consistent with a power law having an index of 0.43 +/- 0.09 over the range -4.7 to -3.6 in log (O/H). One possible interpretation of this trend is that the most metal-poor galaxies are the youngest and dominated by the products of early enrichment by massive stars, while more metal-rich galaxies show increasing, delayed contributions of carbon from intermediate-mass stars. Our results also suggest that it may not be appropiate to combine abundances in irregular galaxies with those in spiral galaxies to study the evolution of chemical abundances. Our measured C/O ratios in the most metal-poor galaxies are consistent with predictions of nucleosynthesis from massive stars for Weaver & Woosley's best estimate for the 12C(alpha, gamma) 16O nuclear reaction rate, assuming negligible contanmination from carbon produced in intermediate-mass stars in these galaxies. We detect a weak N III 1750 A multiplet in SMC N88A and obtain interesting upper limits for two other objects. Our 2 sigma uppr limits on the 1750 A feature indicate that the N(+2)/O(+2) ratios in these objects are not significantly larger than the N(+)/O(+) ratios measured from optical spectra. This behavior is consistent with predictions of photionization models, although better detections of N III are needed to confirm the results.

  1. EVOLUTION OF GASEOUS DISK VISCOSITY DRIVEN BY SUPERNOVA EXPLOSION. II. STRUCTURE AND EMISSIONS FROM STAR-FORMING GALAXIES AT HIGH REDSHIFT

    International Nuclear Information System (INIS)

    Yan Changshuo; Wang Jianmin

    2010-01-01

    High spatial resolution observations show that high-redshift galaxies are undergoing intensive evolution of dynamical structure and morphologies displayed by the Hα, Hβ, [O III], and [N II] images. It has been shown that supernova explosion (SNexp) of young massive stars during the star formation epoch, as kinetic feedback to host galaxies, can efficiently excite the turbulent viscosity. We incorporate the feedback into the dynamical equations through mass dropout and angular momentum transportation driven by the SNexp-excited turbulent viscosity. The empirical Kennicutt-Schmidt law is used for star formation rates (SFRs). We numerically solve the equations and show that there can be intensive evolution of structure of the gaseous disk. Secular evolution of the disk shows interesting characteristics: (1) high viscosity excited by SNexp can efficiently transport the gas from 10 kpc to ∼1 kpc forming a stellar disk whereas a stellar ring forms for the case with low viscosity; (2) starbursts trigger SMBH activity with a lag of ∼10 8 yr depending on SFRs, prompting the joint evolution of SMBHs and bulges; and (3) the velocity dispersion is as high as ∼100 km s -1 in the gaseous disk. These results are likely to vary with the initial mass function (IMF) that the SNexp rates rely on. Given the IMF, we use the GALAXEV code to compute the spectral evolution of stellar populations based on the dynamical structure. In order to compare the present models with the observed dynamical structure and images, we use the incident continuum from the simple stellar synthesis and CLOUDY to calculate emission line ratios of Hα, Hβ, [O III], and [N II], and Hα brightness of gas photoionized by young massive stars formed on the disks. The models can produce the main features of emission from star-forming galaxies. We apply the present model to two galaxies, BX 389 and BX 482 observed in the SINS high-z sample, which are bulge and disk-dominated, respectively. Two successive

  2. CHEMODYNAMIC EVOLUTION OF DWARF GALAXIES IN TIDAL FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Williamson, David; Martel, Hugo [Département de physique, de génie physique et d’optique, Université Laval, Québec, QC, G1V 0A6 (Canada); Romeo, Alessandro B., E-mail: david-john.williamson.1@ulaval.ca [Department of Earth and Space Sciences, Chalmers University of Technology, SE-41296 Gothenburg (Sweden)

    2016-11-01

    The mass–metallicity relation shows that the galaxies with the lowest mass have the lowest metallicities. As most dwarf galaxies are in group environments, interaction effects such as tides could contribute to this trend. We perform a series of smoothed particle hydrodynamics simulations of dwarf galaxies in external tidal fields to examine the effects of tides on their metallicities and metallicity gradients. In our simulated galaxies, gravitational instabilities drive gas inwards and produce centralized star formation and a significant metallicity gradient. Strong tides can contribute to these instabilities, but their primary effect is to strip the outer low-metallicity gas, producing a truncated gas disk with a large metallicity. This suggests that the effect of tides on the mass–metallicity relation is to move dwarf galaxies to higher metallicities.

  3. Charting the evolution of the ages and metallicities of massive galaxies since z = 0.7

    Energy Technology Data Exchange (ETDEWEB)

    Gallazzi, Anna; Zibetti, Stefano [INAF-Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48109 (United States); Brinchmann, Jarle [Leiden Observatory, Leiden University, 2300RA, Leiden (Netherlands); Kelson, Daniel D., E-mail: gallazzi@arcetri.astro.it [Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101 (United States)

    2014-06-10

    Detailed studies of the stellar populations of intermediate-redshift galaxies can shed light onto the processes responsible for the growth of the massive galaxy population in the last 8 billion years. We here take a step toward this goal by means of deep, multiobject rest-frame optical spectroscopy, performed with the Inamori Magellan Areal Camera and Spectrograph on the Magellan telescope, of a sample of ∼70 galaxies in the Extended Chandra Deep Field South survey with redshift 0.65 ≤ z ≤ 0.75, apparent R > 22.7 mag{sub Vega}, and stellar mass >10{sup 10} M {sub ☉}. We measure velocity dispersion and stellar absorption features for individual sources. We interpret them by means of a large Monte Carlo library of star formation histories, following the Bayesian approach adopted for previous low redshift studies, and derive constraints on the stellar mass, mean stellar age, and stellar metallicity of these galaxies. We characterize for the first time the relations between stellar age and stellar mass and between stellar metallicity and stellar mass at z ∼ 0.7 for the galaxy population as a whole and for quiescent and star-forming galaxies separately. These relations of increasing age and metallicity with galaxy mass for the galaxy population as a whole have a similar shape as the z ∼ 0.1 analog derived for Sloan Digital Sky Survey galaxies but are shifted by –0.28 dex in age and by –0.13 dex in metallicity, at odds with simple passive evolution. Considering z = 0.7 quiescent galaxies alone, we find that no additional star formation and chemical enrichment are required for them to evolve into the present-day quiescent population. However, other observations require the quiescent population to grow from z = 0.7 to the present day. This growth could be supplied by the quenching of a fraction of z = 0.7 M {sub *} > 10{sup 11} M {sub ☉} star-forming galaxies with metallicities already comparable to those of quiescent galaxies, thus leading to the

  4. Star formation rates and abundance gradients in disk galaxies

    International Nuclear Information System (INIS)

    Wyse, R.F.G.; Silk, J.

    1989-01-01

    Analytic models for the evolution of disk galaxies are presented, placing special emphasis on the radial properties. These models are straightforward extensions of the original Schmidt (1959, 1963) models, with a dependence of star formation rate on gas density. The models provide successful descriptions of several measures of galactic disk evolution, including solar neighborhood chemical evolution, the presence and amplitude of metallicity and color gradients in disk galaxies, and the global rates of star formation in disk galaxies, and aid in the understanding of the apparent connection between young and old stellar populations in spiral galaxies. 67 refs

  5. SAGE-SMC: Surveying the Agents of Galaxy Evolution in the Tidally-Disrupted, Low-Metallicity Small Magellanic Cloud

    Science.gov (United States)

    Gordon, Karl; Babler, Brian; Bernard, Jean-Philippe; Block, Miwa; Blum, Robert; Bolatto, Alberto; Bot, Caroline; Bracker, Steve; Carlson, Lynn; Churchwell, Ed; Clayton, Geoffrey; Cohen, Martin; Engelbracht, Charles; Fukui, Yasuo; Gorjian, Varoujan; Harris, Jason; Hony, Sacha; Hora, Joseph; Indebetouw, Remy; Israel, Frank; Kawamura, Akiko; Leroy, Adam; Li, Aigen; Madden, Suzanne; Markwick-Kemper, Ciska; Meade, Marilyn; Meixner, Margaret; Misselt, Karl; Mizuno, Norikazu; Mizuno, Akira; Muller, Erik; Oliveira, Joana; Olsen, Knut; Onishi, Toshikazu; Paladini, Roberta; Points, Sean; Reach, William; Robitaille, Thomas; Rubin, Douglas; Sandstrom, Karin; Sato, Shuji; Sewilo, Marta; Shibai, Hiroshi; Simon, Josh; Smith, Linda; Srinivasan, Sundar; Tielens, Xander; van Dyk, Schuyler; van Loon, Jacco; Vijh, Uma; Volk, Kevin; Whitney, Barbara; Zaritsky, Dennis

    2007-05-01

    The observable properties of galaxy evolution are largely driven by the life-cycle of baryonic matter: stars precipitate out of a complex, multi-phase interstellar medium; and eventually, evolved stellar populations return enriched material back to the ISM via stellar winds or supernova explosions. As demonstrated by the SAGE-LMC survey, comprehensive Spitzer imaging of a nearby galaxy provides an incredibly rich view of this baryonic lifecycle, allowing for an unprecedented understanding of the physical processes which drive galaxy evolution. This proposal will extend the SAGE analysis to the whole SMC (Bar, Wing, and high-density portion of the Magellanic Bridge), a galaxy whose properties are uniquely similar to those of star-forming galaxies at high redshift. Specifically, the SMC's metallicity is below the critical threshold (1/3-1/4 Z_sun) where interstellar medium properties are observed to change dramatically (sharp reduction in the PAH dust mass fraction, reduced dust-to-gas ratio, and extreme ultraviolet extinction curve variations). In addition, the SMC has been profoundly influenced by past interactions with the LMC and Milky Way, allowing us to study the impact of periodic interactions on the structure of the ISM and the physical processes of star formation. We will gain crucial insight into the ISM and star formation in a known tidal debris structure (Bridge portion of SMC), which has a metallicity 4 times lower than the rest of the SMC. When combined with observations of the Milky Way (GLIMPSE, MIPSGAL) and the LMC (SAGE-LMC), our survey of the SMC (SAGE-SMC) will provide a complete and detailed picture of the life-cycle of baryons in galactic environments spanning orders of magnitude in metallicity, and wide ranges in star formation history. This understanding will equip us to properly interpret the infrared properties of more distant galaxies, both in the local (e.g., SINGS) and high-redshift (e.g., GOODS and SWIRE) universe.

  6. Galaxy correlations and cosmology

    International Nuclear Information System (INIS)

    Fall, S.M.

    1979-01-01

    Correlations in the distribution of galaxies provide some important clues about the structure and evolution of the Universe on scales larger than individual galaxies. In recent years much effort has been devoted to estimating and interpreting galaxy correlations. This is a review of these efforts. It is meant to provide both an introductory overview of the subject and a critical assessment of some recent developments

  7. Radio galaxies radiation transfer, dynamics, stability and evolution of a synchrotron plasmon

    CERN Document Server

    Pacholczyk, A G

    1977-01-01

    Radio Galaxies: Radiation Transfer, Dynamics, Stability and Evolution of a Synchrotron Plasmon deals with the physics of a region in space containing magnetic field and thermal and relativistic particles (a plasmon). The synchrotron emission and absorption of this region are discussed, along with the properties of its spectrum; its linear and circular polarization; transfer of radiation through such a region; its dynamics and expansion; and interaction with external medium.Comprised of eight chapters, this volume explores the stability, turbulence, and acceleration of particles in a synchrotro

  8. Observations of Superwinds in Dwarf Galaxies

    Science.gov (United States)

    Marlowe, A. T.; Heckman, T. M.; Wyse, R.; Schommer, R.

    1993-12-01

    Dwarf galaxies are important in developing our understanding of the formation and evolution of galaxies, and of the structure in the universe. The concept of supernova-driven mass outflows is a vital ingredient in theories of the structure and evolution of dwarfs galaxies. We have begun a detailed multi-waveband search for outflows in starbursting dwarf galaxies, and have obtained Fabry-Perot images and Echelle spectra of 20 nearby actively-star-forming dwarf galaxies. In about half the sample, the Fabry-Perot Hα images show loops and filaments with sizes of one to a few kpc. The Echelle spectra taken through the loops and filaments show kinematics consistent with expanding bubble-like structures. We describe these data, and present seven dwarfs in our sample that have the strongest evidence of outflows.

  9. The Sloan Digital Sky Survey Quasar Lens Search. VI. Constraints on Dark Energy and the Evolution of Massive Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Oguri, Masamune [Univ. of Tokyo (Japan); et al.

    2012-05-01

    We present a statistical analysis of the final lens sample from the Sloan Digital Sky Survey Quasar Lens Search (SQLS). The number distribution of a complete subsample of 19 lensed quasars selected from 50,836 source quasars is compared with theoretical expectations, with particular attention to the selection function. Assuming that the velocity function of galaxies does not evolve with redshift, the SQLS sample constrains the cosmological constant to \\Omega_\\Lambda=0.79^{+0.06}_{-0.07}(stat.)^{+0.06}_{-0.06}(syst.) for a flat universe. The dark energy equation of state is found to be consistent with w=-1 when the SQLS is combined with constraints from baryon acoustic oscillation (BAO) measurements or results from the Wilkinson Microwave Anisotropy Probe (WMAP). We also obtain simultaneous constraints on cosmological parameters and redshift evolution of the galaxy velocity function, finding no evidence for redshift evolution at z<1 in any combinations of constraints. For instance, number density evolution quantified as \

  10. The Metallicity of Void Dwarf Galaxies

    NARCIS (Netherlands)

    Kreckel, K.; Croxall, K.; Groves, B.; van de Weygaert, R.; Pogge, R. W.

    The current ΛCDM cosmological model predicts that galaxy evolution proceeds more slowly in lower density environments, suggesting that voids are a prime location to search for relatively pristine galaxies that are representative of the building blocks of early massive galaxies. To test the

  11. The Evolution of Galaxies by the Incompatibility between Dark Matter and Baryonic Matter

    OpenAIRE

    Chung, Ding-Yu

    2001-01-01

    In this paper, the evolution of galaxies is by the incompatibility between dark matter and baryonic matter. Due to the structural difference, baryonic matter and dark matter are incompatible to each other as oil droplet and water in emulsion. In the interfacial zone between dark matter and baryonic matter, this incompatibility generates the modification of Newtonian dynamics to keep dark matter and baryonic matter apart. The five periods of baryonic structure development in the order of incre...

  12. Low-Surface-Brightness Galaxies: Hidden Galaxies Revealed

    Science.gov (United States)

    Bothun, G.; Impey, C.; McGaugh, S.

    1997-07-01

    In twenty years, low surface brightness (LSB) galaxies have evolved from being an idiosyncratic notion to being one of the major baryonic repositories in the Universe. The story of their discovery and the characterization of their properties is told here. Their recovery from the noise of the night sky background is a strong testament to the severity of surface brightness selection effects. LSB galaxies have a number of remarkable properties which distinguish them from the more familiar Hubble Sequence of spirals. The two most important are 1) they evolve at a significantly slower rate and may well experience star formation outside of the molecular cloud environment, 2) they are embedded in dark matter halos which are of lower density and more extended than the halos around high surface brightness (HSB) disk galaxies. Compared to HSB disks, LSB disks are strongly dark matter dominated at all radii and show a systematic increase in $M/L$ with decreasing central surface brightness. In addition, the recognition that large numbers of LSB galaxies actually exist has changed the form of the galaxy luminosity function and has clearly increased the space density of galaxies at z =0. Recent CCD surveys have uncovered a population of red LSB disks that may be related to the excess of faint blue galaxies detected at moderate redshifts. LSB galaxies offer us a new window into galaxy evolution and formation which is every bit as important as those processes which have produced easy to detect galaxies. Indeed, the apparent youth of some LSB galaxies suggest that galaxy formation is a greatly extended process. While the discovery of LSB galaxies have lead to new insights, it remains unwise to presume that we now have a representative sample which encompasses all galaxy types and forms. (SECTION: Invited Review Paper)

  13. Kinematic Modeling of Distant Galaxies

    Directory of Open Access Journals (Sweden)

    Kipper Rain

    2012-12-01

    Full Text Available Evolution of galaxies is one of the most actual topics in astrophysics. Among the most important factors determining the evolution are two galactic components which are difficult or even impossible to detect optically: the gaseous disks and the dark matter halo. We use deep Hubble Space Telescope images to construct a two-component (bulge + disk model for stellar matter distribution of galaxies. Properties of the galactic components are derived using a three-dimensional galaxy modeling software, which also estimates disk thickness and inclination angle. We add a gas disk and a dark matter halo and use hydrodynamical equations to calculate gas rotation and dispersion profiles in the resultant gravitational potential. We compare the kinematic profiles with the Team Keck Redshift Survey observations. In this pilot study, two galaxies are analyzed deriving parameters for their stellar components; both galaxies are found to be disk-dominated. Using the kinematical model, the gas mass and stellar mass ratio in the disk are estimated.

  14. The extreme flare in III Zw 2: evolution of a radio jet in a Seyfert galaxy

    NARCIS (Netherlands)

    Brunthaler, A.; Falcke, H.D.E.; Bower, G.C.; Aller, M.F.; Aller, H.D.; Teraesranta, H.

    2005-01-01

    A very detailed monitoring of a radio flare in the Seyfert I galaxy III Zw 2 with the VLA and the VLBA is presented. The relative astrometry in the VLBA observations was precise on a level of a few microarcseconds. Spectral and spatial evolution of the source are closely linked and these

  15. Stochastic 2-D galaxy disk evolution models. Resolved stellar populations in the galaxy M33

    Science.gov (United States)

    Mineikis, T.; Vansevičius, V.

    We improved the stochastic 2-D galaxy disk models (Mineikis & Vansevičius 2014a) by introducing enriched gas outflows from galaxies and synthetic color-magnitude diagrams of stellar populations. To test the models, we use the HST/ACS stellar photometry data in four fields located along the major axis of the galaxy M33 (Williams et al. 2009) and demonstrate the potential of the models to derive 2-D star formation histories in the resolved disk galaxies.

  16. Cosmological aspects and properties evolution of galaxy clusters

    International Nuclear Information System (INIS)

    Majerowicz, Sebastien

    2003-01-01

    In the standard scenario for galaxy cluster formation, galaxy clusters form by material accretion and violent merger events. Between two merger events, galaxy cluster components which are the dark matter (75 %), the intra-cluster medium (20 %) and the galaxies (5 %), reach for equilibrium. The intra-cluster medium is the main baryonic component. This is a hot optically thin gas and its temperature tells something about the gravitational potential well. This well is essentially the consequence of the dark matter distribution. The intra-cluster medium is so hot than its emission produces only x-ray photons. We studied the properties of the intra-cluster medium for some clusters by using the observations coming from the european satellite XMM-NEWTON [fr

  17. The MUSIC of Galaxy Clusters - III. Properties, evolution and Y-M scaling relation of protoclusters of galaxies

    Science.gov (United States)

    Sembolini, Federico; De Petris, Marco; Yepes, Gustavo; Foschi, Emma; Lamagna, Luca; Gottlöber, Stefan

    2014-06-01

    In this work, we study the properties of protoclusters of galaxies by employing the MultiDark SImulations of galaxy Clusters (MUSIC) set of hydrodynamical simulations, featuring a sample of 282 resimulated clusters with available merger trees up to z = 4. We study the characteristics and redshift evolution of the mass and the spatial distribution for all the protoclusters, which we define as the most massive progenitors of the clusters identified at z = 0. We extend the study of the baryon content to redshifts larger than 1 also in terms of gas and stars budgets: no remarkable variations with redshift are discovered. Furthermore, motivated by the proven potential of Sunyaev-Zel'dovich surveys to blindly search for faint distant objects, we compute the scaling relation between total object mass and integrated Compton y-parameter. We find that the slope of this scaling law is steeper than what expected for a self-similarity assumption among these objects, and it increases with redshift mainly when radiative processes are included. We use three different criteria to account for the dynamical state of the protoclusters, and find no significant dependence of the scaling parameters on the level of relaxation. We exclude the dynamical state as the cause of the observed deviations from self-similarity in protoclusters.

  18. Galaxy and Mass Assembly (GAMA): Morphological transformation of galaxies across the green valley

    Science.gov (United States)

    Bremer, M. N.; Phillipps, S.; Kelvin, L. S.; De Propris, R.; Kennedy, Rebecca; Moffett, Amanda J.; Bamford, S.; Davies, L. J. M.; Driver, S. P.; Häußler, B.; Holwerda, B.; Hopkins, A.; James, P. A.; Liske, J.; Percival, S.; Taylor, E. N.

    2018-05-01

    We explore constraints on the joint photometric and morphological evolution of typical low redshift galaxies as they move from the blue cloud through the green valley and on to the red sequence. We select Galaxy And Mass Assembly (GAMA) survey galaxies with 10.25 sensitive K-band profiles of red and green galaxy populations are very similar while g-band profiles indicate more disc-like morphologies for the green galaxies: apparent (optical) morphological differences arise primarily from radial mass-to-light ratio variations. Two-component fits show that most green galaxies have significant bulge and disc components and that the blue to red evolution is driven by colour change in the disc. Together, these strongly suggest that galaxies evolve from blue to red through secular disc fading and that a strong bulge is present prior to any decline in star formation. The relative abundance of the green population implies a typical time-scale for traversing the green valley ˜1-2 Gyr and is independent of environment, unlike that of the red and blue populations. While environment likely plays a rôle in triggering the passage across the green valley, it appears to have little effect on time taken. These results are consistent with a green valley population dominated by (early type) disc galaxies that are insufficiently supplied with gas to maintain previous levels of disc star formation, eventually attaining passive colours. No single event is needed to quench their star formation.

  19. How robust are the constraints on cosmology and galaxy evolution from the lens-redshift test?

    Energy Technology Data Exchange (ETDEWEB)

    Capelo, Pedro R [Astronomy Department, Yale University, PO Box 208101, New Haven, CT 06520-8101 (United States); Natarajan, Priyamvada [Astronomy Department, Yale University, PO Box 208101, New Haven, CT 06520-8101 (United States)

    2007-12-15

    The redshift distribution of galaxy lenses in known gravitational lens systems provides a powerful test that can potentially discriminate amongst cosmological models. However, applications of this elegant test have been curtailed by two factors: our ignorance of how galaxies evolve with redshift, and the absence of methods to deal with the effect of incomplete information in lensing systems. In this paper, we investigate both issues in detail. We explore how to extract the properties of evolving galaxies, assuming that the cosmology is well determined by other techniques. We propose a new nested Monte Carlo method to quantify the effects of incomplete data. We apply the lens-redshift test to an improved sample of seventy lens systems derived from recent observations, primarily from the SDSS, SLACS and the CLASS surveys. We find that the limiting factor in applying the lens-redshift test derives from poor statistics, including incomplete information samples and biased sampling. Many lenses that uniformly sample the underlying true image separation distribution will be needed to use this test as a complementary method to measure the value of the cosmological constant or the properties of evolving galaxies. Planned future surveys by missions like the SNAP satellite or LSST are likely to usher in a new era for strong lensing studies that utilize this test. With expected catalogues of thousands of new strong lenses, the lens-redshift test could offer a powerful tool to probe cosmology as well as galaxy evolution.

  20. How robust are the constraints on cosmology and galaxy evolution from the lens-redshift test?

    International Nuclear Information System (INIS)

    Capelo, Pedro R; Natarajan, Priyamvada

    2007-01-01

    The redshift distribution of galaxy lenses in known gravitational lens systems provides a powerful test that can potentially discriminate amongst cosmological models. However, applications of this elegant test have been curtailed by two factors: our ignorance of how galaxies evolve with redshift, and the absence of methods to deal with the effect of incomplete information in lensing systems. In this paper, we investigate both issues in detail. We explore how to extract the properties of evolving galaxies, assuming that the cosmology is well determined by other techniques. We propose a new nested Monte Carlo method to quantify the effects of incomplete data. We apply the lens-redshift test to an improved sample of seventy lens systems derived from recent observations, primarily from the SDSS, SLACS and the CLASS surveys. We find that the limiting factor in applying the lens-redshift test derives from poor statistics, including incomplete information samples and biased sampling. Many lenses that uniformly sample the underlying true image separation distribution will be needed to use this test as a complementary method to measure the value of the cosmological constant or the properties of evolving galaxies. Planned future surveys by missions like the SNAP satellite or LSST are likely to usher in a new era for strong lensing studies that utilize this test. With expected catalogues of thousands of new strong lenses, the lens-redshift test could offer a powerful tool to probe cosmology as well as galaxy evolution

  1. Dust Evolution in Low-Metallicity Environments: Bridging the Gap Between Local Universe and Primordial Galaxies

    Science.gov (United States)

    Galliano, Frederic; Barlow, Mike; Bendo, George; Boselli, Alessandro; Buat, Veronique; Chanial, Pierre; Clements, David; Davies, Jon; Eales, Steve; Gomez, Haley; Isaak, Kate; Madden, Suzanne; Page, Mathew; Perez Fournon, Ismael; Sauvage, Marc; Spinoglio, Luigi; Vaccari, Mattia; Wilson, Christine

    2008-03-01

    The local galaxy Science Advisory Group (SAG 2) in the Herschel/SPIRE consortium, has constructed a Guaranteed Time Key Program using the PACS and SPIRE insruments to obtain 60 to 550 micron photometry of a statistically significant sample of 51 dwarf galaxies in our local universe chosen to cover an impressivly broad range of physical conditions. Here we propose the necessary complementary IRAC, MIPS and IRS Spitzer observations which together with the Herschel GT database will provide a rich database to the community to perform the dust and gas analyses in unprecedented detail in low metallicity galaxies ranging between 1/50 to 1 solar metallicity. Due to their chemical youth, and to the extreme conditions they experience, low metallicity environments constitute a keystone to understand dust evolution. The primary goal of this combined Herschel and Spitzer project is to study in details the physical processes at play within the ISM of these galaxies. We will take advantage of the powerful combination of Spitzer, Herschel and ancillary data to decompose the SED into the emission coming from the main phases of the ISM. Such a decomposition will provide reliable estimate of the abundances of the principal dust species, as a fonction of metallicity and physical conditions. These results will be exploited to compare the various evolutionary processes affecting the dust content of galaxies. All these outstanding scientific advances will be the true legacy value that this project brings to the community.

  2. The extreme flare in III Zw 2:. Evolution of a radio jet in a Seyfert galaxy

    NARCIS (Netherlands)

    Brunthaler, A.; Falcke, H.D.E.; Bower, G.C.; Aller, M.F.; Aller, H.D.; Teräsranta, H.

    2005-01-01

    A very detailed monitoring of a radio flare in the Seyfert I galaxy III Zw 2 with the VLA and the VLBA is presented. The relative astrometry in the VLBA observations was precise to a few muas. The spectral and spatial evolutions of the source are closely linked, and these observations allowed us to

  3. Bar-spheroid interaction in galaxies

    Science.gov (United States)

    Hernquist, Lars; Weinberg, Martin D.

    1992-01-01

    N-body simulation and linear analysis is employed to investigate the secular evolution of barred galaxies, with emphasis on the interaction between bars and spheroidal components of galaxies. This interaction is argued to drive secular transfer of angular momentum from bars to spheroids, primarily through resonant coupling. A moderately strong bar, having mass within corotation about 0.3 times the enclosed spheroid mass, is predicted to shed all its angular momentum typically in less than about 10 exp 9 yr. Even shorter depletion time scales are found for relatively more massive bars. It is suggested either that spheroids around barred galaxies are structured so as to inhibit strong coupling with bars, or that bars can form by unknown processes long after disks are established. The present models reinforce the notion that bars can drive secular evolution in galaxies.

  4. COSMIC EVOLUTION OF STAR FORMATION ENHANCEMENT IN CLOSE MAJOR-MERGER GALAXY PAIRS SINCE z = 1

    International Nuclear Information System (INIS)

    Xu, C. K.; Shupe, D. L.; Bock, J.; Bridge, C.; Cooray, A.; Lu, N.; Schulz, B.; Béthermin, M.; Aussel, H.; Elbaz, D.; Le Floc'h, E.; Riguccini, L.; Berta, S.; Lutz, D.; Magnelli, B.; Conley, A.; Franceschini, A.; Marsden, G.; Oliver, S. J.; Pozzi, F.

    2012-01-01

    The infrared (IR) emission of 'M * galaxies' (10 10.4 ≤ M star ≤ 10 11.0 M ☉ ) in galaxy pairs, derived using data obtained in Herschel (PEP/HerMES) and Spitzer (S-COSMOS) surveys, is compared to that of single-disk galaxies in well-matched control samples to study the cosmic evolution of the star formation enhancement induced by galaxy-galaxy interaction. Both the mean IR spectral energy distribution and mean IR luminosity of star-forming galaxies (SFGs) in SFG+SFG (S+S) pairs in the redshift bin of 0.6 < z < 1 are consistent with no star formation enhancement. SFGs in S+S pairs in a lower redshift bin of 0.2 < z < 0.6 show marginal evidence for a weak star formation enhancement. Together with the significant and strong sSFR enhancement shown by SFGs in a local sample of S+S pairs (obtained using previously published Spitzer observations), our results reveal a trend for the star formation enhancement in S+S pairs to decrease with increasing redshift. Between z = 0 and z = 1, this decline of interaction-induced star formation enhancement occurs in parallel with the dramatic increase (by a factor of ∼10) of the sSFR of single SFGs, both of which can be explained by the higher gas fraction in higher-z disks. SFGs in mixed pairs (S+E pairs) do not show any significant star formation enhancement at any redshift. The difference between SFGs in S+S pairs and in S+E pairs suggests a modulation of the sSFR by the intergalactic medium (IGM) in the dark matter halos hosting these pairs.

  5. Morphological Evolution in High-Redshift Radio Galaxies and the Formation of Giant Elliptical Galaxies

    International Nuclear Information System (INIS)

    Breugel, W.J. van; Stanford, S.A.; Spinrad, H.; Stern, D.; Graham, J.R.

    1998-01-01

    We present deep near-infrared images of high-redshift radio galaxies (HzRGs) obtained with the near-infrared camera (NIRC) on the Keck I telescope. In most cases, the near-IR data sample rest wavelengths that are free of contamination from strong emission lines and at λ rest > 4000 Angstrom, where older stellar populations, if present, might dominate the observed flux. At z > 3, the rest-frame optical morphologies generally have faint, large-scale (∼50 kpc) emission surrounding multiple, ∼10 kpc components. The brightest of these components are often aligned with the radio structures. These morphologies change dramatically at 2 rest ) ∼ -20 to -22] of the individual components in the z > 3 HzRGs are similar to the total sizes and luminosities of normal radio-quiet star forming galaxies at z = 3 - 4. For objects where such data are available, our observations show that the line-free, near-IR colors of the z > 3 galaxies are very blue, consistent with models in which recent star formation dominates the observed light. Direct spectroscopic evidence for massive star formation in one of the z > 3 HzRGs exists (4C 41.17). Our results suggest that the z > 3 HzRGs evolve into much more massive systems than the radio-quiet galaxies and that they are qualitatively consistent with models in which massive galaxies form in hierarchical fashion through the merging of smaller star-forming systems. The presence of relatively luminous subcomponents along the radio axes of the z > 3 galaxies suggests a causal connection with the AGN. We compare the radio and near-IR sizes as a function of redshift and suggest that this parameter may be a measure of the degree to which the radio sources have induced star formation in the parent objects. We also discuss the Hubble diagram of radio galaxies, the possibility of a radio power dependence in the K-z relation, and its implications for radio galaxy formation. Finally, we present for the first time in published format basic radio and

  6. Properties of the Photometric Components of Lenticular Galaxies

    Directory of Open Access Journals (Sweden)

    J. Alfonso L. Aguerri

    2012-01-01

    their origin and evolution. I also explain the different properties of the lenticular galaxies that have evolved through each of these formation processes. A unique opportunity for understanding the origin of S0 galaxies will shortly be forthcoming. This is due to the morphological classifications of large galaxy samples that have recently been published. These classifications have given us our first ever opportunity to study large samples of lenticulars within a wide range of masses and located in a great variety of environments. These large samples will provide us with a real census of nearby lenticular galaxies and could be crucial in finally helping us to understand the origin and evolution of these galaxies.

  7. Spatially-resolved star formation histories of CALIFA galaxies. Implications for galaxy formation

    Science.gov (United States)

    González Delgado, R. M.; Pérez, E.; Cid Fernandes, R.; García-Benito, R.; López Fernández, R.; Vale Asari, N.; Cortijo-Ferrero, C.; de Amorim, A. L.; Lacerda, E. A. D.; Sánchez, S. F.; Lehnert, M. D.; Walcher, C. J.

    2017-11-01

    This paper presents the spatially resolved star formation history (SFH) of nearby galaxies with the aim of furthering our understanding of the different processes involved in the formation and evolution of galaxies. To this end, we apply the fossil record method of stellar population synthesis to a rich and diverse data set of 436 galaxies observed with integral field spectroscopy in the CALIFA survey. The sample covers a wide range of Hubble types, with stellar masses ranging from M⋆ 109 to 7 × 1011 M⊙. Spectral synthesis techniques are applied to the datacubes to retrieve the spatially resolved time evolution of the star formation rate (SFR), its intensity (ΣSFR), and other descriptors of the 2D SFH in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd) and five bins of stellar mass. Our main results are that (a) galaxies form very fast independently of their current stellar mass, with the peak of star formation at high redshift (z > 2). Subsequent star formation is driven by M⋆ and morphology, with less massive and later type spirals showing more prolonged periods of star formation. (b) At any epoch in the past, the SFR is proportional to M⋆, with most massive galaxies having the highest absolute (but lowest specific) SFRs. (c) While today, the ΣSFR is similar for all spirals and significantly lower in early-type galaxies (ETG), in the past, the ΣSFR scales well with morphology. The central regions of today's ETGs are where the ΣSFR reached the highest values (> 103 M⊙ Gyr-1 pc-2), similar to those measured in high-redshift star-forming galaxies. (d) The evolution of ΣSFR in Sbc systems matches that of models for Milky Way-like galaxies, suggesting that the formation of a thick disk may be a common phase in spirals at early epochs. (e) The SFR and ΣSFR in outer regions of E and S0 galaxies show that they have undergone an extended phase of growth in mass between z = 2 and 0.4. The mass assembled in this phase is in agreement with

  8. Disk Galaxies : Building Blocks of the Universe?

    OpenAIRE

    Bower, Richard

    2016-01-01

    In my talk I look at the origin of disk galaxies from the theoretical perspective. In particular I look at simple ways to use the properties of disk galaxies, and their evolution, to test our current paradigm for galaxy formation within the CDM scenario.

  9. The EAGLE simulations: atomic hydrogen associated with galaxies

    NARCIS (Netherlands)

    Crain, Robert A.; Bahé, Yannick M.; Lagos, Claudia del P.; Rahmati, Alireza; Schaye, Joop; McCarthy, Ian G.; Marasco, Antonino; Bower, Richard G.; Schaller, Matthieu; Theuns, Tom; van der Hulst, Thijs

    2017-01-01

    We examine the properties of atomic hydrogen (H I) associated with galaxies in the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations of galaxy formation. EAGLE's feedback parameters were calibrated to reproduce the stellar mass function and galaxy sizes at z = 0.1, and we

  10. A Modern Picture of Barred Galaxy Dynamics

    Science.gov (United States)

    Petersen, Michael; Weinberg, Martin; Katz, Neal

    2018-01-01

    Observations of disk galaxies suggest that bars are responsible for altering global galaxy parameters (e.g. structures, gas fraction, star formation rate). The canonical understanding of the mechanisms underpinning bar-driven secular dynamics in disk galaxies has been largely built upon the analysis of linear theory, despite galactic bars being clearly demonstrated to be nonlinear phenomena in n-body simulations. We present simulations of barred Milky Way-like galaxy models designed to elucidate nonlinear barred galaxy dynamics. We have developed two new methodologies for analyzing n-body simulations that give the best of both powerful analytic linear theory and brute force simulation analysis: orbit family identification and multicomponent torque analysis. The software will be offered publicly to the community for their own simulation analysis.The orbit classifier reveals that the details of kinematic components in galactic disks (e.g. the bar, bulge, thin disk, and thick disk components) are powerful discriminators of evolutionary paradigms (i.e. violent instabilities and secular evolution) as well as the basic parameters of the dark matter halo (mass distribution, angular momentum distribution). Multicomponent torque analysis provides a thorough accounting of the transfer of angular momentum between orbits, global patterns, and distinct components in order to better explain the underlying physics which govern the secular evolution of barred disk galaxies.Using these methodologies, we are able to identify the successes and failures of linear theory and traditional n-body simulations en route to a detailed understanding of the control bars exhibit over secular evolution in galaxies. We present explanations for observed physical and velocity structures in observations of barred galaxies alongside predictions for how structures will vary with dynamical properties from galaxy to galaxy as well as over the lifetime of a galaxy, finding that the transfer of angular

  11. Our galaxy is exploding

    International Nuclear Information System (INIS)

    Closets, Francois de.

    1977-01-01

    Improvements made in radioastronomy, and infrared, X and γ emission studies of the Galaxy have allowed to study the galactic nucleus, which is characterized by an intense activity. The most recent hypotheses made to explain this activity and replace it in the general context of the evolution of the galaxies are presented [fr

  12. Globular Clusters - Guides to Galaxies

    CERN Document Server

    Richtler, Tom; Joint ESO-FONDAP Workshop on Globular Clusters

    2009-01-01

    The principal question of whether and how globular clusters can contribute to a better understanding of galaxy formation and evolution is perhaps the main driving force behind the overall endeavour of studying globular cluster systems. Naturally, this splits up into many individual problems. The objective of the Joint ESO-FONDAP Workshop on Globular Clusters - Guides to Galaxies was to bring together researchers, both observational and theoretical, to present and discuss the most recent results. Topics covered in these proceedings are: internal dynamics of globular clusters and interaction with host galaxies (tidal tails, evolution of cluster masses), accretion of globular clusters, detailed descriptions of nearby cluster systems, ultracompact dwarfs, formations of massive clusters in mergers and elsewhere, the ACS Virgo survey, galaxy formation and globular clusters, dynamics and kinematics of globular cluster systems and dark matter-related problems. With its wide coverage of the topic, this book constitute...

  13. THE SL2S GALAXY-SCALE LENS SAMPLE. II. COSMIC EVOLUTION OF DARK AND LUMINOUS MASS IN EARLY-TYPE GALAXIES

    International Nuclear Information System (INIS)

    Ruff, Andrea J.; Marshall, Philip J.; Treu, Tommaso; Auger, Matthew W.; Gavazzi, Raphael; Brault, Florence

    2011-01-01

    We present a joint gravitational lensing and stellar-dynamical analysis of 11 early-type galaxies (median deflector redshift z d = 0.5) from Strong Lenses in the Legacy Survey (SL2S). Using newly measured redshifts and stellar velocity dispersions from Keck spectroscopy with lens models from Paper I, we derive the total mass-density slope inside the Einstein radius for each of the 11 lenses. The average total density slope is found to be (γ') = 2.16 +0.09 -0.09 (ρ tot ∝r -γ ' ), with an intrinsic scatter of 0.25 +0.10 -0.07 . We also determine the dark matter fraction for each lens within half the effective radius, R eff /2, and find the average-projected dark matter mass fraction to be 0.42 +0.08 -0.08 with a scatter of 0.20 +0.09 -0.07 for a Salpeter initial mass function. By combining the SL2S results with those from the Sloan Lens ACS Survey (median z d = 0.2) and the Lenses Structure and Dynamics Survey (median z d = 0.8), we investigate cosmic evolution of γ' and find a mild trend ∂(γ')/∂z d = -0.25 +0.10 -0.12 . This suggests that the total density profile of massive galaxies has become slightly steeper over cosmic time. If this result is confirmed by larger samples, it would indicate that dissipative processes played some role in the growth of massive galaxies since z ∼ 1.

