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Sample records for large interacting galaxy

  1. Automatic quantitative morphological analysis of interacting galaxies

    CERN Document Server

    Shamir, Lior; Wallin, John

    2013-01-01

    The large number of galaxies imaged by digital sky surveys reinforces the need for computational methods for analyzing galaxy morphology. While the morphology of most galaxies can be associated with a stage on the Hubble sequence, morphology of galaxy mergers is far more complex due to the combination of two or more galaxies with different morphologies and the interaction between them. Here we propose a computational method based on unsupervised machine learning that can quantitatively analyze morphologies of galaxy mergers and associate galaxies by their morphology. The method works by first generating multiple synthetic galaxy models for each galaxy merger, and then extracting a large set of numerical image content descriptors for each galaxy model. These numbers are weighted using Fisher discriminant scores, and then the similarities between the galaxy mergers are deduced using a variation of Weighted Nearest Neighbor analysis such that the Fisher scores are used as weights. The similarities between the ga...

  2. Interacting Galaxies with MOND

    CERN Document Server

    Tiret, O

    2007-01-01

    We compare N-body simulations performed in MOND with analogs in Newtonian gravity with dark matter (DM). We have developed a code which solves the Poisson equation in both gravity models. It is a grid solver using adaptive mesh refinement techniques, allowing us to study isolated galaxies as well as interacting galaxies. Galaxies in MOND are found to form bars faster and stronger than in the DM model. In Newton dynamics, it is difficult to reproduce the observed high frequency of strong bars, while MOND appears to fit better the observations. Galaxy interactions and mergers, such as the Antennae, are also simulated with Newton and MOND dynamics. In the latter, dynamical friction is much weaker, and merging time-scales are longer. The formation of tidal dwarf galaxies in tidal tails are also compared in MOND and Newton+DM models.

  3. Featured Image: Interacting Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-06-01

    This beautiful image shows two galaxies, IC 2163 and NGC 2207, as they undergo a grazing collision 114 million light-years away. The image is composite, constructed from Hubble (blue), Spitzer (green), and ALMA (red) data. In a recent study, Debra Elmegreen (Vassar College) and collaborators used this ALMA data to trace the individual molecular clouds in the two interacting galaxies, identifying a total of over 200 clouds that each contain a mass of over a million solar masses. These clouds represent roughly half the molecular gas in the two galaxies total. Elmegreen and collaborators track the properties of these clouds and their relation to star-forming regions observed with Hubble. For more information about their observations, check out the paper linked below.A closer look at the ALMA observations for these galaxies, with the different emission regions labeled. Most of the molecular gas emission comes from the eyelids of IC 2163, and the nuclear ring and Feature i in NGC 2207. [Elmegreen et al. 2017]CitationDebra Meloy Elmegreen et al 2017 ApJ 841 43. doi:10.3847/1538-4357/aa6ba5

  4. Large-Scale Galaxy Bias

    CERN Document Server

    Desjacques, Vincent; Schmidt, Fabian

    2016-01-01

    This review presents a comprehensive overview of galaxy bias, that is, the statistical relation between the distribution of galaxies and matter. We focus on large scales where cosmic density fields are quasi-linear. On these scales, the clustering of galaxies can be described by a perturbative bias expansion, and the complicated physics of galaxy formation is absorbed by a finite set of coefficients of the expansion, called bias parameters. The review begins with a pedagogical proof of this very important result, which forms the basis of the rigorous perturbative description of galaxy clustering, under the assumptions of General Relativity and Gaussian, adiabatic initial conditions. Key components of the bias expansion are all leading local gravitational observables, which includes the matter density but also tidal fields and their time derivatives. We hence expand the definition of local bias to encompass all these contributions. This derivation is followed by a presentation of the peak-background split in i...

  5. Unveiling Galaxy Interactions: Watching the Tides Roll

    CERN Document Server

    Keel, William C

    2009-01-01

    I set the stage for discussion of the stellar populations in interacting galaxies by looking back over the slow development of our understanding of these systems. From early anecdotal collections, to systematic cataloging, and finally to increasingly sophisticated n-body calculations, we have seen how gravity in distributed systems can produce the stunning variety of structures we see. At the same time, measures across the spectrum have made it clear that galaxy interactions are linked to star formation, albeit with the physical mechanisms much less clear. Improved data sets, including HST imaging, deep IR data, and large samples with well-defined selection criteria, have started to reveal correlations with dynamical parameters pointing to detailed histories of starbirth during collisions. The merger hypothesis for elliptical galaxies has broadened into seeing interactions and mergers as important parts of the overall evolution of galaxies. The connection becomes more important as we look to higher redshift, ...

  6. How ubiquitous are massive starbursts in interacting galaxies?

    CERN Document Server

    Di Matteo, P; Martig, M; Combes, F; Melchior, A -L; Semelin, B

    2009-01-01

    Many evidences exist for a connection between galaxy interactions and induced star formation. However, a large range of responses of galaxies to tidal interactions is found, both in observations and in numerical simulations. We will discuss some recent results obtained analysing a large sample (~ 1000) of simulations of interacting pairs and their agreement with the most recent observational works.

  7. The Metallicity Evolution of Interacting Galaxies

    CERN Document Server

    Torrey, Paul; Kewley, Lisa; Hernquist, Lars

    2011-01-01

    Nuclear inflows of metal-poor interstellar gas triggered by galaxy interactions can account for the systematically lower central oxygen abundances observed in local interacting galaxies. Here, we investigate the metallicity evolution of a large set of simulations of colliding galaxies. Our models include cooling, star formation, feedback, and a new stochastic method for tracking the mass recycled back to the interstellar medium from stellar winds and supernovae. We study the influence of merger-induced inflows, enrichment, gas consumption, and galactic winds in determining the nuclear metallicity. The central metallicity is primarily a competition between the inflow of low-metallicity gas and enrichment from star formation. An average depression in the nuclear metallicity of ~0.07 is found for gas-poor disk-disk interactions. Gas-rich disk-disk interactions, on the other hand, typically have an enhancement in the central metallicity that is positively correlated with the gas content. The simulations fare reas...

  8. Tracking Evolutionary Processes with Large Samples of Galaxy Pairs

    CERN Document Server

    Barton, Elizabeth J; Bullock, James S; Wright, Shelley A

    2009-01-01

    Modern redshift surveys enable the identification of large samples of galaxies in pairs, taken from many different environments. Meanwhile, cosmological simulations allow a detailed understanding of the statistical properties of the selected pair samples. Using these tools in tandem leads to a quantitative understanding of the effects of galaxy-galaxy interactions and, separately, the effects quenching processes in the environments of even very small groups. In the era of the next generation of large telescopes, detailed studies of interactions will be enabled to much higher redshifts.

  9. Interacting galaxies and cosmological parameters

    CERN Document Server

    Reboul, H

    2006-01-01

    We propose a (physical)-geometrical method to measure the present rates of the density cosmological parameters for a Friedmann-Lemaitre universe. The distribution of linear separations between two interacting galaxies,when both of them undergo a first massive starburst, is used as a standard of length. Statistical properties of the linear separations of such pairs of ``interactivated'' galaxies are estimated from the data in the Two Degree Field Galaxy Redshift Survey. Synthetic samples of interactivated pairs are generated with random orientations and a likely distribution of redshifts. The resolution of the inverse problem provides the probability densities of the retrieved cosmological parameters. The accuracies that can be achieved by that method on matter and cosmological constant densities parameters are computed depending on the size of ongoing real samples. Observational prospects are investigated as the foreseeable surface densities on the sky and magnitudes of those objects.

  10. Galaxy alignment on large and small scales

    Science.gov (United States)

    Kang, X.; Lin, W. P.; Dong, X.; Wang, Y. O.; Dutton, A.; Macciò, A.

    2016-10-01

    Galaxies are not randomly distributed across the universe but showing different kinds of alignment on different scales. On small scales satellite galaxies have a tendency to distribute along the major axis of the central galaxy, with dependence on galaxy properties that both red satellites and centrals have stronger alignment than their blue counterparts. On large scales, it is found that the major axes of Luminous Red Galaxies (LRGs) have correlation up to 30Mpc/h. Using hydro-dynamical simulation with star formation, we investigate the origin of galaxy alignment on different scales. It is found that most red satellite galaxies stay in the inner region of dark matter halo inside which the shape of central galaxy is well aligned with the dark matter distribution. Red centrals have stronger alignment than blue ones as they live in massive haloes and the central galaxy-halo alignment increases with halo mass. On large scales, the alignment of LRGs is also from the galaxy-halo shape correlation, but with some extent of mis-alignment. The massive haloes have stronger alignment than haloes in filament which connect massive haloes. This is contrary to the naive expectation that cosmic filament is the cause of halo alignment.

  11. Galaxy alignment on large and small scales

    CERN Document Server

    Kang, X; Wang, Y O; Dutton, A; Macciò, A

    2014-01-01

    Galaxies are not randomly distributed across the universe but showing different kinds of alignment on different scales. On small scales satellite galaxies have a tendency to distribute along the major axis of the central galaxy, with dependence on galaxy properties that both red satellites and centrals have stronger alignment than their blue counterparts. On large scales, it is found that the major axes of Luminous Red Galaxies (LRGs) have correlation up to 30Mpc/h. Using hydro-dynamical simulation with star formation, we investigate the origin of galaxy alignment on different scales. It is found that most red satellite galaxies stay in the inner region of dark matter halo inside which the shape of central galaxy is well aligned with the dark matter distribution. Red centrals have stronger alignment than blue ones as they live in massive haloes and the central galaxy-halo alignment increases with halo mass. On large scales, the alignment of LRGs is also from the galaxy-halo shape correlation, but with some ex...