  14. The Evolution of Normal Galaxy X-Ray Emission Through Cosmic History: Constraints from the 6 MS Chandra Deep Field-South

    Science.gov (United States)

    Lehmer, B. D.; Basu-Zych, A. R.; Mineo, S.; Brandt, W. N.; Eurfrasio, R. T.; Fragos, T.; Hornschemeier, A. E.; Lou, B.; Xue, Y. Q.; Bauer, F. E.; hide

    2016-01-01

    We present measurements of the evolution of normal-galaxy X-ray emission from z (is) approx. 0-7 using local galaxies and galaxy samples in the approx. 6 Ms Chandra Deep Field-South (CDF-S) survey. The majority of the CDF-S galaxies are observed at rest-frame energies above 2 keV, where the emission is expected to be dominated by X-ray binary (XRB) populations; however, hot gas is expected to provide small contributions to the observed-frame (is) less than 1 keV emission at z (is) less than 1. We show that a single scaling relation between X-ray luminosity (L(sub x)) and star-formation rate (SFR) literature, is insufficient for characterizing the average X-ray emission at all redshifts. We establish that scaling relations involving not only SFR, but also stellar mass and redshift, provide significantly improved characterizations of the average X-ray emission from normal galaxy populations at z (is) approx. 0-7. We further provide the first empirical constraints on the redshift evolution of X-ray emission from both low-mass XRB (LMXB) and high-mass XRB (HMXB) populations and their scalings with stellar mass and SFR, respectively. We find L2 -10 keV(LMXB)/stellar mass alpha (1+z)(sub 2-3) and L2 -10 keV(HMXB)/SFR alpha (1+z), and show that these relations are consistent with XRB population-synthesis model predictions, which attribute the increase in LMXB and HMXB scaling relations with redshift as being due to declining host galaxy stellar ages and metallicities, respectively. We discuss how emission from XRBs could provide an important source of heating to the intergalactic medium in the early universe, exceeding that of active galactic nuclei.

  15. Joint analysis of galaxy-galaxy lensing and galaxy clustering: Methodology and forecasts for Dark Energy Survey

    International Nuclear Information System (INIS)

    Park, Y.; Krause, E.; Dodelson, S.; Jain, B.; Amara, A.

    2016-01-01

    Here, the joint analysis of galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth function of large-scale structure. Anticipating a near future application of this analysis to Dark Energy Survey (DES) measurements of galaxy positions and shapes, we develop a practical approach to modeling the assumptions and systematic effects affecting the joint analysis of small-scale galaxy-galaxy lensing and large-scale galaxy clustering. Introducing parameters that characterize the halo occupation distribution (HOD), photometric redshift uncertainties, and shear measurement errors, we study how external priors on different subsets of these parameters affect our growth constraints. Degeneracies within the HOD model, as well as between the HOD and the growth function, are identified as the dominant source of complication, with other systematic effects being subdominant. The impact of HOD parameters and their degeneracies necessitate the detailed joint modeling of the galaxy sample that we employ. We conclude that DES data will provide powerful constraints on the evolution of structure growth in the Universe, conservatively/optimistically constraining the growth function to 7.9%/4.8% with its first-year data that cover over 1000 square degrees, and to 3.9%/2.3% with its full five-year data that will survey 5000 square degrees, including both statistical and systematic uncertainties.

  16. Confusion-limited galaxy fields. II. Classical analyses

    International Nuclear Information System (INIS)

    Chokshi, A.; Wright, E.L.

    1989-01-01

    Chokshi and Wright presented a detailed model for simulating angular distribution of galaxy images in fields that extended to very high redshifts. Standard tools are used to analyze these simulated galaxy fields for the Omega(O) = 0 and the Omega(O) = 1 cases in order to test the discriminatory power of these tools. Classical number-magnitude diagrams and surface brightness-color-color diagrams are employed to study crowded galaxy fields. An attempt is made to separate the effects due to stellar evolution in galaxies from those due to the space time geometry. The results show that this discrimination is maximized at near-infrared wavelengths where the stellar photospheres are still visible but stellar evolution effects are less severe than those observed at optical wavelenghts. Rapid evolution of the stars on the asymptotic giant branch is easily recognized in the simulated data for both cosmologies and serves to discriminate between the two extreme values of Omega(O). Measurements of total magnitudes of individual galaxies are not essential for studying light distribution in galaxies as a function of redshift. Calculations for the extragalactic background radiation are carried out using the simulated data, and compared to integrals over the evolutionary models used. 29 refs

  17. The galaxy major merger fraction to {z} 1

    Science.gov (United States)

    López-Sanjuan, C.; Balcells, M.; Pérez-González, P. G.; Barro, G.; García-Dabó, C. E.; Gallego, J.; Zamorano, J.

    2009-07-01

    Aims: The importance of disc-disc major mergers in galaxy evolution remains uncertain. We study the major merger fraction in a SPITZER/IRAC-selected catalogue in the GOODS-S field up to z 1 for luminosity- and mass-limited samples. Methods: We select disc-disc merger remnants on the basis of morphological asymmetries/distortions, and address three main sources of systematic errors: (i) we explicitly apply morphological K-corrections; (ii) we measure asymmetries in galaxies artificially redshifted to zd = 1.0 to deal with loss of morphological information with redshift; and (iii) we take into account the observational errors in z and A, which tend to overestimate the merger fraction, though use of maximum likelihood techniques. Results: We obtain morphological merger fractions (f_m^mph) below 0.06 up to z 1. Parameterizing the merger fraction evolution with redshift as f_m^mph(z) = f_m^mph(0) (1+z)^m, we find that m = 1.8 ± 0.5 for MB ≤ -20 galaxies, while m = 5.4 ± 0.4 for Mstar ≥ 1010 M⊙ galaxies. When we translate our merger fractions to merger rates (Re_m^mph), their evolution, parameterized as Re_m^mph(z) = Re_m^mph(0) (1+z)^n, is quite similar in both cases: n = 3.3 ± 0.8 for MB ≤ -20 galaxies, and n = 3.5 ± 0.4 for Mstar ≥ 1010 M⊙ galaxies. Conclusions: Our results imply that only 8% of today's Mstar ≥ 1010 M⊙ galaxies have undergone a disc-disc major merger since z 1. In addition, 21% of Mstar ≥ 1010 M⊙ galaxies at z 1 have undergone one of these mergers since z 1.5. This suggests that disc-disc major mergers are not the dominant process in the evolution of Mstar ≥ 1010 M⊙ galaxies since z 1, with only 0.2 disc-disc major mergers per galaxy, but may be an important process at z > 1, with ˜1 merger per galaxy at 1 < z < 3.

  18. Supernova-driven outflows and chemical evolution of dwarf spheroidal galaxies.

    Science.gov (United States)

    Qian, Yong-Zhong; Wasserburg, G J

    2012-03-27

    We present a general phenomenological model for the metallicity distribution (MD) in terms of [Fe/H] for dwarf spheroidal galaxies (dSphs). These galaxies appear to have stopped accreting gas from the intergalactic medium and are fossilized systems with their stars undergoing slow internal evolution. For a wide variety of infall histories of unprocessed baryonic matter to feed star formation, most of the observed MDs can be well described by our model. The key requirement is that the fraction of the gas mass lost by supernova-driven outflows is close to unity. This model also predicts a relationship between the total stellar mass and the mean metallicity for dSphs in accord with properties of their dark matter halos. The model further predicts as a natural consequence that the abundance ratios [E/Fe] for elements such as O, Mg, and Si decrease for stellar populations at the higher end of the [Fe/H] range in a dSph. We show that, for infall rates far below the net rate of gas loss to star formation and outflows, the MD in our model is very sharply peaked at one [Fe/H] value, similar to what is observed in most globular clusters. This result suggests that globular clusters may be end members of the same family as dSphs.

  19. Galactic evolution

    International Nuclear Information System (INIS)

    Pagel, B.

    1979-01-01

    Ideas are considered concerning the evolution of galaxies which are closely related to those of stellar evolution and the origin of elements. Using information obtained from stellar spectra, astronomers are now able to consider an underlying process to explain the distribution of various elements in the stars, gas and dust clouds of the galaxies. (U.K.)

  20. Star Formation Histories of Nearby Dwarf Galaxies

    OpenAIRE

    Grebel, Eva K.

    2000-01-01

    Properties of nearby dwarf galaxies are briefly discussed. Dwarf galaxies vary widely in their star formation histories, the ages of their subpopulations, and in their enrichment history. Furthermore, many dwarf galaxies show evidence for spatial variations in their star formation history; often in the form of very extended old populations and radial gradients in age and metallicity. Determining factors in dwarf galaxy evolution appear to be both galaxy mass and environment. We may be observi...

  1. Beyond the Borders of a Galaxy

    Science.gov (United States)

    2008-01-01

    [figure removed for brevity, see original site] Side-by-Side Comparison Click on image for larger view The outlying regions around the Southern Pinwheel galaxy, or M83, are highlighted in this composite image from NASA's Galaxy Evolution Explorer and the National Science Foundation's Very Large Array in New Mexico. The blue and pink pinwheel in the center is the galaxy's main stellar disk, while the flapping, ribbon-like structures are its extended arms. The Galaxy Evolution Explorer is an ultraviolet survey telescope. Its observations, shown here in blue and green, highlight the galaxy's farthest-flung clusters of young stars up to 140,000 light-years from its center. The Very Large Array observations show the radio emission in red. They highlight gaseous hydrogen atoms, or raw ingredients for stars, which make up the lengthy, extended arms. Astronomers are excited that the clusters of baby stars match up with the extended arms, because this helps them better understand how stars can be created out in the 'backwoods' of a galaxy. In this image, far-ultraviolet light is blue, near-ultraviolet light is green and radio emission at a wavelength of 21 centimeters is red. What Lies Beyond the Edge of a Galaxy The side-by-side comparison shows the Southern Pinwheel galaxy, or M83, as seen in ultraviolet light (right) and at both ultraviolet and radio wavelengths (left). While the radio data highlight the galaxy's long, octopus-like arms stretching far beyond its main spiral disk (red), the ultraviolet data reveal clusters of baby stars (blue) within the extended arms. The ultraviolet image was taken by NASA's Galaxy Evolution Explorer between March 15 and May 20, 2007, at scheduled intervals. Back in 2005, the telescope first photographed M83 over a shorter period of time. That picture was the first to reveal far-flung baby stars forming up to 63,000 light-years from the edge of the main spiral disk. This came as a surprise to astronomers because a galaxy's outer

  2. Hot Gas Halos in Galaxies

    Science.gov (United States)

    Mulchaey, John

    Most galaxy formation models predict that massive low-redshift disk galaxies are embedded in extended hot halos of externally accreted gas. Such gas appears necessary to maintain ongoing star formation in isolated spirals like the Milky Way. To explain the large population of red galaxies in rich groups and clusters, most galaxy evolution models assume that these hot gas halos are stripped completely when a galaxy enters a denser environment. This simple model has been remarkably successful at reproducing many observed properties of galaxies. Although theoretical arguments suggest hot gas halos are an important component in galaxies, we know very little about this gas from an observational standpoint. In fact, previous observations have failed to detect soft X-ray emission from such halos in disk galaxies. Furthermore, the assumption that hot gas halos are stripped completely when a galaxy enters a group or cluster has not been verified. We propose to combine proprietary and archival XMM-Newton observations of galaxies in the field, groups and clusters to study how hot gas halos are impacted by environment. Our proposed program has three components: 1) The deepest search to date for a hot gas halo in a quiescent spiral galaxy. A detection will confirm a basic tenet of disk galaxy formation models, whereas a non-detection will seriously challenge these models and impose new constraints on the growth mode and feedback history of disk galaxies. 2) A detailed study of the hot gas halos properties of field early-type galaxies. As environmental processes such as stripping are not expected to be important in the field, a study of hot gas halos in this environment will allow us to better understand how feedback and other internal processes impact hot gas halos. 3) A study of hot gas halos in the outskirts of groups and clusters. By comparing observations with our suite of simulations we can begin to understand what role the stripping of hot gas halos plays in galaxy

  3. Cosmological constraints from galaxy clustering and the mass-to-number ratio of galaxy clusters: marginalizing over the physics of galaxy formation

    Energy Technology Data Exchange (ETDEWEB)

    Reddick, Rachel M.; Wechsler, Risa H.; Lu, Yu [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, Stanford University, Stanford, CA 94305 (United States); Tinker, Jeremy L., E-mail: rmredd@stanford.edu, E-mail: rwechsler@stanford.edu [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10003 (United States)

    2014-03-10

    Many approaches to obtaining cosmological constraints rely on the connection between galaxies and dark matter. However, the distribution of galaxies is dependent on their formation and evolution as well as on the cosmological model, and galaxy formation is still not a well-constrained process. Thus, methods that probe cosmology using galaxies as tracers for dark matter must be able to accurately estimate the cosmological parameters. This can be done without knowing details of galaxy formation a priori as long as the galaxies are well represented by a halo occupation distribution (HOD). We apply this reasoning to the method of obtaining Ω {sub m} and σ{sub 8} from galaxy clustering combined with the mass-to-number ratio of galaxy clusters. To test the sensitivity of this method to variations due to galaxy formation, we consider several different models applied to the same cosmological dark matter simulation. The cosmological parameters are then estimated using the observables in each model, marginalizing over the parameters of the HOD. We find that for models where the galaxies can be well represented by a parameterized HOD, this method can successfully extract the desired cosmological parameters for a wide range of galaxy formation prescriptions.

  4. Cosmological constraints from galaxy clustering and the mass-to-number ratio of galaxy clusters: marginalizing over the physics of galaxy formation

    International Nuclear Information System (INIS)

    Reddick, Rachel M.; Wechsler, Risa H.; Lu, Yu; Tinker, Jeremy L.

    2014-01-01

    Many approaches to obtaining cosmological constraints rely on the connection between galaxies and dark matter. However, the distribution of galaxies is dependent on their formation and evolution as well as on the cosmological model, and galaxy formation is still not a well-constrained process. Thus, methods that probe cosmology using galaxies as tracers for dark matter must be able to accurately estimate the cosmological parameters. This can be done without knowing details of galaxy formation a priori as long as the galaxies are well represented by a halo occupation distribution (HOD). We apply this reasoning to the method of obtaining Ω m and σ 8 from galaxy clustering combined with the mass-to-number ratio of galaxy clusters. To test the sensitivity of this method to variations due to galaxy formation, we consider several different models applied to the same cosmological dark matter simulation. The cosmological parameters are then estimated using the observables in each model, marginalizing over the parameters of the HOD. We find that for models where the galaxies can be well represented by a parameterized HOD, this method can successfully extract the desired cosmological parameters for a wide range of galaxy formation prescriptions.

  5. Quasars in galaxy cluster environments

    International Nuclear Information System (INIS)

    Ellingson, E.

    1989-01-01

    The evolution of radio loud quasars is found to be strongly dependent upon their galaxy cluster environment. Previous studies have shown that bright quasars are found in rich clusters, while high luminosity quasars are found only in poorer environments. The analysis of low luminosity radio quiet quasars indicate that they are never found in rich environments, suggesting that they are a physically different class of objects. Properties of the quasar environment are investigated to determine constraints on the physical mechanisms of quasar formation and evolution. The optical cluster morphology indicates that the cluster cores have smaller radii and higher galaxy densities than are typical for low redshift clusters of similar richness. Radio morphologies may indicate that the formation of a dense intra-cluster medium is associated with the quasars' fading at these epochs. Galaxy colors appear to be normal, but there may be a tendency for clusters associated with high luminosity quasars to contain a higher fraction of gas-rich galaxies than those associated with low luminosity quasars. Multislit spectroscopic observations of galaxies associated with high luminosity quasars indicate that quasars are preferentially located in regions of low relative velocity dispersion, either in rich clusters of abnormally low dispersion, or in poor groups which are dynamically normal. This suggests that galaxy-galaxy interactions may play a role in quasar formation and sustenanace. Virialization of rich clusters and the subsequent increase in galaxy velocities may therefore be responsible for the fading of quasars in rich environments

  6. Galaxies in the Early Universe

    DEFF Research Database (Denmark)

    Krogager, Jens-Kristian

    Understanding how galaxies evolved from the early Universe through cosmic time is a fundamental part of modern astrophysics. In order to study this evolution it is important to sample the galaxies at various times in a consistent way through time. In regular luminosity selected samples, our...

  7. Lyα EMITTING GALAXIES AS EARLY STAGES IN GALAXY FORMATION

    International Nuclear Information System (INIS)

    Cowie, Lennox L.; Barger, Amy J.; Hu, Esther M.

    2011-01-01

    We present optical spectroscopy of two samples of Galaxy Evolution Explorer grism selected Lyα emitters (LAEs): one at z = 0.195-0.44 and the other at z = 0.65-1.25. We have also observed a comparison sample of galaxies in the same redshift intervals with the same UV magnitude distributions but with no detected Lyα. We use the optical spectroscopy to eliminate active galactic nuclei and to obtain the optical emission-line properties of the samples. We compare the luminosities of the LAEs in the two redshift intervals and show that there is dramatic evolution in the maximum Lyα luminosity over z = 0-1. Focusing on the z = 0.195-0.44 samples alone, we show that there are tightly defined relations between all of the galaxy parameters and the rest-frame equivalent width (EW) of Hα. The higher EW(Hα) sources all have lower metallicities, bluer colors, smaller sizes, and less extinction, consistent with their being in the early stages of the galaxy formation process. We find that 75% ± 12% of the LAEs have EW(Hα) >100 A and, conversely, that 31% ± 13% of galaxies with EW(Hα) >100 A are LAEs. We correct the broadband magnitudes for the emission-line contributions and use spectral synthesis fits to estimate the ages of the galaxies. We find a median age of 1.1 x 10 8 yr for the LAE sample and 1.4 x 10 9 yr for the UV-continuum sample without detected Lyα. The median metallicity of the LAE sample is 12 + log (O/H) = 8.24, or about 0.4 dex lower than the UV-continuum sample.

  8. Effect of increasing helium content and disk dwarfs evolution on the chemical enrichment of the galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Caimmi, R [Padua Univ. (Italy). Ist. di Astronomia

    1979-07-01

    The author deals with two main effects: First the empirical metal abundance distribution in Main Sequence disk dwarfs of the solar neighbourhood, and second, the theoretical possibility of (i) an increased helium content as the Galaxy evolves, and (ii) the presence of evolutionary effects in disk dwarfs (i.e., the age of some or all stars considered up to the subgiant phase is not necessarily longer than the age of the galactic disk). Account is taken of a linear increase of helium content with metal content, and some constraints are imposed relative to initial, solar and present-day observed values of Y and Z, and to observed relative helium to heavy element enrichment, ..delta..Y/..delta..Z. In this way, little influence is found on the empirical metal abundance distribution in the range 0<=..delta..Y/..delta..Z<=3, while larger values of ..delta..Y/..delta..Zwould lead to a more significant influence. 'Evolved' and 'unevolved' theoretical metal abundance distributions are derived by accounting for a two-phase model of chemical evolution of galaxies and for a linear mass dependence of star lifetimes in the spectral range G2V-G8V and are compared with the empirical distribution. All are in satisfactory agreement due to systematic shift data by different observations; several values of collapse time Tsub(c) and age of the Galaxy T are also considered. Finally, models of chemical evolution invoking homogeneous collapse without infall and inhomogeneous collapse with infall, are briefly discussed relative to the empirical metal abundance distribution in Main Sequence disk dwarfs of the solar neighbourhood.

  9. Diversity among galaxy clusters

    International Nuclear Information System (INIS)

    Struble, M.F.; Rood, H.J.

    1988-01-01

    The classification of galaxy clusters is discussed. Consideration is given to the classification scheme of Abell (1950's), Zwicky (1950's), Morgan, Matthews, and Schmidt (1964), and Morgan-Bautz (1970). Galaxies can be classified based on morphology, chemical composition, spatial distribution, and motion. The correlation between a galaxy's environment and morphology is examined. The classification scheme of Rood-Sastry (1971), which is based on clusters's morphology and galaxy population, is described. The six types of clusters they define include: (1) a cD-cluster dominated by a single large galaxy, (2) a cluster dominated by a binary, (3) a core-halo cluster, (4) a cluster dominated by several bright galaxies, (5) a cluster appearing flattened, and (6) an irregularly shaped cluster. Attention is also given to the evolution of cluster structures, which is related to initial density and cluster motion

  10. Galaxy number counts: Pt. 2

    International Nuclear Information System (INIS)

    Metcalfe, N.; Shanks, T.; Fong, R.; Jones, L.R.

    1991-01-01

    Using the Prime Focus CCD Camera at the Isaac Newton Telescope we have determined the form of the B and R galaxy number-magnitude count relations in 12 independent fields for 21 m ccd m and 19 m ccd m 5. The average galaxy count relations lie in the middle of the wide range previously encompassed by photographic data. The field-to-field variation of the counts is small enough to define the faint (B m 5) galaxy count to ±10 per cent and this variation is consistent with that expected from galaxy clustering considerations. Our new data confirm that the B, and also the R, galaxy counts show evidence for strong galaxy luminosity evolution, and that the majority of the evolving galaxies are of moderately blue colour. (author)

  11. THE AGE SPREAD OF QUIESCENT GALAXIES WITH THE NEWFIRM MEDIUM-BAND SURVEY: IDENTIFICATION OF THE OLDEST GALAXIES OUT TO z ∼ 2

    International Nuclear Information System (INIS)

    Whitaker, Katherine E.; Van Dokkum, Pieter G.; Brammer, Gabriel; Bezanson, Rachel; Lee, Kyoung-Soo; Muzzin, Adam; Wake, David A.; Kriek, Mariska; Franx, Marijn; Quadri, Ryan F.; Labbe, Ivo; Marchesini, Danilo; Illingworth, Garth D.; Rudnick, Gregory

    2010-01-01

    With a complete, mass-selected sample of quiescent galaxies from the NEWFIRM Medium-Band Survey, we study the stellar populations of the oldest and most massive galaxies (>10 11 M sun ) to high redshift. The sample includes 570 quiescent galaxies selected based on their extinction-corrected U - V colors out to z = 2.2, with accurate photometric redshifts, σ z /(1 + z) ∼ 2%, and rest-frame colors, σ U-V ∼ 0.06 mag. We measure an increase in the intrinsic scatter of the rest-frame U - V colors of quiescent galaxies with redshift. This scatter in color arises from the spread in ages of the quiescent galaxies, where we see both relatively quiescent red, old galaxies and quiescent blue, younger galaxies toward higher redshift. The trends between color and age are consistent with the observed composite rest-frame spectral energy distributions (SEDs) of these galaxies. The composite SEDs of the reddest and bluest quiescent galaxies are fundamentally different, with remarkably well-defined 4000 A and Balmer breaks, respectively. Some of the quiescent galaxies may be up to four times older than the average age and up to the age of the universe, if the assumption of solar metallicity is correct. By matching the scatter predicted by models that include growth of the red sequence by the transformation of blue galaxies to the observed intrinsic scatter, the data indicate that most early-type galaxies formed their stars at high redshift with a burst of star formation prior to migrating to the red sequence. The observed U - V color evolution with redshift is weaker than passive evolution predicts; possible mechanisms to slow the color evolution include increasing amounts of dust in quiescent galaxies toward higher redshift, red mergers at z ∼< 1, and a frosting of relatively young stars from star formation at later times.

  12. Tracking Galaxy Evolution Through Low-Frequency Radio Continuum Observations using SKA and Citizen-Science Research using Multi-Wavelength Data

    Science.gov (United States)

    Hota, Ananda; Konar, C.; Stalin, C. S.; Vaddi, Sravani; Mohanty, Pradeepta K.; Dabhade, Pratik; Dharmik Bhoga, Sai Arun; Rajoria, Megha; Sethi, Sagar

    2016-12-01

    We present a brief review of progress in the understanding of general spiral and elliptical galaxies, through merger, star formation and AGN activities. With reference to case studies performed with the GMRT, we highlight the unique aspects of studying galaxies in the radio wavelengths where powerful quasars and bright radio galaxies are traditionally the dominating subjects. Though AGN or quasar activity is extremely energetic, it is extremely short-lived. This justify focussing on transitional galaxies to find relic-evidences of the immediate past AGN-feedback which decide the future course of evolution of a galaxy. Relic radio lobes can be best detected in low frequency observations with the GMRT, LOFAR and in future SKA. The age of these relic radio plasma can be as old as a few hundred Myr. There is a huge gap between this and what is found in optical bands. The very first relic-evidences of a past quasar activity (Hanny's Voorwerp) was discovered in 2007 by a Galaxy Zoo citizen-scientist, a school teacher, in the optical bands. This relic is around a few tens of thousand years old. More discoveries needed to match these time-scales with star formation time-scales in AGN host galaxies to better understand black hole galaxy co-evolution process via feedback-driven quenching of star formation. It is now well-accepted that discovery and characterization of such faint fuzzy relic features can be more efficiently done by human eye than a machine. Radio interferometry images are more complicated than optical and need the citizen-scientists to be trained. RAD@home, the only Indian citizen-science research project in astronomy, analysing TIFR GMRT Sky Survey (TGSS) 150 MHz data and observing from the Giant Meterwave Radio Telescope (GMRT), was launched in April 2013. Unique, zero-infrastructure zero-funded design of RAD@home as a collaboratory of 69 trained e-astronomers is briefly described. Some of the new-found objects like episodic radio galaxies, radio-jet and

  13. Exploring the nearby galaxies 0 present and future

    Indian Academy of Sciences (India)

    Galaxies: . Content l Stars. Gas, Dust . Structure & Kinematics . Dynamics & Ecology . Formation & Evolution. Star formation. Chemical evolution. Dynamic evolution. Interaction with neighbours . Galactic Centre ...

  14. The Taxonomy of Blue Amorphous Galaxies. I. Hα and UBVI Data

    Science.gov (United States)

    Marlowe, Amanda T.; Meurer, Gerhardt R.; Heckman, Timothy M.; Schommer, Robert

    1997-10-01

    Dwarf galaxies play an important role in our understanding of galaxy formation and evolution. We have embarked on a systematic study of 12 nearby dwarf galaxies (most of which have been classified as amorphous) selected preferentially by their blue colors. The properties of the galaxies in the sample suggest that they are in a burst or postburst state. It seems likely that these amorphous galaxies are closely related to other ``starburst'' dwarfs such as blue compact dwarfs (BCDs) and H II galaxies but are considerably closer and therefore easier to study. If so, these galaxies may offer important insights into dwarf galaxy evolution. In an effort to clarify the role of starbursts in evolutionary scenarios for dwarf galaxies, we present Hα and UBVI data for our sample. Blue amorphous galaxies, like BCDs and H II galaxies, have surface brightness profiles that are exponential in the outer regions (r >~ 1.5re) but have a predominantly blue central excess, which suggests a young burst in an older, redder galaxy. Seven of the galaxies have the bubble or filamentary Hα morphology and double-peaked emission lines that are the signature of superbubbles or superwind activity. These galaxies are typically the ones with the strongest central excesses. The underlying exponential galaxies are very similar to those found in BCDs and H II galaxies. How amorphous galaxies fit into the dwarf irregular-``starburst dwarf''-dwarf elliptical evolutionary debate is less clear. In this paper, we present our data and make some preliminary comparisons between amorphous galaxies and other classes of dwarf galaxies. In a future companion paper, we will compare this sample more quantitatively with other dwarf galaxy samples in an effort to determine if amorphous galaxies are a physically different class of object from other starburst dwarfs such as BCDs and H II galaxies and also investigate their place in dwarf galaxy evolution scenarios.

  15. STAR FORMATION HISTORY AND CHEMICAL EVOLUTION OF THE SEXTANS DWARF SPHEROIDAL GALAXY

    International Nuclear Information System (INIS)

    Lee, Myung Gyoon; Yuk, In-Soo; Park, Hong Soo; Harris, Jason; Zaritsky, Dennis

    2009-01-01

    We present the star formation history (SFH) and chemical evolution of the Sextans dSph galaxy as a function of a galactocentric distance. We derive these from the VI photometry of stars in the 42' x 28' field using the SMART model developed by Yuk and Lee and adopting a closed-box model for chemical evolution. For the adopted age of Sextans 15 Gyr, we find that >84% of the stars formed prior to 11 Gyr ago, significant star formation extends from 15 to 11 Gyr ago (∼ 65% of the stars formed 13-15 Gyr ago, while ∼ 25% formed 11-13 Gyr ago), detectable star formation continued to at least 8 Gyr ago, the SFH is more extended in the central regions than the outskirts, and the difference in star formation rates between the central and outer regions is most marked 11-13 Gyr ago. Whether blue straggler stars are interpreted as intermediate-age main-sequence stars affects conclusions regarding the SFH for times 4-8 Gyr ago, but this is at most only a trace population. We find that the metallicity of the stars increased rapidly up to [Fe/H] = -1.6 in the central region and to [Fe/H] = -1.8 in the outer region within the first Gyr, and has varied slowly since then. The abundance ratios of several elements derived in this study are in good agreement with the observational data based on the high-resolution spectroscopy in the literature. We conclude that the primary driver for the radial gradient of the stellar population in this galaxy is the SFH, which self-consistently drives the chemical enrichment history.

  16. The three phases of galaxy formation

    Science.gov (United States)

    Clauwens, Bart; Schaye, Joop; Franx, Marijn; Bower, Richard G.

    2018-05-01

    We investigate the origin of the Hubble sequence by analysing the evolution of the kinematic morphologies of central galaxies in the EAGLE cosmological simulation. By separating each galaxy into disc and spheroidal stellar components and tracing their evolution along the merger tree, we find that the morphology of galaxies follows a common evolutionary trend. We distinguish three phases of galaxy formation. These phases are determined primarily by mass, rather than redshift. For M* ≲ 109.5M⊙ galaxies grow in a disorganised way, resulting in a morphology that is dominated by random stellar motions. This phase is dominated by in-situ star formation, partly triggered by mergers. In the mass range 109.5M⊙ ≲ M* ≲ 1010.5M⊙ galaxies evolve towards a disc-dominated morphology, driven by in-situ star formation. The central spheroid (i.e. the bulge) at z = 0 consists mostly of stars that formed in-situ, yet the formation of the bulge is to a large degree associated with mergers. Finally, at M* ≳ 1010.5M⊙ growth through in-situ star formation slows down considerably and galaxies transform towards a more spheroidal morphology. This transformation is driven more by the buildup of spheroids than by the destruction of discs. Spheroid formation in these galaxies happens mostly by accretion at large radii of stars formed ex-situ (i.e. the halo rather than the bulge).

  17. Galaxy Evolution Over the Past Eleven Billion Years

    DEFF Research Database (Denmark)

    Man, Wing Shan

    mechanism in evolving the sizes and stellar masses of quiescent galaxies? Are quiescent galaxies truly passive, or are their stellar populations in fact not old but reddened by dust? The goal of this thesis is to address these two outstanding questions, in order to verify the existence of such an extreme...

  18. SPATIAL ANISOTROPY OF GALAXY KINEMATICS IN SLOAN DIGITAL SKY SURVEY GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Skielboe, Andreas; Wojtak, Radosław; Pedersen, Kristian; Rozo, Eduardo; Rykoff, Eli S.

    2012-01-01

    Measurements of galaxy cluster kinematics are important in understanding the dynamical state and evolution of clusters of galaxies, as well as constraining cosmological models. While it is well established that clusters exhibit non-spherical geometries, evident in the distribution of galaxies on the sky, azimuthal variations of galaxy kinematics within clusters have yet to be observed. Here we measure the azimuthal dependence of the line-of-sight velocity dispersion profile in a stacked sample of 1743 galaxy clusters from the Sloan Digital Sky Survey (SDSS). The clusters are drawn from the SDSS DR8 redMaPPer catalog. We find that the line-of-sight velocity dispersion of galaxies lying along the major axis of the central galaxy is larger than those that lie along the minor axis. This is the first observational detection of anisotropic kinematics of galaxies in clusters. We show that the result is consistent with predictions from numerical simulations. Furthermore, we find that the degree of projected anisotropy is strongly dependent on the line-of-sight orientation of the galaxy cluster, opening new possibilities for assessing systematics in optical cluster finding.

  19. Counts and colors of faint galaxies

    International Nuclear Information System (INIS)

    Kron, R.G.

    1980-01-01

    The color distribution of faint galaxies is an observational dimension which has not yet been fully exploited, despite the important constraints obtainable for galaxy evolution and cosmology. Number-magnitude counts alone contain very diluted information about the state of things because galaxies from a wide range in redshift contribute to the counts at each magnitude. The most-frequently-seen type of galaxy depends on the luminosity function and the relative proportions of galaxies of different spectral classes. The addition of color as a measured quantity can thus considerably sharpen the interpretation of galaxy counts since the apparent color depends on the redshift and rest-frame spectrum. (Auth.)

  20. Exploring galaxy evolution with latent space walks

    Science.gov (United States)

    Schawinski, Kevin; Turp, Dennis; Zhang, Ce

    2018-01-01

    We present a new approach using artificial intelligence to perform data-driven forward models of astrophysical phenomena. We describe how a variational autoencoder can be used to encode galaxies to latent space, independently manipulate properties such as the specific star formation rate, and return it to real space. Such transformations can be used for forward modeling phenomena using data as the only constraints. We demonstrate the utility of this approach using the question of the quenching of star formation in galaxies.

  1. Archaeology of active galaxies across the electromagnetic spectrum

    NARCIS (Netherlands)

    Morganti, Raffaella

    2017-01-01

    Analytical and numerical galaxy-formation models indicate that active galactic nuclei (AGNs) likely play a prominent role in the formation and evolution of galaxies. However, quantifying this effect requires knowledge of how the nuclear activity proceeds throughout the life of a galaxy, whether it

  2. Towards Understanding The Origin And Evolution Of Ultra-Diffuse Galaxies

    OpenAIRE

    Burg, van der, R.F.J.; Sifon, Andalaft C.J.; Muzzin, A.; Hoekstra, H.; Collaboration, K.

    2017-01-01

    Recent observations have shown that Ultra-Diffuse Galaxies (UDGs, which have the luminosities of dwarfs but sizes of giant galaxies) are surprisingly abundant in clusters of galaxies. The origin of these galaxies remains unclear, since one would naively expect them to be easily disrupted by tidal interactions in the cluster environment. Several formation scenarios have been proposed for UDGs, but these make a wide range of different testable observational predictions. I’ll summarise recent re...

  3. The Greater Impact of Mergers on the Growth of Massive Galaxies: Implications for Mass Assembly and Evolution since z sime 1

    Science.gov (United States)

    Bundy, Kevin; Fukugita, Masataka; Ellis, Richard S.; Targett, Thomas A.; Belli, Sirio; Kodama, Tadayuki

    2009-06-01

    Using deep infrared observations conducted with the MOIRCS imager on the Subaru Telescope in the northern GOODS field combined with public surveys in GOODS-S, we investigate the dependence on stellar mass, M *, and galaxy type of the close pair fraction (5 h -1 kpc implied merger rate. In terms of combined depth and survey area, our publicly available mass-limited sample represents a significant improvement over earlier infrared surveys used for this purpose. In common with some recent studies, we find that the fraction of paired systems that could result in major mergers is low (~4%) and does not increase significantly with redshift to z ≈ 1.2, with vprop(1 + z)1.6±1.6. Our key finding is that massive galaxies with M *>1011 M sun are more likely to host merging companions than less massive systems (M * ~ 1010 M sun). We find evidence for a higher pair fraction for red, spheroidal hosts compared to blue, late-type systems, in line with expectations based on clustering at small scales. The so-called "dry" mergers between early-type galaxies devoid of star formation (SF) represent nearly 50% of close pairs with M *>3 × 1010 M sun at z ~ 0.5, but less than 30% at z ~ 1. This result can be explained by the increasing abundance of red, early-type galaxies at these masses. We compare the volumetric merger rate of galaxies with different masses to mass-dependent trends in galaxy evolution. Our results reaffirm the conclusion of Bundy et al. that major mergers do not fully account for the formation of spheroidal galaxies since z ~ 1. In terms of mass assembly, major mergers contribute little to galaxy growth below M * ~ 3 × 1010 M sun but play a more significant role among galaxies with M * gsim 1011 M sun ~ 30% of which have undergone mostly dry mergers over the observed redshift range. Overall, the relatively rapid and recent coalescence of high-mass galaxies mirrors the expected hierarchical growth of halos and is consistent with recent model predictions, even if

  4. Galaxy Alignments: Theory, Modelling & Simulations

    Science.gov (United States)

    Kiessling, Alina; Cacciato, Marcello; Joachimi, Benjamin; Kirk, Donnacha; Kitching, Thomas D.; Leonard, Adrienne; Mandelbaum, Rachel; Schäfer, Björn Malte; Sifón, Cristóbal; Brown, Michael L.; Rassat, Anais

    2015-11-01

    The shapes of galaxies are not randomly oriented on the sky. During the galaxy formation and evolution process, environment has a strong influence, as tidal gravitational fields in the large-scale structure tend to align nearby galaxies. Additionally, events such as galaxy mergers affect the relative alignments of both the shapes and angular momenta of galaxies throughout their history. These "intrinsic galaxy alignments" are known to exist, but are still poorly understood. This review will offer a pedagogical introduction to the current theories that describe intrinsic galaxy alignments, including the apparent difference in intrinsic alignment between early- and late-type galaxies and the latest efforts to model them analytically. It will then describe the ongoing efforts to simulate intrinsic alignments using both N-body and hydrodynamic simulations. Due to the relative youth of this field, there is still much to be done to understand intrinsic galaxy alignments and this review summarises the current state of the field, providing a solid basis for future work.

  5. EVOLUTION OF THE MOST LUMINOUS DUSTY GALAXIES

    International Nuclear Information System (INIS)

    Weedman, Daniel W.; Houck, James R.

    2009-01-01

    A summary of mid-infrared continuum luminosities arising from dust is given for very luminous galaxies, L IR > 10 12 L sun , with 0.005 0.7 in the 9.7 μm silicate absorption feature (i.e., half of the continuum is absorbed) and having equivalent width of the 6.2 μm polycyclic aromatic hydrocarbon feature ν (8 μm) for the most luminous obscured AGNs is found to scale as (1+z) 2.6 to z = 2.8. For unobscured AGNs, the scaling with redshift is similar, but luminosities νL ν (8 μm) are approximately three times greater for the most luminous sources. Using both obscured and unobscured AGNs having total infrared fluxes from the Infrared Astronomical Satellite, empirical relations are found between νL ν (8 μm) and L IR . Combining these relations with the redshift scaling of luminosity, we conclude that the total infrared luminosities for the most luminous obscured AGNs, L IR (AGN obscured ) in L sun , scale as log L IR (AGN obscured ) = 12.3 ± 0.25 + 2.6(±0.3)log(1+z), and for the most luminous unobscured AGNs, scale as log L IR (AGN1) = 12.6(±0.15) + 2.6(±0.3)log(1+z). We previously determined that the most luminous starbursts scale as log L IR (SB) = 11.8 ± 0.3 + 2.5(±0.3)log(1+z), indicating that the most luminous AGNs are about 10 times more luminous than the most luminous starbursts. Results are consistent with obscured and unobscured AGNs having the same total luminosities with differences arising only from orientation, such that the obscured AGNs are observed through very dusty clouds which extinct about 50% of the intrinsic luminosity at 8 μm. Extrapolations of observable f ν (24 μm) to z = 6 are made using evolution results for these luminous sources. Both obscured and unobscured AGNs should be detected to z ∼ 6 by Spitzer surveys with f ν (24 μm) > 0.3 mJy, even without luminosity evolution for z > 2.5. By contrast, the most luminous starbursts cannot be detected for z > 3, even if luminosity evolution continues beyond z = 2.5.

  6. Galaxy morphologies in the era of big-data surveys

    Science.gov (United States)

    Huertas-Company, M.

    Galaxy morphology is a first-order descriptor of a galaxy and a useful proxy to identify physical processes. The 100 years old Hubble fork describes the structural diversity of galaxies in the local universe. Unveiling the origins of this galaxy zoology is a key challenge in galaxy evolution. In this review talk, I first summarized some key advances in our understanding of the morphological evolution of galaxies from z ~ 0 to z ~ 3, thank you in particular to the SDSS and HST legacies. In the second part, I focused on the classification techniques. With the emergence in the last years of large surveys the samples of study have increased by several orders of magnitude going from a few tens to several millions of objects. This trend will clearly continue in the next decade with coming surveys/missions such as EUCLID and WFIRST. While galaxy classification is still a required step in any survey, visual inspection of galaxies is becoming prohibitively time-consuming. Under these circumstances, the techniques used to estimate galaxy morphologies need to be updated.

  7. Atomic hydrogen properties of active galactic nuclei host galaxies: H I in 16 nuclei of galaxies (NUGA) sources

    International Nuclear Information System (INIS)

    Haan, Sebastian; Schinnerer, Eva; Mundell, Carole G.; García-Burillo, Santiago; Combes, Francoise

    2008-01-01

    We present a comprehensive spectroscopic imaging survey of the distribution and kinematics of atomic hydrogen (H I) in 16 nearby spiral galaxies hosting low luminosity active galactic nuclei (AGN), observed with high spectral and spatial resolution (resolution: ∼20'', ∼5 km s –1 ) using the NRAO Very Large Array (VLA). The sample contains a range of nuclear types ranging from Seyfert to star-forming nuclei, and was originally selected for the NUclei of GAlaxies project (NUGA)—a spectrally and spatially resolved interferometric survey of gas dynamics in nearby galaxies designed to identify the fueling mechanisms of AGN and the relation to host galaxy evolution. Here we investigate the relationship between the H I properties of these galaxies, their environment, their stellar distribution, and their AGN type. The large-scale H I morphology of each galaxy is classified as ringed, spiral, or centrally concentrated; comparison of the resulting morphological classification with the AGN type reveals that ring structures are significantly more common in low-ionization narrow emission-line regions (LINER) than in Seyfert host galaxies, suggesting a time evolution of the AGN activity together with the redistribution of the neutral gas. Dynamically disturbed H I disks are also more prevalent in LINER host galaxies than in Seyfert host galaxies. While several galaxies are surrounded by companions (some with associated H I emission), there is no correlation between the presence of companions and the AGN type (Seyfert/LINER).

  8. Dynamical aspects of galaxy clustering

    International Nuclear Information System (INIS)

    Fall, S.M.

    1980-01-01

    Some recent work on the origin and evolution of galaxy clustering is reviewed, particularly within the context of the gravitational instability theory and the hot big-bang cosmological model. Statistical measures of clustering, including correlation functions and multiplicity functions, are explained and discussed. The close connection between galaxy formation and clustering is emphasized. Additional topics include the dependence of galaxy clustering on the spectrum of primordial density fluctuations and the mean mass density of the Universe. (author)

  9. THE ROLE OF QUENCHING TIME IN THE EVOLUTION OF THE MASS–SIZE RELATION OF PASSIVE GALAXIES FROM THE WISP SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Zanella, A.; Scarlata, C.; Rutkowski, M. J. [Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis MN 55455 (United States); Corsini, E. M.; Bontà, E. Dalla [Dipartimento di Fisica e Astronomia “G. Galilei,” Università di Padova, vicolo dell’Osservatorio 3, I-35122 Padova (Italy); Bedregal, A. G. [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Atek, H. [Spitzer Science Center, Caltech, Pasadena, CA 91125 (United States); Bunker, A. J. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX13RH (United Kingdom); Colbert, J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Dai, Y. S. [Infrared Processing and Analysis Center, 770 South Wilson Avenue, Pasadena, CA 91125 (United States); Henry, A.; Rafelski, M. [Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Malkan, M. [Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095 (United States); Martin, C. [Department of Physics, University of California, Santa Barbara, CA, 93106 (United States); Siana, B. [Department of Physics and Astronomy, University of California Riverside, Riverside, CA 92521 (United States); Teplitz, H., E-mail: anita.zanella@cea.fr, E-mail: cmartin@physics.ucsb.edu [Infrared Processing and Analysis Center, Caltech, Pasadena, CA 91125 (United States)

    2016-06-20

    We analyze how passive galaxies at z ∼ 1.5 populate the mass–size plane as a function of their stellar age, to understand if the observed size growth with time can be explained with the appearance of larger quenched galaxies at lower redshift. We use a sample of 32 passive galaxies extracted from the Wide Field Camera 3 Infrared Spectroscopic Parallel (WISP) survey with spectroscopic redshift 1.3 ≲ z ≲ 2.05, specific star formation rates lower than 0.01 Gyr{sup −1}, and stellar masses above 4.5 × 10{sup 10} M {sub ⊙}. All galaxies have spectrally determined stellar ages from fitting of their rest-frame optical spectra and photometry with stellar population models. When dividing our sample into young (age ≤2.1 Gyr) and old (age >2.1 Gyr) galaxies we do not find a significant trend in the distributions of the difference between the observed radius and that predicted by the mass–size relation. This result indicates that the relation between the galaxy age and its distance from the mass–size relation, if it exists, is rather shallow, with a slope α ≳ −0.6. At face value, this finding suggests that multiple dry and/or wet minor mergers, rather than the appearance of newly quenched galaxies, are mainly responsible for the observed time evolution of the mass–size relation in passive galaxies.

  10. The AGN Luminosity Fraction in Galaxy Mergers

    Science.gov (United States)

    Dietrich, Jeremy; Weiner, Aaron; Ashby, Matthew; Martinez-Galarza, Juan Rafael; Smith, Howard Alan

    2017-01-01

    Galaxy mergers are key events in galaxy evolution, generally triggering massive starbursts and AGNs. However, in these chaotic systems, it is not yet known what fraction each of these two mechanisms contributes to the total luminosity. Here we measure and model spectral energy distributions (SEDs) using the Code for Investigating Galaxy Emission (CIGALE) in up to 33 broad bands from the UV to the far-IR for 23 IR-luminous galaxies to estimate the fraction of the bolometric IR luminosity that can be attributed to the AGN. The galaxies are split nearly evenly into two subsamples: late-stage mergers, found in the IRAS Revised Bright Galaxy Sample or Faint Source Catalog, and early-stage mergers found in the Spitzer Interacting Galaxy Sample. We find that the AGN contribution to the total IR luminosity varies greatly from system to system, from 0% up to ~90%, but is substantially greater in the later-stage and brighter mergers. This is consistent with what is known about galaxy evolution and the triggering of AGNs.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851, and by the Smithsonian Institution.

  11. Measuring the Evolution of Stellar Populations And Gas Metallicity in Galaxies with Far-Infrared Space Spectroscopy

    Science.gov (United States)

    Stacey, Gordon

    We propose a study of the evolution of stellar populations and gas metallicities in about 80 nearby star forming galaxies based on mining the NASA data archives for observations of the [NIII] 57 µm, [OIII] 52 µm and/or 88 µm, [NII] 122 and [CII] 158 µm far-infrared (FIR) fine- structure lines and other archives for thermal radio continuum. These lines are powerful probes of both stellar populations and gas properties and our primary science derives from these tracers. For sources that show both signs of active galactic nuclei (AGN) and star formation, we will take advantage of the readily available NASA Spitzer IRS data base that includes mid-IR [NeII] 12.8 µm, [NeIII] 15.6 µm and [NeV] 14.3 µm, [OIV] 25.9 µm and PAH observations. These complementary data reveal the relative fractions of the FIR line emission that might arise from star formation and the narrow line regions (NLR) associated with an AGN, thereby providing a robust set of observations to compare with star formation models. Subsets of the FIR lines have been detected from hundreds of nearby galaxies. From both theoretical studies and the results of these pioneering observations we know that these lines can be powerful probes of stellar populations and star formation in galaxies. Here we plan to use various combinations of the lines to constrain (1) the age of the stellar populations (through lines that trace the hardness of the stellar radiation fields, hence stellar spectral type), (2) the degree of processing of the interstellar medium (through lines that trace growth of secondary to primary element abundances for example, the N/O ratio), (3) the efficiency of star formation (through growth in absolute abundances of N and O, the N/H and O/H ratios), and (4) the current day mass function of upper main sequence stars. Surprisingly, there has been no systematic study of the large sample of these line detections made with PACS on Herschel in order to truly assess and calibrate their diagnostic

  12. Star clusters in evolving galaxies

    Science.gov (United States)

    Renaud, Florent

    2018-04-01

    Their ubiquity and extreme densities make star clusters probes of prime importance of galaxy evolution. Old globular clusters keep imprints of the physical conditions of their assembly in the early Universe, and younger stellar objects, observationally resolved, tell us about the mechanisms at stake in their formation. Yet, we still do not understand the diversity involved: why is star cluster formation limited to 105M⊙ objects in the Milky Way, while some dwarf galaxies like NGC 1705 are able to produce clusters 10 times more massive? Why do dwarfs generally host a higher specific frequency of clusters than larger galaxies? How to connect the present-day, often resolved, stellar systems to the formation of globular clusters at high redshift? And how do these links depend on the galactic and cosmological environments of these clusters? In this review, I present recent advances on star cluster formation and evolution, in galactic and cosmological context. The emphasis is put on the theory, formation scenarios and the effects of the environment on the evolution of the global properties of clusters. A few open questions are identified.

  13. Massive stars in galaxies

    International Nuclear Information System (INIS)

    Humphreys, R.M.

    1987-01-01

    The relationship between the morphologic type of a galaxy and the evolution of its massive stars is explored, reviewing observational results for nearby galaxies. The data are presented in diagrams, and it is found that the massive-star populations of most Sc spiral galaxies and irregular galaxies are similar, while those of Sb spirals such as M 31 and M 81 may be affected by morphology (via differences in the initial mass function or star-formation rate). Consideration is also given to the stability-related upper luminosity limit in the H-R diagram of hypergiant stars (attributed to radiation pressure in hot stars and turbulence in cool stars) and the goals of future observation campaigns. 88 references

  14. GALAXY INFALL BY INTERACTING WITH ITS ENVIRONMENT: A COMPREHENSIVE STUDY OF 340 GALAXY CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Liyi [SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands); Wen, Zhonglue [National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012 (China); Gandhi, Poshak [School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Inada, Naohisa [Department of Physics, Nara National College of Technology, Yamatokohriyama, Nara 639-1080 (Japan); Kawaharada, Madoka [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 229-8510 (Japan); Kodama, Tadayuki [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Konami, Saori [Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan); Nakazawa, Kazuhiro; Makishima, Kazuo [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Xu, Haiguang [Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Minhang, Shanghai 200240 (China)

    2016-07-20

    To study systematically the evolution of the angular extents of the galaxy, intracluster medium (ICM), and dark matter components in galaxy clusters, we compiled the optical and X-ray properties of a sample of 340 clusters with redshifts <0.5, based on all the available data from the Sloan Digital Sky Survey and Chandra / XMM-Newton . For each cluster, the member galaxies were determined primarily with photometric redshift measurements. The radial ICM mass distribution, as well as the total gravitational mass distribution, was derived from a spatially resolved spectral analysis of the X-ray data. When normalizing the radial profile of galaxy number to that of the ICM mass, the relative curve was found to depend significantly on the cluster redshift; it drops more steeply toward the outside in lower-redshift subsamples. The same evolution is found in the galaxy-to-total mass profile, while the ICM-to-total mass profile varies in an opposite way. The behavior of the galaxy-to-ICM distribution does not depend on the cluster mass, suggesting that the detected redshift dependence is not due to mass-related effects, such as sample selection bias. Also, it cannot be ascribed to various redshift-dependent systematic errors. We interpret that the galaxies, the ICM, and the dark matter components had similar angular distributions when a cluster was formed, while the galaxies traveling in the interior of the cluster have continuously fallen toward the center relative to the other components, and the ICM has slightly expanded relative to the dark matter although it suffers strong radiative loss. This cosmological galaxy infall, accompanied by an ICM expansion, can be explained by considering that the galaxies interact strongly with the ICM while they are moving through it. The interaction is considered to create a large energy flow of 10{sup 4445} erg s{sup 1} per cluster from the member galaxies to their environment, which is expected to continue over cosmological timescales.

  15. On the evolution of galaxy clustering and cosmological N-body simulations

    International Nuclear Information System (INIS)

    Fall, S.M.

    1978-01-01

    Some aspects of the problem of simulating the evolution of galaxy clustering by N-body computer experiments are discussed. The results of four 1000-body experiments are presented and interpreted on the basis of simple scaling arguments for the gravitational condensation of bound aggregates. They indicate that the internal dynamics of condensed aggregates are negligible in determining the form of the pair-correlation function xi. On small scales the form of xi is determined by discreteness effects in the initial N-body distribution and is not sensitive to this distribution. The experiments discussed here test the simple scaling arguments effectively for only one value of the cosmological density parameter (Ω = 1) and one form of the initial fluctuation spectrum (n = 0). (author)

  16. The Far-Infrared Properties of the Most Isolated Galaxies

    Science.gov (United States)

    Lisenfeld, U.; Verdes-Montenegro, L.; Sulentic, J.; Leon, S.; Espada, D.; Bergond, G.; García, E.; Sabater, J.; Santander-Vela, J. D.; Verley, S.

    2007-05-01

    A long-standing question in galaxy evolution involves the role of nature (self-regulation) vs. nurture (environment) on the observed properties (and evolution) of galaxies. A collaboration centreed at the Instituto de Astrofisica de Andalucia (Granada, Spain) is trying to address this question by producing a observational database for a sample of 1050 isolated galaxies from the catalogue of Karachentseva (1973) with the overarching goal being the generation of a "zero-point" sample against which effects of environment on galaxies can be assessed. The AMIGA (Analysis of the Interstellar Medium of Isolated Galaxies) database (see www.iaa.es/AMIGA.html) will include optical, IR and radio line and continuum measures. The galaxies in the sample represent the most isolated galaxies in the local universe. In the present contribution, we will present the project, as well as the results of an analysis of the far-infrared (FIR) and molecular gas properties of this sample.

  17. Anomalous Evolution of the Dwarf Galaxy HIPASS J1321-31

    OpenAIRE

    Pritzl, Barton J.; Knezek, Patricia M.; Gallagher III, John S.; Grossi, Marco; Disney, Mike J.; Minchin, Robert F.; Freeman, Kenneth C.; Tolstoy, Eline; Saha, Abi

    2003-01-01

    We present HST/WFPC2 observations of the dwarf galaxy HIPASS J1321-31. This unusual galaxy lies in the direction of the Centaurus A group of galaxies, and has a color-magnitude diagram with a distinctive red plume of luminous stars. This feature could arise from (a) a red giant branch if the galaxy were much nearer than previously recognized, (b) a peculiar asymptotic giant branch, or, (c) an ~1 Gigayear old population of intermediate mass red supergiants, which we find to be the most likely ...

  18. ngVLA Key Science Goal 3: Charting the Assembly, Structure, and Evolution of Galaxies Over Cosmic Time

    Science.gov (United States)

    Riechers, Dominik A.; Bolatto, Alberto D.; Carilli, Chris; Casey, Caitlin M.; Decarli, Roberto; Murphy, Eric Joseph; Narayanan, Desika; Walter, Fabian; ngVLA Galaxy Assembly through Cosmic Time Science Working Group, ngVLA Galaxy Ecosystems Science Working Group

    2018-01-01

    The Next Generation Very Large Array (ngVLA) will fundamentally advance our understanding of the formation processes that lead to the assembly of galaxies throughout cosmic history. The combination of large bandwidth with unprecedented sensitivity to the critical low-level CO lines over virtually the entire redshift range will open up the opportunity to conduct large-scale, deep cold molecular gas surveys, mapping the fuel for star formation in galaxies over substantial cosmic volumes. Imaging of the sub-kiloparsec scale distribution and kinematic structure of molecular gas in both normal main-sequence galaxies and large starbursts back to early cosmic epochs will reveal the physical processes responsible for star formation and black hole growth in galaxies over a broad range in redshifts. In the nearby universe, the ngVLA has the capability to survey the structure of the cold, star-forming interstellar medium at parsec-resolution out to the Virgo cluster. A range of molecular tracers will be accessible to map the motion, distribution, and physical and chemical state of the gas as it flows in from the outer disk, assembles into clouds, and experiences feedback due to star formation or accretion into central super-massive black holes. These investigations will crucially complement studies of the star formation and stellar mass histories with the Large UV/Optical/Infrared Surveyor and the Origins Space Telescope, providing the means to obtain a comprehensive picture of galaxy evolution through cosmic times.

  19. The visibility of high-redshift galaxies

    International Nuclear Information System (INIS)

    Phillipps, S.; Davies, J.I.; Disney, M.J.

    1990-01-01

    The most visible galaxies - that is, those which have the largest apparent sizes and isophotal luminosities when seen at a given distance - are those with a particular observed surface brightness. Extending this argument to high-redshift galaxies, it is clear that this optimum surface brightness moves progressively to brighter intrinsic surface brightnesses, so as to counteract the effect of K-corrections and cosmological dimming. Thus the galaxies appearing in faint surveys will be from a population distinctly different from those 'normal' galaxies observed nearby. Galaxies in deep surveys are more likely to be spirals and to be of high surface brightness. This has very important implications for observational studies of galaxy evolution. (author)

  20. The Carnegie-Spitzer-IMACS redshift survey of galaxy evolution since z = 1.5. I. Description and methodology

    Energy Technology Data Exchange (ETDEWEB)

    Kelson, Daniel D.; Williams, Rik J.; Dressler, Alan; McCarthy, Patrick J.; Shectman, Stephen A.; Mulchaey, John S.; Villanueva, Edward V.; Crane, Jeffrey D.; Quadri, Ryan F. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2014-03-10

    We describe the Carnegie-Spitzer-IMACS (CSI) Survey, a wide-field, near-IR selected spectrophotometric redshift survey with the Inamori Magellan Areal Camera and Spectrograph (IMACS) on Magellan-Baade. By defining a flux-limited sample of galaxies in Spitzer Infrared Array Camera 3.6 μm imaging of SWIRE fields, the CSI Survey efficiently traces the stellar mass of average galaxies to z ∼ 1.5. This first paper provides an overview of the survey selection, observations, processing of the photometry and spectrophotometry. We also describe the processing of the data: new methods of fitting synthetic templates of spectral energy distributions are used to derive redshifts, stellar masses, emission line luminosities, and coarse information on recent star formation. Our unique methodology for analyzing low-dispersion spectra taken with multilayer prisms in IMACS, combined with panchromatic photometry from the ultraviolet to the IR, has yielded high-quality redshifts for 43,347 galaxies in our first 5.3 deg{sup 2} of the SWIRE XMM-LSS field. We use three different approaches to estimate our redshift errors and find robust agreement. Over the full range of 3.6 μm fluxes of our selection, we find typical redshift uncertainties of σ {sub z}/(1 + z) ≲ 0.015. In comparisons with previously published spectroscopic redshifts we find scatters of σ {sub z}/(1 + z) = 0.011 for galaxies at 0.7 ≤ z ≤ 0.9, and σ {sub z}/(1 + z) = 0.014 for galaxies at 0.9 ≤ z ≤ 1.2. For galaxies brighter and fainter than i = 23 mag, we find σ {sub z}/(1 + z) = 0.008 and σ {sub z}/(1 + z) = 0.022, respectively. Notably, our low-dispersion spectroscopy and analysis yields comparable redshift uncertainties and success rates for both red and blue galaxies, largely eliminating color-based systematics that can seriously bias observed dependencies of galaxy evolution on environment.

  1. LOCAL BENCHMARKS FOR THE EVOLUTION OF MAJOR-MERGER GALAXIES-SPITZER OBSERVATIONS OF A K-BAND SELECTED SAMPLE

    International Nuclear Information System (INIS)

    Xu, C. Kevin; Cheng Yiwen; Lu Nanyao; Mazzarella, Joseph M.; Cutri, Roc; Domingue, Donovan; Huang Jiasheng; Gao Yu; Sun, W.-H.; Surace, Jason

    2010-01-01

    We present Spitzer observations for a sample of close major-merger galaxy pairs (KPAIR sample) selected from cross-matches between the Two Micron All Sky Survey and Sloan Digital Sky Survey Data Release 3. The goals are to study the star formation activity in these galaxies and to set a local bench mark for the cosmic evolution of close major mergers. The Spitzer KPAIR sample (27 pairs, 54 galaxies) includes all spectroscopically confirmed spiral-spiral (S+S) and spiral-elliptical (S+E) pairs in a parent sample that is complete for primaries brighter than K = 12.5 mag, projected separations of 5 h -1 kpc ≤ s ≤ 20 h -1 kpc, and mass ratios ≤2.5. The Spitzer data, consisting of images in seven bands (3.6, 4.5, 5.8, 8, 24, 70, 160 μm), show very diversified IR emission properties. Compared to single spiral galaxies in a control sample, only spiral galaxies in S+S pairs show significantly enhanced specific star formation rate (sSFR = SFR/M), whereas spiral galaxies in S+E pairs do not. Furthermore, the SFR enhancement of spiral galaxies in S+S pairs is highly mass-dependent. Only those with M ∼> 10 10.5 M sun show significant enhancement. Relatively low-mass (M ∼ 10 10 M sun ) spirals in S+S pairs have about the same SFR/M compared to their counterparts in the control sample, while those with 10 11 M sun have on average a ∼3 times higher SFR/M than single spirals. There is evidence for a correlation between the global star formation activities (but not the nuclear activities) of the component galaxies in massive S+S major-merger pairs (the H olmberg effect ) . There is no significant difference in the SFR/M between the primaries and the secondaries, nor between spirals of SEP KPAIR =2.54 x 10 -4 (M sun yr -1 Mpc -3 ).

  2. EVOLUTION OF THE SIZES OF GALAXIES OVER 7 < z < 12 REVEALED BY THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Yoshiaki; Ouchi, Masami [Institute for Cosmic Ray Research, The University of Tokyo, Kashiwa 277-8582 (Japan); Curtis-Lake, Emma; McLure, Ross J.; Dunlop, James S.; Bowler, Rebecca A. A.; Rogers, Alexander B.; Cirasuolo, Michele [Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom); Schenker, Matthew A.; Ellis, Richard S. [Department of Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Robertson, Brant E.; Schneider, Evan; Stark, Daniel P. [Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Koekemoer, Anton M. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Charlot, Stephane [UPMC-CNRS, UMR7095, Institut d' Astrophysique, F-75014 Paris (France); Shimasaku, Kazuhiro [Department of Astronomy, Graduate School of Science, The University of Tokyo, Tokyo 113-0033 (Japan); Furlanetto, Steven R., E-mail: ono@icrr.u-tokyo.ac.jp [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)

    2013-11-10

    We analyze the redshift- and luminosity-dependent sizes of dropout galaxy candidates in the redshift range z ∼ 7-12 using deep images from the 2012 Hubble Ultra Deep Field (UDF12) campaign, which offers two advantages over that used in earlier work. First, we utilize the increased signal-to-noise ratio offered by the UDF12 imaging to provide improved measurements for known galaxies at z ≅ 6.5-8 in the HUDF. Second, because the UDF12 data have allowed the construction of the first robust galaxy sample in the HUDF at z > 8, we have been able to extend the measurement of average galaxy size out to higher redshifts. Restricting our measurements to sources detected at >15σ, we confirm earlier indications that the average half-light radii of z ∼ 7-12 galaxies are extremely small, 0.3-0.4 kpc, comparable to the sizes of giant molecular associations in local star-forming galaxies. We also confirm that there is a clear trend of decreasing half-light radius with increasing redshift, and provide the first evidence that this trend continues beyond z ≅ 8. Modeling the evolution of the average half-light radius as a power law, ∝(1 + z) {sup s}, we obtain a best-fit index of s=-1.30{sup +0.12}{sub -0.14} over z ∼ 4-12. A clear size-luminosity relation is evident in our dropout samples. This relation can be interpreted in terms of a constant surface density of star formation over a range in luminosity of 0.05-1.0 L{sub z=3}. The average star formation surface density in dropout galaxies is 2-3 orders of magnitude lower than that found in extreme starburst galaxies, but is comparable to that seen today in the centers of normal disk galaxies.

  3. EVOLUTION OF THE SIZES OF GALAXIES OVER 7 < z < 12 REVEALED BY THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN

    International Nuclear Information System (INIS)

    Ono, Yoshiaki; Ouchi, Masami; Curtis-Lake, Emma; McLure, Ross J.; Dunlop, James S.; Bowler, Rebecca A. A.; Rogers, Alexander B.; Cirasuolo, Michele; Schenker, Matthew A.; Ellis, Richard S.; Robertson, Brant E.; Schneider, Evan; Stark, Daniel P.; Koekemoer, Anton M.; Charlot, Stephane; Shimasaku, Kazuhiro; Furlanetto, Steven R.

    2013-01-01

    We analyze the redshift- and luminosity-dependent sizes of dropout galaxy candidates in the redshift range z ∼ 7-12 using deep images from the 2012 Hubble Ultra Deep Field (UDF12) campaign, which offers two advantages over that used in earlier work. First, we utilize the increased signal-to-noise ratio offered by the UDF12 imaging to provide improved measurements for known galaxies at z ≅ 6.5-8 in the HUDF. Second, because the UDF12 data have allowed the construction of the first robust galaxy sample in the HUDF at z > 8, we have been able to extend the measurement of average galaxy size out to higher redshifts. Restricting our measurements to sources detected at >15σ, we confirm earlier indications that the average half-light radii of z ∼ 7-12 galaxies are extremely small, 0.3-0.4 kpc, comparable to the sizes of giant molecular associations in local star-forming galaxies. We also confirm that there is a clear trend of decreasing half-light radius with increasing redshift, and provide the first evidence that this trend continues beyond z ≅ 8. Modeling the evolution of the average half-light radius as a power law, ∝(1 + z) s , we obtain a best-fit index of s=-1.30 +0.12 -0.14 over z ∼ 4-12. A clear size-luminosity relation is evident in our dropout samples. This relation can be interpreted in terms of a constant surface density of star formation over a range in luminosity of 0.05-1.0 L z=3 . The average star formation surface density in dropout galaxies is 2-3 orders of magnitude lower than that found in extreme starburst galaxies, but is comparable to that seen today in the centers of normal disk galaxies

  4. Green Ocean Amazon 2014/15 Terrestrial Ecosystem Project (Geco) Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Jardine, Kolby [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2016-06-01

    In conjunction with the U.S. Department of Energy (DOE)’s Atmospheric Radiation Measurement (ARM) Climate Research Facility GoAmazon campaign, the Terrestrial Ecosystem Science (TES)-funded Green Ocean Amazon (GoAmazon 2014/15) terrestrial ecosystem project (Geco) was designed to: • evaluate the strengths and weaknesses of leaf-level algorithms for biogenic volatile organic compounds (BVOCs) emissions in Amazon forests near Manaus, Brazil, and • conduct mechanistic field studies to characterize biochemical and physiological processes governing leaf- and landscape-scale tropical forest BVOC emissions, and the influence of environmental drivers that are expected to change with a warming climate. Through a close interaction between modeling and observational activities, including the training of MS and PhD graduate students, post-doctoral students, and technicians at the National Institute for Amazon Research (INPA), the study aimed at improving the representation of BVOC-mediated biosphere-atmosphere interactions and feedbacks under a warming climate. BVOCs can form cloud condensation nuclei (CCN) that influence precipitation dynamics and modify the quality of down welling radiation for photosynthesis. However, our ability to represent these coupled biosphere-atmosphere processes in Earth system models suffers from poor understanding of the functions, identities, quantities, and seasonal patterns of BVOC emissions from tropical forests as well as their biological and environmental controls. The Model of Emissions of Gases and Aerosols from Nature (MEGAN), the current BVOC sub-model of the Community Earth System Model (CESM), was evaluated to explore mechanistic controls over BVOC emissions. Based on that analysis, a combination of observations and experiments were studied in forests near Manaus, Brazil, to test existing parameterizations and algorithm structures in MEGAN. The model was actively modified as needed to improve tropical BVOC emission simulations on

  5. The FourStar Galaxy Evolution Survey (ZFOURGE): Ultraviolet to Far-infrared Catalogs, Medium-bandwidth Photometric Redshifts with Improved Accuracy, Stellar Masses, and Confirmation of Quiescent Galaxies to z ˜ 3.5

    Science.gov (United States)

    Straatman, Caroline M. S.; Spitler, Lee R.; Quadri, Ryan F.; Labbé, Ivo; Glazebrook, Karl; Persson, S. Eric; Papovich, Casey; Tran, Kim-Vy H.; Brammer, Gabriel B.; Cowley, Michael; Tomczak, Adam; Nanayakkara, Themiya; Alcorn, Leo; Allen, Rebecca; Broussard, Adam; van Dokkum, Pieter; Forrest, Ben; van Houdt, Josha; Kacprzak, Glenn G.; Kawinwanichakij, Lalitwadee; Kelson, Daniel D.; Lee, Janice; McCarthy, Patrick J.; Mehrtens, Nicola; Monson, Andrew; Murphy, David; Rees, Glen; Tilvi, Vithal; Whitaker, Katherine E.

    2016-10-01

    The FourStar galaxy evolution survey (ZFOURGE) is a 45 night legacy program with the FourStar near-infrared camera on Magellan and one of the most sensitive surveys to date. ZFOURGE covers a total of 400 arcmin2 in cosmic fields CDFS, COSMOS and UDS, overlapping CANDELS. We present photometric catalogs comprising >70,000 galaxies, selected from ultradeep K s -band detection images (25.5-26.5 AB mag, 5σ, total), and >80% complete to K s inclusion of FourStar medium bands. σ z,pairs is smallest for bright, blue star-forming samples, while red star-forming galaxies have the worst σ z,pairs. Including FourStar medium bands reduces σ z,pairs by 50% at 1.5 ×15. This paper contains data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas observatory, Chile

  6. The Galaxy mass function up to z =4 in the GOODS-MUSIC sample: into the epoch of formation of massive galaxies

    Science.gov (United States)

    Fontana, A.; Salimbeni, S.; Grazian, A.; Giallongo, E.; Pentericci, L.; Nonino, M.; Fontanot, F.; Menci, N.; Monaco, P.; Cristiani, S.; Vanzella, E.; de Santis, C.; Gallozzi, S.

    2006-12-01

    Aims.The goal of this work is to measure the evolution of the Galaxy Stellar Mass Function and of the resulting Stellar Mass Density up to redshift ≃4, in order to study the assembly of massive galaxies in the high redshift Universe. Methods: .We have used the GOODS-MUSIC catalog, containing 3000 Ks-selected galaxies with multi-wavelength coverage extending from the U band to the Spitzer 8 μm band, of which 27% have spectroscopic redshifts and the remaining fraction have accurate photometric redshifts. On this sample we have applied a standard fitting procedure to measure stellar masses. We compute the Galaxy Stellar Mass Function and the resulting Stellar Mass Density up to redshift ≃4, taking into proper account the biases and incompleteness effects. Results: .Within the well known trend of global decline of the Stellar Mass Density with redshift, we show that the decline of the more massive galaxies may be described by an exponential timescale of ≃6 Gyr up to z≃ 1.5, and proceeds much faster thereafter, with an exponential timescale of ≃0.6 Gyr. We also show that there is some evidence for a differential evolution of the Galaxy Stellar Mass Function, with low mass galaxies evolving faster than more massive ones up to z≃ 1{-}1.5 and that the Galaxy Stellar Mass Function remains remarkably flat (i.e. with a slope close to the local one) up to z≃ 1{-}1.3. Conclusions: .The observed behaviour of the Galaxy Stellar Mass Function is consistent with a scenario where about 50% of present-day massive galaxies formed at a vigorous rate in the epoch between redshift 4 and 1.5, followed by a milder evolution until the present-day epoch.

  7. Anomalous evolution of the dwarf galaxy HIPASS J1321-31

    NARCIS (Netherlands)

    Pritzl, BJ; Knezek, PM; Gallagher, JS; Grossi, M; Disney, MJ; Minchin, RF; Freeman, KC; Tolstoy, E; Saha, A

    2003-01-01

    We present Hubble Space Telescope/WFPC2 observations of the dwarf galaxy HIPASS J1321-31. This unusual galaxy lies in the direction of the Centaurus A group of galaxies and has a color-magnitude diagram with a distinctive red plume of luminous stars. This feature could arise from (1) a red giant

  8. New Views on the Early Evolution of Oxygen in the Galaxy

    Science.gov (United States)

    Rebolo, R.; Israelian, G.; García López, R. J.

    We have performed a detailed oxygen abundance analysis of 23 metal-poor (-3.0 Abia & Rebolo 1989; Tomkin et al. 1992; Cavallo, Pilachowski, & Rebolo 1997). Contrary to the previously accepted picture, our oxygen abundances, derived from low-excitation OH lines, agree well with those derived from high-excitation lines of the triplet. For nine stars in common with Tomkin et al. we obtain a mean difference of 0.00 plus or minus 0.11dex with respect to the abundances determined from the triplet using the same stellar parameters and model photospheres. Our new results show a smooth extension of the Edvardsson et al.'s (1993) [O/Fe] versus metallicity curve to much lower abundances. The oxygen abundances of unevolved stars when compared with values in the literature for giants of similar metallicity imply that the latter may have suffered a process of oxygen depletion. It appears that unevolved metal-poor stars are better tracers of the early chemical evolution of the Galaxy. The extrapolation of our results to very low metallicities indicates that the ratio of oxygen to iron emerging from the first Type II SNe in the early Galaxy was indeed close to unity. The higher [O/Fe] ratios we find in dwarfs has an impact on the age determination of globular clusters, and suggest that current age estimates have to be reduced by about 1-2 Gyr.

  9. The slingshot ejections in merging galaxies

    International Nuclear Information System (INIS)

    Mikkola, S.; Valtonen, M.J.

    1990-01-01

    The evolution of black hole systems in multiple mergers of galaxies has been investigated, using a particular galaxy merger process with a continuous distribution of the black hole masses. Two types of escapes represented the most common line of evolution: the nearly symmetric escapes and the one-sided escapes. Symmetric escapes dominate at low velocities, and one-sided escapes dominate at high velocities. An exception to this rule is made by those one-sided escape trails where the escape speed is low; the number of such trails is only about 10 percent of the number of symmetric escape trails. In the present form of the slingshot model, the degree of symmetry of the black hole separations from the center of the galaxy is very close to the degree of symmetry by which the lobes of the 3C double radio sources are placed relative to the center of the radio galaxy. 46 refs

  10. Dynamical evolution in clusters of galaxies with low-frequency radio emission

    International Nuclear Information System (INIS)

    Guthrie, B.N.G.

    1977-01-01

    Clusters of galaxies in which radio emission at low frequencies ( approximately 10 9 yr). Confinement would probably occur for radio sources associated with bright galaxies in the cores of clusters and cD galaxies in clusters. However, cD galaxies may have recurrent radio outbursts so that steep spectra are not always observed. (Auth.)

  11. A close nuclear black-hole pair in the spiral galaxy NGC 3393.

    Science.gov (United States)

    Fabbiano, G; Wang, Junfeng; Elvis, M; Risaliti, G

    2011-08-31

    The current picture of galaxy evolution advocates co-evolution of galaxies and their nuclear massive black holes, through accretion and galactic merging. Pairs of quasars, each with a massive black hole at the centre of its galaxy, have separations of 6,000 to 300,000 light years (refs 2 and 3; 1 parsec = 3.26 light years) and exemplify the first stages of this gravitational interaction. The final stages of the black-hole merging process, through binary black holes and final collapse into a single black hole with gravitational wave emission, are consistent with the sub-light-year separation inferred from the optical spectra and light-variability of two such quasars. The double active nuclei of a few nearby galaxies with disrupted morphology and intense star formation (such as NGC 6240 with a separation of about 2,600 light years and Mrk 463 with a separation of about 13,000 light years between the nuclei) demonstrate the importance of major mergers of equal-mass spiral galaxies in this evolution; such mergers lead to an elliptical galaxy, as in the case of the double-radio-nucleus elliptical galaxy 0402+379 (with a separation of about 24 light years between the nuclei). Minor mergers of a spiral galaxy with a smaller companion should be a more common occurrence, evolving into spiral galaxies with active massive black-hole pairs, but have hitherto not been seen. Here we report the presence of two active massive black holes, separated by about 490 light years, in the Seyfert galaxy NGC 3393 (50 Mpc, about 160 million light years). The regular spiral morphology and predominantly old circum-nuclear stellar population of this galaxy, and the closeness of the black holes embedded in the bulge, provide a hitherto missing observational point to the study of galaxy/black hole evolution. Comparison of our observations with current theoretical models of mergers suggests that they are the result of minor merger evolution. © 2011 Macmillan Publishers Limited. All rights

  12. Symposium “Mapping the Galaxy and Nearby Galaxies”

    CERN Document Server

    Wada, Keiichi; ASTROPHYSICS AND SPACE SCIENCE PROCEEDINGS

    2008-01-01

    This is a proceedings book of the symposium "Mapping the Galaxy and Nearby Galaxies" held on Ishigaki Island, Okinawa, Japan, on June 25 – 30, 2006. The symposium focused on mapping the interstellar media and other components in galaxies. Latest results of the following main topics are presented in the volume: Our Galaxy -- mass distribution, local ISM, supermassive black holes and their environments Central part of nearby galaxies -- ISM around starbursts, fueling mechanisms Nearby Galaxies -- molecular gas and star formation, gas dynamics Galactic environment and evolution -- formation of our Galaxy, origin of supermassive black holes The nature of the Dark Matter component -- effects on the internal structures of galaxies

  13. Galaxy evolution in groups. NGC 3447/NGC 3447A: the odd couple in LGG 225

    Science.gov (United States)

    Mazzei, P.; Marino, A.; Rampazzo, R.; Plana, H.; Rosado, M.; Arias, L.