  12. Galaxy bachelors, couples, spouses: Star formation in interacting galaxies

    Science.gov (United States)

    Sun, Jing; Barger, Kathleen; Richstein, Hannah; SDSS-IV/MaNGA

    2017-01-01

    We investigate the star formation activity in three galaxy systems in different stages of interaction to determine how the environment of galaxies affects their star forming ability and potential. These systems include an isolated galaxy, a pair of interacting galaxies, and a pair of merging galaxies. All of the target galaxies in these systems have similar stellar masses and similar radii and are at similar redshifts. We trace the star formation activity over the past 1-2 Gyr using spatially and kinematically resolved H-alpha emission, H-alpha equivalent width, and 4000-Angstrom break maps. This work is based on data from the fourth-generation Sloan Digital Sky Survey (SDSS-IV)/Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), and is part of the Project No.0285 in SDSS-IV.

  13. Measuring dark matter by modeling interacting galaxies

    CERN Document Server

    Petsch, H P; Theis, Ch

    2009-01-01

    The dark matter content of galaxies is usually determined from galaxies in dynamical equilibrium, mainly from rotationally supported galactic components. Such determinations restrict measurements to special regions in galaxies, e.g. the galactic plane(s), whereas other regions are not probed at all. Interacting galaxies offer an alternative, because extended tidal tails often probe outer or off-plane regions of galaxies. However, these systems are neither in dynamical equilibrium nor simple, because they are composed of two or more galaxies, by this increasing the associated parameter space.We present our genetic algorithm based modeling tool which allows to investigate the extended parameter space of interacting galaxies. From these studies, we derive the dynamical history of (well observed) galaxies. Among other parameters we constrain the dark matter content of the involved galaxies. We demonstrate the applicability of this strategy with examples ranging from stellar streams around theMilkyWay to extended ...

  14. Internal kinematics of modelled interacting disc galaxies

    CERN Document Server

    Kronberger, T; Schindler, S; Böhm, A; Kutdemir, E; Ziegler, B L

    2006-01-01

    We present an investigation of galaxy-galaxy interactions and their effects on the velocity fields of disc galaxies in combined N-body/hydrodynamic simulations, which include cooling, star formation with feedback, and galactic winds. Rotation curves (RCs) of the gas are extracted from these simulations in a way that follows the procedure applied in observations of distant, small, and faint galaxies as closely as possible. We show that galaxy-galaxy mergers and fly-bys significantly disturb the velocity fields and hence the RCs of the interacting galaxies, leading to asymmetries and distortions in the RCs. Typical features of disturbed kinematics are rising or falling profiles in direction to the companion galaxy and bumps in the RCs. In addition, tidal tails can leave strong imprints on the rotation curve. All these features are observable for intermediate redshift galaxies, on which we focus our investigations. The appearance of these distortions depends, however, strongly on the viewing angle. The velocity ...

  15. Central star formation and metallicity in CALIFA interacting galaxies

    CERN Document Server

    Barrera-Ballesteros, J K; García-Lorenzo, B; Falcón-Barroso, J; Mast, D; García-Benito, R; Husemann, B; van de Ven, G; Iglesias-Páramo, J; Rosales-Ortega, F F; Pérez-Torres, M A; Márquez, I; Kehrig, C; Vilchez, J M; Galbany, L; López-Sánchez, Á R; Walcher, C J

    2015-01-01

    We use optical integral-field spectroscopic (IFS) data from 103 nearby galaxies at different stages of the merging event, from close pairs to merger remnants provided by the CALIFA survey, to study the impact of the interaction in the specific star formation and oxygen abundance on different galactic scales. To disentangle the effect of the interaction and merger from internal processes, we compared our results with a control sample of 80 non-interacting galaxies. We confirm the moderate enhancement (2-3 times) of specific star formation for interacting galaxies in central regions as reported by previous studies; however, the specific star formation is comparable when observed in extended regions. We find that control and interacting star-forming galaxies have similar oxygen abundances in their central regions, when normalized to their stellar masses. Oxygen abundances of these interacting galaxies seem to decrease compared to the control objects at the large aperture sizes measured in effective radius. Altho...

  16. Galaxy Zoo: Mergers - Dynamical Models of Interacting Galaxies

    CERN Document Server

    Holincheck, Anthony J; Borne, Kirk; Fortson, Lucy; Lintott, Chris; Smith, Arfon M; Bamford, Steven; Keel, William C; Parrish, Michael

    2016-01-01

    The dynamical history of most merging galaxies is not well understood. Correlations between galaxy interaction and star formation have been found in previous studies, but require the context of the physical history of merging systems for full insight into the processes that lead to enhanced star formation. We present the results of simulations that reconstruct the orbit trajectories and disturbed morphologies of pairs of interacting galaxies. With the use of a restricted three-body simulation code and the help of Citizen Scientists, we sample 10^5 points in parameter space for each system. We demonstrate a successful recreation of the morphologies of 62 pairs of interacting galaxies through the review of more than 3 million simulations. We examine the level of convergence and uniqueness of the dynamical properties of each system. These simulations represent the largest collection of models of interacting galaxies to date, providing a valuable resource for the investigation of mergers. This paper presents the ...

  17. Interaction-Triggered Star Formation in Distant Galaxies and the Role of Mergers in Galaxy Evolution

    CERN Document Server

    Lin, Lihwai

    2009-01-01

    The evolution of galaxy merger rates and its impact on galaxy properties have been studied intensively over the last decade. It becomes clear now that various types of mergers, i.e. gas-rich (wet), gas-poor (dry), or mixed mergers, affect the merger products in different ways. The epoch when each type of merger dominates also differs. In this talk, I review the recent progress on the measurements of galaxy merger rates out to z ~ 3 and the level of interaction-triggered star formation using large samples from various redshift surveys. These results provide insights to the importance of mergers in the mass assembly history of galaxies and in the evolution of galaxy properties. I also present new results in characterizing the environment of galaxy mergers, and discuss their implications in the built up of red-sequence galaxies.

  18. Galaxy-environment Interactions as Revealed by the Circumgalactic Medium

    Science.gov (United States)

    Burchett, Joseph; Tripp, Todd M.; Wang, Daniel; Willmer, Christopher; Prochaska, Jason X.; Werk, Jessica; Bordoloi, Rongmon; Katz, Neal; Tumlinson, Jason

    2017-01-01

    Galaxies do not live in isolation, and their star formation activity and gas supply are closely tied to the density of the environment in which they reside. The circumgalactic medium (CGM) serves as the point of first contact between a galaxy and its environment and mediates the gas accretion and outflow processes that regulate the galaxy ecosystem. Employing a combination of ultraviolet QSO spectroscopy, optical galaxy surveys, and X-ray imaging and spectroscopy, I will show that the metal-enriched gas and cool, photoionized H I in the CGM gas reflect the galaxy’s large-scale environment from scales of modest groups to clusters. Thus, QSO absorption line spectroscopy provides uniquely sensitive multiphase gas diagnostics of the physical conditions at the sites of galaxy-environment interactions. By shock-heating or stripping the CGM gas, as is indicated by its absorption, these interactions may deplete or deprive the galaxy's gas supply and quench its star formation.

  19. Galaxy interactions II: High density environments

    CERN Document Server

    Alonso, Sol; Padilla, Nelson; Lambas, Diego G

    2011-01-01

    With the aim to assess the role of dense environments in galaxy interactions, properties we present an analysis of close galaxy pairs in groups and clusters, obtained from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7). We identified pairs that reside in groups by cross-correlating the total galaxy pair catalogue with the SDSS-DR7 group catalogue from Zapata et al. (2009). We classify pair galaxies according to the intensity of interaction. We analysed the effect of high density environments on different classes of galaxy-galaxy interactions and we have also studied the impact of the group global environment on pair galaxies. We find that galaxy pairs are more concentrated towards the group centres with respect to the other group galaxy members, and disturbed pairs show a preference to contain the brightest galaxy in the groups. The color-magnitude relation exhibits significant differences between pair galaxies and the control sample, consisting in color tails with a clear excess of extremely blue and...

  20. Global environmental effects versus galaxy interactions

    CERN Document Server

    Perez, Josefa; Padilla, Nelson; Alonso, M Sol; Lambas, Diego G

    2009-01-01

    We explore properties of close galaxy pairs and merging systems selected from the SDSS-DR4 in different environments with the aim to assess the relative importance of the role of interactions over global environmental processes. For this purpose, we perform a comparative study of galaxies with and without close companions as a function of local density and host-halo mass, carefully removing sources of possible biases. We find that at low and high local density environments, colours and morphologies of close galaxy pairs are very similar to those of isolated galaxies. At intermediate densities, we detect significant differences, indicating that close pairs could have experienced a more rapid transition onto the red sequence than isolated galaxies. The presence of a correlation between colours and morphologies indicates that the physical mechanism responsible for the colour transformation also operates changing galaxy morphologies. Regardless of dark matter halo mass, we show that the percentage of red galaxies...

  1. Galaxy Zoo: Mergers - Dynamical models of interacting galaxies

    Science.gov (United States)

    Holincheck, Anthony J.; Wallin, John F.; Borne, Kirk; Fortson, Lucy; Lintott, Chris; Smith, Arfon M.; Bamford, Steven; Keel, William C.; Parrish, Michael

    2016-06-01

    The dynamical history of most merging galaxies is not well understood. Correlations between galaxy interaction and star formation have been found in previous studies, but require the context of the physical history of merging systems for full insight into the processes that lead to enhanced star formation. We present the results of simulations that reconstruct the orbit trajectories and disturbed morphologies of pairs of interacting galaxies. With the use of a restricted three-body simulation code and the help of citizen scientists, we sample 105 points in parameter space for each system. We demonstrate a successful recreation of the morphologies of 62 pairs of interacting galaxies through the review of more than 3 million simulations. We examine the level of convergence and uniqueness of the dynamical properties of each system. These simulations represent the largest collection of models of interacting galaxies to date, providing a valuable resource for the investigation of mergers. This paper presents the simulation parameters generated by the project. They are now publicly available in electronic format at http://data.galaxyzoo.org/mergers.html. Though our best-fitting model parameters are not an exact match to previously published models, our method for determining uncertainty measurements will aid future comparisons between models. The dynamical clocks from our models agree with previous results of the time since the onset of star formation from starburst models in interacting systems and suggest that tidally induced star formation is triggered very soon after closest approach.