    2018-02-01

    Context. Local Group (LG) analogs (LGAs) are galaxy associations dominated by a few bright spirals reminiscent of the LG. The NGC 3447/NGC 3447A system is a member of the LGG 225 group, a nearby LGA. This system is considered a physical pair composed of an intermediate-luminosity late-type spiral, NGC 3447 itself, and an irregular companion, NGC 3447A, linked by a faint, short filament of matter. A ring-like structure in the NGC 3447 outskirts has been emphasised by Galaxy Evolution Explorer (GALEX) observations. Aims: This work aims to contribute to the study of galaxy evolution in low-density environments, a favourable habitat to highly effective encounters, shedding light on the evolution of the NGC 3447/NGC 3447A system. Methods: We performed a multi-λ analysis of the surface photometry of this system to derive its spectral energy distribution and structural properties using ultraviolet (UV), Swift UVOT, and optical Sloan Digital Sky Survey (SDSS) images complemented with available far-IR observations. We also characterised the velocity field of the pair using two-dimensional Hα kinematical observations of the system obtained with PUMA Fabry-Perot interferometer at the 2.1 m telescope of San Pedro Mártir (Mexico). All these data are used to constrain smooth particle hydrodynamic simulations with chemo-photometric implementation to shed light on the evolution of this system. Results: The luminosity profiles, from UV to optical wavelengths, are all consistent with the presence of a disc extending and including NGC 3447A. The overall velocity field does not emphasise any significant rotation pattern, rather a small velocity gradient between NGC 3447 and NGC 3447A. Our simulation, detached from a large grid explored to best-fit the global properties of the system, suggests that this arises from an encounter between two halos of equal mass. Conclusions: NGC 3447 and NGC 3447A belong to the same halo, NGC 3447A being a substructure of the same disk including NGC

  14. The role of interactions in galaxy evolution: A new perspective from the CALIFA and MaNGA Integral Field Spectroscopic surveys.

    Science.gov (United States)

    Barrera-Ballesteros, J. K.; Sanchez, S. F.; Califa Collaboration

    2016-06-01

    Interactions and mergers have been playing a paramount role to understand how galaxies evolve. In recent years integral field spectroscopic (IFS) observations have become routinely allowing researchers to conduct large IFS surveys. In this context, these surveys are providing a new observational scenario to probe the properties of galaxies at different stages of the interaction —from close pairs to post-merger galaxies. Even more, these surveys also include homogeneous observations of non-interacting galaxies which in turns allows to distinguish the processes induce by secular evolution from those driven by interactions. In this talk, We review the studies of interacting studies from the CALIFA survey. They consider from the thorough analysis of a single interactive systems (e.g., the Mice, Wild et al. 2014) to the the statistical study of physical properties of a large sample of interacting/merging galaxies such as their internal structure via their stellar and gas line-of-sight kinematic maps (Barrera-Ballesteros et al. 2015a) or the spatial distribution of the star-forming gas in these galaxies (Barrera-Ballesteros et al. 2015b). Then we present some of the on-going studies within the MaNGA survey. Due to its statistical power (sample size ~10000 objects), this survey will allow us to probe the properties of galaxies in a wide range of the interaction-parameter space. This in turn provides a unique view on the key parameters that affect the internal structure and properties of galaxies during the interaction and subsequent merger.

  15. GALAXY ENVIRONMENTS OVER COSMIC TIME: THE NON-EVOLVING RADIAL GALAXY DISTRIBUTIONS AROUND MASSIVE GALAXIES SINCE z = 1.6

    International Nuclear Information System (INIS)

    Tal, Tomer; Van Dokkum, Pieter G.; Leja, Joel; Franx, Marijn; Wake, David A.; Whitaker, Katherine E.

    2013-01-01

    We present a statistical study of the environments of massive galaxies in four redshift bins between z = 0.04 and z = 1.6, using data from the Sloan Digital Sky Survey and the NEWFIRM Medium Band Survey. We measure the projected radial distribution of galaxies in cylinders around a constant number density selected sample of massive galaxies and utilize a statistical subtraction of contaminating sources. Our analysis shows that massive primary galaxies typically live in group halos and are surrounded by 2-3 satellites with masses more than one-tenth of the primary galaxy mass. The cumulative stellar mass in these satellites roughly equals the mass of the primary galaxy itself. We further find that the radial number density profile of galaxies around massive primaries has not evolved significantly in either slope or overall normalization in the past 9.5 Gyr. A simplistic interpretation of this result can be taken as evidence for a lack of mergers in the studied groups and as support for a static evolution model of halos containing massive primaries. Alternatively, there exists a tight balance between mergers and accretion of new satellites such that the overall distribution of galaxies in and around the halo is preserved. The latter interpretation is supported by a comparison to a semi-analytic model, which shows a similar constant average satellite distribution over the same redshift range.

  16. SUPERDENSE MASSIVE GALAXIES IN WINGS LOCAL CLUSTERS

    International Nuclear Information System (INIS)

    Valentinuzzi, T.; D'Onofrio, M.; Fritz, J.; Poggianti, B. M.; Bettoni, D.; Fasano, G.; Moretti, A.; Omizzolo, A.; Varela, J.; Cava, A.; Couch, W. J.; Dressler, A.; Moles, M.; Kjaergaard, P.; Vanzella, E.

    2010-01-01

    Massive quiescent galaxies at z > 1 have been found to have small physical sizes, and hence to be superdense. Several mechanisms, including minor mergers, have been proposed for increasing galaxy sizes from high- to low-z. We search for superdense massive galaxies in the WIde-field Nearby Galaxy-cluster Survey (WINGS) of X-ray selected galaxy clusters at 0.04 10 M sun , are mostly S0 galaxies, have a median effective radius (R e ) = 1.61 ± 0.29 kpc, a median Sersic index (n) = 3.0 ± 0.6, and very old stellar populations with a median mass-weighted age of 12.1 ± 1.3 Gyr. We calculate a number density of 2.9 x 10 -2 Mpc -3 for superdense galaxies in local clusters, and a hard lower limit of 1.3 x 10 -5 Mpc -3 in the whole comoving volume between z = 0.04 and z = 0.07. We find a relation between mass, effective radius, and luminosity-weighted age in our cluster galaxies, which can mimic the claimed evolution of the radius with redshift, if not properly taken into account. We compare our data with spectroscopic high-z surveys and find that-when stellar masses are considered-there is consistency with the local WINGS galaxy sizes out to z ∼ 2, while a discrepancy of a factor of 3 exists with the only spectroscopic z > 2 study. In contrast, there is strong evidence for a large evolution in radius for the most massive galaxies with M * > 4 x 10 11 M sun compared to similarly massive galaxies in WINGS, i.e., the brightest cluster galaxies.

  17. Separating intrinsic alignment and galaxy-galaxy lensing

    International Nuclear Information System (INIS)

    Blazek, Jonathan; Seljak, Uroš; Mandelbaum, Rachel; Nakajima, Reiko

    2012-01-01

    The coherent physical alignment of galaxies is an important systematic for gravitational lensing studies as well as a probe of the physical mechanisms involved in galaxy formation and evolution. We develop a formalism for treating this intrinsic alignment (IA) in the context of galaxy-galaxy lensing and present an improved method for measuring IA contamination, which can arise when sources physically associated with the lens are placed behind the lens due to photometric redshift scatter. We apply the technique to recent Sloan Digital Sky Survey (SDSS) measurements of Luminous Red Galaxy lenses and typical ( ∼ L * ) source galaxies with photometric redshifts selected from the SDSS imaging data. Compared to previous measurements, this method has the advantage of being fully self-consistent in its treatment of the IA and lensing signals, solving for the two simultaneously. We find an IA signal consistent with zero, placing tight constraints on both the magnitude of the IA effect and its potential contamination to the lensing signal. While these constraints depend on source selection and redshift quality, the method can be applied to any measurement that uses photometric redshifts. We obtain a model-independent upper-limit of roughly 10% IA contamination for projected separations of r p ≈ 0.1–10 h −1 Mpc. With more stringent photo-z cuts and reasonable assumptions about the physics of intrinsic alignments, this upper limit is reduced to 1–2%. These limits are well below the statistical error of the current lensing measurements. Our results suggest that IA will not present intractable challenges to the next generation of galaxy-galaxy lensing experiments, and the methods presented here should continue to aid in our understanding of alignment processes and in the removal of IA from the lensing signal

  18. Violence in the hearts of galaxies: aberration or adolescence?

    Science.gov (United States)

    Mundell, Carole G

    2002-12-15

    Violent activity in the nuclei of galaxies has long been considered a curiosity in its own right; manifestations of this phenomenon include distant quasars in the early Universe and comparatively nearby Seyfert galaxies, both thought to be powered by the release of gravitational potential energy as material from the host galaxy accretes onto a central supermassive black hole (SMBH). Traditionally, the broader study of the formation, structure and evolution of galaxies has largely excluded active galactic nuclei. Recently, however, this situation has changed dramatically, both observationally and theoretically, with the realization that the growth and influence of the SMBH, the origin and development of galaxies and nuclear activity at different epochs in the Universe may be intimately related. The most spectacular fireworks seen in distant quasars may be relatively easy to explain, since the era of greatest quasar activity seems to coincide with turbulent dynamics at the epoch of galaxy formation in the young, gas-rich Universe. Ubiquitous black holes are believed to be a legacy of this violent birth. Alternatively, black holes may be the seeds that drive galaxy formation in the first place. Closer to home, and hence more recently in the history of the Universe, a fraction of comparatively ordinary galaxies, similar to our own, has reignited their central engines, albeit at a lower level of activity. Since these galaxies are more established than their younger and more distant counterparts, the activity here is all the more puzzling. Whatever the mechanisms involved, they are likely to play an important role in galaxy evolution. I review the intriguing evidence for causal links between SMBHs, nuclear activity and the formation and evolution of galaxies, and describe opportunities for testing these relationships using the next generation of earthbound and space-borne astronomical facilities.

  19. Violence in the hearts of galaxies: aberration or adolescence?

    Science.gov (United States)

    Mundell, Carole G.

    2002-12-01

    Violent activity in the nuclei of galaxies has long been considered a curiosity in its own right; manifestations of this phenomenon include distant quasars in the early Universe and comparatively nearby Seyfert galaxies, both thought to be powered by the release of gravitational potential energy as material from the host galaxy accretes onto a central supermassive black hole (SMBH). Traditionally, the broader study of the formation, structure and evolution of galaxies has largely excluded active galactic nuclei. Recently, however, this situation has changed dramatically, both observationally and theoretically, with the realization that the growth and influence of the SMBH, the origin and development of galaxies and nuclear activity at different epochs in the Universe may be intimately related. The most spectacular fireworks seen in distant quasars may be relatively easy to explain, since the era of greatest quasar activity seems to coincide with turbulent dynamics at the epoch of galaxy formation in the young, gas-rich Universe. Ubiquitous black holes are believed to be a legacy of this violent birth. Alternatively, black holes may be the seeds that drive galaxy formation in the first place. Closer to home, and hence more recently in the history of the Universe, a fraction of comparatively ordinary galaxies, similar to our own, has reignited their central engines, albeit at a lower level of activity. Since these galaxies are more established than their younger and more distant counterparts, the activity here is all the more puzzling. Whatever the mechanisms involved, they are likely to play an important role in galaxy evolution. I review the intriguing evidence for causal links between SMBHs, nuclear activity and the formation and evolution of galaxies, and describe opportunities for testing these relationships using the next generation of earthbound and space-borne astronomical facilities.

  20. Reconstructing galaxy histories from globular clusters.

    Science.gov (United States)

    West, Michael J; Côté, Patrick; Marzke, Ronald O; Jordán, Andrés

    2004-01-01

    Nearly a century after the true nature of galaxies as distant 'island universes' was established, their origin and evolution remain great unsolved problems of modern astrophysics. One of the most promising ways to investigate galaxy formation is to study the ubiquitous globular star clusters that surround most galaxies. Globular clusters are compact groups of up to a few million stars. They generally formed early in the history of the Universe, but have survived the interactions and mergers that alter substantially their parent galaxies. Recent advances in our understanding of the globular cluster systems of the Milky Way and other galaxies point to a complex picture of galaxy genesis driven by cannibalism, collisions, bursts of star formation and other tumultuous events.

  1. THE IMACS CLUSTER BUILDING SURVEY. III. THE STAR FORMATION HISTORIES OF FIELD GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Oemler, Augustus Jr.; Dressler, Alan [Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101-1292 (United States); Gladders, Michael G.; Abramson, Louis [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Fritz, Jacopo [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Poggianti, Bianca M.; Vulcani, Benedetta [INAF-Osservatorio Astronomico di Padova, vicolo dell' Osservatorio 5, I-35122 Padova (Italy)

    2013-06-10

    Using data from the IMACS Cluster Building Survey and from nearby galaxy surveys, we examine the evolution of the rate of star formation in field galaxies from z = 0.60 to the present. Fitting the luminosity function to a standard Schechter form, we find a rapid evolution of M{sub B}{sup *} consistent with that found in other deep surveys; at the present epoch M{sub B}{sup *} is evolving at the rate of 0.38 Gyr{sup -1}, several times faster than the predictions of simple models for the evolution of old, coeval galaxies. The evolution of the distribution of specific star formation rates (SSFRs) is also too rapid to explain by such models. We demonstrate that starbursts cannot, even in principle, explain the evolution of the SSFR distribution. However, the rapid evolution of both M{sub B}{sup *} and the SSFR distribution can be explained if some fraction of galaxies have star formation rates characterized by both short rise and fall times and by an epoch of peak star formation more recent than the majority of galaxies. Although galaxies of every stellar mass up to 1.4 Multiplication-Sign 10{sup 11} M{sub Sun} show a range of epochs of peak star formation, the fraction of ''younger'' galaxies falls from about 40% at a mass of 4 Multiplication-Sign 10{sup 10} M{sub Sun} to zero at a mass of 1.4 Multiplication-Sign 10{sup 11} M{sub Sun }. The incidence of younger galaxies appears to be insensitive to the density of the local environment; but does depend on group membership: relatively isolated galaxies are much more likely to be young than are group members.

  2. Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies

    OpenAIRE

    Leloudas, G.; Schulze, S.; Kruehler, T.; Gorosabel, J.; Christensen, L.; Mehner, A.; Postigo, A. de Ugarte; Amorin, R.; Thoene, C. C.; Anderson, J. P.; Bauer, F. E.; Gallazzi, A.; Helminiak, K. G.; Hjorth, J.; Ibar, E.

    2014-01-01

    Superluminous supernovae (SLSNe) are very bright explosions that were only discovered recently and that show a preference for occurring in faint dwarf galaxies. Understanding why stellar evolution yields different types of stellar explosions in these environments is fundamental in order to both uncover the elusive progenitors of SLSNe and to study star formation in dwarf galaxies. In this paper, we present the first results of our project to study SUperluminous Supernova Host galaxIES, focusi...

  3. THE EVOLUTION OF BLACK HOLE SCALING RELATIONS IN GALAXY MERGERS

    International Nuclear Information System (INIS)

    Johansson, Peter H.; Burkert, Andreas; Naab, Thorsten

    2009-01-01

    We study the evolution of black holes (BHs) on the M BH -σ and M BH -M bulge planes as a function of time in disk galaxies undergoing mergers. We begin the simulations with the progenitor BH masses being initially below (Δlog M BH,i ∼ -2), on (Δlog M BH,i ∼ 0), and above (Δlog M BH,i ∼ 0.5) the observed local relations. The final relations are rapidly established after the final coalescence of the galaxies and their BHs. Progenitors with low initial gas fractions (f gas = 0.2) starting below the relations evolve onto the relations (Δlog M BH,f ∼ -0.18), progenitors on the relations stay there (Δlog M BH,f ∼ 0), and finally progenitors above the relations evolve toward the relations, but still remain above them (Δlog M BH,f ∼ 0.35). Mergers in which the progenitors have high initial gas fractions (f gas = 0.8) evolve above the relations in all cases (Δlog M BH,f ∼ 0.5). We find that the initial gas fraction is the prime source of scatter in the observed relations, dominating over the scatter arising from the evolutionary stage of the merger remnants. The fact that BHs starting above the relations do not evolve onto the relations indicates that our simulations rule out the scenario in which overmassive BHs evolve onto the relations through gas-rich mergers. By implication our simulations thus disfavor the picture in which supermassive BHs develop significantly before their parent bulges.

  4. HI gas in galaxies from z = 0 to z = 0.2

    NARCIS (Netherlands)

    van Gorkom, Jacqueline

    2008-01-01

    Probing the evolution of galaxies through the neutral hydrogen window has until recently been limited to studies of environmentally driven evolution in the local universe. Detailed imaging studies of galaxies in Virgo and volume limited surveys of clusters out to z = 0.08 show that ram pressure

  5. Galaxy Zoo: A Catalog of Overlapping Galaxy Pairs for Dust Studies

    Science.gov (United States)

    Keel, William C.; Manning, Anna M.; Holwerda, Benne W.; Mezzoprete, Massimo; Lintott, Chris J.; Schawinski, Kevin; Gay, Pamela; Masters, Karen L.

    2013-01-01

    Analysis of galaxies with overlapping images offers a direct way to probe the distribution of dust extinction and its effects on the background light. We present a catalog of 1990 such galaxy pairs selected from the Sloan Digital Sky Survey (SDSS) by volunteers of the Galaxy Zoo project. We highlight subsamples which are particularly useful for retrieving such properties of the dust distribution as UV extinction, the extent perpendicular to the disk plane, and extinction in the inner parts of disks. The sample spans wide ranges of morphology and surface brightness, opening up the possibility of using this technique to address systematic changes in dust extinction or distribution with galaxy type. This sample will form the basis for forthcoming work on the ranges of dust distributions in local disk galaxies, both for their astrophysical implications and as the low-redshift part of a study of the evolution of dust properties. Separate lists and figures show deep overlaps, where the inner regions of the foreground galaxy are backlit, and the relatively small number of previously-known overlapping pairs outside the SDSS DR7 sky coverage.

  6. MASS AND ENVIRONMENT AS DRIVERS OF GALAXY EVOLUTION IN SDSS AND zCOSMOS AND THE ORIGIN OF THE SCHECHTER FUNCTION

    NARCIS (Netherlands)

    Peng, Ying-Jie; Lilly, Simon J.; Kovac, Katarina; Bolzonella, Micol; Pozzetti, Lucia; Renzini, Alvio; Zamorani, Gianni; Ilbert, Olivier; Knobel, Christian; Iovino, Angela; Maier, Christian; Cucciati, Olga; Tasca, Lidia; Carollo, C. Marcella; Silverman, John; Kampczyk, Pawel; De Ravel, Loic; Sanders, David; Scoville, Nicholas; Contini, Thierry; Mainieri, Vincenzo; Scodeggio, Marco; Kneib, Jean-Paul; Le Fevre, Olivier; Bardelli, Sandro; Bongiorno, Angela; Caputi, Karina; Coppa, Graziano; de la Torre, Sylvain; Franzetti, Paolo; Garilli, Bianca; Lamareille, Fabrice; Le Borgne, Jean-Francois; Le Brun, Vincent; Mignoli, Marco; Montero, Enrique Perez; Pello, Roser; Ricciardelli, Elena; Tanaka, Masayuki; Tresse, Laurence; Vergani, Daniela; Welikala, Niraj; Zucca, Elena; Oesch, Pascal; Abbas, Ummi; Barnes, Luke; Bordoloi, Rongmon; Bottini, Dario; Cappi, Alberto; Cassata, Paolo; Cimatti, Andrea; Fumana, Marco; Hasinger, Gunther; Koekemoer, Anton; Leauthaud, Alexei; Maccagni, Dario; Marinoni, Christian; McCracken, Henry; Memeo, Pierdomenico; Meneux, Baptiste; Nair, Preethi; Porciani, Cristiano; Presotto, Valentina; Scaramella, Roberto

    2010-01-01

    We explore the simple inter-relationships between mass, star formation rate, and environment in the SDSS, zCOSMOS, and other deep surveys. We take a purely empirical approach in identifying those features of galaxy evolution that are demanded by the data and then explore the analytic consequences of

  7. Galaxy Collisions Forging New Worlds from Cosmic Crashes

    CERN Document Server

    Struck, Curtis

    2011-01-01

    Galaxy collisions are the key process in building galaxies, triggering the formation of stars and the build-up of heavy elements that allow the formation of planets and solar systems. This book presents the revolutionary research advances achieved in the last decade and lucidly explains the underlying dynamical processes. Galaxy Collisions takes a comprehensive trip through the visually spectacular world of galaxy collisions; investigates the interactions of stars, gas clouds, and dark matter in galaxy collisions; uses analogies and metaphors to help comprehend the bizarre world of galaxies; presents recent research results to enhance the understanding of galaxy formation and evolution; includes discoveries of minor collisions within our own group of galaxies; shows how a galaxy collision might affect a solar system, or a planet like ours.

  8. The Physical Origin of Galaxy Morphologies and Scaling Laws

    Science.gov (United States)

    Steinmetz, Matthias; Navarro, Julio F.

    2002-01-01

    We propose a numerical study designed to interpret the origin and evolution of galaxy properties revealed by space- and ground-based imaging and spectroscopical surveys. Our aim is to unravel the physical processes responsible for the development of different galaxy morphologies and for the establishment of scaling laws such as the Tully-Fisher relation for spirals and the Fundamental Plane of ellipticals. In particular, we plan to address the following major topics: (1) The morphology and observability of protogalaxies, and in particular the relationship between primordial galaxies and the z approximately 3 'Ly-break' systems identified in the Hubble Deep Field and in ground-based searches; (2) The origin of the disk and spheroidal components in galaxies, the timing and mode of their assembly, the corresponding evolution in galaxy morphologies and its sensitivity to cosmological parameters; (3) The origin and redshift evolution of the scaling laws that link the mass, luminosity size, stellar content, and metal abundances of galaxies of different morphological types. This investigation will use state-of-the-art N-body/gasdynamical codes to provide a spatially resolved description of the galaxy formation process in hierarchically clustering universes. Coupled with population synthesis techniques. our models can be used to provide synthetic 'observations' that can be compared directly with observations of galaxies both nearby and at cosmologically significant distances. This study will thus provide insight into the nature of protogalaxies and into the formation process of galaxies like our own Milky Way. It will also help us to assess the cosmological significance of these observations within the context of hierarchical theories of galaxy formation and will supply a theoretical context within which current and future observations can be interpreted.

  9. Galaxy formation hydrodynamics: From cosmic flows to star-forming clouds

    International Nuclear Information System (INIS)

    Bournaud, F.

    2011-01-01

    Major progress has been made over the last few years in understanding hydrodynamical processes on cosmological scales, in particular how galaxies get their baryons. There is increasing recognition that a large part of the baryons accrete smoothly onto galaxies, and that internal evolution processes play a major role in shaping galaxies mergers are not necessarily the dominant process. However, predictions from the various assembly mechanisms are still in large disagreement with the observed properties of galaxies in the nearby Universe. Small-scale processes have a major impact on the global evolution of galaxies over a Hubble time and the usual sub-grid models account for them in a far too uncertain way. Understanding when, where and at which rate galaxies formed their stars becomes crucial to understand the formation of galaxy populations. I discuss recent improvements and current limitations in 'resolved' modeling of star formation, aiming at explicitly capturing star-foul-ling instabilities, in cosmological and galaxy-sized simulations. Such models need to develop three-dimensional turbulence in the ISM, which requires parsec-scale resolution at redshift zero. (authors)

  10. Galaxy bias from the Dark Energy Survey Science Verification data: combining galaxy density maps and weak lensing maps

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C.; Pujol, A.; Gaztañaga, E.; Amara, A.; Réfrégier, A.; Bacon, D.; Becker, M. R.; Bonnett, C.; Carretero, J.; Castander, F. J.; Crocce, M.; Fosalba, P.; Giannantonio, T.; Hartley, W.; Jarvis, M.; Kacprzak, T.; Ross, A. J.; Sheldon, E.; Troxel, M. A.; Vikram, V.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Rosell, A. Carnero; Kind, M. Carrasco; Cunha, C. E.; D' Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Estrada, J.; Evrard, A. E.; Flaugher, B.; Frieman, J.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; Jain, B.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; Marshall, J. L.; Martini, P.; Melchior, P.; Miller, C. J.; Miquel, R.; Mohr, J. J.; Nichol, R. C.; Nord, B.; Ogando, R.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Rykoff, E. S.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Walker, A. R.

    2016-04-15

    We measure the redshift evolution of galaxy bias from a magnitude-limited galaxy sample by combining the galaxy density maps and weak lensing shear maps for a $\\sim$116 deg$^{2}$ area of the Dark Energy Survey (DES) Science Verification data. This method was first developed in Amara et al. (2012) and later re-examined in a companion paper (Pujol et al., in prep) with rigorous simulation tests and analytical treatment of tomographic measurements. In this work we apply this method to the DES SV data and measure the galaxy bias for a magnitude-limited galaxy sample. We find the galaxy bias and 1$\\sigma$ error bars in 4 photometric redshift bins to be 1.33$\\pm$0.18 (z=0.2-0.4), 1.19$\\pm$0.23 (z=0.4-0.6), 0.99$\\pm$0.36 ( z=0.6-0.8), and 1.66$\\pm$0.56 (z=0.8-1.0). These measurements are consistent at the 1-2$\\sigma$ level with mea- surements on the same dataset using galaxy clustering and cross-correlation of galaxies with CMB lensing. In addition, our method provides the only $\\sigma_8$-independent constraint among the three. We forward-model the main observational effects using mock galaxy catalogs by including shape noise, photo-z errors and masking effects. We show that our bias measurement from the data is consistent with that expected from simulations. With the forthcoming full DES data set, we expect this method to provide additional constraints on the galaxy bias measurement from more traditional methods. Furthermore, in the process of our measurement, we build up a 3D mass map that allows further exploration of the dark matter distribution and its relation to galaxy evolution.

  11. Formation of hot intergalactic gas by gas ejection from a galaxy in an early explosive era

    International Nuclear Information System (INIS)

    Ikeuchi, Satoru

    1977-01-01

    Chemical evolution of a galaxy in an early explosive era is studied by means of one zone model. Calculating the thermal properties of interstellar gas and the overlapping factor of expanding supernova-remnant shells, the gas escape conditions from a galaxy are examined. From these, it is shown that the total mass of ejected gas from a galaxy amounts to 10 -- 40% of the initial mass of a galaxy. The ejected gas extends to the intergalactic space and the whole universe. The mass, the heavy-element abundance and other physical properties of thus formed intergalactic gas are investigated for various parameters of galactic evolution. Some other effects of gas release on the evolution of a galaxy and the evolution of the universe are discussed. (auth.)

  12. The Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS): survey design, data catalogue and GAMA/WiggleZ spectroscopy

    Science.gov (United States)

    Ching, John H. Y.; Sadler, Elaine M.; Croom, Scott M.; Johnston, Helen M.; Pracy, Michael B.; Couch, Warrick J.; Hopkins, A. M.; Jurek, Russell J.; Pimbblet, K. A.

    2017-01-01

    We present the Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS), a spectroscopic catalogue of radio sources designed to include the full range of radio AGN populations out to redshift z ˜ 0.8. The catalogue covers ˜800 deg2 of sky, and provides optical identifications for 19 179 radio sources from the 1.4 GHz Faint Images of the Radio Sky at Twenty-cm (FIRST) survey down to an optical magnitude limit of Imod point-like objects are included, and no colour cuts are applied. In collaboration with the WiggleZ and Galaxy And Mass Assembly (GAMA) spectroscopic survey teams, we have obtained new spectra for over 5000 objects in the LARGESS sample. Combining these new spectra with data from earlier surveys provides spectroscopic data for 12 329 radio sources in the survey area, of which 10 856 have reliable redshifts. 85 per cent of the LARGESS spectroscopic sample are radio AGN (median redshift z = 0.44), and 15 per cent are nearby star-forming galaxies (median z = 0.08). Low-excitation radio galaxies (LERGs) comprise the majority (83 per cent) of LARGESS radio AGN at z < 0.8, with 12 per cent being high-excitation radio galaxies (HERGs) and 5 per cent radio-loud QSOs. Unlike the more homogeneous LERG and QSO sub-populations, HERGs are a heterogeneous class of objects with relatively blue optical colours and a wide dispersion in mid-infrared colours. This is consistent with a picture in which most HERGs are hosted by galaxies with recent or ongoing star formation as well as a classical accretion disc.

  13. Effects of Galaxy collisions on the structure and evolution of Galaxy clusters. I. Mass and luminosity functions and background light

    International Nuclear Information System (INIS)

    Miller, G.E.; Department of Astronomy, University of Texas at Austin)

    1983-01-01

    The role of galaxy collisions in controlling the form of the galaxy mass and luminosity functions and in creating a diffuse background light is investigated by means of a direct computer simulation. Galaxy collisions are treated in a realistic manner, including both galaxy mergers and tidal encounters. A large number of theoretical studies of a galaxy collisions were consulted to formulate the basic input physics of collision cross sections. Despite this large number of studies, there remains considerable uncertainty in the effects of a collision on a galaxy due mainly to our lack of knowledge of the orbital distribution of matter in galaxies. To improve this situation, some methods of semiempirical calibration are suggested: for example, a survey of background light in clusters of different richness and morphological classes. If real galaxies are represented by galaxy models where the bulk of the matter is on radial, rather than circular, orbits, then tidal collisions are more damaging and there are a number of interesting effects: Repeated tidal encounters lead to galaxy mass and luminosity functions which are largely independent of model parameters and the initial galaxy mass function. It appears unlikely that the form of the average present-day luminosity function characteristic of both field and cluster galaxies is due to collisions, but certain observed deviations from the average found by Heiligman and Turner and by Dressler may be a signature of collisions, in particular a flat faint-end slope. The amount of luminous matter stripped from the galaxies in the simulations agrees with the amount of diffuse background light seen in the Coma Cluster

  14. The Redshift Evolution of Rest-UV Spectroscopic Properties in Lyman-break Galaxies at z ∼ 2–4

    Science.gov (United States)

    Du, Xinnan; Shapley, Alice E.; Reddy, Naveen A.; Jones, Tucker; Stark, Daniel P.; Steidel, Charles C.; Strom, Allison L.; Rudie, Gwen C.; Erb, Dawn K.; Ellis, Richard S.; Pettini, Max

    2018-06-01

    We present the first comprehensive evolutionary analysis of the rest-frame UV spectroscopic properties of star-forming galaxies at z ∼ 2–4. We match samples at different redshifts in UV luminosity and stellar mass, and perform systematic measurements of spectral features and stellar population modeling. By creating composite spectra grouped according to Lyα equivalent width (EW) and various galaxy properties, we study the evolutionary trends among Lyα, low- and high-ionization interstellar (LIS and HIS) absorption features, and integrated galaxy properties. We also examine the redshift evolution of Lyα and LIS absorption kinematics, and fine-structure emission EWs. The connections among the strengths of Lyα, LIS lines, and dust extinction are redshift independent, as is the decoupling of the Lyα and HIS line strengths, and the bulk outflow kinematics as traced by the LIS lines. Stronger Lyα emission is observed at higher redshift at fixed UV luminosity, stellar mass, SFR, and age. Much of this variation in the average Lyα strength with redshift, and the variation in Lyα strength at fixed redshift, can be explained in terms of variations in the neutral gas covering fraction and/or dust content in the ISM and CGM. However, based on the connection between Lyα and C III] emission strengths, we additionally find evidence for variations in the intrinsic production rate of Lyα photons at the highest Lyα EWs. The challenge now is to understand the observed evolution of the neutral gas covering fraction and dust extinction within a coherent model for galaxy formation, and make robust predictions for the escape of ionizing radiation at z > 6.

  15. Properties of galaxies reproduced by a hydrodynamic simulation

    Science.gov (United States)

    Vogelsberger, M.; Genel, S.; Springel, V.; Torrey, P.; Sijacki, D.; Xu, D.; Snyder, G.; Bird, S.; Nelson, D.; Hernquist, L.

    2014-05-01

    Previous simulations of the growth of cosmic structures have broadly reproduced the `cosmic web' of galaxies that we see in the Universe, but failed to create a mixed population of elliptical and spiral galaxies, because of numerical inaccuracies and incomplete physical models. Moreover, they were unable to track the small-scale evolution of gas and stars to the present epoch within a representative portion of the Universe. Here we report a simulation that starts 12 million years after the Big Bang, and traces 13 billion years of cosmic evolution with 12 billion resolution elements in a cube of 106.5 megaparsecs a side. It yields a reasonable population of ellipticals and spirals, reproduces the observed distribution of galaxies in clusters and characteristics of hydrogen on large scales, and at the same time matches the `metal' and hydrogen content of galaxies on small scales.

  16. Seeing Baby Dwarf Galaxies

    Science.gov (United States)

    2009-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Visible/DSS Click on image for larger version Ultraviolet/GALEX Click on image for larger version Poster Version Click on image for larger version The unique ultraviolet vision of NASA's Galaxy Evolution Explorer reveals, for the first time, dwarf galaxies forming out of nothing more than pristine gas likely leftover from the early universe. Dwarf galaxies are relatively small collections of stars that often orbit around larger galaxies like our Milky Way. The forming dwarf galaxies shine in the far ultraviolet spectrum, rendered as blue in the call-out on the right hand side of this image. Near ultraviolet light, also obtained by the Galaxy Evolution Explorer, is displayed in green, and visible light from the blue part of the spectrum here is represented by red. The clumps (in circles) are distinctively blue, indicating they are primarily detected in far ultraviolet light. The faint blue overlay traces the outline of the Leo Ring, a huge cloud of hydrogen and helium that orbits around two massive galaxies in the constellation Leo (left panel). The cloud is thought likely to be a primordial object, an ancient remnant of material that has remained relatively unchanged since the very earliest days of the universe. Identified about 25 years ago by radio waves, the ring cannot be seen in visible light. Only a portion of the Leo Ring has been imaged in the ultraviolet, but this section contains the telltale ultraviolet signature of recent massive star formation within this ring of pristine gas. Astronomers have previously only seen dwarf galaxies form out of gas that has already been cycled through a galaxy and enriched with metals elements heavier than helium produced as stars evolve. The visible data come from the Digitized Sky Survey of the Space Telescope Science Institute in Baltimore, Md. The Leo Ring visible image (left

  17. The formation of galaxies from pregalactic stars

    International Nuclear Information System (INIS)

    Jones, Janet

    1982-01-01

    A knowledge of how and when the first stars formed is vital for our understanding of the formation and early evolution of galaxies. Evidence is given that the first stars were pregalactic: indeed, that at least two generations of stars had formed before galaxies collapsed. A model is presented describing the effects of pregalactic stars on galaxy evolution. The first generation -primordial stars- were massive and few in number. A brief description is given for the formation of such a star. The second generation included stars of all masses and involved widespread star formation. Gas ejected from these stars on timescales of 6 x 10 7 to 6 x 10 8 years induced a qualitative change into the dynamics of collapsing perturbations, leading to a characteristic mass of galaxies of 10 10 - 10 12 M 0 . Variations in the rate of gas ejection were responsible for different morphological structures - elliptical and spirals. A few comments are made on some other implications of the model

  18. Paired and interacting galaxies: Conference summary

    International Nuclear Information System (INIS)

    Norman, C.A.

    1990-01-01

    The author gives a summary of the conference proceedings. The conference began with the presentation of the basic data sets on pairs, groups, and interacting galaxies with the latter being further discussed with respect to both global properties and properties of the galactic nuclei. Then followed the theory, modelling and interpretation using analytic techniques, simulations and general modelling for spirals and ellipticals, starbursts and active galactic nuclei. Before the conference the author wrote down the three questions concerning pairs, groups and interacting galaxies that he hoped would be answered at the meeting: (1) How do they form, including the role of initial conditions, the importance of subclustering, the evolution of groups to compact groups, and the fate of compact groups; (2) How do they evolve, including issues such as relevant timescales, the role of halos and the problem of overmerging, the triggering and enhancement of star formation and activity in the galactic nuclei, and the relative importance of dwarf versus giant encounters; and (3) Are they important, including the frequency of pairs and interactions, whether merging and interactions are very important aspects of the life of a normal galaxy at formation, during its evolution, in forming bars, shells, rings, bulges, etc., and in the formation and evolution of active galaxies? Where possible he focuses on these three central issues in the summary

  19. Probing galaxy growth through metallicity scaling relations over the past 12 Gyr of cosmic history

    Science.gov (United States)

    Sanders, Ryan; MOSDEF team

    2018-01-01

    A primary goal of galaxy evolution studies is to understand the processes governing the growth of the baryonic content of galaxies over cosmic history. Observations of galaxy metallicity scaling relations and their evolution with redshift, in combination with chemical evolution models, provide unique insight into the interplay between star formation, gas accretion, and feedback/outflows. I present measurements of the stellar mass-gas phase metallicity relation and its evolution over the past 12 Gyr from z~0 to z~3.5, utilizing data from the Mosfire Deep Evolution Field survey that uniquely provides rest-frame optical spectra of >1000 uniformly-selected galaxies at z=1.3-3.8. We find evolution towards lower metallicity at fixed stellar mass with increasing redshift that is consistent with current cosmological simulations including chemical evolution, with a large evolution of ~0.3 dex from z~0 to z~2.5 and minor evolution of 2, and discuss the potential of current and next-generation observational facilities to obtain statistical auroral-line samples at high redshifts.

  20. EVIDENCE FOR MORPHOLOGY AND LUMINOSITY TRANSFORMATION OF GALAXIES AT HIGH REDSHIFTS

    International Nuclear Information System (INIS)

    Hwang, Ho Seong; Park, Changbom

    2009-01-01

    We study the galaxy morphology-luminosity-environmental relation and its redshift evolution using a spectroscopic sample of galaxies in the Great Observatories Origins Deep Survey. In the redshift range of 0.4 ≤ z ≤ 1.0, we detect conformity in morphology between neighboring galaxies. The realm of conformity is confined within the virialized region associated with each galaxy plus dark matter halo system. When a galaxy is located within the virial radius of its nearest neighbor galaxy, its morphology strongly depends on the neighbor's distance and morphology: the probability for a galaxy to be an early type (f E ) increases as it approaches an early-type neighbor, but decreases as it approaches a late-type neighbor. We find that f E evolves much faster in high-density regions than in low-density regions, and that the morphology-density relation becomes significantly weaker at z ∼ 1. This may be because the rate of galaxy-galaxy interactions is higher in high-density regions, and a series of interactions and mergers over the course of galaxy life eventually transform late types into early types. We find more isolated galaxies are more luminous, which supports luminosity transformation through mergers at these redshifts. Our results are consistent with those from nearby galaxies, and demonstrate that galaxy-galaxy interactions have been strongly affecting the galaxy evolution over a long period of time.

  1. Galaxy Evolution in the Radio Band: The Role of Star-forming Galaxies and Active Galactic Nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Mancuso, C.; Prandoni, I. [INAF-IRA, Via P. Gobetti 101, I-40129 Bologna (Italy); Lapi, A.; Obi, I.; Perrotta, F.; Bressan, A.; Celotti, A.; Danese, L. [SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Gonzalez-Nuevo, J. [Departamento de Fisica, Universidad de Oviedo, C. Calvo Sotelo s/n, E-33007 Oviedo (Spain)

    2017-06-20

    We investigate the astrophysics of radio-emitting star-forming galaxies and active galactic nuclei (AGNs) and elucidate their statistical properties in the radio band, including luminosity functions, redshift distributions, and number counts at sub-mJy flux levels, which will be crucially probed by next-generation radio continuum surveys. Specifically, we exploit the model-independent approach by Mancuso et al. to compute the star formation rate functions, the AGN duty cycles, and the conditional probability of a star-forming galaxy to host an AGN with given bolometric luminosity. Coupling these ingredients with the radio emission properties associated with star formation and nuclear activity, we compute relevant statistics at different radio frequencies and disentangle the relative contribution of star-forming galaxies and AGNs in different radio luminosity, radio flux, and redshift ranges. Finally, we highlight that radio-emitting star-forming galaxies and AGNs are expected to host supermassive black holes accreting with different Eddington ratio distributions and to occupy different loci in the galaxy main-sequence diagrams. These specific predictions are consistent with current data sets but need to be tested with larger statistics via future radio data with multiband coverage on wide areas, as will become routinely achievable with the advent of the Square Kilometre Array and its precursors.

  2. On the Nature and History of Blue Amorphous Galaxies

    Science.gov (United States)

    Marlowe, Amanda True

    1998-07-01

    Dwarf galaxies play an important role in our understanding of galaxy formation and evolution. We have embarked on a systematic study of 12 blue amorphous galaxies (BAGs) whose properties suggest that they are dwarf galaxies in a starburst or post-burst state. It seems likely that BAGs are related to other 'starburst' dwarfs such as blue compact dwarfs (BCDs) and HII galaxies. The BAGs in our sample, however, are considerably closer than BCDs and HII galaxies in other samples, and therefore easier to study. These galaxies may offer important insights into dwarf galaxy evolution. In an effort to clarify the role of BAGs in evolutionary scenarios for dwarf galaxies, we present and analyze Hα and UBVI data for our sample. BAGs, like BCDs and HII galaxies, have surface brightness profiles that are exponential in the outer regions but have a predominantly blue central blue excess, suggesting a young burst in an older, redder galaxy. Seven of the galaxies have the bubble or filamentary Hα morphology and double peaked emission lines that are the signature of superbubbles or superwind activity. These galaxies are typically the ones with the strongest central excesses. The starbursting regions are young events compared to the older underlying galaxy, which follow an exponential surface brightness law. Not all of the galaxies develop superwinds: the appearance of superwinds is most sensitive to the concentration and rate of star formation in the starbursting core. The underlying exponential galaxies are very similar to those found in BCDs and HII galaxies, though the 'burst' colors are slightly redder than those found in HII galaxies. BAGs are structurally similar to BCDs and HII galaxies. How BAGs fit into the dwarf galaxy evolutionary debate is less clear. While some compact dIs have properties similar to those of the underlying exponential galaxy in our sample, issues such as mass loss from superwinds, the impact of the starbursting core on the underlying galaxy, and

  3. The Post-starburst Evolution of Tidal Disruption Event Host Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    French, K. Decker; Zabludoff, Ann [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Arcavi, Iair [Department of Physics, University of California, Santa Barbara, CA 93106-9530 (United States)

    2017-02-01

    We constrain the recent star formation histories of the host galaxies of eight optical/UV-detected tidal disruption events (TDEs). Six hosts had quick starbursts of <200 Myr duration that ended 10–1000 Myr ago, indicating that TDEs arise at different times in their hosts’ post-starburst evolution. If the disrupted star formed in the burst or before, the post-burst age constrains its mass, generally excluding O, most B, and highly massive A stars. If the starburst arose from a galaxy merger, the time since the starburst began limits the coalescence timescale and thus the merger mass ratio to more equal than 12:1 in most hosts. This uncommon ratio, if also that of the central supermassive black hole (SMBH) binary, disfavors the scenario in which the TDE rate is boosted by the binary but is insensitive to its mass ratio. The stellar mass fraction created in the burst is 0.5%–10% for most hosts, not enough to explain the observed 30–200× boost in TDE rates, suggesting that the host’s core stellar concentration is more important. TDE hosts have stellar masses 10{sup 9.4}–10{sup 10.3} M {sub ☉}, consistent with the Sloan Digital Sky Survey volume-corrected, quiescent Balmer-strong comparison sample and implying SMBH masses of 10{sup 5.5}–10{sup 7.5} M {sub ☉}. Subtracting the host absorption line spectrum, we uncover emission lines; at least five hosts have ionization sources inconsistent with star formation that instead may be related to circumnuclear gas, merger shocks, or post-AGB stars.

  4. STAR FORMATION IN DISK GALAXIES. I. FORMATION AND EVOLUTION OF GIANT MOLECULAR CLOUDS VIA GRAVITATIONAL INSTABILITY AND CLOUD COLLISIONS

    International Nuclear Information System (INIS)

    Tasker, Elizabeth J.; Tan, Jonathan C.

    2009-01-01

    We investigate the formation and evolution of giant molecular clouds (GMCs) in a Milky-Way-like disk galaxy with a flat rotation curve. We perform a series of three-dimensional adaptive mesh refinement numerical simulations that follow both the global evolution on scales of ∼20 kpc and resolve down to scales ∼ H ≥ 100 cm -3 and track the evolution of individual clouds as they orbit through the galaxy from their birth to their eventual destruction via merger or via destructive collision with another cloud. After ∼140 Myr a large fraction of the gas in the disk has fragmented into clouds with masses ∼10 6 M sun and a mass spectrum similar to that of Galactic GMCs. The disk settles into a quasi-steady-state in which gravitational scattering of clouds keeps the disk near the threshold of global gravitational instability. The cloud collision time is found to be a small fraction, ∼1/5, of the orbital time, and this is an efficient mechanism to inject turbulence into the clouds. This helps to keep clouds only moderately gravitationally bound, with virial parameters of order unity. Many other observed GMC properties, such as mass surface density, angular momentum, velocity dispersion, and vertical distribution, can be accounted for in this simple model with no stellar feedback.

  5. Chemical evolution of the galactic disk

    International Nuclear Information System (INIS)

    Wyse, R.F.G.; Gilmore, G.

    1987-01-01

    The distribution of enriched material in the stars and gas of their Galaxy contains information pertaining to the chemical evolution of the Milky Way from its formation epoch to the present day, and provides general constraints on theories of galaxy formation. The separate stellar components of the Galaxy cannot readily be understood if treated in isolation, but a reasonably self-consistent model for Galactic chemical evolution may be found if one considers together the chemical properties of the extreme spheroid, thick disk and thin disk populations of the Galaxy. The three major stellar components of the Galaxy are characterized by their distinct spatial distributions, metallicity structure, and kinematics, with the newly-identified thick disk being approximately three times more massive than the classical metal-poor, non-rotating extreme spheroid. Stellar evolution in the thick disk straightforwardly provides the desired pre-enrichment for resolution of the thin disk G dwarf problem

  6. Automatic Approach to Morphological Classification of Galaxies With Analysis of Galaxy Populations in Clusters

    Science.gov (United States)

    Sultanova, Madina; Barkhouse, Wayne; Rude, Cody

    2018-01-01

    The classification of galaxies based on their morphology is a field in astrophysics that aims to understand galaxy formation and evolution based on their physical differences. Whether structural differences are due to internal factors or a result of local environment, the dominate mechanism that determines galaxy type needs to be robustly quantified in order to have a thorough grasp of the origin of the different types of galaxies. The main subject of my Ph.D. dissertation is to explore the use of computers to automatically classify and analyze large numbers of galaxies according to their morphology, and to analyze sub-samples of galaxies selected by type to understand galaxy formation in various environments. I have developed a computer code to classify galaxies by measuring five parameters from their images in FITS format. The code was trained and tested using visually classified SDSS galaxies from Galaxy Zoo and the EFIGI data set. I apply my morphology software to numerous galaxies from diverse data sets. Among the data analyzed are the 15 Abell galaxy clusters (0.03 Frontier Field galaxy clusters. The high resolution of HST allows me to compare distant clusters with those nearby to look for evolutionary changes in the galaxy cluster population. I use the results from the software to examine the properties (e.g. luminosity functions, radial dependencies, star formation rates) of selected galaxies. Due to the large amount of data that will be available from wide-area surveys in the future, the use of computer software to classify and analyze the morphology of galaxies will be extremely important in terms of efficiency. This research aims to contribute to the solution of this problem.

  7. GALAXY FORMATION WITH COLD GAS ACCRETION AND EVOLVING STELLAR INITIAL MASS FUNCTION

    International Nuclear Information System (INIS)

    Kang Xi; Lin, W. P.; Skibba, Ramin; Chen, D. N.

    2010-01-01

    The evolution of the galaxy stellar mass function is especially useful to test the current model of galaxy formation. Observational data have revealed a few inconsistencies with predictions from the ΛCDM model. For example, most massive galaxies have already been observed at very high redshifts, and they have experienced only mild evolution since then. In conflict with this, semi-analytical models (SAMs) of galaxy formation predict an insufficient number of massive galaxies at high redshift and a rapid evolution between redshift 1 and 0. In addition, there is a strong correlation between star formation rate (SFR) and stellar mass for star-forming galaxies, which can be roughly reproduced with the model, but with a normalization that is too low at high redshift. Furthermore, the stellar mass density obtained from the integral of the cosmic star formation history is higher than the measured one by a factor of 2. In this paper, we study these issues using an SAM that includes (1) cold gas accretion in massive halos at high redshift; (2) tidal stripping of stellar mass from satellite galaxies; and (3) an evolving stellar initial mass function (IMF; bottom-light) with a higher gas recycle fraction. Our results show that the combined effects from (1) and (2) can predict sufficiently massive galaxies at high redshifts and reproduce their mild evolution at low redshift, while the combined effects of (1) and (3) can reproduce the correlation between SFR and stellar mass for star-forming galaxies across a wide range of redshifts. A bottom-light/top-heavy stellar IMF could partly resolve the conflict between the stellar mass density and cosmic star formation history.

  8. Interstellar matter within elliptical galaxies

    Science.gov (United States)

    Jura, Michael

    1988-01-01

    Multiwavelength observations of elliptical galaxies are reviewed, with an emphasis on their implications for theoretical models proposed to explain the origin and evolution of the interstellar matter. Particular attention is given to interstellar matter at T less than 100 K (atomic and molecular gas and dust), gas at T = about 10,000 K, and gas at T = 10 to the 6th K or greater. The data are shown to confirm the occurrence of mass loss from evolved stars, significant accretion from companion galaxies, and cooling inflows; no evidence is found for large mass outflow from elliptical galaxies.

  9. Interpretation of galaxy counts

    International Nuclear Information System (INIS)

    Tinsely, B.M.

    1980-01-01

    New models are presented for the interpretation of recent counts of galaxies to 24th magnitude, and predictions are shown to 28th magnitude for future comparison with data from the Space Telescope. The results supersede earlier, more schematic models by the author. Tyson and Jarvis found in their counts a ''local'' density enhancement at 17th magnitude, on comparison with the earlier models; the excess is no longer significant when a more realistic mixture of galaxy colors is used. Bruzual and Kron's conclusion that Kron's counts show evidence for evolution at faint magnitudes is confirmed, and it is predicted that some 23d magnitude galaxies have redshifts greater than unity. These may include spheroidal systems, elliptical galaxies, and the bulges of early-type spirals and S0's, seen during their primeval rapid star formation

  10. Hierarchical structure in the distribution of galaxies

    International Nuclear Information System (INIS)

    Schulman, L.S.; Seiden, P.E.; Technion - Israel Institute of Technology, Haifa; IBM Thomas J. Watson Research Center, Yorktown Heights, NY)

    1986-01-01

    The distribution of galaxies has a hierarchical structure with power-law correlations. This is usually thought to arise from gravity alone acting on an originally uniform distributioon. If, however, the original process of galaxy formation occurs through the stimulated birth of one galaxy due to a nearby recently formed galaxy, and if this process occurs near its percolation threshold, then a hierarchical structure with power-law correlations arises at the time of galaxy formation. If subsequent gravitational evolution within an expanding cosmology is such as to retain power-law correlations, the initial r exp -1 dropoff can steepen to the observed r exp -1.8. The distribution of galaxies obtained by this process produces clustering and voids, as observed. 23 references

  11. INTRINSIC ALIGNMENT OF CLUSTER GALAXIES: THE REDSHIFT EVOLUTION

    International Nuclear Information System (INIS)

    Hao Jiangang; Kubo, Jeffrey M.; Feldmann, Robert; Annis, James; Johnston, David E.; Lin Huan; McKay, Timothy A.

    2011-01-01

    We present measurements of two types of cluster galaxy alignments based on a volume limited and highly pure (≥90%) sample of clusters from the GMBCG catalog derived from Data Release 7 of the Sloan Digital Sky Survey (SDSS DR7). We detect a clear brightest cluster galaxy (BCG) alignment (the alignment of major axis of the BCG toward the distribution of cluster satellite galaxies). We find that the BCG alignment signal becomes stronger as the redshift and BCG absolute magnitude decrease and becomes weaker as BCG stellar mass decreases. No dependence of the BCG alignment on cluster richness is found. We can detect a statistically significant (≥3σ) satellite alignment (the alignment of the major axes of the cluster satellite galaxies toward the BCG) only when we use the isophotal fit position angles (P.A.s), and the satellite alignment depends on the apparent magnitudes rather than the absolute magnitudes of the BCGs. This suggests that the detected satellite alignment based on isophotal P.A.s from the SDSS pipeline is possibly due to the contamination from the diffuse light of nearby BCGs. We caution that this should not be simply interpreted as non-existence of the satellite alignment, but rather that we cannot detect them with our current photometric SDSS data. We perform our measurements on both SDSS r-band and i-band data, but do not observe a passband dependence of the alignments.

  12. WITNESSING THE KEY EARLY PHASE OF QUASAR EVOLUTION: AN OBSCURED ACTIVE GALACTIC NUCLEUS PAIR IN THE INTERACTING GALAXY IRAS 20210+1121

    International Nuclear Information System (INIS)

    Piconcelli, Enrico; Fiore, Fabrizio; Maiolino, Roberto; Nicastro, Fabrizio; Vignali, Cristian; Bianchi, Stefano; Mathur, Smita; Guainazzi, Matteo; Lanzuisi, Giorgio

    2010-01-01

    We report the discovery of an active galactic nucleus (AGN) pair in the interacting galaxy system IRAS 20210+1121 at z = 0.056. An XMM-Newton observation reveals the presence of an obscured (N H ∼ 5 x 10 23 cm -2 ), Seyfert-like (L 2-10keV = 4.7 x 10 42 erg s -1 ) nucleus in the northern galaxy, which lacks unambiguous optical AGN signatures. Our spectral analysis also provides strong evidence that the IR-luminous southern galaxy hosts a Type 2 quasar embedded in a bright starburst emission. In particular, the X-ray primary continuum from the nucleus appears totally depressed in the XMM-Newton band as expected in the case of a Compton-thick absorber, and only the emission produced by Compton scattering ('reflection') of the continuum from circumnuclear matter is seen. As such, IRAS 20210+1121 seems to provide an excellent opportunity to witness a key, early phase in the quasar evolution predicted by the theoretical models of quasar activation by galaxy collisions.

  13. THE KMOS3D SURVEY: DESIGN, FIRST RESULTS, AND THE EVOLUTION OF GALAXY KINEMATICS FROM 0.7 ≤ z ≤ 2.7

    International Nuclear Information System (INIS)

    Wisnioski, E.; Förster Schreiber, N. M.; Wuyts, S.; Wuyts, E.; Bandara, K.; Genzel, R.; Bender, R.; Davies, R.; Lang, P.; Mendel, J. T.; Beifiori, A.; Chan, J.; Fabricius, M.; Fudamoto, Y.; Kulkarni, S.; Kurk, J.; Lutz, D.; Wilman, D.; Fossati, M.; Brammer, G.

    2015-01-01

    We present the KMOS 3D survey, a new integral field survey of over 600 galaxies at 0.7 < z < 2.7 using KMOS at the Very Large Telescope. The KMOS 3D survey utilizes synergies with multi-wavelength ground- and space-based surveys to trace the evolution of spatially resolved kinematics and star formation from a homogeneous sample over 5 Gyr of cosmic history. Targets, drawn from a mass-selected parent sample from the 3D-HST survey, cover the star formation-stellar mass (M * ) and rest-frame (U – V) – M * planes uniformly. We describe the selection of targets, the observations, and the data reduction. In the first-year of data we detect Hα emission in 191 M * = 3 × 10 9 -7 × 10 11 M ☉  galaxies at z = 0.7-1.1 and z = 1.9-2.7. In the current sample 83% of the resolved galaxies are rotation dominated, determined from a continuous velocity gradient and v rot /σ 0 > 1, implying that the star-forming ''main sequence'' is primarily composed of rotating galaxies at both redshift regimes. When considering additional stricter criteria, the Hα kinematic maps indicate that at least ∼70% of the resolved galaxies are disk-like systems. Our high-quality KMOS data confirm the elevated velocity dispersions reported in previous integral field spectroscopy studies at z ≳ 0.7. For rotation-dominated disks, the average intrinsic velocity dispersion decreases by a factor of two from 50 km s –1 at z ∼ 2.3 to 25 km s –1 at z ∼ 0.9. Combined with existing results spanning z ∼ 0-3, we show that disk velocity dispersions follow an evolution that is consistent with the dependence of velocity dispersion on gas fractions predicted by marginally stable disk theory

  14. MaNGA: Mapping Nearby Galaxies at Apache Point Observatory

    Science.gov (United States)

    Weijmans, A.-M.; MaNGA Team

    2016-10-01

    MaNGA (Mapping Nearby Galaxies at APO) is a galaxy integral-field spectroscopic survey within the fourth generation Sloan Digital Sky Survey (SDSS-IV). It will be mapping the composition and kinematics of gas and stars in 10,000 nearby galaxies, using 17 differently sized fiber bundles. MaNGA's goal is to provide new insights in galaxy formation and evolution, and to deliver a local benchmark for current and future high-redshift studies.

  15. Recent star formation in interacting galaxies

    International Nuclear Information System (INIS)

    Joseph, R.D.; Wright, G.S.

    1985-01-01

    The subset of galaxy-galaxy interactions which have resulted in a merger are, as a class, ultraluminous IR galaxies. Their IR luminosities span a narrow range which overlaps with the most luminous Seyfert galaxies. However, in contrast with Seyfert galaxies, the available optical, IR, and radio properties of mergers show no evidence for a compact non-thermal central source, and are easily understood in terms of a burst of star formation of extraordinary intensity and spatial extent; they are 'super starbursts'. We argue that super starbursts occur in the evolution of most mergers, and discuss the implications of super starbursts for the suggestion that mergers evolve into elliptical galaxies. Finally, we note that merger-induced shocks are likely to leave the gas from both galaxies in dense molecular form which will rapidly cool, collapse, and fragment. Thus a merger might in fact be expected to result in a burst of star formation of exceptional intensity and spatial extent, i.e. a super starburst. (author)

  16. Measuring Extinction in Local Group Galaxies Using Background Galaxies

    Science.gov (United States)

    Wyder, T. K.; Hodge, P. W.

    1999-05-01

    Knowledge of the distribution and quantity of dust in galaxies is important for understanding their structure and evolution. The goal of our research is to measure the total extinction through Local Group galaxies using measured properties of background galaxies. Our method relies on the SExtractor software as an objective and automated method of detecting background galaxies. In an initial test, we have explored two WFPC2 fields in the SMC and two in M31 obtained from the HST archives. The two pointings in the SMC are fields around the open clusters L31 and B83 while the two M31 fields target the globular clusters G1 and G170. Except for the G1 observations of M31, the fields chosen are very crowded (even when observed with HST) and we chose them as a particularly stringent test of the method. We performed several experiments using a series of completeness tests that involved superimposing comparison fields, adjusted to the equivalent exposure time, from the HST Medium-Deep and Groth-Westphal surveys. These tests showed that for crowded fields, such as the two in the core of the SMC and the one in the bulge of M31, this automated method of detecting galaxies can be completely dominated by the effects of crowding. For these fields, only a small fraction of the added galaxies was recovered. However, in the outlying G1 field in M31, almost all of the added galaxies were recovered. The numbers of actual background galaxies in this field are consistent with zero extinction. As a follow-up experiment, we used image processing techniques to suppress stellar objects while enhancing objects with non-stellar, more gradual luminosity profiles. This method yielded significant numbers of background galaxies in even the most crowded fields, which we are now analyzing to determine the total extinction and reddening caused by the foreground galaxy.

  17. The physical properties and evolution of Lyα emitting galaxies

    Science.gov (United States)

    Pentericci, L.; Grazian, A.; Fontana, A.

    2009-05-01

    A significant fraction of high redshift starburst galaxies presents strong Lyα emission. Understanding the nature of these galaxies is important to assess the role they played in the early Universe and to shed light on the relation between the narrow band selected Lyα emitters and the Lyman break galaxies: are the Lyα emitters a subset of the general LBG population? or do they represent the youngest galaxies in their early phases of formation? We studied a sample of UV continuum selected galaxies from z~2.5 to z~6 (U, B, V and i-dropouts) from the GOODS-South survey, that have been observed spectroscopically. Using the GOODS-MUSIC catalog we investigated their physical properties, such as total masses, ages, SFRs, extinction etc as determined from a spectrophotometric fit to the multi-wavelength (U band to mid-IR) SEDs, and their dependence on the emission line characteristics. In particular we determined the nature of the LBGs with Lyα in emission and compared them to the properties of narrow band selected Lyα emitters. For U and B-dropouts we also compared the properties of LBGs with and without the Lyα emission line.

  18. Star Formation Histories of Dwarf Irregular Galaxies

    Science.gov (United States)

    Skillman, Evan

    1995-07-01

    We propose to obtain deep WFPC2 `BVI' color-magnitude diagrams {CMDs} for the dwarf irregular {dI} Local Group galaxies GR 8, Leo A, Pegasus, and Sextans A. In addition to resolved stars, we will use star clusters, and especially any globulars, to probe the history of intense star formation. These data will allow us to map the Pop I and Pop II stellar components, and thereby construct the first detailed star formation histories for non-interacting dI galaxies. Our results will bear on a variety of astrophysical problems, including the evolution of small galaxies, distances in the Local Group, age-metallicity distributions in small galaxies, ages of dIs, and the physics of star formation. The four target galaxies are typical dI systems in terms of luminosity, gas content, and H II region abundance, and represent a range in current star forming activity. They are sufficiently near to allow us to reach to stars at M_V = 0, have 0.1 of the luminosity of the SMC and 0.25 of its oxygen abundance. Unlike the SMC, these dIs are not near giant galaxies. This project will allow the extension of our knowledge of stellar populations in star forming galaxies from the spirals in the Local Group down to its smallest members. We plan to take maximum advantage of the unique data which this project will provide. Our investigator team brings extensive and varied experience in studies of dwarf galaxies, stellar populations, imaging photometry, and stellar evolution to this project.

  19. Morphological type correlation between nearest neighbor pairs of galaxies

    Science.gov (United States)

    Yamagata, Tomohiko

    1990-01-01

    Although the morphological type of galaxies is one of the most fundamental properties of galaxies, its origin and evolutionary processes, if any, are not yet fully understood. It has been established that the galaxy morphology strongly depends on the environment in which the galaxy resides (e.g., Dressler 1980). Galaxy pairs correspond to the smallest scales of galaxy clustering and may provide important clues to how the environment influences the formation and evolution of galaxies. Several investigators pointed out that there is a tendency for pair galaxies to have similar morphological types (Karachentsev and Karachentseva 1974, Page 1975, Noerdlinger 1979). Here, researchers analyze morphological type correlation for 18,364 nearest neighbor pairs of galaxies identified in the magnetic tape version of the Center for Astrophysics Redshift Catalogue.

  20. Star-formation complexes in the `galaxy-sized' supergiant shell of the galaxy Holmberg I

    Science.gov (United States)

    Egorov, Oleg V.; Lozinskaya, Tatiana A.; Moiseev, Alexei V.; Smirnov-Pinchukov, Grigory V.

    2018-05-01

    We present the results of observations of the galaxy Holmberg I carried out at the Russian 6-m telescope in the narrow-band imaging, long-slit spectroscopy, and scanning Fabry-Perot interferometer modes. A detailed analysis of gas kinematics, ionization conditions, and metallicity of star-forming regions in the galaxy is presented. The aim of the paper is to analyse the propagation of star formation in the galaxy and to understand the role of the ongoing star formation in the evolution of the central `galaxy-sized' supergiant H I shell (SGS), where all regions of star formation are observed. We show that star formation in the galaxy occurs in large unified complexes rather than in individual giant H II regions. Evidence of the triggered star formation is observed both on scales of individual complexes and of the whole galaxy. We identified two supernova-remnant candidates and one late-type WN star and analysed their spectrum and surrounding-gas kinematics. We provide arguments indicating that the SGS in Holmberg I is destructing by the influence of star formation occurring on its rims.

  1. Mining MaNGA for Merging Galaxies: A New Imaging and Kinematic Technique from Hydrodynamical Simulations

    Science.gov (United States)

    Nevin, Becky; Comerford, Julia M.; Blecha, Laura

    2018-06-01

    Merging galaxies play a key role in galaxy evolution, and progress in our understanding of galaxy evolution is slowed by the difficulty of making accurate galaxy merger identifications. Mergers are typically identified using imaging alone, which has its limitations and biases. With the growing popularity of integral field spectroscopy (IFS), it is now possible to use kinematic signatures to improve galaxy merger identifications. I use GADGET-3 hydrodynamical simulations of merging galaxies with the radiative transfer code SUNRISE, the later of which enables me to apply the same analysis to simulations and observations. From the simulated galaxies, I have developed the first merging galaxy classification scheme that is based on kinematics and imaging. Utilizing a Linear Discriminant Analysis tool, I have determined which kinematic and imaging predictors are most useful for identifying mergers of various merger parameters (such as orientation, mass ratio, gas fraction, and merger stage). I will discuss the strengths and limitations of the classification technique and then my initial results for applying the classification to the >10,000 observed galaxies in the MaNGA (Mapping Nearby Galaxies at Apache Point) IFS survey. Through accurate identification of merging galaxies in the MaNGA survey, I will advance our understanding of supermassive black hole growth in galaxy mergers and other open questions related to galaxy evolution.

  2. GALAXY ROTATION AND RAPID SUPERMASSIVE BINARY COALESCENCE

    Energy Technology Data Exchange (ETDEWEB)

    Holley-Bockelmann, Kelly [Vanderbilt University, Nashville, TN (United States); Khan, Fazeel Mahmood, E-mail: k.holley@vanderbilt.edu [Institute of Space Technology (IST), Islamabad (Pakistan)

    2015-09-10

    Galaxy mergers usher the supermassive black hole (SMBH) in each galaxy to the center of the potential, where they form an SMBH binary. The binary orbit shrinks by ejecting stars via three-body scattering, but ample work has shown that in spherical galaxy models, the binary separation stalls after ejecting all the stars in its loss cone—this is the well-known final parsec problem. However, it has been shown that SMBH binaries in non-spherical galactic nuclei harden at a nearly constant rate until reaching the gravitational wave regime. Here we use a suite of direct N-body simulations to follow SMBH binary evolution in both corotating and counterrotating flattened galaxy models. For N > 500 K, we find that the evolution of the SMBH binary is convergent and is independent of the particle number. Rotation in general increases the hardening rate of SMBH binaries even more effectively than galaxy geometry alone. SMBH binary hardening rates are similar for co- and counterrotating galaxies. In the corotating case, the center of mass of the SMBH binary settles into an orbit that is in corotation resonance with the background rotating model, and the coalescence time is roughly a few 100 Myr faster than a non-rotating flattened model. We find that counterrotation drives SMBHs to coalesce on a nearly radial orbit promptly after forming a hard binary. We discuss the implications for gravitational wave astronomy, hypervelocity star production, and the effect on the structure of the host galaxy.

  3. GALAXY ROTATION AND RAPID SUPERMASSIVE BINARY COALESCENCE

    International Nuclear Information System (INIS)

    Holley-Bockelmann, Kelly; Khan, Fazeel Mahmood

    2015-01-01

    Galaxy mergers usher the supermassive black hole (SMBH) in each galaxy to the center of the potential, where they form an SMBH binary. The binary orbit shrinks by ejecting stars via three-body scattering, but ample work has shown that in spherical galaxy models, the binary separation stalls after ejecting all the stars in its loss cone—this is the well-known final parsec problem. However, it has been shown that SMBH binaries in non-spherical galactic nuclei harden at a nearly constant rate until reaching the gravitational wave regime. Here we use a suite of direct N-body simulations to follow SMBH binary evolution in both corotating and counterrotating flattened galaxy models. For N > 500 K, we find that the evolution of the SMBH binary is convergent and is independent of the particle number. Rotation in general increases the hardening rate of SMBH binaries even more effectively than galaxy geometry alone. SMBH binary hardening rates are similar for co- and counterrotating galaxies. In the corotating case, the center of mass of the SMBH binary settles into an orbit that is in corotation resonance with the background rotating model, and the coalescence time is roughly a few 100 Myr faster than a non-rotating flattened model. We find that counterrotation drives SMBHs to coalesce on a nearly radial orbit promptly after forming a hard binary. We discuss the implications for gravitational wave astronomy, hypervelocity star production, and the effect on the structure of the host galaxy

  4. Galaxy evolution in the metric of the cosmic web

    Science.gov (United States)

    Kraljic, K.; Arnouts, S.; Pichon, C.; Laigle, C.; de la Torre, S.; Vibert, D.; Cadiou, C.; Dubois, Y.; Treyer, M.; Schimd, C.; Codis, S.; de Lapparent, V.; Devriendt, J.; Hwang, H. S.; Le Borgne, D.; Malavasi, N.; Milliard, B.; Musso, M.; Pogosyan, D.; Alpaslan, M.; Bland-Hawthorn, J.; Wright, A. H.

    2018-02-01

    The role of the cosmic web in shaping galaxy properties is investigated in the Galaxy And Mass Assembly (GAMA) spectroscopic survey in the redshift range 0.03 ≤ z ≤ 0.25. The stellar mass, u - r dust corrected colour and specific star formation rate (sSFR) of galaxies are analysed as a function of their distances to the 3D cosmic web features, such as nodes, filaments and walls, as reconstructed by DisPerSE. Significant mass and type/colour gradients are found for the whole population, with more massive and/or passive galaxies being located closer to the filament and wall than their less massive and/or star-forming counterparts. Mass segregation persists among the star-forming population alone. The red fraction of galaxies increases when closing in on nodes, and on filaments regardless of the distance to nodes. Similarly, the star-forming population reddens (or lowers its sSFR) at fixed mass when closing in on filament, implying that some quenching takes place. These trends are also found in the state-of-the-art hydrodynamical simulation HORIZON-AGN. These results suggest that on top of stellar mass and large-scale density, the traceless component of the tides from the anisotropic large-scale environment also shapes galactic properties. An extension of excursion theory accounting for filamentary tides provides a qualitative explanation in terms of anisotropic assembly bias: at a given mass, the accretion rate varies with the orientation and distance to filaments. It also explains the absence of type/colour gradients in the data on smaller, non-linear scales.

  5. The interstellar medium in galaxies - An overview

    Science.gov (United States)

    Knapp, G. R.

    1990-01-01

    Recent observational developments on the subject of the interstellar medium in galaxies are summarized, with emphasis placed on global properties. The properties and distribution of the ISM in the solar neighborhood and in the Galactic plane are examined and a number of results from the most important observational probes (HI, CO, and infrared) are described. A recent development is the observation of the ISM in galaxies of all morphological types, early to late. These developments are summarized and the properties of different types of galaxies are compared to one another. The origin of radio galaxies, the effect of environment, and the prospects for direct observations of ISM evolution in galaxies are discussed.

  6. The Cold Side of Galaxy Formation: Dense Gas Through Cosmic Time

    Science.gov (United States)

    Riechers, Dominik A.; ngVLA Galaxy Assembly through Cosmic Time Science Working Group, ngVLA Galaxy Ecosystems Science Working Group

    2018-01-01

    The processes that lead to the formation and evolution of galaxies throughout the history of the Universe involve the complex interplay between hierarchical merging of dark matter halos, accretion of primordial and recycled gas, transport of gas within galaxy disks, accretion onto central super-massive black holes, and the formation of molecular clouds which subsequently collapse and fragment. The resulting star formation and black hole accretion provide large sources of energy and momentum that light up galaxies and lead to feedback. The ngVLA will be key to further understand how gas is accreted onto galaxies, and the processes that regulate the growth of galaxies through cosmic history. It will reveal how and on which timescales star formation and black hole accretion impact the gas in galaxies, and how the physical properties and chemical state of the gas change as gas cycles between different phases for different galaxy populations over a broad range in redshifts. The ngVLA will have the capability to carry out unbiased, large cosmic volume surveys at virtually any redshift down to an order of magnitude lower gas masses than currently possible in the critical low-level CO lines, thus exposing the evolution of gaseous reservoirs from the earliest epochs to the peak of the cosmic history of star formation. It will also image routinely and systematically the sub-kiloparsec scale distribution and kinematic structure of molecular gas in both normal main-sequence galaxies and large starbursts. The ngVLA thus is poised to revolutionize our understanding of galaxy evolution through cosmic time.

  7. WISE Discovery of Hyper Luminous Galaxies at z=2-4 and Their Implications for Galaxy and AGN Evolution

    Science.gov (United States)

    Tsai, Chao Wei; Eisenhardt, Peter; Wu, Jingwen; Bridge, Carrie; Assef, Roberto; Benford, Dominic; Blain, Andrew; Cutri, Roc; Griffith, Robert L.; Jarrett, Thomas; hide

    2014-01-01

    On behalf of the WISE Science team, we present the discovery of a class of distant dust-enshrouded galaxies with extremely high luminosity. These galaxies are selected to have extreme red colors in the mid-IR using NASA's Wide-field Infrared Survey Explorer (WISE). They are faint in the optical and near-IR, predominantly at zeta = 2-4, and with IR luminosity > 10(exp 13) Solar Luminosity, making them Hyper-Luminous Infrared Galaxies (HyLIRGs). SEDs incorporating the WISE, Spitzer, and Herschel PACS and SPIRE photometry indicate hot dust dominates the bolometric luminosity, presumably powered by AGN. Preliminary multi-wavelength follow-up suggests that they are different from normal populations in the local M-sigma relation. Their low source density implies that these objects are either intrinsically rare, or a short-lived phase in a more numerous population. If the latter is the case, these hot, dust-enshrouded galaxies may be an early stage in the interplay between AGN and galaxies.

  8. X-ray spectroscopy of clusters of galaxies and of the cosmic web

    NARCIS (Netherlands)

    Werner, N.

    2008-01-01

    I present the results on the study of the chemical evolution of the intra-cluster medium (ICM) and on the evolution of clusters of galaxies in the context of the cosmic web. Clusters of galaxies are excellent laboratories to study the chemical enrichment history of the Universe. This thesis presents

  9. Kinematic properties and dark matter fraction of Virgo dwarf early-type galaxies

    NARCIS (Netherlands)

    Toloba, E.; Boselli, A.; Peletier, R.; Gorgas, J.

    2012-01-01

    What happens to dwarf galaxies as they enter the cluster potential well is one of the main unknowns in studies of galaxy evolution. Several evidence suggests that late-type galaxies enter the cluster and are transformed to dwarf early-type galaxies (dEs). We study the Virgo cluster to understand

  10. The Leoncino Dwarf: The Lowest Metallicity Star-Forming Galaxy in the Nearby Universe

    Science.gov (United States)

    McQuinn, Kristen

    2017-08-01

    Extremely metal-poor (XMP) galaxies are dwarf irregular galaxies with very low metallicities, traced by their gas-phase oxygen abundance. Galaxy evolution scenarios suggest three pathways to form an XMP: (1) secular evolution at low galaxy masses, (2) slow evolution in voids, or (3) dilution of measured abundances from infall of pristine gas. These scenarios have proven challenging to test because, despite concerted efforts, XMP galaxies in the nearby universe have proven hard to find. A notable exception is the recently discovered dwarf galaxy Leoncino. Leoncino has the lowest gas-phase oxygen abundance ever measured in a galaxy in the local Universe. From optical spectroscopy, the oxygen abundance is 12+log(O/H)=7.02+/-0.03, more than 40% lower than the iconic low-metallicity galaxy I Zw 18 and less than 2% Z_sun. Despite a precision oxygen abundance measurement, the evolutionary context of Leoncino remains uncertain without a secure distance. We propose HST WFC3 high-resolution optical imaging of Leoncino to accurately measure the distance to the galaxy using the tip of the red giant branch (TRGB) method. The distance will determine whether Leoncino is located in a typical field environment or in a void, and whether the galaxy is consistent with the luminosity-metallicity relation at low galaxy masses. The detailed study of Leoncino will provide benchmark results for future XMP discoveries in the nearby Universe, and an exceptionally timely comparison for studies of chemically primitive, high-redshift galaxies that will be observable in the JWST era.

  11. LEDA 074886: A REMARKABLE RECTANGULAR-LOOKING GALAXY

    International Nuclear Information System (INIS)

    Graham, Alister W.; Spitler, Lee R.; Forbes, Duncan A.; Lisker, Thorsten; Janz, Joachim; Moore, Ben

    2012-01-01

    We report the discovery of an interesting and rare rectangular-shaped galaxy. At a distance of 21 Mpc, the dwarf galaxy LEDA 074886 has an absolute R-band magnitude of –17.3 mag. Adding to this galaxy's intrigue is the presence of an embedded, edge-on stellar disk (of extent 2 R e,disk = 12'' = 1.2 kpc) for which Forbes et al. reported v rot /σ ≈ 1.4. We speculate that this galaxy may be the remnant of two (nearly edge-on) merged disk galaxies in which the initial gas was driven inward and subsequently formed the inner disk, while the stars at larger radii effectively experienced a dissipationless merger event resulting in this 'emerald cut galaxy' having very boxy isophotes with a 4 /a = –0.05 to –0.08 from 3 to 5 kpc. This galaxy suggests that knowledge from simulations of both 'wet' and 'dry' galaxy mergers may need to be combined to properly understand the various paths that galaxy evolution can take, with a particular relevance to blue elliptical galaxies.

  12. Constructing a WISE High Resolution Galaxy Atlas

    Science.gov (United States)

    Jarrett, T. H.; Masci, F.; Tsai, C. W.; Petty, S.; Cluver, M.; Assef, Roberto J.; Benford, D.; Blain, A.; Bridge, C.; Donoso, E.; hide

    2012-01-01

    After eight months of continuous observations, the Wide-field Infrared Survey Explorer (WISE) mapped the entire sky at 3.4 micron, 4.6 micron, 12 micron, and 22 micron. We have begun a dedicated WISE High Resolution Galaxy Atlas project to fully characterize large, nearby galaxies and produce a legacy image atlas and source catalog. Here we summarize the deconvolution techniques used to significantly improve the spatial resolution of WISE imaging, specifically designed to study the internal anatomy of nearby galaxies. As a case study, we present results for the galaxy NGC 1566, comparing the WISE enhanced-resolution image processing to that of Spitzer, Galaxy Evolution Explorer, and ground-based imaging. This is the first paper in a two-part series; results for a larger sample of nearby galaxies are presented in the second paper.

  13. ENVIRONMENTAL EFFECTS ON THE METAL ENRICHMENT OF LOW-MASS GALAXIES IN NEARBY CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Petropoulou, V.; Vilchez, J.; Iglesias-Paramo, J. [Instituto de Astrofisica de Andalucia-C.S.I.C., Glorieta de la Astronomia, 18008 Granada (Spain)

    2012-04-20

    In this paper, we study the chemical history of low-mass star-forming (SF) galaxies in the local universe clusters Coma, A1367, A779, and A634. The aim of this work is to search for the imprint of the environment on the chemical evolution of these galaxies. Galaxy chemical evolution is linked to the star formation history, as well as to the gas interchange with the environment, and low-mass galaxies are well known to be vulnerable systems to environmental processes affecting both these parameters. For our study we have used spectra from the SDSS-III DR8. We have examined the spectroscopic properties of SF galaxies of stellar masses 10{sup 8}-10{sup 10} M{sub Sun }, located from the core to the cluster's outskirts. The gas-phase O/H and N/O chemical abundances have been derived using the latest empirical calibrations. We have examined the mass-metallicity relation of cluster galaxies, finding well-defined sequences. The slope of these sequences, for galaxies in low-mass clusters and galaxies at large cluster-centric distances, follows the predictions of recent hydrodynamic models. A flattening of this slope has been observed for galaxies located in the core of the two more massive clusters of the sample, principally in Coma, suggesting that the imprint of the cluster environment on the chemical evolution of SF galaxies should be sensitive to both the galaxy mass and the host cluster mass. The H I gas content of Coma and A1367 galaxies indicates that low-mass SF galaxies, located at the core of these clusters, have been severely affected by ram-pressure stripping (RPS). The observed mass-dependent enhancement of the metal content of low-mass galaxies in dense environments seems plausible, according to hydrodynamic simulations. This enhanced metal enrichment could be produced by the combination of effects such as wind reaccretion, due to pressure confinement by the intracluster medium (ICM), and the truncation of gas infall, as a result of the RPS. Thus, the

  14. ENVIRONMENTAL EFFECTS ON THE METAL ENRICHMENT OF LOW-MASS GALAXIES IN NEARBY CLUSTERS

    International Nuclear Information System (INIS)

    Petropoulou, V.; Vílchez, J.; Iglesias-Páramo, J.