  2. Galaxy Formation and Large Scale Structure

    CERN Document Server

    Ellis, R

    1999-01-01

    Galaxies represent the visible fabric of the Universe and there has been considerable progress recently in both observational and theoretical studies. The underlying goal is to understand the present-day diversity of galaxy forms, masses and luminosities in the context of theories for the growth of structure. Popular models predict the bulk of the galaxy population assembled recently, in apparent agreement with optical and near-infrared observations. However, detailed conclusions rely crucially on the choice of the cosmological parameters. Although the star formation history has been sketched to early times, uncertainties remain, particularly in connecting to the underlying mass assembly rate. I discuss the expected progress in determining the cosmological parameters and address the question of which observations would most accurately check contemporary models for the origin of the Hubble sequence. The new generation of ground-based and future space-based large telescopes, equipped with instrumentation approp...

  3. The SAMI Galaxy Survey: Galaxy Interactions and Kinematic Anomalies in Abell 119

    Science.gov (United States)

    Oh, Sree; Yi, Sukyoung K.; Cortese, Luca; van de Sande, Jesse; Mahajan, Smriti; Jeong, Hyunjin; Sheen, Yun-Kyeong; Allen, James T.; Bekki, Kenji; Bland-Hawthorn, Joss; Bloom, Jessica V.; Brough, Sarah; Bryant, Julia J.; Colless, Matthew; Croom, Scott M.; Fogarty, L. M. R.; Goodwin, Michael; Green, Andy; Konstantopoulos, Iraklis S.; Lawrence, Jon; López-Sánchez, Á. R.; Lorente, Nuria P. F.; Medling, Anne M.; Owers, Matt S.; Richards, Samuel; Scott, Nicholas; Sharp, Rob; Sweet, Sarah M.

    2016-11-01

    Galaxy mergers are important events that can determine the fate of a galaxy by changing its morphology, star formation activity and mass growth. Merger systems have commonly been identified from their disturbed morphologies, and we now can employ integral field spectroscopy to detect and analyze the impact of mergers on stellar kinematics as well. We visually classified galaxy morphology using deep images ({μ }{{r}}=28 {mag} {{arcsec}}-2) taken by the Blanco 4 m telescope at the Cerro Tololo Inter-American Observatory. In this paper we investigate 63 bright ({M}{{r}}\\lt -19.3) spectroscopically selected galaxies in Abell 119, of which 53 are early type and 20 show a disturbed morphology by visual inspection. A misalignment between the major axes in the photometric image and the kinematic map is conspicuous in morphologically disturbed galaxies. Our sample is dominated by early-type galaxies, yet it shows a surprisingly tight Tully-Fisher relation except for the morphologically disturbed galaxies which show large deviations. Three out of the eight slow rotators in our sample are morphologically disturbed. The morphologically disturbed galaxies are generally more asymmetric, visually as well as kinematically. Our findings suggest that galaxy interactions, including mergers and perhaps fly-bys, play an important role in determining the orientation and magnitude of a galaxy’s angular momentum.

  4. Interactions of Galaxies outside Clusters and Massive Groups

    CERN Document Server

    Yadav, Jaswant K

    2014-01-01

    We investigate the dependence of physical properties on small and large scale density environment. The galaxy population consists of mainly passively evolving galaxies in comparatively low density regions of Sloan Digital Sky Survey (SDSS). The environment is defined by (i) local density using adaptive smoothing kernel, (ii)projected distance, $r_p$, to the nearest neighbor and (iii) the morphology of the nearest neighbor. In order to detect long-range interaction effects we divide galaxy interactions into four cases depending on morphology of target and neighbor galaxies. We report that the impact of interaction on galaxy properties is detectable at least out to the pair separation corresponding to the virial radius of (the neighbor) galaxies in our sample, which is mostly between 210 and 360 $h^{-1}$kpc. We show that early type fraction, for isolated galaxies with $r_p > r_{vir,nei}$ are almost ignorant of the background density and, has a very weak density dependence for closed pairs. Star formation activi...

  5. Star formation triggered by galaxy interactions in modified gravity

    CERN Document Server

    Renaud, Florent; Kroupa, Pavel

    2016-01-01

    Together with interstellar turbulence, gravitation is one key player in star formation. It acts both at galactic scales in the assembly of gas into dense clouds, and inside those structures for their collapse and the formation of pre-stellar cores. To understand to what extent the large scale dynamics govern the star formation activity of galaxies, we present hydrodynamical simulations in which we generalise the behaviour of gravity to make it differ from Newtonian dynamics in the low acceleration regime. We focus on the extreme cases of interacting galaxies, and compare the evolution of galaxy pairs in the dark matter paradigm to that in the Milgromian Dynamics (MOND) framework. Following up on the seminal work by Tiret & Combes, this paper documents the first simulations of galaxy encounters in MOND with a detailed Eulerian hydrodynamical treatment of baryonic physics, including star formation and stellar feedback. We show that similar morphologies of the interacting systems can be produced by both the ...

  6. An Interacting Galaxy System along a Filament in a Void

    NARCIS (Netherlands)

    Beygu, B.; Kreckel, K.; van de Weijgaert, R.; van der Hulst, J. M.; van Gorkom, J. H.

    2013-01-01

    Cosmological voids provide a unique environment for the study of galaxy formation and evolution. The galaxy population in their interiors has properties significantly different from average field galaxies. As part of our Void Galaxy Survey (VGS), we have found a system of three interacting galaxies

  7. Optimising large galaxy surveys for ISW detection

    CERN Document Server

    Douspis, Marian; Caprini, Chiara; Aghanim, Nabila

    2008-01-01

    We report on investigations of the power of next generation cosmic microwave background and large scale structure surveys in constraining the nature of dark energy through the cross-correlation of the Integrated Sachs Wolfe effect and the galaxy distribution. First we employ a signal to noise analysis to find the most appropriate properties of a survey in order to detect the correlated signal at a level of more than 4 sigma: such a survey should cover more than 35% of the sky, the galaxy distribution should be probed with a median redshift higher than 0.8, and the number of galaxies detected should be higher than a few per squared arcmin. We consider the forthcoming surveys DUNE, LSST, SNAP, PanSTARRS. We then compute the constraints that the DUNE survey can put on the nature of dark energy (through different parametrizations of its equation of state) with a standard Fisher matrix analysis. We confirm that, with respect to pure CMB constraints, cross-correlation constraints help in breaking degeneracies among...

  8. Signatures of Galaxy-Cluster Interactions Spiral Galaxy Rotation Curve Asymmetry, Shape, and Extent

    CERN Document Server

    Dale, D A; Haynes, M P; Hardy, E; Campusano, L E; Dale, Daniel A.; Giovanelli, Riccardo; Haynes, Martha P.; Hardy, Eduardo; Campusano, Luis E.

    2001-01-01

    The environmental dependencies of the characteristics of spiral galaxy rotation curves are studied in this work. We use our large, homogeneously collected sample of 510 cluster spiral galaxy rotation curves to test the claim that the shape of a galaxy's rotation curve strongly depends on its location within the cluster, and thus presumably on the strength of the local intracluster medium and on the frequency and strength of tidal interactions with the cluster and cluster galaxies. Our data do not corroborate such a scenario, consistent with the fact that Tully-Fisher residuals are independent of galaxy location within the cluster; while the average late-type spiral galaxy shows more rise in the outer parts of its rotation curve than does the typical early-type spiral galaxy, there is no apparent trend for either subset with cluster environment. We also investigate as a function of cluster environment rotation curve asymmetry and the radial distribution of H II region tracers within galactic disks. Mild trends...

  9. Traces de l'interaction entre galaxies

    Science.gov (United States)

    Duc, Pierre-Alain

    2016-08-01

    Within a galaxy, collisions between stars are exceptional; collisions between galaxies are themselves much more frequent. They are even supposed to play a major role in the formation of structures according to the standard hierarchical cosmological model. Gravitational interactions, tidal forces and following mergers shape the morphology of galaxies, and leave vestiges which can survive for a few Gyr. They consist of stellar shells, streams, tails and plumes which emit a diffuse and extended optical light. Several deep imaging projects use telescopes of all sizes to try to detect this light. We detail here what the census of collisional debris can tel us about the past history of galaxies and about the models and simulations supposedly accounting for it.

  10. Star formation triggered by galaxy interactions in modified gravity

    Science.gov (United States)

    Renaud, Florent; Famaey, Benoit; Kroupa, Pavel

    2016-09-01

    Together with interstellar turbulence, gravitation is one key player in star formation. It acts both at galactic scales in the assembly of gas into dense clouds, and inside those structures for their collapse and the formation of pre-stellar cores. To understand to what extent the large scale dynamics govern the star formation activity of galaxies, we present hydrodynamical simulations in which we generalise the behaviour of gravity to make it differ from Newtonian dynamics in the low acceleration regime. We focus on the extreme cases of interacting galaxies, and compare the evolution of galaxy pairs in the dark matter paradigm to that in the Milgromian Dynamics (MOND) framework. Following up on the seminal work by Tiret & Combes, this paper documents the first simulations of galaxy encounters in MOND with a detailed Eulerian hydrodynamical treatment of baryonic physics, including star formation and stellar feedback. We show that similar morphologies of the interacting systems can be produced by both the dark matter and MOND formalisms, but require a much slower orbital velocity in the MOND case. Furthermore, we find that the star formation activity and history are significantly more extended in space and time in MOND interactions, in particular in the tidal debris. Such differences could be used as observational diagnostics and make interacting galaxies prime objects in the study of the nature of gravitation at galactic scales.

  11. Using large galaxy surveys to distinguish z~0.5 quiescent galaxy models

    CERN Document Server

    Cohn, J D

    2013-01-01

    One of the most striking properties of galaxies is the bimodality in their star-formation rates. A major puzzle is why any given galaxy is star-forming or quiescent, and a wide range of physical mechanisms have been proposed as solutions. We consider how observations, such as might be available in upcoming large galaxy surveys, might distinguish different galaxy quenching scenarios. To do this, we combine an N-body simulation and multiple prescriptions from the literature to create several quiescent galaxy mock catalogues. Each prescription uses a different set of galaxy properties (such as history, environment, centrality) to assign individual simulation galaxies as quiescent. We find how and how much the resulting quiescent galaxy distributions differ from each other, both intrinsically and observationally. In addition to tracing observational consequences of different quenching mechanisms, our results indicate which sorts of quenching models might be most readily disentangled by upcoming observations and w...

  12. Modeling Interacting Galaxies: NGC 4449 revisited

    Science.gov (United States)

    Theis, C.; Jungwirth, G.; Petsch, H.; Walter, F.

    2011-01-01

    Observing nearby interacting galaxies is a key to understanding galactic physics provided that we know the spatial and temporal perturbations acting on these galaxies. Thus, we have to know the orbits and the gross internal properties of the galaxies. In order to cope with the related extended parameter space, we developed the code MINGA which combines a genetic algorithm with a fast N-body method. As an example for this method, we present a re-analysis of the prototypical system NGC 4449 which is now based on both, the full HI data cube of the NGC 4449 system and on improved determinations of the galactic orbits within a restricted N-body calculation.

  13. How much a galaxy knows about its large-scale environment ? : An information theoretic perspective

    CERN Document Server

    Pandey, Biswajit

    2016-01-01

    The small-scale environment characterized by the local density is known to play a crucial role in deciding the galaxy properties but the role of large-scale environment on galaxy formation and evolution still remain a less clear issue. We propose an information theoretic framework to investigate the influence of large-scale environment on galaxy properties and apply it to the data from the Galaxy Zoo project which provides the visual morphological classifications of $\\sim 1$ million galaxies from the Sloan Digital Sky Survey. We find a non-zero mutual information between morphology and environment which decreases with increasing length scales but persists throughout the entire length scales probed. We estimate the conditional mutual information and the interaction information between morphology and environment by conditioning the environment on different length scales and find a synergic interaction between them which operates upto at least a length scales of $ \\sim 30 \\, h^{-1}\\, {\\rm Mpc}$. Our analysis ind...

  14. 2D velocity fields of simulated interacting disc galaxies

    CERN Document Server

    Kronberger, T; Schindler, S; Ziegler, B L

    2007-01-01

    We investigate distortions in the velocity fields of disc galaxies and their use to reveal the dynamical state of interacting galaxies at different redshift. For that purpose, we model disc galaxies in combined N-body/hydrodynamic simulations. 2D velocity fields of the gas are extracted from these simulations which we place at different redshifts from z=0 to z=1 to investigate resolution effects on the properties of the velocity field. To quantify the structure of the velocity field we also perform a kinemetry analysis. If the galaxy is undisturbed we find that the rotation curve extracted from the 2D field agrees well with long-slit rotation curves. This is not true for interacting systems, as the kinematic axis is not well defined and does in general not coincide with the photometric axis of the system. For large (Milky way type) galaxies we find that distortions are still visible at intermediate redshifts but partly smeared out. Thus a careful analysis of the velocity field is necessary before using it for...

  15. Simulated Galaxy Interactions as Probes of Merger Spectral Energy Distributions

    CERN Document Server

    Lanz, Lauranne; Zezas, Andreas; Smith, Howard A; Ashby, Matthew L N; Brassington, Nicola; Fazio, Giovanni G; Hernquist, Lars

    2014-01-01

    We present the first systematic comparison of ultraviolet-millimeter spectral energy distributions (SEDs) of observed and simulated interacting galaxies. Our sample is drawn from the Spitzer Interacting Galaxy Survey, and probes a range of galaxy interaction parameters. We use 31 galaxies in 14 systems which have been observed with Herschel, Spitzer, GALEX, and 2MASS. We create a suite of GADGET-3 hydrodynamic simulations of isolated and interacting galaxies with stellar masses comparable to those in our sample of interacting galaxies. Photometry for the simulated systems is then calculated with the SUNRISE radiative transfer code for comparison with the observed systems. For most of the observed systems, one or more of the simulated SEDs match reasonably well. The best matches recover the infrared luminosity and the star formation rate of the observed systems, and the more massive systems preferentially match SEDs from simulations of more massive galaxies. The most morphologically distorted systems in our sa...

  16. Gravitational Interactions in Poor Galaxy Groups

    CERN Document Server

    Davis, D S; Mulchaey, J S; Henning, P A; Davis, David S.; Keel, William C.; Mulchaey, John S.; Henning, Patricia A.

    1997-01-01

    We report the results of the spatial analysis of deep ROSAT HRI observations, optical imaging and spectroscopy, and high-resolution VLA H I and continuum imaging of NGC 1961 and NGC 2276. These spirals were selected as showing some previous evidence for interaction with a surrounding (hot) diffuse medium. Our results favor most aspects of these galaxies as being shaped by gravitational interactions with companions, rather than the asymmetric pressure from motion through an external medium. The old stars follow the asymmetric structures of young stars and ionized gas, which suggests a tidal origin for the lopsided appearance of these galaxies. In NGC 2276, the H I and star-forming regions are strongly concentrated along the western edge of the disk. In this case, the ROSAT HRI detects the brightest star-forming regions as well as the diffuse disk emission, the most distant galaxy with such a detection. An asymmetric ionization gradient in the H II regions suggests radial movement of gas, which might have occur...

  17. Alignment between galaxies and large-scale structure

    Institute of Scientific and Technical Information of China (English)

    A. Faltenbacher; Cheng Li; Simon D. M. White; Yi-Peng Jing; Shu-De Mao; Jie Wang

    2009-01-01

    Based on the Sloan Digital Sky Survey DR6 (SDSS) and the Millennium Simulation (MS), we investigate the alignment between galaxies and large-scale struc-ture. For this purpose, we develop two new statistical tools, namely the alignment cor-relation function and the cos(20)-statistic. The former is a two-dimensional extension of the traditional two-point correlation function and the latter is related to the ellipticity correlation function used for cosmic shear measurements. Both are based on the cross correlation between a sample of galaxies with orientations and a reference sample which represents the large-scale structure. We apply the new statistics to the SDSS galaxy cat-alog. The alignment correlation function reveals an overabundance of reference galaxies along the major axes of red, luminous (L L*) galaxies out to projected separations of 60 h-1Mpc. The signal increases with central galaxy luminosity. No alignment signal is detected for blue galaxies. The cos(2θ)-statistic yields very similar results. Starting from a MS semi-analytic galaxy catalog, we assign an orientation to each red, luminous and central galaxy, based on that of the central region of the host halo (with size similar to that of the stellar galaxy). As an alternative, we use the orientation of the host halo itself. We find a mean projected misalignment between a halo and its central region of ~ 25°. The misalignment decreases slightly with increasing luminosity of the central galaxy. Using the orientations and luminosities of the semi-analytic galaxies, we repeat our alignment analysis on mock surveys of the MS. Agreement with the SDSS results is good if the central orientations are used. Predictions using the halo orientations as proxies for cen-tral galaxy orientations overestimate the observed alignment by more than a factor of 2. Finally, the large volume of the MS allows us to generate a two-dimensional map of the alignment correlation function, which shows the reference galaxy

  18. A Comparative Study of Knots of Star Formation in Interacting vs. Spiral Galaxies

    CERN Document Server

    Smith, Beverly J; Struck, Curtis; Olmsted, Susan; Jones, Keith

    2016-01-01

    Interacting galaxies are known to have higher global rates of star formation on average than normal galaxies, relative to their stellar masses. Using UV and IR photometry combined with new and published H-alpha images, we have compared the star formation rates of ~700 star forming complexes in 46 nearby interacting galaxy pairs with those of regions in 39 normal spiral galaxies. The interacting galaxies have proportionally more regions with high star formation rates than the spirals. The most extreme regions in the interacting systems lie at the intersections of spiral/tidal structures, where gas is expected to pile up and trigger star formation. Published Hubble Telescope images show unusually large and luminous star clusters in the highest luminosity regions. The star formation rates of the clumps correlate with measures of the dust attenuation, consistent with the idea that regions with more interstellar gas have more star formation. For the clumps with the highest star formation rates, the apparent dust a...

  19. Galaxy And Mass Assembly (GAMA): The large scale structure of galaxies and comparison to mock universes

    CERN Document Server

    Alpaslan, Mehmet; Driver, Simon; Norberg, Peder; Baldry, Ivan; Bauer, Amanda E; Bland-Hawthorn, Joss; Brown, Michael; Cluver, Michelle; Colless, Matthew; Foster, Caroline; Hopkins, Andrew; Van Kampen, Eelco; Kelvin, Lee; Lara-Lopez, Maritza A; Liske, Jochen; Lopez-Sanchez, Angel R; Loveday, Jon; McNaught-Roberts, Tamsyn; Merson, Alexander; Pimbblet, Kevin

    2014-01-01

    From a volume limited sample of 45,542 galaxies and 6,000 groups with $z \\leq 0.213$ we use an adapted minimal spanning tree algorithm to identify and classify large scale structures within the Galaxy and Mass Assembly (GAMA) survey. Using galaxy groups, we identify 643 filaments across the three equatorial GAMA fields that span up to 200 $h^{-1}$ Mpc in length, each with an average of 8 groups within them. By analysing galaxies not belonging to groups we identify a secondary population of smaller coherent structures composed entirely of galaxies, dubbed `tendrils' that appear to link filaments together, or penetrate into voids, generally measuring around 10 $h^{-1}$ Mpc in length and containing on average 6 galaxies. Finally we are also able to identify a population of isolated void galaxies. By running this algorithm on GAMA mock galaxy catalogues we compare the characteristics of large scale structure between observed and mock data; finding that mock filaments reproduce observed ones extremely well. This p...