    2012-01-01

    In this paper, we study the chemical history of low-mass star-forming (SF) galaxies in the local universe clusters Coma, A1367, A779, and A634. The aim of this work is to search for the imprint of the environment on the chemical evolution of these galaxies. Galaxy chemical evolution is linked to the star formation history, as well as to the gas interchange with the environment, and low-mass galaxies are well known to be vulnerable systems to environmental processes affecting both these parameters. For our study we have used spectra from the SDSS-III DR8. We have examined the spectroscopic properties of SF galaxies of stellar masses 10 8 -10 10 M ☉ , located from the core to the cluster's outskirts. The gas-phase O/H and N/O chemical abundances have been derived using the latest empirical calibrations. We have examined the mass-metallicity relation of cluster galaxies, finding well-defined sequences. The slope of these sequences, for galaxies in low-mass clusters and galaxies at large cluster-centric distances, follows the predictions of recent hydrodynamic models. A flattening of this slope has been observed for galaxies located in the core of the two more massive clusters of the sample, principally in Coma, suggesting that the imprint of the cluster environment on the chemical evolution of SF galaxies should be sensitive to both the galaxy mass and the host cluster mass. The H I gas content of Coma and A1367 galaxies indicates that low-mass SF galaxies, located at the core of these clusters, have been severely affected by ram-pressure stripping (RPS). The observed mass-dependent enhancement of the metal content of low-mass galaxies in dense environments seems plausible, according to hydrodynamic simulations. This enhanced metal enrichment could be produced by the combination of effects such as wind reaccretion, due to pressure confinement by the intracluster medium (ICM), and the truncation of gas infall, as a result of the RPS. Thus, the properties of the ICM

  15. Connecting Global to Local Parameters in Barred Galaxy Models

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Key words. Galaxies: barred—orbits—global and local parameters. .... series near the stable Lagrange point L1, which coincides with the origin. Doing so, .... Toomre, A. 1981, In: The Structure and Evolution of Normal Galaxies, (eds) S. M. Fall,.

  16. Chemical analysis of the Fornax Dwarf galaxy

    NARCIS (Netherlands)

    Letarte, Bruno

    2007-01-01

    This thesis is entitled “Chemical Analysis of the Fornax Dwarf Galaxy”, and it’s main goal is to determine what are the chemical elements present in the stars of this galaxy in order to try and understand it’s evolution. Galaxies are not “static” objects, they move, form stars and can interact with

  17. Snapshot Survey of the Globular Cluster Populations of Isolated Early Type Galaxies

    Science.gov (United States)

    Gregg, Michael

    2017-08-01

    We propose WFC3/UVIS snapshot observations of a sample of 75 isolated early type galaxiesresiding in cosmic voids or extremely low density regions. The primary aim is to usetheir globular cluster populations to reconstruct their evolutionary history, revealingif, how, and why void ellipticals differ from cluster ellipticals. The galaxies span arange of luminosities, providing a varied sample for comparison with the well-documentedglobular cluster populations in denser environments. This proposed WFC3 study of isolatedearly type galaxies breaks new ground by targeting a sample which has thus far receivedlittle attention, and, significantly, this will be the first such study with HST.Characterizing early type galaxies in voids and their GC systems promises to increase ourunderstanding of galaxy formation and evolution of galaxies in general because isolatedobjects are the best approximation to a control sample that we have for understanding theinfluence of environment on formation and evolution. Whether these isolated objects turnout to be identical to or distinct from counterparts in other regions of the Universe,they will supply insight into the formation and evolution of all galaxies. Parallel ACSimaging will help to characterize the near field environments of the sample.

  18. The effect of stellar evolution uncertainties on the rest-frame ultraviolet stellar lines of C IV and He II in high-redshift Lyman-break galaxies

    Science.gov (United States)

    Eldridge, John J.; Stanway, Elizabeth R.

    2012-01-01

    Young, massive stars dominate the rest-frame ultraviolet (UV) spectra of star-forming galaxies. At high redshifts (z > 2), these rest-frame UV features are shifted into the observed-frame optical and a combination of gravitational lensing, deep spectroscopy and spectral stacking analysis allows the stellar population characteristics of these sources to be investigated. We use our stellar population synthesis code Binary Population and Spectral Synthesis (BPASS) to fit two strong rest-frame UV spectral features in published Lyman-break galaxy spectra, taking into account the effects of binary evolution on the stellar spectrum. In particular, we consider the effects of quasi-homogeneous evolution (arising from the rotational mixing of rapidly rotating stars), metallicity and the relative abundance of carbon and oxygen on the observed strengths of He IIλ1640 Å and C IVλ1548, 1551 Å spectral lines. We find that Lyman-break galaxy spectra at z ˜ 2-3 are best fitted with moderately sub-solar metallicities, and with a depleted carbon-to-oxygen ratio. We also find that the spectra of the lowest metallicity sources are best fitted with model spectra in which the He II emission line is boosted by the inclusion of the effect of massive stars being spun-up during binary mass transfer so these rapidly rotating stars experience quasi-homogeneous evolution.

  19. The clustering evolution of distant red galaxies in the GOODS-MUSIC sample

    Science.gov (United States)

    Grazian, A.; Fontana, A.; Moscardini, L.; Salimbeni, S.; Menci, N.; Giallongo, E.; de Santis, C.; Gallozzi, S.; Nonino, M.; Cristiani, S.; Vanzella, E.

    2006-07-01

    Aims.We study the clustering properties of Distant Red Galaxies (DRGs) to test whether they are the progenitors of local massive galaxies. Methods.We use the GOODS-MUSIC sample, a catalog of ~3000 Ks-selected galaxies based on VLT and HST observation of the GOODS-South field with extended multi-wavelength coverage (from 0.3 to 8~μm) and accurate estimates of the photometric redshifts to select 179 DRGs with J-Ks≥ 1.3 in an area of 135 sq. arcmin.Results.We first show that the J-Ks≥ 1.3 criterion selects a rather heterogeneous sample of galaxies, going from the targeted high-redshift luminous evolved systems, to a significant fraction of lower redshift (1mass, like groups or small galaxy clusters. Low-z DRGs, on the other hand, will likely evolve into slightly less massive field galaxies.

  20. The rotation of galaxies: clues to their formation

    International Nuclear Information System (INIS)

    Fall, S.M.

    1982-01-01

    The rotation of galaxies of different morphological types is closely linked with their structural features and therefore with the processes by which they formed. In this context, the most important distinction is between galaxies that are dominated by a spheroid or bulge component - the ellipticals and some lenticulars - and galaxies that are dominated by a disk component - some lenticulars, the spirals and some irregulars. As the result of improvements in spectroscopic techniques, we now have reliable kinematic data for galaxies of most types in a wide range of masses and sizes. The author discusses the observational results and their implications for several views of the origin and evolution of galaxies. (Auth.)

  1. Nearby galaxies as pointers to a better theory of cosmic evolution.

    Science.gov (United States)

    Peebles, P J E; Nusser, Adi

    2010-06-03

    The great advances in the network of cosmological tests show that the relativistic Big Bang theory is a good description of our expanding Universe. However, the properties of nearby galaxies that can be observed in greatest detail suggest that a better theory would describe a mechanism by which matter is more rapidly gathered into galaxies and groups of galaxies. This more rapid growth occurs in some theoretical ideas now under discussion.

  2. Outskirts of galaxies

    CERN Document Server

    Lee, Janice; Paz, Armando

    2017-01-01

    This book consists of invited reviews written by world-renowned experts on the subject of the outskirts of galaxies, an upcoming field which has been understudied so far. These regions are faint and hard to observe, yet hide a tremendous amount of information on the origin and early evolution of galaxies. They thus allow astronomers to address some of the most topical problems, such as gaseous and satellite accretion, radial migration, and merging. The book is published in conjunction with the celebration of the end of the four-year DAGAL project, an EU-funded initial training network, and with a major international conference on the topic held in March 2016 in Toledo. It thus reflects not only the views of the experts, but also the scientific discussions and progress achieved during the project and the meeting. The reviews in the book describe the most modern observations of the outer regions of our own Galaxy, and of galaxies in the local and high-redshift Universe. They tackle disks, haloes, streams, and a...

  3. Star Formation in the Central Regions of Galaxies

    Science.gov (United States)

    Tsai, Mengchun

    2015-08-01

    The galactic central region connects the galactic nucleus to the host galaxy. If the central black hole co-evolved with the host galaxies, there should be some evidence left in the central region. We use the environmental properties in the central regions such as star-forming activity, stellar population and molecular abundance to figure out a possible scenario of the evolution of galaxies. In this thesis at first we investigated the properties of the central regions in the host galaxies of active and normal galaxies. We used radio emission around the nuclei of the host galaxies to represent activity of active galactic nuclei (AGNs), and used infrared ray (IR) emission to represent the star-forming activity and stellar population of the host galaxies. We determined that active galaxies have higher stellar masses (SMs) within the central kiloparsec radius than normal galaxies do independent of the Hubble types of the host galaxies; but both active and normal galaxies exhibit similar specific star formation rates (SSFRs). We also discovered that certain AGNs exhibit substantial inner stellar structures in the IR images; most of the AGNs with inner structures are Seyferts, whereas only a few LINERs exhibit inner structures. We note that the AGNs with inner structures show a positive correlation between the radio activity of the AGNs and the SFRs of the host galaxies, but the sources without inner structures show a negative correlation between the radio power and the SFRs. These results might be explained with a scenario of starburst-AGN evolution. In this scenario, AGN activities are triggered following a nuclear starburst; during the evolution, AGN activities are accompanied by SF activity in the inner regions of the host galaxies; at the final stage of the evolution, the AGNs might transform into LINERs, exhibiting weak SF activity in the central regions of the host galaxies. For further investigation about the inner structure, we choose the most nearby and luminous

  4. STRUCTURAL EVOLUTION OF EARLY-TYPE GALAXIES TO z = 2.5 IN CANDELS

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yu-Yen; Van der Wel, Arjen; Rix, Hans-Walter [Max-Planck Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Holden, Bradford; Faber, S. M.; Mozena, Mark; Guo Yicheng; Kocevski, Dale D. [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); McGrath, Elizabeth J. [Department of Physics and Astronomy, Colby College, Waterville, ME 04901 (United States); Wuyts, Stijn [Max-Planck-Institut fuer Extraterrestrische Physik, Postfach 1312, Giessenbachstr., D-85741 Garching (Germany); Haeussler, Boris [Schools of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom); Barden, Marco [Institute of Astro- and Particle Physics, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck (Austria); Ferguson, Henry C.; Grogin, Norman A.; Koekemoer, Anton M.; Huang, Kuang-Han [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Galametz, Audrey [INAF-Osservatorio di Roma, Via Frascati 33, I-00040 Monteporzio (Italy); Dekel, Avishai [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Hathi, Nimish P., E-mail: chang@mpia.de [Observatories of the Carnegie Institution for Science, Pasadena, CA (United States); and others

    2013-08-20

    Projected axis ratio measurements of 880 early-type galaxies at redshifts 1 < z < 2.5 selected from CANDELS are used to reconstruct and model their intrinsic shapes. The sample is selected on the basis of multiple rest-frame colors to reflect low star-formation activity. We demonstrate that these galaxies as an ensemble are dust-poor and transparent and therefore likely have smooth light profiles, similar to visually classified early-type galaxies. Similar to their present-day counterparts, the z > 1 early-type galaxies show a variety of intrinsic shapes; even at a fixed mass, the projected axis ratio distributions cannot be explained by the random projection of a set of galaxies with very similar intrinsic shapes. However, a two-population model for the intrinsic shapes, consisting of a triaxial, fairly round population, combined with a flat (c/a {approx} 0.3) oblate population, adequately describes the projected axis ratio distributions of both present-day and z > 1 early-type galaxies. We find that the proportion of oblate versus triaxial galaxies depends both on the galaxies' stellar mass, and-at a given mass-on redshift. For present-day and z < 1 early-type galaxies the oblate fraction strongly depends on galaxy mass. At z > 1, this trend is much weaker over the mass range explored here (10{sup 10} < M{sub *}/M{sub Sun} < 10{sup 11}), because the oblate fraction among massive (M{sub *} {approx} 10{sup 11} M{sub Sun }) was much higher in the past: 0.59 {+-} 0.10 at z > 1, compared to 0.20 {+-} 0.02 at z {approx} 0.1. When combined with previous findings that the number density and sizes of early-type galaxies substantially increase over the same redshift range, this can be explained by the gradual emergence of merger-produced elliptical galaxies, at the expense of the destruction of pre-existing disks that were common among their high-redshift progenitors. In contrast, the oblate fraction among low-mass early-type galaxies (log (M{sub *}/M{sub Sun }) < 10

  5. Three-Dimensional View of Ionized Gas Conditions in Galaxies

    Science.gov (United States)

    Juneau, Stephanie; NOAO Data Lab

    2018-06-01

    We present a 3D version of common emission line diagnostic diagrams used to identify the source of ionization in galaxies, and highlight interesting features in this new 3D space, which are associated with global galaxy properties. Namely, we combine the BPT and Mass-Excitation (MEx) diagrams, and apply it to a set of >300,000 galaxies from the SDSS survey. Among other features, we show that the usual “branch” of star-forming galaxies becomes a curved surface in the new 3D space. Understanding the underlying reasons can shed light on the nearby galaxy population but also aid our interpretation of high-redshift surveys, which indicate a strong evolution of emission line ratios. Despite efforts to explain the origin of this strong evolution, a consensus has not yet been reached. Yet, the implications are crucial to our understanding of galaxy growth across cosmic time, and in particular to assess how star forming regions differed at earlier times (gas properties? stellar properties? a combination?). We perform this analysis within the framework of the NOAO Data Lab (datalab.noao.edu) jointly with public visualization tools. The final workflow will be released publicly.

  6. THE ZURICH ENVIRONMENTAL STUDY OF GALAXIES IN GROUPS ALONG THE COSMIC WEB. I. WHICH ENVIRONMENT AFFECTS GALAXY EVOLUTION?

    Energy Technology Data Exchange (ETDEWEB)

    Carollo, C. Marcella; Cibinel, Anna; Lilly, Simon J.; Miniati, Francesco; Cameron, Ewan; Peng, Yingjie; Pipino, Antonio; Rudick, Craig S. [Institute for Astronomy, ETH Zurich, CH-8093 Zurich (Switzerland); Norberg, Peder [Department of Physics, Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Silverman, John D. [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, Chiba 277-8583 (Japan); Van Gorkom, Jacqueline [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Finoguenov, Alexis, E-mail: marcella@phys.ethz.ch [Max-Planck-Institut für extraterrestrische Physik, D-84571 Garching (Germany)

    2013-10-20

    The Zurich Environmental Study (ZENS) is based on a sample of ∼1500 galaxy members of 141 groups in the mass range ∼10{sup 12.5-14.5} M{sub ☉} within the narrow redshift range 0.05 < z < 0.0585. ZENS adopts novel approaches, described here, to quantify four different galactic environments, namely: (1) the mass of the host group halo; (2) the projected halo-centric distance; (3) the rank of galaxies as central or satellites within their group halos; and (4) the filamentary large-scale structure density. No self-consistent identification of a central galaxy is found in ∼40% of <10{sup 13.5} M{sub ☉} groups, from which we estimate that ∼15% of groups at these masses are dynamically unrelaxed systems. Central galaxies in relaxed and unrelaxed groups generally have similar properties, suggesting that centrals are regulated by their mass and not by their environment. Centrals in relaxed groups have, however, ∼30% larger sizes than in unrelaxed groups, possibly due to accretion of small satellites in virialized group halos. At M > 10{sup 10} M{sub ☉}, satellite galaxies in relaxed and unrelaxed groups have similar size, color, and (specific) star formation rate distributions; at lower galaxy masses, satellites are marginally redder in relaxed relative to unrelaxed groups, suggesting quenching of star formation in low-mass satellites by physical processes active in relaxed halos. Overall, relaxed and unrelaxed groups show similar stellar mass populations, likely indicating similar stellar mass conversion efficiencies. In the enclosed ZENS catalog, we publish all environmental diagnostics as well as the galaxy structural and photometric measurements described in companion ZENS papers II and III.

  7. GALAXY EVOLUTION. An over-massive black hole in a typical star-forming galaxy, 2 billion years after the Big Bang.

    Science.gov (United States)

    Trakhtenbrot, Benny; Urry, C Megan; Civano, Francesca; Rosario, David J; Elvis, Martin; Schawinski, Kevin; Suh, Hyewon; Bongiorno, Angela; Simmons, Brooke D

    2015-07-10

    Supermassive black holes (SMBHs) and their host galaxies are generally thought to coevolve, so that the SMBH achieves up to about 0.2 to 0.5% of the host galaxy mass in the present day. The radiation emitted from the growing SMBH is expected to affect star formation throughout the host galaxy. The relevance of this scenario at early cosmic epochs is not yet established. We present spectroscopic observations of a galaxy at redshift z = 3.328, which hosts an actively accreting, extremely massive BH, in its final stages of growth. The SMBH mass is roughly one-tenth the mass of the entire host galaxy, suggesting that it has grown much more efficiently than the host, contrary to models of synchronized coevolution. The host galaxy is forming stars at an intense rate, despite the presence of a SMBH-driven gas outflow. Copyright © 2015, American Association for the Advancement of Science.

  8. The gas content in starburst galaxies

    International Nuclear Information System (INIS)

    Mirabel, I.F.; Sanders, D.B.

    1987-01-01

    The results from two large and homogeneous surveys, one in HI, the other in CO, are used for a statistical review of the gaseous properties of bright infrared galaxies. A constant ratio between the thermal far-infrared radiation and non-thermal radio emission is a universal property of star formation in spiral galaxies. The current rate of star formation in starburst galaxies is found to be 3-20 times larger than in the Milky Way. Galaxies with the higher far-infrared luminosities and warmer dust, have the larger mass fractions of molecular to atomic interstellar gas, and in some instances, striking deficiencies of neutral hydrogen are found. A statistical blueshift of the optical systemic velocities relative to the radio systemic velocities, may be due to an outward motion of the optical line-emitting gas. From the high rates of star formation, and from the short times required for the depletion of the interstellar gas, we conclude that the most luminous infrared galaxies represent a brief but important phase in the evolution of some galaxies, when two galaxies merge changing substantially their overall properties

  9. Galaxy Zoo: Comparing the visual morphology of synthetic galaxies from the Illustris simulation with those in the real Universe.

    Science.gov (United States)

    Dickinson, Hugh; Lintott, Chris; Scarlata, Claudia; Fortson, Lucy; Bamford, Steven; Cardamone, Carolin; Keel, William C.; Kruk, Sandor; Masters, Karen; Simmons, Brooke D.; Vogelsberger, Mark; Torrey, Paul; Snyder, Gregory; Galaxy Zoo Science Team

    2018-01-01

    We present a comparision between the Illustris simulations and classifications from Galaxy Zoo, aiming to test the ability of modern large-scale cosmological simulations to accurately reproduce the local galaxy population. This comparison is enabled by the increasingly high spatial and temporal resolution obtained by such surveys.Using classifications that were accumulated via the Galaxy Zoo citizen science interface, we compare the visual morphologies for simulated images of Illustris galaxies with a compatible sample of images drawn from the Sloan Digital Sky Survey (SDSS) Legacy Survey.For simulated galaxies with stellar masses less than 1011 M⊙, significant differences are identified, which are most likely due to the limited resolution of the simulation, but could be revealing real differences in the dynamical evolution of populations of galaxies in the real and model universes. Above 1011 M⊙, Illustris galaxy morphologies correspond better with those of their SDSS counterparts, although even in this mass range the simulation appears to underproduce obviously disk-like galaxies. Morphologies of Illustris galaxies less massive than 1011 M⊙ should be treated with care.

  10. Do You See What I See? Exploring the Consequences of Luminosity Limits in Black Hole–Galaxy Evolution Studies

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Mackenzie L.; Hickox, Ryan C.; DiPompeo, Michael A. [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States); Mutch, Simon J. [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Croton, Darren J. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, VIC 3122 (Australia); Ptak, Andrew F. [NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States)

    2017-07-10

    In studies of the connection between active galactic nuclei (AGNs) and their host galaxies, there is widespread disagreement on some key aspects of the connection. These disagreements largely stem from a lack of understanding of the nature of the full underlying AGN population. Recent attempts to probe this connection utilize both observations and simulations to correct for a missed population, but presently are limited by intrinsic biases and complicated models. We take a simple simulation for galaxy evolution and add a new prescription for AGN activity to connect galaxy growth to dark matter halo properties and AGN activity to star formation. We explicitly model selection effects to produce an “observed” AGN population for comparison with observations and empirically motivated models of the local universe. This allows us to bypass the difficulties inherent in models that attempt to infer the AGN population by inverting selection effects. We investigate the impact of selecting AGNs based on thresholds in luminosity or Eddington ratio on the “observed” AGN population. By limiting our model AGN sample in luminosity, we are able to recreate the observed local AGN luminosity function and specific star formation-stellar mass distribution, and show that using an Eddington ratio threshold introduces less bias into the sample by selecting the full range of growing black holes, despite the challenge of selecting low-mass black holes. We find that selecting AGNs using these various thresholds yield samples with different AGN host galaxy properties.

  11. Dwarf Galaxies in the Chandra COSMOS Legacy Survey

    Science.gov (United States)

    Civano, Francesca Maria; Mezcua, Mar; Fabbiano, Giuseppina; Marchesi, Stefano; Suh, Hyewon; Volonteri, Marta; cyrille

    2018-01-01

    The existence of intermediate mass black holes (100 7. While detecting these seed black holes in the young Universe is observationally challenging, the nuclei of local dwarf galaxies are among the best places where to look for them as these galaxies resemble in mass and metallicity the first galaxies and they have not significantly grown through merger and accretion processes. We present a sample of 40 AGN in dwarf galaxies (107 0.5, our sample constitutes the highest-redshift discovery of AGN in dwarf galaxies. One of the dwarf galaxies is the least massive galaxy (M* = 6.6x107 Msun) found so far to host an active BH. We also present for the first time the evolution of the AGN fraction with stellar mass, X-ray luminosity, and redshift in dwarf galaxies out to z = 0.7, finding that it decreases with X-ray luminosity and stellar mass. Unlike massive galaxies, the AGN fraction is found to decrease with redshift, suggesting that AGN in dwarf galaxies evolve differently than those in high-mass galaxies.

  12. The X-ray properties of normal galaxies

    Science.gov (United States)

    Fabbiano, G.

    1986-01-01

    X-ray observations with the Einstein satellite have shown that normal galaxies of all morphological types are spatially extended sources of X-ray emission with luminosities in the range of L(x) of about 10 to the 39th to 10 to the 41st erg/s. Although this is only a small fraction of the total energy output of a normal galaxy, X-ray observations are uniquely suited to study phenomena that are otherwise elusive. In X-rays one can study directly the end products of stellar evolution (SNRs and compact remnants). X-ray observations have led to the discovery of gaseous outflows linked to starburst nuclear activity in spiral galaxies and to the detection of a hot interstellar medium in early-type galaxies. Through X-ray observations it is possible to set constraints on structural galaxy parameters, such as the mass of elliptical galaxies, and perhaps get new insight on the origin of cosmic rays and the properties of the magnetic fields of spiral galaxies.

  13. The Origin of Stellar Species: constraining stellar evolution scenarios with Local Group galaxy surveys

    Science.gov (United States)

    Sarbadhicary, Sumit; Badenes, Carles; Chomiuk, Laura; Maldonado, Jessica; Caprioli, Damiano; Heger, Mairead; Huizenga, Daniel

    2018-01-01

    Our understanding of the progenitors of many stellar species, such as supernovae, massive and low-mass He-burning stars, is limited because of many poorly constrained aspects of stellar evolution theory. For my dissertation, I have focused on using Local Group galaxy surveys to constrain stellar evolution scenarios by measuring delay-time distributions (DTD). The DTD is the hypothetical occurrence rate of a stellar object per elapsed time after a brief burst of star formation. It is the measured distribution of timescales on which stars evolve, and therefore serves as a powerful observational constraint on theoretical progenitor models. The DTD can be measured from a survey of stellar objects and a set of star-formation histories of the host galaxy, and is particularly effective in the Local Group, where high-quality star-formation histories are available from resolved stellar populations. I am currently calculating a SN DTD with supernova remnants (SNRs) in order to provide the strongest constraints on the progenitors of thermonuclear and core-collapse supernovae. However, most SNRs do not have reliable age measurements and their evolution depends on the ambient environment. For this reason, I wrote a radio light curve model of an SNR population to extract the visibility times and rates of supernovae - crucial ingredients for the DTD - from an SNR survey. The model uses observational constraints on the local environments from multi-wavelength surveys, accounts for missing SNRs and employs the latest models of shock-driven particle acceleration. The final calculation of the SN DTD in the Local Group is awaiting completion of a systematic SNR catalog from deep radio-continuum images, now in preparation by a group led by Dr. Laura Chomiuk. I have also calculated DTDs for the LMC population of RR Lyrae and Cepheid variables, which serve as important distance calibrators and stellar population tracers. We find that Cepheids can have delay-times between 10 Myrs - 1 Gyr

  14. Enriched gas in clusters and the dynamics of galaxies and clusters: implications for theories of galaxy formation

    International Nuclear Information System (INIS)

    Binney, J.; Silk, J.

    1978-01-01

    Recent developments in relation to the origin of galaxies are cited: the discovery that the intergalactic medium which seems to pervade rich clusters of galaxies has an iron abundance that lies within an order of magnitude of the solar value; the discovery that elliptical galaxies rotate much more slowly than the models of these galaxies had predicted; and the results of studies of cosmological infall in the context of the formation of galaxies and galaxy clusters, which have shown that the resulting density profile is fairly insensitive to initial conditions. After discussing the implications of these recent observations of X-ray clusters and of the rotation of elliptical galaxies, an attempt is made to construct a picture of the formation of elliptical and spiral galaxies in which galaxies form continuously from redshift z approximately 100 onwards. It is suggested that at a redshift z of roughly 5, a fundamental change occurred in the manner in which the cosmic material fragmented into stellar objects. It seems possible that explanations of a variety of puzzling aspects of galactic evolution, including the formation of Population I disks, the origin of the hot intracluster gas, the mass-to-light ratio stratification of galaxies, and the nature of the galaxy luminosity function, should all be sought in the context of this change of regime. Some remarks are made about gas in poor groups of galaxies and the interaction of disk galaxies with their environments. (U.K.)

  15. Dust formation in a galaxy with primitive abundances.

    Science.gov (United States)

    Sloan, G C; Matsuura, M; Zijlstra, A A; Lagadec, E; Groenewegen, M A T; Wood, P R; Szyszka, C; Bernard-Salas, J; van Loon, J Th

    2009-01-16

    Interstellar dust plays a crucial role in the evolution of galaxies. It governs the chemistry and physics of the interstellar medium. In the local universe, dust forms primarily in the ejecta from stars, but its composition and origin in galaxies at very early times remain controversial. We report observational evidence of dust forming around a carbon star in a nearby galaxy with a low abundance of heavy elements, 25 times lower than the solar abundance. The production of dust by a carbon star in a galaxy with such primitive abundances raises the possibility that carbon stars contributed carbonaceous dust in the early universe.

  16. STRUCTURAL EVOLUTION OF EARLY-TYPE GALAXIES TO z = 2.5 IN CANDELS

    International Nuclear Information System (INIS)

    Chang, Yu-Yen; Van der Wel, Arjen; Rix, Hans-Walter; Holden, Bradford; Faber, S. M.; Mozena, Mark; Guo Yicheng; Kocevski, Dale D.; Bell, Eric F.; McGrath, Elizabeth J.; Wuyts, Stijn; Häussler, Boris; Barden, Marco; Ferguson, Henry C.; Grogin, Norman A.; Koekemoer, Anton M.; Huang, Kuang-Han; Galametz, Audrey; Dekel, Avishai; Hathi, Nimish P.

    2013-01-01

    Projected axis ratio measurements of 880 early-type galaxies at redshifts 1 1 early-type galaxies show a variety of intrinsic shapes; even at a fixed mass, the projected axis ratio distributions cannot be explained by the random projection of a set of galaxies with very similar intrinsic shapes. However, a two-population model for the intrinsic shapes, consisting of a triaxial, fairly round population, combined with a flat (c/a ∼ 0.3) oblate population, adequately describes the projected axis ratio distributions of both present-day and z > 1 early-type galaxies. We find that the proportion of oblate versus triaxial galaxies depends both on the galaxies' stellar mass, and—at a given mass—on redshift. For present-day and z 1, this trend is much weaker over the mass range explored here (10 10 * /M ☉ 11 ), because the oblate fraction among massive (M * ∼ 10 11 M ☉ ) was much higher in the past: 0.59 ± 0.10 at z > 1, compared to 0.20 ± 0.02 at z ∼ 0.1. When combined with previous findings that the number density and sizes of early-type galaxies substantially increase over the same redshift range, this can be explained by the gradual emergence of merger-produced elliptical galaxies, at the expense of the destruction of pre-existing disks that were common among their high-redshift progenitors. In contrast, the oblate fraction among low-mass early-type galaxies (log (M * /M ☉ ) 1 to 0.72 ± 0.06 at z = 0. We speculate that this lower incidence of disks at early cosmic times can be attributed to two factors: low-mass, star-forming progenitors at z > 1 were not settled into stable disks to the same degree as at later cosmic times, and the stripping of gas from star-forming disk galaxies in dense environments is an increasingly important process at lower redshifts

  17. The small-scale structure of the Magellanic stream as a foundation for galaxy evolution

    Directory of Open Access Journals (Sweden)

    Stanimirović S.

    2010-01-01

    Full Text Available The Magellanic Stream (MS is the nearest example of a gaseous trail formed by interacting galaxies. While the substantial gas masses in these kinds of circumgalactic structures are postulated to represent important sources of fuel for future star formation, the mechanisms whereby this material might be accreted back into galaxies remain unclear. Recent neutral hydrogen (HI observations have demonstrated that the northern portion of the MS, which probably has been interacting with the Milky Way's hot gaseous halo for close to 1000 Myr, has a larger spatial extent than previously recognized, while also containing significant amounts of small-scale structure. After a brief consideration of the large-scale kinematics of the MS as traced by the recently-discovered extension of the MS, we explore the aging process of the MS gas through the operation of various hydrodynamic instabilities and interstellar turbulence. This in turn leads to consideration of processes whereby MS material survives as cool gas, and yet also evidently fails to form stars. Parallels between the MS and extragalactic tidal features are brie'y discussed with an emphasis on steps toward establishing what the MS reveals about the critical role of local processes in determining the evolution of these kinds of systems.

  18. The Small-Scale Structure of the Magellanic Stream as a Foundation for Galaxy Evolution

    Directory of Open Access Journals (Sweden)

    Nigra, L.

    2010-06-01

    Full Text Available The Magellanic Stream (MS is the nearest example of agaseous trail formed by interacting galaxies. While the substantial gas masses in these kinds of circumgalactic structures are postulated to represent important sources of fuel for future star formation, the mechanisms whereby this material might be accreted back into galaxies remain unclear. Recent neutral hydrogen (HI observations have demonstrated that the northern portion of the MS, which probably has been interacting with the Milky Way's hot gaseous halo for close to 1000~Myr, has a larger spatial extent than previously recognized, while also containing significant amounts of small-scale structure. After a brief consideration of the large-scale kinematics of the MS as traced by the recently-discovered extension of the MS, we explore the aging process of the MS gas through the operation of various hydrodynamic instabilities and interstellar turbulence. This in turn leads to consideration of processes whereby MS material survives as cool gas, and yet also evidently fails to form stars.Parallels between the MS and extragalactic tidal features are briefly discussed with an emphasis on steps toward establishing what the MS reveals about the critical role of local processes in determining the evolution of these kinds of systems.

  19. ORIGIN OF THE GALAXY MASS-METALLICITY-STAR FORMATION RELATION

    International Nuclear Information System (INIS)

    Harwit, Martin; Brisbin, Drew

    2015-01-01

    We describe an equilibrium model that links the metallicity of low-redshift galaxies to stellar evolution models. It enables the testing of different stellar initial mass functions and metal yields against observed galaxy metallicities. We show that the metallicities of more than 80,000 Sloan Digital Sky Survey galaxies in the low-redshift range 0.07 ≤ z ≤ 0.3 considerably constrain stellar evolution models that simultaneously relate galaxy stellar mass, metallicity, and star formation rates to the infall rate of low-metallicity extragalactic gas and outflow of enriched matter. A feature of our model is that it encompasses both the active star forming phases of a galaxy and epochs during which the same galaxy may lie fallow. We show that the galaxy mass-metallicity-star formation relation can be traced to infall of extragalactic gas mixing with native gas from host galaxies to form stars of observed metallicities, the most massive of which eject oxygen into extragalactic space. Most consequential among our findings is that, on average, extragalactic infall accounts for one half of the gas required for star formation, a ratio that is remarkably constant across galaxies with stellar masses ranging at least from M* = 2 × 10 9 to 6 × 10 10 M ☉ . This leads us to propose that star formation is initiated when extragalactic infall roughly doubles the mass of marginally stable interstellar clouds. The processes described may also account quantitatively for the metallicity of extragalactic space, though to check this the fraction of extragalactic baryons will need to be more firmly established

  20. ORIGIN OF THE GALAXY MASS-METALLICITY-STAR FORMATION RELATION

    Energy Technology Data Exchange (ETDEWEB)

    Harwit, Martin; Brisbin, Drew, E-mail: harwit@verizon.net [Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853 (United States)

    2015-02-20

    We describe an equilibrium model that links the metallicity of low-redshift galaxies to stellar evolution models. It enables the testing of different stellar initial mass functions and metal yields against observed galaxy metallicities. We show that the metallicities of more than 80,000 Sloan Digital Sky Survey galaxies in the low-redshift range 0.07 ≤ z ≤ 0.3 considerably constrain stellar evolution models that simultaneously relate galaxy stellar mass, metallicity, and star formation rates to the infall rate of low-metallicity extragalactic gas and outflow of enriched matter. A feature of our model is that it encompasses both the active star forming phases of a galaxy and epochs during which the same galaxy may lie fallow. We show that the galaxy mass-metallicity-star formation relation can be traced to infall of extragalactic gas mixing with native gas from host galaxies to form stars of observed metallicities, the most massive of which eject oxygen into extragalactic space. Most consequential among our findings is that, on average, extragalactic infall accounts for one half of the gas required for star formation, a ratio that is remarkably constant across galaxies with stellar masses ranging at least from M* = 2 × 10{sup 9} to 6 × 10{sup 10} M {sub ☉}. This leads us to propose that star formation is initiated when extragalactic infall roughly doubles the mass of marginally stable interstellar clouds. The processes described may also account quantitatively for the metallicity of extragalactic space, though to check this the fraction of extragalactic baryons will need to be more firmly established.

  1. Star formation quenching in quasar host galaxies

    Science.gov (United States)

    Carniani, Stefano

    2017-10-01

    Galaxy evolution is likely to be shaped by negative feedback from active galactic nuclei (AGN). In the whole range of redshifts and luminosities studied so far, galaxies hosting an AGN frequently show fast and extended outflows consisting in both ionised and molecular gas. Such outflows could potentially quench the start formation within the host galaxy, but a clear evidence of negative feedback in action is still missing. Hereby I will analyse integral-field spectroscopic data for six quasars at z ˜2.4 obtained with SINFONI in the H- and K-band. All the quasars show [OIII]λ5007 line detection of fast, extended outflows. Also, the high signal-to-noise SINFONI observations allow the identification of faint narrow Hα emission (FWHM anti-correlated with star-formation powered emission, i.e. star formation is suppressed in the area affected by the outflow. Nonetheless as narrow, spatially-extended Hα emission, indicating star formation rates of at least 50 - 100 M⊙/yr, has been detected, either AGN feedback is not affecting the whole host galaxy, or star formation is completely quenched only by several feedback episodes. On the other hand, a positive feedback scenario, supported by narrow emission in Hα extending along the edges of the outflow cone, suggests that galaxy-wide outflows could also have a twofold role in the evolution of the host galaxy. Finally, I will present CO(3-2) ALMA data for three out of the six QSOs observed with SINFONI. Flux maps obtained for the CO(3-2) transition suggest that molecular gas within the host galaxy is swept away by fast winds. A negative-feedback scenario is supported by the inferred molecular gas mass in all three objects, which is significantly below what observed in non-active main-sequence galaxies at high-z.

  2. The Subaru FMOS galaxy redshift survey (FastSound). V. Intrinsic alignments of emission-line galaxies at z ˜ 1.4

    Science.gov (United States)

    Tonegawa, Motonari; Okumura, Teppei; Totani, Tomonori; Dalton, Gavin; Glazebrook, Karl; Yabe, Kiyoto

    2018-04-01

    Intrinsic alignments (IA), the coherent alignment of intrinsic galaxy orientations, can be a source of a systematic error of weak lensing surveys. The redshift evolution of IA also contains information about the physics of galaxy formation and evolution. This paper presents the first measurement of IA at high redshift, z ˜ 1.4, using the spectroscopic catalog of blue star-forming galaxies of the FastSound redshift survey, with the galaxy shape information from the Canada-Hawaii-France telescope lensing survey. The IA signal is consistent with zero with power-law amplitudes fitted to the projected correlation functions for density-shape and shape-shape correlation components, Aδ+ = -0.0071 ± 0.1340 and A++ = -0.0505 ± 0.0848, respectively. These results are consistent with those obtained from blue galaxies at lower redshifts (e.g., A _{δ +}=0.0035_{-0.0389}^{+0.0387} and A_{++}=0.0045_{-0.0168}^{+0.0166} at z = 0.51 from the WiggleZ survey). The upper limit of the constrained IA amplitude corresponds to a few percent contamination to the weak-lensing shear power spectrum, resulting in systematic uncertainties on the cosmological parameter estimations by -0.052 < Δσ8 < 0.039 and -0.039 < ΔΩm < 0.030.

  3. PRIMUS: CONSTRAINTS ON STAR FORMATION QUENCHING AND GALAXY MERGING, AND THE EVOLUTION OF THE STELLAR MASS FUNCTION FROM z = 0-1

    Energy Technology Data Exchange (ETDEWEB)

    Moustakas, John [Department of Physics and Astronomy, Siena College, 515 Loudon Road, Loudonville, NY 12211 (United States); Coil, Alison L.; Mendez, Alexander J. [Center for Astrophysics and Space Sciences, Department of Physics, University of California, 9500 Gilman Dr., La Jolla, CA 92093 (United States); Aird, James [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Blanton, Michael R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Cool, Richard J. [MMT Observatory, University of Arizona, 1540 E Second Street, Tucson, AZ 85721 (United States); Eisenstein, Daniel J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Wong, Kenneth C. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Zhu, Guangtun [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Arnouts, Stephane, E-mail: jmoustakas@siena.edu [Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743 (United States)

    2013-04-10

    We measure the evolution of the stellar mass function (SMF) from z = 0-1 using multi-wavelength imaging and spectroscopic redshifts from the PRism MUlti-object Survey (PRIMUS) and the Sloan Digital Sky Survey (SDSS). From PRIMUS we construct an i < 23 flux-limited sample of {approx}40, 000 galaxies at z = 0.2-1.0 over five fields totaling Almost-Equal-To 5.5 deg{sup 2}, and from the SDSS we select {approx}170, 000 galaxies at z = 0.01-0.2 that we analyze consistently with respect to PRIMUS to minimize systematic errors in our evolutionary measurements. We find that the SMF of all galaxies evolves relatively little since z = 1, although we do find evidence for mass assembly downsizing; we measure a Almost-Equal-To 30% increase in the number density of {approx}10{sup 10} M{sub sun} galaxies since z Almost-Equal-To 0.6, and a {approx}< 10% change in the number density of all {approx}> 10{sup 11} M{sub sun} galaxies since z Almost-Equal-To 1. Dividing the sample into star-forming and quiescent using an evolving cut in specific star formation rate, we find that the number density of {approx}10{sup 10} M{sub sun} star-forming galaxies stays relatively constant since z Almost-Equal-To 0.6, whereas the space density of {approx}> 10{sup 11} M{sub sun} star-forming galaxies decreases by Almost-Equal-To 50% between z Almost-Equal-To 1 and z Almost-Equal-To 0. Meanwhile, the number density of {approx}10{sup 10} M{sub sun} quiescent galaxies increases steeply toward low redshift, by a factor of {approx}2-3 since z Almost-Equal-To 0.6, while the number of massive quiescent galaxies remains approximately constant since z Almost-Equal-To 1. These results suggest that the rate at which star-forming galaxies are quenched increases with decreasing stellar mass, but that the bulk of the stellar mass buildup within the quiescent population occurs around {approx}10{sup 10.8} M{sub sun}. In addition, we conclude that mergers do not appear to be a dominant channel for the stellar mass

  4. Evolution of stellar systems

    International Nuclear Information System (INIS)

    Vader, P.

    1981-01-01

    The stellar systems of which the evolution will be considered in this thesis, are either galaxies, which contain about 10 11 stars, or binary systems, which consist of only two stars. It is seen that binary systems can give us some insight into the relative age of the nucleus of M31. The positive correlation between the metal content of a galaxy and its mass, first noted for elliptical galaxies, seems to be a general property of galaxies of all types. The observed increase of metallicity with galaxy mass is too large to be accounted for by differences in the evolutionary stage of galaxies. To explain the observed correlation it is proposed that a relatively larger proportion of massive stars is formed in more massive galaxies. The physical basis is that the formation of massive stars seems to be tied to the enhanced gas-dynamical activity in more massive galaxies. A specific aspect of the production of heavy elements by massive stars is investigated in some detail. In 1979 a cluster of 18 point X-ray sources within 400 pc of the centre of M31 was detected with the Einstein satellite. This is a remarkable result since no equivalent of this cluster has been observed in the nucleus of our own Galaxy, which otherwise is very similar to that of M31. An explanation for this phenomenon is proposed, suggesting that X-ray binaries are the products of the long-term evolution of nova systems. (Auth.)

  5. Recently Quenched Galaxies at z = 0.2–4.8 in the COSMOS UltraVISTA Field

    Energy Technology Data Exchange (ETDEWEB)

    Ichikawa, Akie; Matsuoka, Yoshiki, E-mail: ichikawa@cosmos.phys.sci.ehime-u.ac.jp [Research Center for Space and Cosmic Evolution, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577 (Japan)

    2017-07-01

    We present a new analysis of the stellar mass function and morphology of recently quenched galaxies (RQGs), whose star formation has been recently quenched for some reason. The COSMOS2015 catalog was exploited to select those galaxies at 0.2 < z < 4.8, over 1.5 deg{sup 2} of the Cosmic Evolution Survey (COSMOS) UltraVISTA field. This is the first time that RQGs are consistently selected and studied in such a wide range of redshift. We find increasing number density of RQGs with time in a broad mass range at z > 1, while low-mass RQGs start to grow very rapidly at z < 1. We also demonstrate that the migration of RQGs may largely drive the evolution of the stellar mass function of passive galaxies. Moreover, we find that the morphological type distribution of RQGs are intermediate between those of star-forming and passive galaxies. These results indicate that RQGs represent a major transitional phase of galaxy evolution, in which star-forming galaxies turn into passive galaxies, accompanied by the build up of spheroidal component.

  6. Galaxies in the X-ray Band

    Science.gov (United States)

    Hornschemeier, Ann

    2008-01-01

    This talk will provide a brief review of progress on X-ray emission from normal (non-AGN) galaxy populations, including important constraints on the evolution of accreting binary populations over important cosmological timescales. We will also look to the future, anticipating constraints from near-term imaging hard X-ray missions such as NuSTAR, Simbol-X and NeXT and then the longer-term prospects for studying galaxies with the Generation-X mission.

  7. DISCOVERY OF A PSEUDOBULGE GALAXY LAUNCHING POWERFUL RELATIVISTIC JETS

    Energy Technology Data Exchange (ETDEWEB)

    Kotilainen, Jari K.; Olguín-Iglesias, Alejandro [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, FI-21500 Piikkiö (Finland); León-Tavares, Jonathan; Baes, Maarten [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281-S9, B-9000 Gent (Belgium); Anórve, Christopher [Facultad de Ciencias de la Tierra y del Espacio de la Universidad Autónoma de Sinaloa, Blvd. de la Americas y Av. Universitarios S/N, Ciudad Universitaria, C.P. 80010, Culiacán Sinaloa, México (Mexico); Chavushyan, Vahram; Carrasco, Luis, E-mail: jarkot@utu.fi [Instituto Nacional de Astrofísica Óptica y Electrónica (INAOE), Apartado Postal 51 y 216, 72000 Puebla (Mexico)

    2016-12-01

    Supermassive black holes launching plasma jets at close to the speed of light, producing gamma-rays, have ubiquitously been found to be hosted by massive elliptical galaxies. Since elliptical galaxies are generally believed to be built through galaxy mergers, active galactic nuclei (AGN) launching relativistic jets are associated with the latest stages of galaxy evolution. We have discovered a pseudobulge morphology in the host galaxy of the gamma-ray AGN PKS 2004-447. This is the first gamma-ray emitter radio-loud AGN found to have been launched from a system where both the black hole and host galaxy have been actively growing via secular processes. This is evidence of an alternative black hole–galaxy co-evolutionary path to develop powerful relativistic jets, which is not merger driven.

  8. GALAXY EVOLUTION AT HIGH REDSHIFT: OBSCURED STAR FORMATION, GRB RATES, COSMIC REIONIZATION, AND MISSING SATELLITES

    Energy Technology Data Exchange (ETDEWEB)

    Lapi, A.; Mancuso, C.; Celotti, A.; Danese, L. [SISSA, Via Bonomea 265, I-34136 Trieste (Italy)

    2017-01-20

    We provide a holistic view of galaxy evolution at high redshifts z ≳ 4, which incorporates the constraints from various astrophysical/cosmological probes, including the estimate of the cosmic star formation rate (SFR) density from UV/IR surveys and long gamma-ray burst (GRBs) rates, the cosmic reionization history following the latest Planck measurements, and the missing satellites issue. We achieve this goal in a model-independent way by exploiting the SFR functions derived by Mancuso et al. on the basis of an educated extrapolation of the latest UV/far-IR data from HST / Herschel , and already tested against a number of independent observables. Our SFR functions integrated down to a UV magnitude limit M {sub UV} ≲ −13 (or SFR limit around 10{sup −2} M {sub ⊙} yr{sup −1}) produce a cosmic SFR density in excellent agreement with recent determinations from IR surveys and, taking into account a metallicity ceiling Z ≲ Z {sub ⊙}/2, with the estimates from long GRB rates. They also yield a cosmic reionization history consistent with that implied by the recent measurements of the Planck mission of the electron scattering optical depth τ {sub es} ≈ 0.058; remarkably, this result is obtained under a conceivable assumption regarding the average value f {sub esc} ≈ 0.1 of the escape fraction for ionizing photons. We demonstrate via the abundance-matching technique that the above constraints concurrently imply galaxy formation becoming inefficient within dark matter halos of mass below a few 10{sup 8} M {sub ⊙}; pleasingly, such a limit is also required so as not to run into the missing satellites issue. Finally, we predict a downturn of the Galaxy luminosity function faintward of M {sub UV} ≲ −12, and stress that its detailed shape, to be plausibly probed in the near future by the JWST , will be extremely informative on the astrophysics of galaxy formation in small halos, or even on the microscopic nature of the dark matter.

  9. A combined N-body and hydrodynamic code for modeling disk galaxies

    International Nuclear Information System (INIS)

    Schroeder, M.C.

    1989-01-01

    A combined N-body and hydrodynamic computer code for the modeling of two dimensional galaxies is described. The N-body portion of the code is used to calculate the motion of the particle component of a galaxy, while the hydrodynamics portion of the code is used to follow the motion and evolution of the fluid component. A complete description of the numerical methods used for each portion of the code is given. Additionally, the proof tests of the separate and combined portions of the code are presented and discussed. Finally, a discussion of the topics researched with the code and results obtained is presented. These include: the measurement of stellar relaxation times in disk galaxy simulations; the effects of two-armed spiral perturbations on stable axisymmetric disks; the effects of the inclusion of an instellar medium (ISM) on the stability of disk galaxies; and the effect of the inclusion of stellar evolution on disk galaxy simulations

  10. The Dependence of galaxy colors on luminosity and environment at z~0.4

    Energy Technology Data Exchange (ETDEWEB)

    Yee, H.K.C.; /Toronto U., Astron. Dept.; Hsieh, B.C.; /Taiwan, Natl. Central U. /Taipei, Inst. Astron. Astrophys.; Lin, Huan; /Fermilab; Gladders, M.D.; /Carnegie Inst.

    2005-08-01

    The authors analyze the B-R{sub c} colors of galaxies as functions of luminosity and local galaxy density using a large photometric redshift catalog based on the Red-Sequence Cluster Survey. They select two samples of galaxies with a magnitude limit of M{sub R{sub e}} < -18.5 and redshift ranges of 0.2 {le} z < 0.4 and 0.4 {le} x < 0.6 containing 10{sup 5} galaxies each. they model the color distributions of subsamples of galaxies and derive the red galaxy fraction and peak colors of red and blue galaxies as functions of galaxy luminosity and environment. The evolution of these relationships over the redshift range of x {approx} 0.5 to z {approx} 0.05 is analyzed in combination with published results from the Sloan Digital Sky Survey. They find that there is a strong evolution in the restframe peak color of bright blue galaxies in that they become redder with decreasing redshift, while the colors of faint blue galaxies remain approximately constant. This effect supports the ''downsizing'' scenario of star formation in galaxies. While the general dependence of the galaxy color distributions on the environment is small, they find that the change of red galaxy fraction with epoch is a function of the local galaxy density, suggesting that the downsizing effect may operate with different timescales in regions of different galaxy densities.

  11. Radio investigations of clusters of galaxies

    International Nuclear Information System (INIS)

    Valentijn, E.A.

    1978-01-01

    This thesis contains a number of papers of the series entitled, A Westerbork Survey of Rich Clusters of Galaxies. The primary aim was to study the radio characteristics of cluster galaxies and especially the question whether their ''radio-activity'' is influenced by their location inside a cluster. It is enquired whether the presence of an intra-cluster medium (ICM), or the typical cluster evolution or cluster dynamical processes can give rise to radio-observable effects on the behaviour of cluster galaxies. 610 MHz WSRT observations of the Coma cluster (and radio observations of the Hercules supercluster) are presented. Extended radio sources in Abell clusters are then described. (Auth.)

  12. The evolution of the dust temperatures of galaxies in the SFR-M∗ plane up to z ∼ 2

    Science.gov (United States)

    Magnelli, B.; Lutz, D.; Saintonge, A.; Berta, S.; Santini, P.; Symeonidis, M.; Altieri, B.; Andreani, P.; Aussel, H.; Béthermin, M.; Bock, J.; Bongiovanni, A.; Cepa, J.; Cimatti, A.; Conley, A.; Daddi, E.; Elbaz, D.; Förster Schreiber, N. M.; Genzel, R.; Ivison, R. J.; Le Floc'h, E.; Magdis, G.; Maiolino, R.; Nordon, R.; Oliver, S. J.; Page, M.; Pérez García, A.; Poglitsch, A.; Popesso, P.; Pozzi, F.; Riguccini, L.; Rodighiero, G.; Rosario, D.; Roseboom, I.; Sanchez-Portal, M.; Scott, D.; Sturm, E.; Tacconi, L. J.; Valtchanov, I.; Wang, L.; Wuyts, S.

    2014-01-01

    We study the evolution of the dust temperature of galaxies in the SFR- M∗ plane up to z ~ 2 using far-infrared and submillimetre observations from the Herschel Space Observatory taken as part of the PACS Evolutionary Probe (PEP) and Herschel Multi-tiered Extragalactic Survey (HerMES) guaranteed time key programmes. Starting from a sample of galaxies with reliable star-formation rates (SFRs), stellar masses (M∗) and redshift estimates, we grid the SFR- M∗parameter space in several redshift ranges and estimate the mean dust temperature (Tdust) of each SFR-M∗ - z bin. Dust temperatures are inferred using the stacked far-infrared flux densities (100-500 μm) of our SFR-M∗ - z bins. At all redshifts, the dust temperature of galaxies smoothly increases with rest-frame infrared luminosities (LIR), specific SFRs (SSFR; i.e., SFR/M∗), and distances with respect to the main sequence (MS) of the SFR- M∗ plane (i.e., Δlog (SSFR)MS = log [SSFR(galaxy)/SSFRMS(M∗,z)]). The Tdust - SSFR and Tdust - Δlog (SSFR)MS correlations are statistically much more significant than the Tdust - LIR one. While the slopes of these three correlations are redshift-independent, their normalisations evolve smoothly from z = 0 and z ~ 2. We convert these results into a recipe to derive Tdust from SFR, M∗ and z, valid out to z ~ 2 and for the stellar mass and SFR range covered by our stacking analysis. The existence of a strong Tdust - Δlog (SSFR)MS correlation provides us with several pieces of information on the dust and gas content of galaxies. Firstly, the slope of the Tdust - Δlog (SSFR)MS correlation can be explained by the increase in the star-formation efficiency (SFE; SFR/Mgas) with Δlog (SSFR)MS as found locally by molecular gas studies. Secondly, at fixed Δlog (SSFR)MS, the constant dust temperature observed in galaxies probing wide ranges in SFR and M∗ can be explained by an increase or decrease in the number of star-forming regions with comparable SFE enclosed in

  13. The Stormy Life of Galaxy Clusters

    Science.gov (United States)

    Rudnick, Lawrence

    2018-01-01

    Galaxy clusters, the largest gravitationally bound structures, hold the full history of their baryonic evolution, serve as important cosmological tools and allow us to probe unique physical regimes in their diffuse plasmas. With characteristic dynamical timescales of 107-109 years, these diffuse thermal and relativistic media continue to evolve, as dark matter drives major mergers and more gentle continuing accretion. The history of this assembly is encoded in the plasmas, and a wide range of observational and theoretical investigations are aimed at decoding their signatures. X-ray temperature and density variations, low Mach number shocks, and "cold front" discontinuities all illuminate clusters' continued evolution. Radio structures and spectra are passive indicators of merger shocks, while radio galaxy distortions reveal the complex motions in the intracluster medium. Deep in cluster cores, AGNs associated with brightest cluster galaxies provide ongoing energy, and perhaps even stabilize the intracluster medium. In this talk, we will recount this evolving picture of the stormy ICM, and suggest areas of likely advance in the coming years.

  14. Pulsating red giants and supergiants as probes of galaxy formation and evolution

    Science.gov (United States)

    Theodorus van Loon, Jacco; Javadi, Atefeh; Khosroshahi, Habib; Rezaei, Sara; Golshan, Roya; Saberi, Maryam

    2015-08-01

    We have developed new techniques to use pulsating red giant and supergiants stars to reconstruct the star formation history of galaxies over cosmological time, as well as using them to map the dust production across their host galaxies. We describe the large programme on the Local Group spiral galaxy Triangulum (M33), which we have monitored at near-infrared wavelengths for several years using the United Kingdom InfraRed Telescope in Hawai'i. We outline the methodology and present the results for the central square kiloparsec (Javadi et al. 2011a,b, 2013) and - fresh from the press - the disc of M33 (Javadi et al. 2015, and in preparation). We also describe the results from our application of this new technique to other nearby galaxies: the Magellanic Clouds (published in Rezaei et al. 2014), the dwarf galaxies NGC 147 and 185 (Golshan et al. in preparation), and Centaurus A.

  15. ON THE ANTICORRELATION BETWEEN GALAXY LIGHT CONCENTRATION AND X-RAY-TO-OPTICAL FLUX RATIO

    International Nuclear Information System (INIS)

    Povic, M.; Perez Garcia, A. M.; Bongiovanni, A.; Fernandez Lorenzo, M.; Lara-Lopez, M. A.; Sanchez-Portal, M.; Cepa, J.; Gonzalez-Serrano, J. I.; Alfaro, E. J.

    2009-01-01

    Active galactic nuclei (AGNs) play an important role in many aspects of modern cosmology, and of particular interest is the issue of the interplay between AGNs and their host galaxy. Using X-ray and optical data sets, we have explored the properties of a large sample of AGNs in the Subaru/XMM-Newton Deep Survey field, and studied their evolution in relation with the evolution of their host galaxy. We present here an anticorrelation between X-ray-to-optical flux (X/O) ratio and galaxy light concentration (C), which has been found for the first time and might suggest that early-type galaxies, having poor matter supply to feed the AGN activity, have lower Eddington rates than those of late-type galaxies.

  16. Clustering of galaxies around AGNs in the HSC Wide survey

    Science.gov (United States)

    Shirasaki, Yuji; Akiyama, Masayuki; Nagao, Tohru; Toba, Yoshiki; He, Wanqiu; Ohishi, Masatoshi; Mizumoto, Yoshihiko; Miyazaki, Satoshi; Nishizawa, Atsushi J.; Usuda, Tomonori

    2018-01-01

    We have measured the clustering of galaxies around active galactic nuclei (AGNs) for which single-epoch virial masses of the super-massive black hole (SMBH) are available to investigate the relation between the large-scale environment of AGNs and the evolution of SMBHs. The AGN samples used in this work were derived from the Sloan Digital Sky Survey (SDSS) observations and the galaxy samples were from the 240 deg2 S15b data of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). The investigated redshift range is 0.6-3.0, and the masses of the SMBHs lie in the range 107.5-1010 M⊙. The absolute magnitude of the galaxy samples reaches to Mλ310 ˜ -18 at rest-frame wavelength 310 nm for the low-redshift end of the samples. More than 70% of the galaxies in the analysis are blue. We found a significant dependence of the cross-correlation length on redshift, which primarily reflects the brightness-dependence of the galaxy clustering. At the lowest redshifts the cross-correlation length increases from 7 h-1 Mpc around Mλ310 = -19 mag to >10 h-1 Mpc beyond Mλ310 = -20 mag. No significant dependence of the cross-correlation length on BH mass was found for whole galaxy samples dominated by blue galaxies, while there was an indication of BH mass dependence in the cross-correlation with red galaxies. These results provides a picture of the environment of AGNs studied in this paper being enriched with blue star-forming galaxies, and a fraction of the galaxies are evolving into red galaxies along with the evolution of SMBHs in that system.

  17. NEW CONSTRAINTS ON THE EVOLUTION OF THE STELLAR-TO-DARK MATTER CONNECTION: A COMBINED ANALYSIS OF GALAXY-GALAXY LENSING, CLUSTERING, AND STELLAR MASS FUNCTIONS FROM z = 0.2 to z = 1

    Energy Technology Data Exchange (ETDEWEB)

    Leauthaud, Alexie [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Chiba 277-8582 (Japan); Tinker, Jeremy [Center for Cosmology and Particle Physics, Department of Physics, New York University, NY (United States); Bundy, Kevin; George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Behroozi, Peter S.; Wechsler, Risa H.; Busha, Michael T.; Schrabback, Tim [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, Stanford University, and SLAC National Accelerator Laboratory, Stanford, CA 94305 (United States); Massey, Richard [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Rhodes, Jason; Benson, Andrew [California Institute of Technology, MC 350-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kneib, Jean-Paul; Ilbert, Olivier; Le Fevre, Oliver [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, 13013 Marseille (France); Capak, Peter [Spitzer Science Center, 314-6 Caltech, 1201 E. California Blvd. Pasadena, CA 91125 (United States); Cortes, Marina [Lawrence Berkeley National Lab, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Lilly, Simon [Institute of Astronomy, Department of Physics, ETH Zurich, CH-8093 (Switzerland); McCracken, Henry J. [Institut d' Astrophysique de Paris, UMR 7095, 98 bis Boulevard Arago, 75014 Paris (France); Salvato, Mara, E-mail: asleauthaud@lbl.gov [SUPA, Institute for Astronomy, The University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom); and others

    2012-01-10

    Using data from the COSMOS survey, we perform the first joint analysis of galaxy-galaxy weak lensing, galaxy spatial clustering, and galaxy number densities. Carefully accounting for sample variance and for scatter between stellar and halo mass, we model all three observables simultaneously using a novel and self-consistent theoretical framework. Our results provide strong constraints on the shape and redshift evolution of the stellar-to-halo mass relation (SHMR) from z = 0.2 to z = 1. At low stellar mass, we find that halo mass scales as M{sub h} {proportional_to}M{sup 0.46}{sub *} and that this scaling does not evolve significantly with redshift from z = 0.2 to z = 1. The slope of the SHMR rises sharply at M{sub *} > 5 Multiplication-Sign 10{sup 10} M{sub Sun} and as a consequence, the stellar mass of a central galaxy becomes a poor tracer of its parent halo mass. We show that the dark-to-stellar ratio, M{sub h} /M{sub *}, varies from low to high masses, reaching a minimum of M{sub h} /M{sub *} {approx} 27 at M{sub *} = 4.5 Multiplication-Sign 10{sup 10} M{sub Sun} and M{sub h} = 1.2 Multiplication-Sign 10{sup 12} M{sub Sun }. This minimum is important for models of galaxy formation because it marks the mass at which the accumulated stellar growth of the central galaxy has been the most efficient. We describe the SHMR at this minimum in terms of the 'pivot stellar mass', M{sup piv}{sub *}, the 'pivot halo mass', M{sup piv}{sub h}, and the 'pivot ratio', (M{sub h} /M{sub *}){sup piv}. Thanks to a homogeneous analysis of a single data set spanning a large redshift range, we report the first detection of mass downsizing trends for both M{sup piv}{sub h} and M{sup piv}{sub *}. The pivot stellar mass decreases from M{sup piv}{sub *} = 5.75 {+-} 0.13 Multiplication-Sign 10{sup 10} M{sub Sun} at z = 0.88 to M{sup piv}{sub *} = 3.55 {+-} 0.17 Multiplication-Sign 10{sup 10} M{sub Sun} at z = 0.37. Intriguingly, however, the corresponding

  18. ON THE DEARTH OF COMPACT, MASSIVE, RED SEQUENCE GALAXIES IN THE LOCAL UNIVERSE

    International Nuclear Information System (INIS)

    Taylor, Edward N.; Franx, Marijn; Brinchmann, Jarle; Glazebrook, Karl; Van der Wel, Arjen; Van Dokkum, Pieter G

    2010-01-01

    We set out to test the claim that the recently identified population of compact, massive, and quiescent galaxies at z ∼ 2.3 must undergo significant size evolution to match the properties of galaxies found in the local universe. Using data from the Sloan Digital Sky Survey (SDSS; Data Release 7), we have conducted a search for local red sequence galaxies with sizes and masses comparable to those found at z ∼ 2.3. The SDSS spectroscopic target selection algorithm excludes high surface brightness objects; we show that this makes incompleteness a concern for such massive, compact galaxies, particularly for low redshifts (z ∼ * >10 10.7 M sun (∼5 x 10 10 M sun ) red sequence galaxies at 0.066 spec 5000. This result cannot be explained by incompleteness: in the 0.066 75% complete for galaxies with the sizes and masses seen at high redshift, although for the very smallest galaxies it may be as low as ∼20%. In order to confirm that the absence of such compact massive galaxies in SDSS is not produced by spectroscopic selection effects, we have also looked for such galaxies in the basic SDSS photometric catalog, using photometric redshifts. While we do find signs of a slight bias against massive, compact galaxies, this analysis suggests that the SDSS spectroscopic sample is missing at most a few objects in the regime we consider. Accepting the high-redshift results, it is clear that massive galaxies must undergo significant structural evolution over z ∼< 2 in order to match the population seen in the local universe. Our results suggest that a highly stochastic mechanism (e.g., major mergers) cannot be the primary driver of this strong size evolution.

  19. Galaxy evolution in the cluster Abell 85: new insights from the dwarf population

    Science.gov (United States)

    Habas, Rebecca; Fadda, Dario; Marleau, Francine R.; Biviano, Andrea; Durret, Florence

    2018-04-01

    We present the first results of a new spectroscopic survey of the cluster Abell 85 targeting 1466 candidate cluster members within the central ˜1 deg2 of the cluster and having magnitudes mr behaviour based on their mass. At the low-mass end, the galaxies have had their star formation recently quenched, while more massive galaxies show no significant change. The time-scales probed here favour fast quenching mechanisms, such as ram-pressure stripping. Galaxies within the green valley, defined similarly, do not show evidence of quenching. Instead, the low-mass galaxies maintain their levels of star-forming activity, while the more massive galaxies have experienced a recent burst.

  20. THE FUNDAMENTAL PLANE OF MASSIVE QUIESCENT GALAXIES OUT TO z ∼ 2

    Energy Technology Data Exchange (ETDEWEB)

    Van de Sande, Jesse; Franx, Marijn [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Kriek, Mariska [Astronomy Department, University of California at Berkeley, Berkeley, CA 94720 (United States); Bezanson, Rachel [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Van Dokkum, Pieter G. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)

    2014-10-01

    The Fundamental Plane (FP) of early-type galaxies, relating the effective radius, velocity dispersion, and surface brightness, has long been recognized as a unique tool for analyzing galaxy structure and evolution. With the discovery of distant quiescent galaxies and the introduction of high sensitivity near-infrared spectrographs, it is now possible to explore the FP out to z ∼ 2. In this Letter we study the evolution of the FP out to z ∼ 2 using kinematic measurements of massive quiescent galaxies (M {sub *} > 10{sup 11} M {sub ☉}). We find preliminary evidence for the existence of an FP out to z ∼ 2. The scatter of the FP, however, increases from z ∼ 0 to z ∼ 2, even when taking into account the larger measurement uncertainties at higher redshifts. We find a strong evolution of the zero point from z ∼ 2 to z ∼ 0: Δlog{sub 10} M/L{sub g} ∝(– 0.49 ± 0.03)z. In order to assess whether our spectroscopic sample is representative of the early-type galaxy population at all redshifts, we compare their rest-frame g – z colors with those from a larger mass complete sample of quiescent galaxies. At z > 1 we find that the spectroscopic sample is bluer. We use the color offsets to estimate a mass-to-light ratio (M/L) correction. The implied FP zero point evolution after correction is significantly smaller: Δlog{sub 10} M/L{sub g} ∝(– 0.39 ± 0.02)z. This is consistent with an apparent formation redshift of z{sub form}=6.62{sub −1.44}{sup +3.19} for the underlying population, ignoring the effects of progenitor bias. A more complete spectroscopic sample is required at z ∼ 2 to properly measure the M/L evolution from the FP evolution.

  1. Star Formation Quenching in Quasar Host Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Carniani, Stefano, E-mail: sc888@mrao.cam.ac.uk [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Kavli Institute for Cosmology, University of Cambridge, Cambridge (United Kingdom)

    2017-10-16

    Galaxy evolution is likely to be shaped by negative feedback from active galactic nuclei (AGN). In the whole range of redshifts and luminosities studied so far, galaxies hosting an AGN frequently show fast and extended outflows consisting in both ionized and molecular gas. Such outflows could potentially quench the start formation within the host galaxy, but a clear evidence of negative feedback in action is still missing. Hereby I will analyse integral-field spectroscopic data for six quasars at z ~ 2.4 obtained with SINFONI in the H- and K-band. All the quasars show [Oiii]λ5007 line detection of fast, extended outflows. Also, the high signal-to-noise SINFONI observations allow the identification of faint narrow Hα emission (FWHM < 500 km/s), which is spatially extended and associated with star formation in the host galaxy. On paper fast outflows are spatially anti-correlated with star-formation powered emission, i.e., star formation is suppressed in the area affected by the outflow. Nonetheless as narrow, spatially-extended Hα emission, indicating star formation rates of at least 50–100 M{sub ⊙} yr{sup −1}, has been detected, either AGN feedback is not affecting the whole host galaxy, or star formation is completely quenched only by several feedback episodes. On the other hand, a positive feedback scenario, supported by narrow emission in Hα extending along the edges of the outflow cone, suggests that galaxy-wide outflows could also have a twofold role in the evolution of the host galaxy. Finally, I will present CO(3-2) ALMA data for three out of the six QSOs observed with SINFONI. Flux maps obtained for the CO(3-2) transition suggest that molecular gas within the host galaxy is swept away by fast winds. A negative-feedback scenario is supported by the inferred molecular gas mass in all three objects, which is significantly below what observed in non-active main-sequence galaxies at high-z.

  2. Star Formation Quenching in Quasar Host Galaxies

    International Nuclear Information System (INIS)

    Carniani, Stefano

    2017-01-01

    Galaxy evolution is likely to be shaped by negative feedback from active galactic nuclei (AGN). In the whole range of redshifts and luminosities studied so far, galaxies hosting an AGN frequently show fast and extended outflows consisting in both ionized and molecular gas. Such outflows could potentially quench the start formation within the host galaxy, but a clear evidence of negative feedback in action is still missing. Hereby I will analyse integral-field spectroscopic data for six quasars at z ~ 2.4 obtained with SINFONI in the H- and K-band. All the quasars show [Oiii]λ5007 line detection of fast, extended outflows. Also, the high signal-to-noise SINFONI observations allow the identification of faint narrow Hα emission (FWHM < 500 km/s), which is spatially extended and associated with star formation in the host galaxy. On paper fast outflows are spatially anti-correlated with star-formation powered emission, i.e., star formation is suppressed in the area affected by the outflow. Nonetheless as narrow, spatially-extended Hα emission, indicating star formation rates of at least 50–100 M ⊙ yr −1 , has been detected, either AGN feedback is not affecting the whole host galaxy, or star formation is completely quenched only by several feedback episodes. On the other hand, a positive feedback scenario, supported by narrow emission in Hα extending along the edges of the outflow cone, suggests that galaxy-wide outflows could also have a twofold role in the evolution of the host galaxy. Finally, I will present CO(3-2) ALMA data for three out of the six QSOs observed with SINFONI. Flux maps obtained for the CO(3-2) transition suggest that molecular gas within the host galaxy is swept away by fast winds. A negative-feedback scenario is supported by the inferred molecular gas mass in all three objects, which is significantly below what observed in non-active main-sequence galaxies at high-z.

  3. Star Formation Quenching in Quasar Host Galaxies

    Directory of Open Access Journals (Sweden)

    Stefano Carniani

    2017-10-01

    Full Text Available Galaxy evolution is likely to be shaped by negative feedback from active galactic nuclei (AGN. In the whole range of redshifts and luminosities studied so far, galaxies hosting an AGN frequently show fast and extended outflows consisting in both ionized and molecular gas. Such outflows could potentially quench the start formation within the host galaxy, but a clear evidence of negative feedback in action is still missing. Hereby I will analyse integral-field spectroscopic data for six quasars at z ~ 2.4 obtained with SINFONI in the H- and K-band. All the quasars show [Oiii]λ5007 line detection of fast, extended outflows. Also, the high signal-to-noise SINFONI observations allow the identification of faint narrow Hα emission (FWHM < 500 km/s, which is spatially extended and associated with star formation in the host galaxy. On paper fast outflows are spatially anti-correlated with star-formation powered emission, i.e., star formation is suppressed in the area affected by the outflow. Nonetheless as narrow, spatially-extended Hα emission, indicating star formation rates of at least 50–100 M⊙ yr−1, has been detected, either AGN feedback is not affecting the whole host galaxy, or star formation is completely quenched only by several feedback episodes. On the other hand, a positive feedback scenario, supported by narrow emission in Hα extending along the edges of the outflow cone, suggests that galaxy-wide outflows could also have a twofold role in the evolution of the host galaxy. Finally, I will present CO(3-2 ALMA data for three out of the six QSOs observed with SINFONI. Flux maps obtained for the CO(3-2 transition suggest that molecular gas within the host galaxy is swept away by fast winds. A negative-feedback scenario is supported by the inferred molecular gas mass in all three objects, which is significantly below what observed in non-active main-sequence galaxies at high-z.

  4. Halo models of HI selected galaxies

    Science.gov (United States)

    Paul, Niladri; Choudhury, Tirthankar Roy; Paranjape, Aseem

    2018-06-01

    Modelling the distribution of neutral hydrogen (HI) in dark matter halos is important for studying galaxy evolution in the cosmological context. We use a novel approach to infer the HI-dark matter connection at the massive end (m_H{I} > 10^{9.8} M_{⊙}) from radio HI emission surveys, using optical properties of low-redshift galaxies as an intermediary. In particular, we use a previously calibrated optical HOD describing the luminosity- and colour-dependent clustering of SDSS galaxies and describe the HI content using a statistical scaling relation between the optical properties and HI mass. This allows us to compute the abundance and clustering properties of HI-selected galaxies and compare with data from the ALFALFA survey. We apply an MCMC-based statistical analysis to constrain the free parameters related to the scaling relation. The resulting best-fit scaling relation identifies massive HI galaxies primarily with optically faint blue centrals, consistent with expectations from galaxy formation models. We compare the Hi-stellar mass relation predicted by our model with independent observations from matched Hi-optical galaxy samples, finding reasonable agreement. As a further application, we make some preliminary forecasts for future observations of HI and optical galaxies in the expected overlap volume of SKA and Euclid/LSST.

  5. THE ACS NEARBY GALAXY SURVEY TREASURY. IX. CONSTRAINING ASYMPTOTIC GIANT BRANCH EVOLUTION WITH OLD METAL-POOR GALAXIES

    International Nuclear Information System (INIS)

    Girardi, Leo; Williams, Benjamin F.; Gilbert, Karoline M.; Rosenfield, Philip; Dalcanton, Julianne J.; Marigo, Paola; Boyer, Martha L.; Dolphin, Andrew; Weisz, Daniel R.; Skillman, Evan; Melbourne, Jason; Olsen, Knut A. G.; Seth, Anil C.

    2010-01-01

    In an attempt to constrain evolutionary models of the asymptotic giant branch (AGB) phase at the limit of low masses and low metallicities, we have examined the luminosity functions and number ratios between AGB and red giant branch (RGB) stars from a sample of resolved galaxies from the ACS Nearby Galaxy Survey Treasury. This database provides Hubble Space Telescope optical photometry together with maps of completeness, photometric errors, and star formation histories for dozens of galaxies within 4 Mpc. We select 12 galaxies characterized by predominantly metal-poor populations as indicated by a very steep and blue RGB, and which do not present any indication of recent star formation in their color-magnitude diagrams. Thousands of AGB stars brighter than the tip of the RGB (TRGB) are present in the sample (between 60 and 400 per galaxy), hence, the Poisson noise has little impact in our measurements of the AGB/RGB ratio. We model the photometric data with a few sets of thermally pulsing AGB (TP-AGB) evolutionary models with different prescriptions for the mass loss. This technique allows us to set stringent constraints on the TP-AGB models of low-mass, metal-poor stars (with M sun , [Fe/H]∼ sun . This is also in good agreement with recent observations of white dwarf masses in the M4 old globular cluster. These constraints can be added to those already derived from Magellanic Cloud star clusters as important mileposts in the arduous process of calibrating AGB evolutionary models.

  6. MOIRCS DEEP SURVEY. V. A UNIVERSAL RELATION FOR STELLAR MASS AND SURFACE BRIGHTNESS OF GALAXIES

    International Nuclear Information System (INIS)

    Ichikawa, Takashi; Kajisawa, Masaru; Yamada, Toru; Akiyama, Masayuki; Yoshikawa, Tomohiro; Onodera, Masato; Konishi, Masahiro

    2010-01-01

    We present a universal linear correlation between the stellar mass and surface brightness (SB) of galaxies at 0.3 -2.0∼-0.8 , in addition to dimming as (1 + z) 4 by the cosmological expansion effect. The brightening depends on galaxy color and stellar mass. The blue population (rest-frame U - V -0.8±0.3 in the rest-V band. On the other hand, the red population (U - V>0) and the massive galaxies (M * >10 10 M sun ) show stronger brightening, (1 + z) -1.5±0.1 . By comparison with galaxy evolution models, the phenomena are well understood by the pure luminosity evolution of galaxies out to z ∼ 3.

  7. PEARS Emission Line Galaxies

    Science.gov (United States)

    Pirzkal, Nor; Rothberg, Barry; Ly, Chun; Rhoads, James E.; Malhotra, Sangeeta; Grogin, Norman A.; Dahlen, Tomas; Meurer, Gerhardt R.; Walsh, Jeremy; Hathi, Nimish P.; hide

    2012-01-01

    We present a full analysis of the Probing Evolution And Reionization Spectroscopically (PEARS) slitless grism spectroscopic data obtained vl'ith the Advanced Camera for Surveys on HST. PEARS covers fields within both the Great Observatories Origins Deep Survey (GOODS) North and South fields, making it ideal as a random surveY of galaxies, as well as the availability of a wide variety of ancillary observations to support the spectroscopic results. Using the PEARS data we are able to identify star forming galaxies within the redshift volume 0 galaxies down to a limiting flux of approx 10 - 18 erg/s/sq cm . The ELRs have also been compared to the properties of the host galaxy, including morphology, luminosity, and mass. From this analysis we find three key results: 1) The computed line luminosities show evidence of a flattening in the luminosity function with increasing redshift; 2) The star forming systems show evidence of disturbed morphologies, with star formation occurring predominantly within one effective (half-light) radius. However, the morphologies show no correlation with host stellar mass; and 3) The number density of star forming galaxies with M(*) >= 10(exp 9) Solar M decreases by an order of magnitude at z<=0.5 relative to the number at 0.5 < z < 0.9 in support of the argument for galaxy downsizing.