  20. Distant galaxy clusters in the XMM Large Scale Structure survey

    CERN Document Server

    Willis, J P; Bremer, M N; Pierre, M; Adami, C; Ilbert, O; Maughan, B; Maurogordato, S; Pacaud, F; Valtchanov, I; Chiappetti, L; Thanjavur, K; Gwyn, S; Stanway, E R; Winkworth, C

    2012-01-01

    (Abridged) Distant galaxy clusters provide important tests of the growth of large scale structure in addition to highlighting the process of galaxy evolution in a consistently defined environment at large look back time. We present a sample of 22 distant (z>0.8) galaxy clusters and cluster candidates selected from the 9 deg2 footprint of the overlapping X-ray Multi Mirror (XMM) Large Scale Structure (LSS), CFHTLS Wide and Spitzer SWIRE surveys. Clusters are selected as extended X-ray sources with an accompanying overdensity of galaxies displaying optical to mid-infrared photometry consistent with z>0.8. Nine clusters have confirmed spectroscopic redshifts in the interval 0.80.8 clusters.

  1. The role of tidal interactions in driving galaxy evolution

    CERN Document Server

    Pérez, J; Lambas, D G; Scannapieco, C; Perez, Josefa; Tissera, Patricia B.; Lambas, Diego G.; Scannapieco, Cecilia

    2006-01-01

    We carry out a statistical analysis of galaxy pairs selected from chemical hydrodynamical simulations with the aim at assessing the capability of hierarchical scenarios to reproduce recent observational results for galaxies in pairs. Particularly, we analyse the effects of mergers and interactions on the star formation (SF) activity, the global mean chemical properties and the colour distribution of interacting galaxies. We also assess the effects of spurious pairs.

  2. Isolated Galaxies versus Interacting Pairs with MaNGA

    CERN Document Server

    Argudo-Fernández, M; Shen, S; Yin, J; Chang, R; Feng, S

    2015-01-01

    We present preliminary results of the spectral analysis on the radial distributions of the star formation history in both, a galaxy merger and a spiral isolated galaxy observed with MaNGA. We find that the central part of the isolated galaxy is composed by older stellar population ($\\sim$2 Gyr) than in the outskirts ($\\sim$7 Gyr). Also, the time-scale is gradually larger from 1 Gyr in the inner part to 3 Gyr in the outer regions of the galaxy. In the case of the merger, the stellar population in the central region is older than in the tails, presenting a longer time-scale in comparison to central part in the isolated galaxy. Our results are in agreement with a scenario where spiral galaxies are built from inside-out. In the case of the merger, we find evidence that interactions enhance star formation in the central part of the galaxy.

  3. Isolated Galaxies versus Interacting Pairs with MaNGA

    Science.gov (United States)

    Fernández, María; Yuan, Fangting; Shen, Shiyin; Yin, Jun; Chang, Ruixiang; Feng, Shuai

    2015-10-01

    We present preliminary results of the spectral analysis on the radial distributions of the star formation history in both, a galaxy merger and a spiral isolated galaxy observed with MaNGA. We find that the central part of the isolated galaxy is composed by older stellar population ($\\sim$2 Gyr) than in the outskirts ($\\sim$7 Gyr). Also, the time-scale is gradually larger from 1 Gyr in the inner part to 3 Gyr in the outer regions of the galaxy. In the case of the merger, the stellar population in the central region is older than in the tails, presenting a longer time-scale in comparison to central part in the isolated galaxy. Our results are in agreement with a scenario where spiral galaxies are built from inside-out. In the case of the merger, we find evidence that interactions enhance star formation in the central part of the galaxy.

  4. An Atlas of GALEX UV Images of Interacting Galaxies

    CERN Document Server

    Giroux, Mark L; Struck, Curtis; Hancock, Mark; Hurlock, Sabrina

    2009-01-01

    We present GALEX ultraviolet images from a survey of strongly interacting galaxy pairs, and compare with images at other wavelengths. The tidal features are particularly striking in the UV images. Numerous knots of star formation are visible throughout the disks and the tails and bridges. We also identify a possible `Taffy' galaxy in our sample, which may have been produced by a head-on collision between two disk galaxies.

  5. Morphology and Interaction of Galaxies using Deep Learning

    Science.gov (United States)

    Caro, Fernando; Huertas-Company, Marc; Cabrera, Guillermo

    2017-06-01

    In order to understand how galaxies form and evolve, the measurement of the parameters related to their morphologies and also to the way they interact is one of the most relevant requirements. Due to the huge amount of data that is generated by surveys, the morphological and interaction analysis of galaxies can no longer rely on visual inspection. For dealing with such issue, new approaches based on machine learning techniques have been proposed in the last years with the aim of automating the classification process. We tested Deep Learning using images of galaxies obtained from CANDELS to study the accuracy achieved by this tool considering two different frameworks. In the first, galaxies were classified in terms of their shapes considering five morphological categories, while in the second, the way in which galaxies interact was employed for defining other five categories. The results achieved in both cases are compared and discussed.

  6. Galaxy And Mass Assembly (GAMA): the effect of close interactions on star formation in galaxies

    CERN Document Server

    Davies, L J M; Driver, S P; Alpaslan, M; Baldry, I K; Bland-Hawthorn, J; Brough, S; Brown, M J I; Cluver, M E; Drinkwater, M J; Foster, C; Grootes, M W; Konstantopoulos, I S; Lara-Lopez, M A; Lopez-Sanchez, A R; Loveday, J; Meyer, M J; Moffett, A J; Norberg, P; Owers, M S; Popescu, C C; De Propris, R; Sharp, R; Tuffs, R J; Wang, L; Wilkins, S M; Bourne, L Dunne N; Smith, M W L

    2015-01-01

    The modification of star formation (SF) in galaxy interactions is a complex process, with SF observed to be both enhanced in major mergers and suppressed in minor pair interactions. Such changes likely to arise on short timescales and be directly related to the galaxy-galaxy interaction time. Here we investigate the link between dynamical phase and direct measures of SF on different timescales for pair galaxies, targeting numerous star-formation rate (SFR) indicators and comparing to pair separation, individual galaxy mass and pair mass ratio. We split our sample into the higher (primary) and lower (secondary) mass galaxies in each pair and find that SF is indeed enhanced in all primary galaxies but suppressed in secondaries of minor mergers. We find that changes in SF of primaries is consistent in both major and minor mergers, suggesting that SF in the more massive galaxy is agnostic to pair mass ratio. We also find that SF is enhanced/suppressed more strongly for short-time duration SFR indicators (e.g. H-a...

  7. A COMPARATIVE STUDY OF KNOTS OF STAR FORMATION IN INTERACTING VERSUS SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Beverly J.; Olmsted, Susan; Jones, Keith [Department of Physics and Astronomy, East Tennessee State University, Johnson City TN 37614 (United States); Zaragoza-Cardiel, Javier [Instituto de Astrofisica de Canarias, La Laguna, Tenerife (Spain); Struck, Curtis, E-mail: smithbj@etsu.edu [Department of Physics and Astronomy, Iowa State University, Ames IA 50011 (United States)

    2016-03-15

    Interacting galaxies are known to have higher global rates of star formation on average than normal galaxies, relative to their stellar masses. Using UV and IR photometry combined with new and published Hα images, we have compared the star formation rates (SFRs) of ∼700 star forming complexes in 46 nearby interacting galaxy pairs with those of regions in 39 normal spiral galaxies. The interacting galaxies have proportionally more regions with high SFRs than the spirals. The most extreme regions in the interacting systems lie at the intersections of spiral/tidal structures, where gas is expected to pile up and trigger star formation. Published Hubble Space Telescope images show unusually large and luminous star clusters in the highest luminosity regions. The SFRs of the clumps correlate with measures of the dust attenuation, consistent with the idea that regions with more interstellar gas have more star formation. For the clumps with the highest SFRs, the apparent dust attenuation is consistent with the Calzetti starburst dust attenuation law. This suggests that the high luminosity regions are dominated by a central group of young stars surrounded by a shell of clumpy interstellar gas. In contrast, the lower luminosity clumps are bright in the UV relative to Hα, suggesting either a high differential attenuation between the ionized gas and the stars, or a post-starburst population bright in the UV but faded in Hα. The fraction of the global light of the galaxies in the clumps is higher on average for the interacting galaxies than for the spirals. Thus either star formation in interacting galaxies is “clumpier” on average, or the star forming regions in interacting galaxies are more luminous, dustier, or younger on average.

  8. Kinematic classification of non-interacting spiral galaxies

    CERN Document Server

    Wiegert, Theresa

    2013-01-01

    Using neutral hydrogen (HI) rotation curves of 79 galaxies, culled from the literature, as well as measured from HI data, we present a method for classifying disk galaxies by their kinematics. In order to investigate fundamental kinematic properties we concentrate on non-interacting spiral galaxies. We employ a simple parameterized form for the rotation curve in order to derive the three parameters: the maximum rotational velocity, the turnover radius and a measure of the slope of the rotation curve beyond the turnover radius. Our approach uses the statistical Hierarchical Clustering method to guide our division of the resultant 3D distribution of galaxies into five classes. Comparing the kinematic classes in this preliminary classification scheme to a number of galaxy properties we find that our class containing galaxies with the largest rotational velocities has a mean morphological type of Sb/Sbc while the other classes tend to later types. Other trends also generally agree with those described by previous...

  9. Simulating disk galaxies and interactions in Milgromian dynamics

    CERN Document Server

    Thies, Ingo; Famaey, Benoit

    2016-01-01

    Since its publication 1983, Milgromian dynamics (aka MOND) has been very successful in modeling the gravitational potential of galaxies from baryonic matter alone. However, the dynamical modeling has long been an unsolved issue. In particular, the setup of a stable galaxy for Milgromian N-body calculations has been a major challenge. Here, I will show a way to set up disc galaxies in MOND for calculations in the PHANTOM OF RAMSES (PoR) code by L\\"ughausen (2015) and Teyssier (2002). The method is done by solving the QUMOND Poisson equations based on a baryonic and a phantom dark matter component. The resulting galaxy models are stable after a brief settling period for a large mass and size range. Simulations of single galaxies as well as colliding galaxies are shown.

  10. An Empirical Relation Between The Large-Scale Magnetic Field And The Dynamical Mass In Galaxies

    CERN Document Server

    Tabatabaei, F S; Knapen, J H; Beckman, J E; Koribalski, B; Elmegreen, B G

    2015-01-01

    The origin and evolution of cosmic magnetic fields as well as the influence of the magnetic fields on the evolution of galaxies are unknown. Though not without challenges, the dynamo theory can explain the large-scale coherent magnetic fields which govern galaxies, but observational evidence for the theory is so far very scarce. Putting together the available data of non-interacting, non-cluster galaxies with known large-scale magnetic fields, we find a tight correlation between the integrated polarized flux density and the rotation speed, v(rot), of galaxies. This leads to an almost linear correlation between the large-scale magnetic field B and v(rot), assuming that the number of cosmic ray electrons is proportional to the star formation rate. This correlation cannot be attributed to an active linear dynamo processes, as no correlation holds with shear or angular speed. It indicates instead a coupling between the large-scale magnetic field and the dynamical mass of the galaxies, B~M(dyn)^{0.2-0.3}. Hence, f...

  11. Galaxy morphologies in the era of large surveys

    Science.gov (United States)

    Huertas-Company, Marc

    2015-08-01

    With the emergence in the last years of large surveys, extragalactic astronomy has made a significant step forward. 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 analyze data and in particular to estimate galaxy morphologies need to be updated.In my talk, I will first review the current state-of-the art techniques/approaches (citizen science, machine learning etc..) to estimate galaxy morphologies at high redshift. I will then focus on a new promising technique based on deep-learning which we have used to provide robust morphologies in all CANDELS fields with unprecedented accuracy. Finally I will show how robust morphological information can be used to infer the physical mechanisms of bulge growth in the progenitors of massive early-type galaxies today.

  12. A BRIGHTEST CLUSTER GALAXY WITH AN EXTREMELY LARGE FLAT CORE

    Energy Technology Data Exchange (ETDEWEB)

    Postman, Marc; Coe, Dan; Koekemoer, Anton; Bradley, Larry [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Lauer, Tod R. [National Optical Astronomy Observatory, P.O. Box 26732, Tucson, AZ 85726 (United States); Donahue, Megan [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Graves, Genevieve [Department of Astronomy, 601 Campbell Hall, University of California, Berkeley, CA 94720 (United States); Moustakas, John [Center for Astrophysics and Space Sciences, University of California, La Jolla, CA 92093 (United States); Ford, Holland C.; Lemze, Doron; Medezinski, Elinor [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Grillo, Claudio [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Mariesvej 30, DK-2100 Copenhagen (Denmark); Zitrin, Adi [University of Heidelberg, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Broadhurst, Tom [Department of Theoretical Physics, University of the Basque Country UPV/EHU, Bizkaia, E-48940 Leioa (Spain); Moustakas, Leonidas [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Ascaso, Begona [Instituto de Astrofisica de Andalucia (CSIC), C/Camino Bajo de Huetor 24, E-18008 Granada (Spain); Kelson, Daniel [The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2012-09-10

    Hubble Space Telescope images of the galaxy cluster A2261, obtained as part of the Cluster Lensing And Supernova survey with Hubble, show that the brightest galaxy in the cluster, A2261-BCG, has the largest core yet detected in any galaxy. The cusp radius of A2261-BCG is 3.2 kpc, twice as big as the next largest core known, and {approx}3 Multiplication-Sign bigger than those typically seen in the most luminous brightest cluster galaxies. The morphology of the core in A2261-BCG is also unusual, having a completely flat interior surface brightness profile, rather than the typical shallow cusp rising into the center. This implies that the galaxy has a core with constant or even centrally decreasing stellar density. Interpretation of the core as an end product of the 'scouring' action of a binary supermassive black hole implies a total black hole mass {approx}10{sup 10} M{sub Sun} from the extrapolation of most relationships between core structure and black hole mass. The core falls 1{sigma} above the cusp radius versus galaxy luminosity relation. Its large size in real terms, and the extremely large black hole mass required to generate it, raises the possibility that the core has been enlarged by additional processes, such as the ejection of the black holes that originally generated the core. The flat central stellar density profile is consistent with this hypothesis. The core is also displaced by 0.7 kpc from the center of the surrounding envelope, consistent with a local dynamical perturbation of the core.

  13. Measuring Dark Matter Halos by Modeling Interacting Galaxies

    Science.gov (United States)

    Theis, C.

    2004-07-01

    The richness of tidal features seen in interacting galaxies allows for the determination of their characteristic parameters, provided one can deal with the extended parameter space. Genetic algorithm based methods -- like our code MINGA -- have proven to be such a tool. Here I discuss the implementation of dark matter halo descriptions in the restricted N-body simulations of MINGA. I show that the final morphology of a galaxy encounter strongly depends on the halo properties. Thus, modeling tidal features of interacting galaxies might allow also for conclusions on the galactic dark matter content.

  14. Cluster Galaxy Dynamics and the Effects of Large Scale Environment

    CERN Document Server

    White, Martin; Smit, Renske

    2010-01-01

    We use a high-resolution N-body simulation to study how the influence of large-scale structure in and around clusters causes correlated signals in different physical probes and discuss some implications this has for multi-physics probes of clusters. We pay particular attention to velocity dispersions, matching galaxies to subhalos which are explicitly tracked in the simulation. We find that not only do halos persist as subhalos when they fall into a larger host, groups of subhalos retain their identity for long periods within larger host halos. The highly anisotropic nature of infall into massive clusters, and their triaxiality, translates into an anisotropic velocity ellipsoid: line-of-sight galaxy velocity dispersions for any individual halo show large variance depending on viewing angle. The orientation of the velocity ellipsoid is correlated with the large-scale structure, and thus velocity outliers correlate with outliers caused by projection in other probes. We quantify this orientation uncertainty and ...

  15. Studying Large and Small Scale Environments of Ultraviolet Luminous Galaxies

    CERN Document Server

    Basu-Zych, Antara R; Heinis, Sebastien; Overzier, Roderik; Heckman, Tim; Zamojski, Michel; Ilbert, Olivier; Koekemoer, Anton M; Barlow, Tom A; Bianchi, Luciana; Conrow, Tim; Donas, Jose; Forster, Karl G; Friedman, Peter G; Lee, Young-Wook; Madore, Barry F; Martin, D Christopher; Milliard, Bruno; Morrissey, Patrick; Neff, Susan G; Salim, R Michael Rich Samir; Seibert, Mark; Small, Todd A; Szalay, A S; Wyder, Ted K; Yi, Sukyoung

    2009-01-01

    Studying the environments of 0.4 =1.0, which is unable to constrain the halo mass for this sample. However, we find that UVLGs form close (separation < 30 kpc) pairs with the ALL sample, but do not frequently form pairs with LRGs. A rare subset of UVLGs, those with the highest FUV surface brightnesses, are believed to be local analogs of high redshift Lyman Break Galaxies (LBGs) and are called Lyman Break Analogs (LBAs). LBGs and LBAs share similar characteristics (i.e., color, size, surface brightness, specific star formation rates, metallicities, and dust content). Recent HST images of z~0.2 LBAs show disturbed morphologies, signs of mergers and interactions. UVLGs may be influenced by interactions with other galaxies and we discuss this result in terms of other high star-forming, merging systems.

  16. Galactic interaction as the trigger for the young radio galaxy MRC B1221-423

    CERN Document Server

    Anderson, Craig; Hunstead, Richard

    2013-01-01

    Mergers between a massive galaxy and a small gas-rich companion (minor mergers) have been proposed as a viable mechanism for triggering radio emission in an active galaxy. Until now the problem has been catching this sequence of events as they occur. With MRC B1221$-$423 we have an active radio galaxy that has only recently been triggered, and a companion galaxy that provides the "smoking gun". Using spectroscopic data taken with the VIMOS Integral Field Unit detector on the European Southern Observatory's Very Large Telescope, we have examined the distribution, ionization state and kinematics of ionized gas in this interacting system. We have also modelled the stellar continuum with synthesised spectra of stellar populations of different ages. From our study of the ionized gas, we have derived preliminary models for the geometry of the interaction, analysed the kinematic behaviour of the ionized gas, and examined the ionization mechanisms at work throughout the system. Our modelling of the stellar continuum ...

  17. Effects of galaxy interactions in different environments

    CERN Document Server

    Alonso, M S; Tissera, P B; Coldwell, G; Lambas, Diego G.; Tissera, Patricia B.; Coldwell, Georgina

    2006-01-01

    We analyse star formation rates derived from photometric and spectroscopic data of galaxies in pairs in different environments using the 2dF Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey (SDSS). The two samples comprise several thousand pairs, suitable to explore into detail the dependence of star formation activity in pairs on orbital parameters and global environment. We use the projected galaxy density derived from the fifth nearest neighbour of each galaxy, with convenient luminosity thresholds to characterise environment in both surveys in a consistent way. Star formation activity is derived through the $\\eta$ parameter in 2dFGRS and through the star formation rate normalised to the total mass in stars, $SFR/M^*$, given by Brinchmann et al. (2004) in the second data release SDSS-DR2. For both galaxy pair catalogs, the star formation birth rate parameter is a strong function of the global environment and orbital parameters. Our analysis on SDSS pairs confirms previous results found with...

  18. Star formation rates and mass distributions in interacting galaxies

    CERN Document Server

    Kapferer, W; Schindler, S; Van Kampen, E

    2005-01-01

    We present a systematic investigation of the star formation rate (hereafter SFR) in interacting disk galaxies. We determine the dependence of the overall SFR on different spatial alignments and impact parameters of more than 50 different configurations in combined N-body/hydrodynamic simulations. We also show mass profiles of the baryonic components. We find that galaxy-galaxy interactions can enrich the surrounding intergalatic medium with metals very efficiently up to distances of several 100 kpc. This enrichment can be explained in terms of indirect processes like thermal driven galactic winds or direct processes like 'kinetic' spreading of baryonic matter. In the case of equal mass mergers the direct -kinetic- redistribution of gaseous matter (after 5 Gyr) is less efficient than the environmental enrichment of the same isolated galaxies by a galactic wind. In the case of non-equal mass mergers however, the direct -kinetic- process dominates the redistribution of gaseous matter. Compared to the isolated sy...