  8. Correlations among Galaxy Properties from the Sloan Digital Sky Survey

    Science.gov (United States)

    Li, Zhongmu; Mao, Caiyan

    2013-07-01

    Galaxies are complex systems with many properties. Correlations among galaxy properties can supply important clues for studying the formation and evolution of galaxies. Using principal component analysis and least-squares fitting, this paper investigates the correlations among galactic parameters involving more properties (color, morphology, stellar population, and absolute magnitude) than previous studies. We use a volume-limited sample (whole sample) of 75,423 galaxies that was selected from the Sloan Digital Sky Survey Data Release 2 and divided into two subsamples (blue and red samples) using a critical color of (g - r) = 0.70 mag. In addition to recovering some previous results, we also obtain some new results. First, all separators for dividing galaxies into two groups can be related via good parameter-first principal component (PC1) correlations. A critical PC1 that indicates whether or not stellar age (or the evolution of a stellar population over time) is important can be used to separate galaxies. This suggests that a statistical parameter, PC1, is helpful in understanding the physical separators of galaxies. In addition, stellar age is shown to be unimportant for red galaxies, while both stellar age and mass are dominating parameters of blue galaxies. This suggests that the various numbers of dominating parameters of galaxies may result from the use of different samples. Finally, some parameters are shown to be correlated, and quantitative fits for a few correlations are obtained, e.g., log(t) = 8.57 + 1.65 (g - r) for the age (log t) and color (g - r) of blue galaxies and log (M *) = 4.31 - 0.30 M r for the stellar mass (log M *) and absolute magnitude (M r) of red galaxies. The median relationships between various parameter pairs are also presented for comparison.

  9. Galaxies in the Universe - 2nd Edition

    Science.gov (United States)

    Sparke, Linda S.; Gallagher, John S., III

    2006-04-01

    This extensively illustrated book presents the astrophysics of galaxies since their beginnings in the early Universe. It has been thoroughly revised to take into account the most recent observational data, and recent discoveries such as dark energy. There are new sections on galaxy clusters, gamma ray bursts and supermassive black holes. The authors explore the basic properties of stars and the Milky Way before working out towards nearby galaxies and the distant Universe. They discuss the structures of galaxies and how galaxies have developed, and relate this to the evolution of the Universe. The book also examines ways of observing galaxies across the whole electromagnetic spectrum, and explores dark matter and its gravitational pull on matter and light. This book is self-contained and includes several homework problems with hints. It is ideal for advanced undergraduate students in astronomy and astrophysics. • Completely updated to take into account the latest observational data and theoretical concepts • Throughly revised with new sections on dark energy, gamma ray bursts, and central black holes in galaxies • Contains problems with hints to the solutions

  10. What Turns Galaxies Off? the Different Morphologies of Star-Forming and Quiescent Galaxies Since z Approximates 2 from CANDELS

    Science.gov (United States)

    Bell, Eric F.; VanDerWel, Arjen; Papovich, Casey; Kocevski, Dale; Lotz, Jennifer; McIntosh, Daniel H.; Kartaltepe, Jeyhan; Faber, S. M.; Ferguson, Harry; Koekemoer, Anton; hide

    2011-01-01

    We use HST/WFC3 imaging from the CANDELS multicyc1e treasury survey, in conjunction with the Sloan Digital Sky Survey, to explore the evolution of galactic structure for galaxies with stellar masses > 3 x 10(exp 10) Solar Mass from Z= 2.2 to the present epoch, a time span of 10 Gyr. We explore the relationship between rest-frame optical color, stellar mass, star formation activity and the structural parameters of galaxies as determined from parametric fits to the surface brightness profiles of galaxies. We confirm the dramatic evolution from z= 2.2 to the present day in the number density of non-star-forming galaxies above 3 x 10(exp 10) Solar Mass reported by other authors. We find that the vast majority of these quiescent systems have concentrated light profiles, as parameterized by the Sersic index, and the population of concentrated galaxies grows similarly rapidly. We examine the joint distribution of star formation activity, Sersic index, stellar mass, mass divided by radius (a proxy for velocity dispersion), and stellar surface density. Quiescence correlates poorly with stellar mass at all z < 2.2 (given the approx < 0.2 dex scatter between halo mass and stellar mass at z approximates 0 inferred by More et al, this argues against halo mass being the only factor determining quiescence). Quiescence correlates better with Sersic index, 'velocity dispersion' and stellar surface density, where Sersic index correlates the best (increasingly so at lower redshift). Yet, there is significant scatter between quiescence and galaxy structure: while the vast majority of quiescent galaxies have prominent bulges, many of them have significant disks, and a number of bulge-dominated galaxies have significant star formation. Noting the rarity of quiescent galaxies without prominent bulges, we argue that a prominent bulge (and, perhaps by association, a supermassive black hole) is a necessary but not sufficient condition for quenching star formation on galactic scales over the

  11. Discovery of a New Fundamental Plane Dictating Galaxy Cluster Evolution from Gravitational Lensing

    Science.gov (United States)

    Fujita, Yutaka; Umetsu, Keiichi; Rasia, Elena; Meneghetti, Massimo; Donahue, Megan; Medezinski, Elinor; Okabe, Nobuhiro; Postman, Marc

    2018-04-01

    In cold dark-matter (CDM) cosmology, objects in the universe have grown under the effect of gravity of dark matter. The intracluster gas in a galaxy cluster was heated when the dark-matter halo formed through gravitational collapse. The potential energy of the gas was converted to thermal energy through this process. However, this process and the thermodynamic history of the gas have not been clearly characterized in connection with the formation and evolution of the internal structure of dark-matter halos. Here, we show that observational CLASH data of high-mass galaxy clusters lie on a plane in the three-dimensional logarithmic space of their characteristic radius r s , mass M s , and X-ray temperature T X with a very small orthogonal scatter. The tight correlation indicates that the gas temperature was determined at a specific cluster formation time, which is encoded in r s and M s . The plane is tilted with respect to T X ∝ M s /r s , which is the plane expected in the case of simplified virial equilibrium. We show that this tilt can be explained by a similarity solution, which indicates that clusters are not isolated but continuously growing through matter accretion from their outer environments. Numerical simulations reproduce the observed plane and its angle. This result holds independently of the gas physics implemented in the code, revealing the fundamental origin of this plane.

  12. Lopsided spiral galaxies

    International Nuclear Information System (INIS)

    Jog, Chanda J.; Combes, Francoise

    2009-01-01

    The light distribution in the disks of many galaxies is 'lopsided' with a spatial extent much larger along one half of a galaxy than the other, as seen in M101. Recent observations show that the stellar disk in a typical spiral galaxy is significantly lopsided, indicating asymmetry in the disk mass distribution. The mean amplitude of lopsidedness is 0.1, measured as the Fourier amplitude of the m=1 component normalized to the average value. Thus, lopsidedness is common, and hence it is important to understand its origin and dynamics. This is a new and exciting area in galactic structure and dynamics, in contrast to the topic of bars and two-armed spirals (m=2) which has been extensively studied in the literature. Lopsidedness is ubiquitous and occurs in a variety of settings and tracers. It is seen in both stars and gas, in the outer disk and the central region, in the field and the group galaxies. The lopsided amplitude is higher by a factor of two for galaxies in a group. The lopsidedness has a strong impact on the dynamics of the galaxy, its evolution, the star formation in it, and on the growth of the central black hole and on the nuclear fuelling. We present here an overview of the observations that measure the lopsided distribution, as well as the theoretical progress made so far to understand its origin and properties. The physical mechanisms studied for its origin include tidal encounters, gas accretion and a global gravitational instability. The related open, challenging problems in this emerging area are discussed

  13. THE KMOS{sup 3D} SURVEY: DESIGN, FIRST RESULTS, AND THE EVOLUTION OF GALAXY KINEMATICS FROM 0.7 ≤ z ≤ 2.7

    Energy Technology Data Exchange (ETDEWEB)

    Wisnioski, E.; Förster Schreiber, N. M.; Wuyts, S.; Wuyts, E.; Bandara, K.; Genzel, R.; Bender, R.; Davies, R.; Lang, P.; Mendel, J. T.; Beifiori, A.; Chan, J.; Fabricius, M.; Fudamoto, Y.; Kulkarni, S.; Kurk, J.; Lutz, D. [Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstr. 1, D-85748 Garching (Germany); Wilman, D.; Fossati, M. [Universitäts-Sternwarte, Ludwig-Maximilians-Universität, Scheinerstrasse 1, D-81679 München (Germany); Brammer, G., E-mail: emily@mpe.mpg.de [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); and others

    2015-02-01

    We present the KMOS{sup 3D} survey, a new integral field survey of over 600 galaxies at 0.7 < z < 2.7 using KMOS at the Very Large Telescope. The KMOS{sup 3D} survey utilizes synergies with multi-wavelength ground- and space-based surveys to trace the evolution of spatially resolved kinematics and star formation from a homogeneous sample over 5 Gyr of cosmic history. Targets, drawn from a mass-selected parent sample from the 3D-HST survey, cover the star formation-stellar mass (M {sub *}) and rest-frame (U – V) – M {sub *} planes uniformly. We describe the selection of targets, the observations, and the data reduction. In the first-year of data we detect Hα emission in 191 M {sub *} = 3 × 10{sup 9}-7 × 10{sup 11} M {sub ☉} galaxies at z = 0.7-1.1 and z = 1.9-2.7. In the current sample 83% of the resolved galaxies are rotation dominated, determined from a continuous velocity gradient and v {sub rot}/σ{sub 0} > 1, implying that the star-forming ''main sequence'' is primarily composed of rotating galaxies at both redshift regimes. When considering additional stricter criteria, the Hα kinematic maps indicate that at least ∼70% of the resolved galaxies are disk-like systems. Our high-quality KMOS data confirm the elevated velocity dispersions reported in previous integral field spectroscopy studies at z ≳ 0.7. For rotation-dominated disks, the average intrinsic velocity dispersion decreases by a factor of two from 50 km s{sup –1}at z ∼ 2.3 to 25 km s{sup –1}at z ∼ 0.9. Combined with existing results spanning z ∼ 0-3, we show that disk velocity dispersions follow an evolution that is consistent with the dependence of velocity dispersion on gas fractions predicted by marginally stable disk theory.

  14. The structural evolution of Milky-Way-like star-forming galaxies since z ∼ 1.3

    International Nuclear Information System (INIS)

    Patel, Shannon G.; Fumagalli, Mattia; Franx, Marijn; Labbé, Ivo; Muzzin, Adam; Van Dokkum, Pieter G.; Leja, Joel; Skelton, Rosalind E.; Momcheva, Ivelina; Nelson, Erica June; Van der Wel, Arjen; Rix, Hans-Walter; Brammer, Gabriel; Whitaker, Katherine E.; Lundgren, Britt; Wake, David A.; Quadri, Ryan F.

    2013-01-01

    We follow the structural evolution of star-forming galaxies (SFGs) like the Milky Way by selecting progenitors to z ∼ 1.3 based on the stellar mass growth inferred from the evolution of the star-forming sequence. We select our sample from the 3D-HST survey, which utilizes spectroscopy from the HST/WFC3 G141 near-IR grism and enables precise redshift measurements for our sample of SFGs. Structural properties are obtained from Sérsic profile fits to CANDELS WFC3 imaging. The progenitors of z = 0 SFGs with stellar mass M = 10 10.5 M ☉ are typically half as massive at z ∼ 1. This late-time stellar mass growth is consistent with recent studies that employ abundance matching techniques. The descendant SFGs at z ∼ 0 have grown in half-light radius by a factor of ∼1.4 since z ∼ 1. The half-light radius grows with stellar mass as r e ∝M 0.29 . While most of the stellar mass is clearly assembling at large radii, the mass surface density profiles reveal ongoing mass growth also in the central regions where bulges and pseudobulges are common features in present day late-type galaxies. Some portion of this growth in the central regions is due to star formation as recent observations of Hα maps for SFGs at z ∼ 1 are found to be extended but centrally peaked. Connecting our lookback study with galactic archeology, we find the stellar mass surface density at R = 8 kpc to have increased by a factor of ∼2 since z ∼ 1, in good agreement with measurements derived for the solar neighborhood of the Milky Way.

  15. Projection Of The Stellar To Halo Mass Relation Into The Scaling Relations Of A Disc Galaxy Population

    Science.gov (United States)

    Mancillas, Brisa; Ávila-Reese, Vladimir; Rodríguez-Puebla, Aldo; Valls-Gabaud, David

    2017-06-01

    Several pieces of evidence suggest that disk formation is the generic process of assembly of galaxies, while the spheroidal component arises from the merging/interactions of disks as well as from their secular evolution. To understand galaxy formation and evolution, a cosmological framework is required. The current cosmological paradigm is summarized in the so-called Λ-cold dark matter model (ΛCDM). The statistical connection between the masses of the observed galaxies and those of the simulated CDM halos in large volumes leads us to the galaxy-halo mass relation, which summarizes the main astrophysical processes of galaxy formation and evolution (gas heating and cooling, SF, SN- and AGN-driven feedback, etc.). An important question is how this relation constrained by semi-empirical methods (e.g., Rodriguez-Puebla et al. 2014) is "projected" into the disk galaxy scaling relations and other galaxy correlations. To explore this question, we generate a synthetic catalog of thousands of disk/halo systems by means of an extended Mo, Mao & White (1998) model, and by using as input the baryonic-to-halo mass relation, fbar(Mh), of local disk galaxy as recently constrained by Calette et al. (2015).

  16. THE NUMBER DENSITY AND MASS DENSITY OF STAR-FORMING AND QUIESCENT GALAXIES AT 0.4 ≤ z ≤ 2.2

    International Nuclear Information System (INIS)

    Brammer, Gabriel B.; Whitaker, K. E.; Van Dokkum, P. G.; Lee, K.-S.; Muzzin, A.; Marchesini, D.; Franx, M.; Kriek, M.; Labbe, I.; Quadri, R. F.; Williams, R.; Rudnick, G.

    2011-01-01

    We study the buildup of the bimodal galaxy population using the NEWFIRM Medium-Band Survey, which provides excellent redshifts and well-sampled spectral energy distributions of ∼27, 000 galaxies with K 3 x 10 10 M sun increases by a factor of ∼10 from z ∼ 2 to the present day, whereas the mass density in star-forming galaxies is flat or decreases over the same time period. Modest mass growth by a factor of ∼2 of individual quiescent galaxies can explain roughly half of the strong density evolution at masses >10 11 M sun , due to the steepness of the exponential tail of the mass function. The rest of the density evolution of massive, quiescent galaxies is likely due to transformation (e.g., quenching) of the massive star-forming population, a conclusion which is consistent with the density evolution we observe for the star-forming galaxies themselves, which is flat or decreasing with cosmic time. Modest mass growth does not explain the evolution of less massive quiescent galaxies (∼10 10.5 M sun ), which show a similarly steep increase in their number densities. The less massive quiescent galaxies are therefore continuously formed by transforming galaxies from the star-forming population.

  17. A Visual Galaxy Classification Interface and its Classroom Application

    Science.gov (United States)

    Kautsch, Stefan J.; Phung, Chau; VanHilst, Michael; Castro, Victor H

    2014-06-01

    Galaxy morphology is an important topic in modern astronomy to understand questions concerning the evolution and formation of galaxies and their dark matter content. In order to engage students in exploring galaxy morphology, we developed a web-based, graphical interface that allows students to visually classify galaxy images according to various morphological types. The website is designed with HTML5, JavaScript, PHP, and a MySQL database. The classification interface provides hands-on research experience and training for students and interested clients, and allows them to contribute to studies of galaxy morphology. We present the first results of a pilot study and compare the visually classified types using our interface with that from automated classification routines.

  18. Galactic chemical evolution in hierarchical formation models

    Science.gov (United States)

    Arrigoni, Matias

    2010-10-01

    The chemical properties and abundance ratios of galaxies provide important information about their formation histories. Galactic chemical evolution has been modelled in detail within the monolithic collapse scenario. These models have successfully described the abundance distributions in our Galaxy and other spiral discs, as well as the trends of metallicity and abundance ratios observed in early-type galaxies. In the last three decades, however, the paradigm of hierarchical assembly in a Cold Dark Matter (CDM) cosmology has revised the picture of how structure in the Universe forms and evolves. In this scenario, galaxies form when gas radiatively cools and condenses inside dark matter haloes, which themselves follow dissipationless gravitational collapse. The CDM picture has been successful at predicting many observed properties of galaxies (for example, the luminosity and stellar mass function of galaxies, color-magnitude or star formation rate vs. stellar mass distributions, relative numbers of early and late-type galaxies, gas fractions and size distributions of spiral galaxies, and the global star formation history), though many potential problems and open questions remain. It is therefore interesting to see whether chemical evolution models, when implemented within this modern cosmological context, are able to correctly predict the observed chemical properties of galaxies. With the advent of more powerfull telescopes and detectors, precise observations of chemical abundances and abundance ratios in various phases (stellar, ISM, ICM) offer the opportunity to obtain strong constraints on galaxy formation histories and the physics that shapes them. However, in order to take advantage of these observations, it is necessary to implement detailed modeling of chemical evolution into a modern cosmological model of hierarchical assembly.

  19. A MULTI-WAVELENGTH STUDY OF LOW-REDSHIFT CLUSTERS OF GALAXIES. II. ENVIRONMENTAL IMPACT ON GALAXY GROWTH

    International Nuclear Information System (INIS)

    Atlee, David W.; Martini, Paul

    2012-01-01

    Galaxy clusters provide powerful laboratories for the study of galaxy evolution, particularly the origin of correlations of morphology and star formation rate (SFR) with density. We construct visible to MIR spectral energy distributions of galaxies in eight low-redshift (z * (>99% confidence) with no dependence on R/R 200 or projected local density at fixed mass. A merged sample of galaxies from the five best measured clusters shows (SFR)∝(R/R 200 ) 1.1±0.3 for galaxies with R/R 200 ≤ 0.4. A decline in the fraction of SFGs toward the cluster center contributes most of this effect, but it is accompanied by a reduction in (SFR) for SFGs with R ≤ 0.1 R 200 . The increase in the fraction of SFGs toward larger R/R 200 and the isolation of SFGs with reduced SFRs near the cluster center are consistent with the truncation of star formation by ram-pressure stripping, as is the tendency for more massive SFGs to have higher SFRs. We conclude that stripping is more likely than slower processes to drive the properties of SFGs with R 200 in clusters. We also find that galaxies near the cluster center are more massive than galaxies farther out in the cluster at ∼3.5σ, which suggests that dynamical relaxation significantly impacts the distribution of cluster galaxies as the clusters evolve.

  20. UV Visibility of Moderate-Redshift Giant Elliptical Galaxies

    Directory of Open Access Journals (Sweden)

    Myung-Hyun Rhee

    1998-06-01

    Full Text Available We show quantitatively whether giant elliptical galaxies would be visible at far UV wavelengths if they were placed at moderate redshift of 0.4-0.5. On the basis of simple cosmological tests, we conclude that giant elliptical galaxies can be detectable upto the redshift of 0.4-0.5 in the proposed GALEX (Galaxy Evolution Explorer Deep Imaging Survey. We also show that obtaining UV color index such as m_1550 - V from upcoming GALEX and SDSS (Sloan Digital Sky Survey observations should be feasible.

  1. The stellar mass-size evolution of galaxies from z=7 to z=0

    NARCIS (Netherlands)

    Mosleh, Moein

    2013-01-01

    One of the important properties of galaxies is their sizes which correlate with their stellar masses. Evidence is provided by many recent studies that the sizes of galaxies were smaller at higher redshifts compared to galaxies of similar mass in the local Universe. It is essential to understand

  2. Post-Starburst Galaxies At The End of The E+A Phase

    Science.gov (United States)

    Liu, Charles; Marinelli, Mariarosa; Chang, Madeleine; Lyczko, Camilla; Vega Orozco, Cecilia; SDSS-IV Collaboration

    2018-06-01

    Post-starburst galaxies, once thought to be rare curiosities, are now recognized to represent a key phase in the galaxy evolution. The post-starburst, or E+A phase, should however not be considered as a single, short-lived phenomenon; rather, it is an extended evolutionary process that occurs a galaxy transitions from an actively star-forming system into a quiescent one. We present a study of nearby galaxies at or near the end of the E+A phase, wherein all star formation has been quenched, the fossilized stellar population of the most recent starburst is highly localized, and the remainder of the galaxy's stellar population is old and quiescent. The luminosity and stellar age distribution of these "end-phase E+As" can provide insights into the evolution of galaxies onto and within the red sequence, from active to passive systems. This work is supported by National Science Foundation grants to CUNY College of Staten Island and the American Museum of Natural History; the College of Staten Island Office of Academic Affairs; the Sherman Fairchild Science Pathways Scholars Program (SP^2) at Barnard College; and the Alfred P. Sloan Foundation.

  3. Diffuse interstellar gas in disk galaxies

    International Nuclear Information System (INIS)

    Vladilo, G.

    1989-01-01

    The physical properties of the diffuse gas in our Galaxy are reviewed and considered as a starting point for interstellar (IS) studies of disk galaxies. Attention is focussed on the atomic and ionic component, detected through radio, optical, ultraviolet (UV) and X-ray observations. The cooling and heating processes in the IS gas are briefly recalled in order to introduce current models of disk and halo gas. Observations of nearby galaxies critical to test IS models are considered, including 21-cm surveys, optical and UV absorptions of bright, extragalactic sources, and X-ray emission from hot halos. Finally, further steps necessary to develop a global model for the structure and evolution of the interstellar medium are indicated. (author)

  4. The ionisation parameter of star-forming galaxies evolves with the specific star formation rate

    Science.gov (United States)

    Kaasinen, Melanie; Kewley, Lisa; Bian, Fuyan; Groves, Brent; Kashino, Daichi; Silverman, John; Kartaltepe, Jeyhan

    2018-04-01

    We investigate the evolution of the ionisation parameter of star-forming galaxies using a high-redshift (z ˜ 1.5) sample from the FMOS-COSMOS survey and matched low-redshift samples from the Sloan Digital Sky Survey. By constructing samples of low-redshift galaxies for which the stellar mass (M*), star formation rate (SFR) and specific star formation rate (sSFR) are matched to the high-redshift sample we remove the effects of an evolution in these properties. We also account for the effect of metallicity by jointly constraining the metallicity and ionisation parameter of each sample. We find an evolution in the ionisation parameter for main-sequence, star-forming galaxies and show that this evolution is driven by the evolution of sSFR. By analysing the matched samples as well as a larger sample of z physically consistent with the definition of the ionisation parameter, a measure of the hydrogen ionising photon flux relative to the number density of hydrogen atoms.

  5. Evolution of the spherical clusters

    International Nuclear Information System (INIS)

    Surdin, V.G.

    1978-01-01

    The possible processes of the Galaxy spherical clusters formation and evolution are described on a popular level. The orbits of spherical cluster motion and their spatial velocities are determined. Given are the distrbutions of spherical cluster stars according to their velocities and the observed distribution of spherical clusters in the area of the Galaxy slow evolution. The dissipation and dynamic friction processes destructing clusters with the mass less than 10 4 of solar mass and bringing about the reduction of clusters in the Galaxy are considered. The paradox of forming mainly X-ray sources in spherical clusters is explained. The schematic image of possible ways of forming X-ray sources in spherical clusters is given

  6. Solving the Mystery of Galaxy Bulges and Bulge Substructure

    Science.gov (United States)

    Erwin, Peter

    2017-08-01

    Understanding galaxy bulges is crucial for understanding galaxy evolution and the growth of supermassive black holes (SMBHs). Recent studies have shown that at least some - perhaps most - disk-galaxy bulges are actually composite structures, with both classical-bulge (spheroid) and pseudobulge (disky) components; this calls into question the standard practice of using simple, low-resolution bulge/disk decompositions to determine spheroid and SMBH mass functions. We propose WFC3 optical and near-IR imaging of a volume- and mass-limited sample of local disk galaxies to determine the full range of pure-classical, pure-pseudobulge, and composite-bulge frequencies and parameters, including stellar masses for classical bulges, disky pseudobulges, and boxy/peanut-shaped bulges. We will combine this with ground-based spectroscopy to determine the stellar-kinematic and population characteristics of the different substructures revealed by our WFC3 imaging. This will help resolve growing uncertainties about the status and nature of bulges and their relation to SMBH masses, and will provide an essential local-universe reference for understanding bulge (and SMBH) formation and evolution.

  7. Dwarf Galaxies with Gentle Star Formation and the Counts of Galaxies in the Hubble Deep Field

    OpenAIRE

    Campos, Ana

    1997-01-01

    In this paper the counts and colors of the faint galaxies observed in the Hubble Deep Field are fitted by means of simple luminosity evolution models that incorporate a numerous population of fading dwarfs. The observed color distribution of the very faint galaxies now allows us to put constraints on the star formation history in dwarfs. It is shown that the star-forming activity in these small systems has to proceed in a gentle way, i.e., through episodes where each one lasts much longer tha...

  8. SUPERDENSE GALAXIES AND THE MASS-SIZE RELATION AT LOW REDSHIFT

    International Nuclear Information System (INIS)

    Poggianti, B. M.; Calvi, R.; Fasano, G.; Vulcani, B.; Bettoni, D.; Gullieuszik, M.; Omizzolo, A.; Bindoni, D.; D'Onofrio, M.; Moretti, A.; Valentinuzzi, T.; Fritz, J.; De Lucia, G.

    2013-01-01

    We search for massive and compact galaxies (superdense galaxies, hereafter SDGs) at z = 0.03-0.11 in the Padova-Millennium Galaxy and Group Catalogue, a spectroscopically complete sample representative of the general field population of the local universe. We find that compact galaxies with radii and mass densities comparable to high-z massive and passive galaxies represent 4.4% of all galaxies with stellar masses above 3 × 10 10 M ☉ , yielding a number density of 4.3 × 10 –4 h 3 Mpc –3 . Most of them are S0s (70%) or ellipticals (23%), are red, and have intermediate-to-old stellar populations, with a median luminosity-weighted age of 5.4 Gyr and a median mass-weighted age of 9.2 Gyr. Their velocity dispersions and dynamical masses are consistent with the small radii and high stellar mass estimates. Comparing with the WINGS sample of cluster galaxies at similar redshifts, the fraction of SDGs is three times smaller in the field than in clusters, and cluster SDGs are on average 4 Gyr older than field SDGs. We confirm the existence of a universal trend of smaller radii for older luminosity-weighted ages at fixed galaxy mass. As a consequence, the median mass-size relation shifts toward smaller radii for galaxies with older stars, but the effect is much more pronounced in clusters than in the field. Our results show that, on top of the well-known dependence of stellar age on galaxy mass, the luminosity-weighted age of galaxies depends on galaxy compactness at fixed mass and, for a fixed mass and radius, on environment. This effect needs to be taken into account in order not to overestimate the evolution of galaxy sizes from high to low z. Our results and hierarchical simulations suggest that a significant fraction of the massive compact galaxies at high z have evolved into compact galaxies in galaxy clusters today. When stellar age and environmental effects are taken into account, the average amount of size evolution of individual galaxies between high and low

  9. Possible Imprints of Cold-mode Accretion on the Present-day Properties of Disk Galaxies

    Science.gov (United States)

    Noguchi, Masafumi

    2018-01-01

    Recent theoretical studies suggest that a significant part of the primordial gas accretes onto forming galaxies as narrow filaments of cold gas without building a shock and experiencing heating. Using a simple model of disk galaxy evolution that combines the growth of dark matter halos predicted by cosmological simulations with a hypothetical form of cold-mode accretion, we investigate how this cold-accretion mode affects the formation process of disk galaxies. It is found that the shock-heating and cold-accretion models produce compatible results for low-mass galaxies owing to the short cooling timescale in such galaxies. However, cold accretion significantly alters the evolution of disk galaxies more massive than the Milky Way and puts observable fingerprints on their present properties. For a galaxy with a virial mass {M}{vir}=2.5× {10}12 {M}ȯ , the scale length of the stellar disk is larger by 41% in the cold-accretion model than in the shock-heating model, with the former model reproducing the steep rise in the size–mass relation observed at the high-mass end. Furthermore, the stellar component of massive galaxies becomes significantly redder (0.66 in u ‑ r at {M}{vir}=2.5× {10}12 {M}ȯ ), and the observed color–mass relation in nearby galaxies is qualitatively reproduced. These results suggest that large disk galaxies with red optical colors may be the product of cold-mode accretion. The essential role of cold accretion is to promote disk formation in the intermediate-evolution phase (0.5< z< 1.5) by providing the primordial gas having large angular momentum and to terminate late-epoch accretion, quenching star formation and making massive galaxies red.

  10. Observations of ultraviolet spectra of H II regions and galaxies with IUE

    International Nuclear Information System (INIS)

    Gondhalekar, P.M.

    1982-08-01

    The ultraviolet spectra, obtained with the International Ultraviolet Explorer, of a sample of H II regions and the nuclear regions of spiral and elliptical galaxies are described. The star formation rates in the nuclei of spiral galaxies are similar to the star formation rate in the solar neighbourhood. The data indicate that the current thinking on the synthesis of carbon and nitrogen in galaxies has to be revised and the K-corrections determined from the ultraviolet spectra of galaxies when compared with the photometry of distant galaxies suggests colour evolution of galaxies at z > 0.3. (author)

  11. A VLT Large Programme to Study Galaxies at z ~ 2: GMASS — the Galaxy Mass Assembly Ultra-deep Spectroscopic Survey

    Science.gov (United States)

    Kurk, Jaron; Cimatti, Andrea; Daddi, Emanuele; Mignoli, Marco; Bolzonella, Micol; Pozzetti, Lucia; Cassata, Paolo; Halliday, Claire; Zamorani, Gianni; Berta, Stefano; Brusa, Marcella; Dickinson, Mark; Franceschini, Alberto; Rodighiero, Guilia; Rosati, Piero; Renzini, Alvio

    2009-03-01

    We report on the motivation, sample selection and first results of our VLT FORS2 Large Programme (173.A-0687), which has obtained the longest targeted spectra of distant galaxies obtained so far with the VLT. These long exposures, up to 77 hours for objects included in three masks, were required to detect spectral features of extremely faint galaxies, such as absorption lines of passive galaxies at z > 1.4, a population that had previously escaped attention due to its faintness in the optical wavelength regime, but which represents a critical phase in the evolution of massive galaxies. The ultra-deep spectroscopy allowed us to estimate the stellar metallicity of star-forming galaxies at z ~ 2, to trace colour bimodality up to z = 2 and to characterise a galaxy cluster progenitor at z = 1.6. The approximately 200 spectra produced by GMASS constitute a lasting legacy, populating the “redshift desert” in GOODS-S.

  12. EVOLUTION OF THE MERGER-INDUCED HYDROSTATIC MASS BIAS IN GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Nelson, Kaylea; Nagai, Daisuke; Rudd, Douglas H.; Shaw, Laurie

    2012-01-01

    In this work, we examine the effects of mergers on the hydrostatic mass estimate of galaxy clusters using high-resolution Eulerian cosmological simulations. We utilize merger trees to isolate the last merger for each cluster in our sample and follow the time evolution of the hydrostatic mass bias as the systems relax. We find that during a merger, a shock propagates outward from the parent cluster, resulting in an overestimate in the hydrostatic mass bias. After the merger, as a cluster relaxes, the bias in hydrostatic mass estimate decreases but remains at a level of –5%-10% with 15%-20% scatter within r 500 . We also investigate the post-merger evolution of the pressure support from bulk motions, a dominant cause of this residual mass bias. At r 500 , the contribution from random motions peaks at 30% of the total pressure during the merger and quickly decays to ∼10%-15% as a cluster relaxes. Additionally, we use a measure of the random motion pressure to correct the hydrostatic mass estimate. We discover that 4 Gyr after mergers, the direct effects of the merger event on the hydrostatic mass bias have become negligible. Thereafter, the mass bias is primarily due to residual bulk motions in the gas which are not accounted for in the hydrostatic equilibrium equation. We present a hydrostatic mass bias correction method that can recover the unbiased cluster mass for relaxed clusters with 9% scatter at r 500 and 11% scatter in the outskirts, within r 200 .

  13. Stellar dynamics and galactic evolution

    International Nuclear Information System (INIS)

    Gilmore, G.; Kuijken, K.; Wyse, R.F.G.

    1989-01-01

    Solar neighbourhood observations have the unique capability of providing detailed study of the consequences of the early evolution of the Galaxy. Important examples of this capability include determination of the distribution of luminous and unseen mass in the Galaxy, and deduction of the rate of star formation and chemical evolution in the proto-Galaxy. We describe a new method to determine the distribution of mass in the Galactic disk. We reinvestigate determinations of the local volume mass density (the Oort limit) and show there to be serious internal inconsistencies in the available data. The most likely value for the local volume mass density, based on old stars and with kinematic models consistent with the age structure of the local disk is ∼ 0.1 solar mass pc -3 , though this value is still poorly determined. Thus, there is no significant evidence for any missing mass associated with the Galactic disk. We also reinvestigate observational data on the chemical abundances and kinematics of old stars in the Galaxy. The (Intermediate Population II) thick disk stars are most likely as old as the globular clusters, and kinematically distinct from the old disk. This favours models of thick disk origin involving a discrete disruptive event, such as the accretion of a satellite of the Galaxy early in the evolution of the Galactic disk. (author)

  14. The gaseous haloes of evolving galaxies: a probe using the linear sizes of radio sources

    International Nuclear Information System (INIS)

    Subramanian, K.; Swarup, G.

    1990-01-01

    As galaxies form and evolve, their gaseous haloes are expected to undergo corresponding evolution. We examine here whether observations of the linear sizes of radio sources can be used to probe such evolution. For this purpose we first represent the gas density at various stages of galaxy formation and evolution by means of simple model density profiles, and then work out the expected linear sizes (l) of radio sources in these models. (author)

  15. The Milky Way galaxy

    International Nuclear Information System (INIS)

    Woerden, H. van; Allen, R.J.; Burton, W.B.

    1985-01-01

    IAU Symposium 106, held at the Kapteyn Institute in Groningen, presents an overview of all major aspects of galactic astronomy. The vast subject is covered in 20 authoritative review papers and 22 invited papers, each with discussion, plus 81 shorter contributions. The book opens with 4 reviews by historians of science, outlining the history of galactic research. Part 2 deals with (i) galactic rotation, (ii) the large-scale distributions of matter, of both old and young stellar populations, and of the atomic, molecular and high-energy components of the interstellar medium, (iii) small-scale structure in the gas, (iv) the galactic nucleus, (v) the high-velocity clouds. Part 3 discusses the dynamics of the local group of Galaxies and of the Milky Way-Magellanic clouds system, the dynamical and chemical evolution of the Galaxy and of its disk and halo components and the formation of the Galaxy. The controversial subject of spiral structure and star formation is analyzed in several extensive reviews and lively discussions, featuring both observational and theoretical developments. Results of extragalactic research are blended with studies of our Galaxy throughout the book, and there is a separate comparison between Andromeda and Milky Way Galaxies. The Symposium featured the first maps produced by IRAS, and results from most major telescopes in a variety of wavebands. Many review papers present material not published elsewhere. The book closes with a lecture on life in the Galaxy and with an imaginative symposium summary. (orig.)

  16. The evolution of the rest-frame J- and H-band luminosity function of galaxies to z=3.5

    OpenAIRE

    Stefanon, Mauro; Marchesini, Danilo

    2011-01-01

    We present the rest-frame J- and H-band luminosity function (LF) of field galaxies, based on a deep multi-wavelength composite sample from the MUSYC, FIRES and FIREWORKS survey public catalogues, covering a total area of 450 arcmin^2. The availability of flux measurements in the Spitzer IRAC 3.6, 4.5, 5.8, and 8 um channels allows us to compute absolute magnitudes in the rest-frame J and H bands up to z=3.5 minimizing the dependence on the stellar evolution models. We compute the LF in the fo...

  17. Feedback in low-mass galaxies in the early Universe.

    Science.gov (United States)

    Erb, Dawn K

    2015-07-09

    The formation, evolution and death of massive stars release large quantities of energy and momentum into the gas surrounding the sites of star formation. This process, generically termed 'feedback', inhibits further star formation either by removing gas from the galaxy, or by heating it to temperatures that are too high to form new stars. Observations reveal feedback in the form of galactic-scale outflows of gas in galaxies with high rates of star formation, especially in the early Universe. Feedback in faint, low-mass galaxies probably facilitated the escape of ionizing radiation from galaxies when the Universe was about 500 million years old, so that the hydrogen between galaxies changed from neutral to ionized-the last major phase transition in the Universe.

  18. Evolution of Isolated Neutron Stars

    OpenAIRE

    Popov, S. B.

    2001-01-01

    In this paper we briefly review our recent results on evolution and properties of isolated neutron stars (INSs) in the Galaxy. As the first step we discuss stochastic period evolution of INSs. We briefly discuss how an INS's spin period evolves under influence of interaction with turbulized interstellar medium. To investigate statistical properties of the INS population we calculate a {\\it census} of INSs in our Galaxy. Then we show that for exponential field decay the range of minimum value ...

  19. THE ASSEMBLY OF GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Berrier, Joel C.; Stewart, Kyle R.; Bullock, James S.; Purcell, Chris W.; Barton, Elizabeth J.; Wechsler, Risa H.

    2009-01-01

    We study the formation of 53 galaxy cluster-size dark matter halos (M = 10 14.0-14.76 M sun ) formed within a pair of cosmological Λ cold dark matter N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host ∼0.3 L * galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters experience no 'preprocessing' in the group environment prior to their accretion into the cluster. On average, 70% of cluster galaxies fall into the cluster potential directly from the field, with no luminous companions in their host halos at the time of accretion; less than 12% are accreted as members of groups with five or more galaxies. Moreover, we find that cluster galaxies are significantly less likely to have experienced a merger in the recent past (∼<6 Gyr) than a field halo of the same mass. These results suggest that local cluster processes such as ram pressure stripping, galaxy harassment, or strangulation play the dominant role in explaining the difference between cluster and field populations at a fixed stellar mass, and that pre-evolution or past merging in the group environment is of secondary importance for setting cluster galaxy properties for most clusters. The accretion times for z = 0 cluster members are quite extended, with ∼20% incorporated into the cluster halo more than 7 Gyr ago and ∼20% within the last 2 Gyr. By comparing the observed morphological fractions in cluster and field populations, we estimate an approximate timescale for late-type to early-type transformation within the cluster environment to be ∼6 Gyr.

  20. EVOLUTION AND DISTRIBUTION OF MAGNETIC FIELDS FROM ACTIVE GALACTIC NUCLEI IN GALAXY CLUSTERS. II. THE EFFECTS OF CLUSTER SIZE AND DYNAMICAL STATE

    International Nuclear Information System (INIS)

    Xu Hao; Li Hui; Collins, David C.; Li, Shengtai; Norman, Michael L.

    2011-01-01

    Theory and simulations suggest that magnetic fields from radio jets and lobes powered by their central super massive black holes can be an important source of magnetic fields in the galaxy clusters. This is Paper II in a series of studies where we present self-consistent high-resolution adaptive mesh refinement cosmological magnetohydrodynamic simulations that simultaneously follow the formation of a galaxy cluster and evolution of magnetic fields ejected by an active galactic nucleus. We studied 12 different galaxy clusters with virial masses ranging from 1 x 10 14 to 2 x 10 15 M sun . In this work, we examine the effects of the mass and merger history on the final magnetic properties. We find that the evolution of magnetic fields is qualitatively similar to those of previous studies. In most clusters, the injected magnetic fields can be transported throughout the cluster and be further amplified by the intracluster medium (ICM) turbulence during the cluster formation process with hierarchical mergers, while the amplification history and the magnetic field distribution depend on the cluster formation and magnetism history. This can be very different for different clusters. The total magnetic energies in these clusters are between 4 x 10 57 and 10 61 erg, which is mainly decided by the cluster mass, scaling approximately with the square of the total mass. Dynamically older relaxed clusters usually have more magnetic fields in their ICM. The dynamically very young clusters may be magnetized weakly since there is not enough time for magnetic fields to be amplified.