  19. Cosmology from Large Scale Galaxy Clustering and Galaxy-Galaxy Lensing with Dark Energy Survey Science Verification Data

    Energy Technology Data Exchange (ETDEWEB)

    Kwan, J.; et al.

    2016-04-26

    We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 square degree contiguous patch of DES data from the Science Verification (SV) period of observations. Using large scale measurements, we constrain the matter density of the Universe as $\\Omega_m = 0.31 \\pm 0.09$ and the clustering amplitude of the matter power spectrum as $\\sigma_8 = 0.74 +\\pm 0.13$ after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into $S_8$ = $\\sigma_8(\\Omega_m/0.3)^{0.16} = 0.74 \\pm 0.12$ for our fiducial lens redshift bin at 0.35 < z < 0.5, while $S_8 = 0.78 \\pm 0.09$ using two bins over the range 0.2 < z < 0.5. We study the robustness of the results under changes in the data vectors, modelling and systematics treatment, including photometric redshift and shear calibration uncertainties, and find consistency in the derived cosmological parameters. We show that our results are consistent with previous cosmological analyses from DES and other data sets and conclude with a joint analysis of DES angular clustering and galaxy-galaxy lensing with Planck CMB data, Baryon Accoustic Oscillations and Supernova type Ia measurements.

  20. Cosmology from large-scale galaxy clustering and galaxy-galaxy lensing with Dark Energy Survey Science Verification data

    Science.gov (United States)

    Kwan, J.; Sánchez, C.; Clampitt, J.; Blazek, J.; Crocce, M.; Jain, B.; Zuntz, J.; Amara, A.; Becker, M. R.; Bernstein, G. M.; Bonnett, C.; DeRose, J.; Dodelson, S.; Eifler, T. F.; Gaztanaga, E.; Giannantonio, T.; Gruen, D.; Hartley, W. G.; Kacprzak, T.; Kirk, D.; Krause, E.; MacCrann, N.; Miquel, R.; Park, Y.; Ross, A. J.; Rozo, E.; Rykoff, E. S.; Sheldon, E.; Troxel, M. A.; Wechsler, R. H.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Benoit-Lévy, A.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Carrasco Kind, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Evrard, A. E.; Fernandez, E.; Finley, D. A.; Flaugher, B.; Fosalba, P.; Frieman, J.; Gerdes, D. W.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Jarvis, M.; Kuehn, K.; Lahav, O.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Martini, P.; Melchior, P.; Mohr, J. J.; Nichol, R. C.; Nord, B.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Vikram, V.; Walker, A. R.; DES Collaboration

    2017-02-01

    We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 deg2 contiguous patch of DES data from the Science Verification (SV) period of observations. Using large-scale measurements, we constrain the matter density of the Universe as Ωm = 0.31 ± 0.09 and the clustering amplitude of the matter power spectrum as σ8 = 0.74 ± 0.13 after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into S8 ≡ σ8(Ωm/0.3)0.16 = 0.74 ± 0.12 for our fiducial lens redshift bin at 0.35 < z < 0.5, while S8 = 0.78 ± 0.09 using two bins over the range 0.2 < z < 0.5. We study the robustness of the results under changes in the data vectors, modelling and systematics treatment, including photometric redshift and shear calibration uncertainties, and find consistency in the derived cosmological parameters. We show that our results are consistent with previous cosmological analyses from DES and other data sets and conclude with a joint analysis of DES angular clustering and galaxy-galaxy lensing with Planck Cosmic Microwave Background data, baryon accoustic oscillations and Supernova Type Ia measurements.

  1. Kinematics of the ionized and molecular gas in nearby luminous infrared interacting galaxies

    CERN Document Server

    Zaragoza-Cardiel, Javier; Font, Joan; Rosado, Margarita; Camps-Fariña, Artemi; Borlaff, Alejandro

    2016-01-01

    We have observed three luminous infrared galaxy systems (LIRGS) which are pairs of interacting galaxies, with the Galaxy H$\\alpha$ Fabry-Perot system (GH$\\alpha$FaS) mounted on the 4.2m William Herschel Telescope at the Roque de los Muchachos Observatory, and combined the observations with the Atacama Large Millimeter Array (ALMA) observations of these systems in CO emission to compare the physical properties of the star formation regions and the molecular gas clouds, and specifically the internal kinematics of the star forming regions. We identified 88 star forming regions in the H$\\alpha$ emission data-cubes, and 27 molecular cloud complexes in the CO emission data-cubes. The surface densities of the star formation rate and the molecular gas are significantly higher in these systems than in non-interacting galaxies and the Galaxy, and are closer to the surface densities of the star formation rate and the molecular gas of extreme star forming galaxies at higher redshifts. The large values of the velocity dis...

  2. Kinematics of the ionized and molecular gas in nearby luminous infrared interacting galaxies

    Science.gov (United States)

    Zaragoza-Cardiel, Javier; Beckman, John; Font, Joan; Rosado, Margarita; Camps-Fariña, Artemi; Borlaff, Alejandro

    2017-03-01

    We have observed three luminous infrared galaxy systems which are pairs of interacting galaxies, with the Galaxy Hα Fabry-Perot system mounted on the 4.2 m William Herschel Telescope at the Roque de los Muchachos Observatory, and combined the observations with the Atacama Large Millimeter Array observations of these systems in CO emission to compare the physical properties of the star formation regions and the molecular gas clouds, and specifically the internal kinematics of the star-forming regions. We identified 88 star-forming regions in the Hα emission data cubes, and 27 molecular cloud complexes in the CO emission data cubes. The surface densities of the star formation rate and the molecular gas are significantly higher in these systems than in non-interacting galaxies and the Galaxy, and are closer to the surface densities of the star formation rate and the molecular gas of extreme star-forming galaxies at higher redshifts. The large values of the velocity dispersion also show the enhanced gas surface density. The H II regions are situated on the SFR - σv envelope, and so are also in virial equilibrium. Since the virial parameter decreases with the surface densities of both the star formation rate and the molecular gas, we claim that the clouds presented here are gravitationally dominated rather than being in equilibrium with the external pressure.

  3. STAR Formation Histories Across the Interacting Galaxy NGC 6872, the Largest-Known Spiral

    Science.gov (United States)

    Eufrasio, Rafael T.; Dwek, E.; Arendt, RIchard G.; deMello, Duilia F.; Gadotti, DImitri A.; Urrutia-Viscarra, Fernanda; deOliveira, CLaudia Mendes; Benford, Dominic J.

    2014-01-01

    NGC6872, hereafter the Condor, is a large spiral galaxy that is interacting with its closest companion, the S0 galaxy IC 4970. The extent of the Condor provides an opportunity for detailed investigation of the impact of the interaction on the current star formation rate and its history across the galaxy, on the age and spatial distribution of its stellar population, and on the mechanism that drives the star formation activity. To address these issues we analyzed the far-ultraviolet (FUV) to near-infrared (near-IR) spectral energy distribution of seventeen 10 kpc diameter regions across the galaxy, and derived their star formation history, current star formation rate, and stellar population and mass. We find that most of the star formation takes place in the extended arms, with very little star formation in the central 5 kpc of the galaxy, in contrast to what was predicted from previous numerical simulations. There is a trend of increasing star formation activity with distance from the nucleus of the galaxy, and no evidence for a recent increase in the current star formation rate due to the interaction. The nucleus itself shows no significant current star formation activity. The extent of the Condor also provides an opportunity to test the applicability of a single standard prescription for conversion of the FUV + IR (22 micrometer) intensities to a star formation rate for all regions. We find that the conversion factor differs from region to region, arising from regional differences in the stellar populations.

  4. Early Hierarchical Formation of Massive Galaxies Triggered By Interactions

    CERN Document Server

    Menci, N; Fontana, A; Giallongo, E; Poli, F; Vittorini, V

    2004-01-01

    To address the problem concerning the early formation of stars in massive galaxies, we present the results of a semi-analytic model of galaxy formation which includes a physical description of starbursts triggered by galaxy interactions. These originate from the destabilization of cold galactic gas occurring in galaxy encounters, which in part feeds the accretion onto black holes powering quasars, and in part drives circumnuclear starsbursts at redshifts $z\\approx 2-4$, preferentially in massive objects. This speeds up the formation of stars in massive galaxies at high redshifts without altering it in low mass galactic halos. Thus, at intermediate $z\\approx 1.5-2$ we find that a considerable fraction of the stellar content of massive galaxies is already in place, at variance with the predictions of previous hierarchical models. The resulting high-$z$ star formation rate and B-band luminosity functions, and the luminosity and redshift distribution of galaxies in K-band at $z\\lesssim 2$ are all in good agreemen...

  5. Cosmology from large scale galaxy clustering and galaxy-galaxy lensing with Dark Energy Survey Science Verification data

    Science.gov (United States)

    Kwan, J.; Sánchez, C.; Clampitt, J.; Blazek, J.; Crocce, M.; Jain, B.; Zuntz, J.; Amara, A.; Becker, M. R.; Bernstein, G. M.; Bonnett, C.; DeRose, J.; Dodelson, S.; Eifler, T. F.; Gaztanaga, E.; Giannantonio, T.; Gruen, D.; Hartley, W. G.; Kacprzak, T.; Kirk, D.; Krause, E.; MacCrann, N.; Miquel, R.; Park, Y.; Ross, A. J.; Rozo, E.; Rykoff, E. S.; Sheldon, E.; Troxel, M. A.; Wechsler, R. H.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Benoit-Lévy, A.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Carrasco Kind, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Evrard, A. E.; Fernandez, E.; Finley, D. A.; Flaugher, B.; Fosalba, P.; Frieman, J.; Gerdes, D. W.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Jarvis, M.; Kuehn, K.; Lahav, O.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Martini, P.; Melchior, P.; Mohr, J. J.; Nichol, R. C.; Nord, B.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Vikram, V.; Walker, A. R.

    2016-10-01

    We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 square degree contiguous patch of DES data from the Science Verification (SV) period of observations. Using large scale measurements, we constrain the matter density of the Universe as Ωm = 0.31 ± 0.09 and the clustering amplitude of the matter power spectrum as σ8 = 0.74 ± 0.13 after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into S8 ≡ σ8(Ωm/0.3)0.16 = 0.74 ± 0.12 for our fiducial lens redshift bin at 0.35 CMB data, Baryon Accoustic Oscillations and Supernova type Ia measurements.

  6. Galaxy interactions and active galactic nuclei in the local universe

    Science.gov (United States)

    Ryan, Christopher J.

    2009-06-01

    It has been suggested that galaxy interactions may be the principal mechanism responsible for triggering non-thermal activity in galactic nuclei. This thesis investigates the possible role of interactions in the local Universe by searching for evidence of a causal relationship between major interactions and the initiation of activity in Seyfert galaxies using high-quality, multiwavelength imaging data. The connection between interacting galaxies and Seyferts is explored by comparing the clustering properties of their environments, as quantified by the spatial cross-correlation function amplitude. If a direct evolutionary relationship exists, the objects should be located in environments that are statistically similar. It was previously demonstrated that Seyferts are found in fields comparable to isolated galaxies. The analysis presented in this work reveals that interacting galaxies are preferentially situated in regions consistent with Abell Richness Classes of 0 to 1. The apparent dissimilarity of their environments provides a strong argument against a link between major interactions and Seyfert galaxies. An examination of the photometric and morphological properties of the interacting systems does not uncover any trends that could be associated with the initiation of nuclear activity. The role of major interactions in triggering low-redshift AGNs is then assessed using near-infrared imagery of a sample of Narrow-Line Seyfert 1 galaxies. It has been postulated that these objects are evolutionarily young AGNs, powered by accretion onto supermassive black holes that are considerably lower in mass than those found in typical broad-line Seyferts. By employing the correlation between black hole mass and host galaxy bulge luminosity, the mean black hole mass, [Special characters omitted.] BH , in solar units for the sample is found to be [left angle bracket]log [Special characters omitted.] ( BH )[right angle bracket] = 7.7 ± 0.1, consistent with typical broad

  7. Modeling the initial conditions of interacting galaxy pairs using Identikit

    Science.gov (United States)

    Mortazavi, S. Alireza; Lotz, Jennifer M.; Barnes, Joshua E.; Snyder, Gregory F.

    2016-01-01

    We develop and test an automated technique to model the dynamics of interacting galaxy pairs. We use Identikit as a tool for modelling and matching the morphology and kinematics of the interacting pairs of equal-mass galaxies. In order to reduce the effect of subjective human judgement, we automate the selection of phase space regions used to match simulations to data, and we explore how selection of these regions affects the random uncertainties of parameters in the best-fitting model. In this work, we use an independent set of GADGET SPH simulations as input data to determine the systematic bias in the measured encounter parameters based on the known initial conditions of these simulations. We test both cold gas and young stellar components in the GADGET simulations to explore the effect of choosing H I versus H α as the line-of-sight velocity tracer. We find that we can group the results into tests with good, fair, and poor convergence based on the distribution of parameters of models close to the best-fitting model. For tests with good and fair convergence, we rule out large fractions of parameter space and recover merger stage, eccentricity, pericentric distance, viewing angle, and initial disc orientations within 3σ of the correct value. All of tests on prograde-prograde systems have either good or fair convergence. The results of tests on edge-on discs are less biased than face-on tests. Retrograde and polar systems do not converge and may require constraints from regions other than the tidal tails and bridges.

  8. Large Scale Structure in the SDSS Galaxy Survey

    CERN Document Server

    Doroshkevich, A G; Tucker, D L

    2004-01-01

    The Large Scale Structure (LSS) in the galaxy distribution is investigated using the Sloan Digital Sky Survey Early Data Release (SDSS EDR). Using the Minimal Spanning Tree technique we have extracted sets of filaments, of wall-like structures, of galaxy groups, and of rich clusters from this unique sample. The physical properties of these structures were then measured and compared with the expectations from Zel'dovich' theory. The measured characteristics of galaxy walls were found to be consistent with those for a spatially flat $\\Lambda$CDM cosmological model with $\\Omega_m\\approx$ 0.3 and $\\Omega_\\Lambda \\approx$ 0.7, and for Gaussian initial perturbations with a Harrison -- Zel'dovich power spectrum. Furthermore, we found that the mass functions of groups and of unrelaxed structure elements generally fit well with the expectations from Zel'dovich' theory, although there was some discrepancy for lower mass groups which may be due to incompleteness in the selected sample of groups. We also note that both g...

  9. Large Scale Structure in the SDSS DR1 Galaxy Survey

    CERN Document Server

    Doroshkevich, A G; Allam, S S; Way, M J

    2003-01-01

    The Large Scale Structure in the galaxy distribution is investigated using The First Data Release of the Sloan Digital Sky Survey. Using the Minimal Spanning Tree technique we have extracted sets of filaments, of wall--like structures, of galaxy groups, and of rich clusters from this unique sample. The physical properties of these structures were then measured and compared with the statistical expectations based on the Zel'dovich' theory. The measured characteristics of galaxy walls were found to be consistent with those for a spatially flat $\\Lambda$CDM cosmological model with $\\Omega_m\\approx$ 0.3 and $\\Omega_\\Lambda \\approx$ 0.7, and for Gaussian initial perturbations with a Harrison -- Zel'dovich power spectrum. Furthermore, we found that the mass functions of groups and of unrelaxed structure elements generally fit well with the expectations from Zel'dovich' theory. We also note that both groups and rich clusters tend to prefer the environments of walls, which tend to be of higher density, rather than th...

  10. Large-scale HI in nearby radio galaxies (II): the nature of classical low-power radio sources

    CERN Document Server

    Emonts, B H C; Struve, C; Oosterloo, T A; van Moorsel, G; Tadhunter, C N; van der Hulst, J M; Brogt, E; Holt, J; Mirabal, N

    2010-01-01

    An important aspect of solving the long-standing question as to what triggers various types of Active Galactic Nuclei involves a thorough understanding of the overall properties and formation history of their host galaxies. This is the second in a series of papers that systematically study the large-scale properties of cold neutral hydrogen (HI) gas in nearby radio galaxies. The main goal is to investigate the importance of gas-rich galaxy mergers and interactions among radio-loud AGN. In this paper we present results of a complete sample of classical low-power radio galaxies. We find that extended Fanaroff & Riley type-I radio sources are generally not associated with gas-rich galaxy mergers or ongoing violent interactions, but occur in early-type galaxies without large (> 10^8 M_sun) amounts of extended neutral hydrogen gas. In contrast, enormous discs/rings of HI gas (with sizes up to 190 kpc and masses up to 2 x 10^10 M_sun) are detected around the host galaxies of a significant fraction of the compac...

  11. Galaxy interactions in the Hickson Compact Group 88

    CERN Document Server

    Brosch, Noah

    2015-01-01

    I present observations of the Hickson Compact Group 88 (HCG88) obtained during the commissioning of a new 28-inch telescope at the Wise Observatory. This galaxy group was advertised to be non-interacting, or to be in a very early interaction stage, but this is not the case. The observations reported here were done using a "luminance" filter, essentially a very broad R filter, reaching a low surface brightness level of about 26 mag per square arcsec. Additional observations were obtained in a narrow spectral band approximately centered on the rest-frame H-alpha line from the group. Contrary to previous studies, my observations show that at least two of the major galaxies have had significant interactions in the past, although probably not between themselves. I report the discovery of a faint extended tail emerging from the brightest of the group galaxies, severe isophote twisting and possible outer shells around another galaxy, and map the HII regions in all the galaxies.

  12. Investigating the AGN-Galaxy Interaction Relationship by Examining the Color and Morphology Measurements of Real and Simulated AGN Host Galaxies

    Science.gov (United States)

    Pierce, Christina M.

    2009-01-01

    UV-optical colors provide a clear distinction between quiescent galaxies and those undergoing star formation. Galaxy morphology measurements, such as the Gini coefficient, M20, concentration, asymmetry, and the Sersic index, allow identification of interacting galaxies and separation of non-interacting galaxies into bulge or disk-dominated systems. Thus, one can use the colors and morphologies of AGN host galaxies to probe the predicted relationship between galaxy interactions and significant black hole growth (an AGN stage). However, due to the UV excess observed in many AGNs (particularly quasars and Seyfert 1 galaxies) and the potentially significant optical contribution from AGNs that are not heavily obscured, one must exercise caution when interpreting the results from color and morphology measurements of AGN host galaxies. With this in mind, we created a set of simulated AGNs to test the reliability of color and morphology measurements of AGN host galaxies. The results were compared to observations of AGN host galaxies at z 1 from the All-wavelength Extended Groth Strip International Survey (AEGIS). Our observed results reveal a population of X-ray luminous AGN hosts that appear to have green UV-optical colors, indicative of recent star-formation, and a largely disk-dominated profile, suggesting a bulge that is not yet fully developed. Comparison with results from our simulated AGNs suggest that at least some of the observational results are not likely to be due to color or morphological contamination from the presence of an AGN. Therefore, the observed AGN hosts seem to represent a real population that may be going through a transition phase, during which significant star-formation has recently ceased, but for which the black hole remains quite luminous.

  13. Triggering optical AGN: the need for cold gas, and the indirect roles of galaxy environment and interactions

    CERN Document Server

    Sabater, J; Heckman, T M

    2014-01-01

    We present a study of the prevalence and luminosity of Active Galactic Nuclei (AGN; traced by optical spectra) as a function of both environment and galaxy interactions. For this study we used a sample of more than 250000 galaxies drawn from the Sloan Digital Sky Survey and, crucially, we controlled for the effect of both stellar mass and central star formation activity. Once these two factors are taken into account, the effect of the local density of galaxies and of one-on-one interactions is minimal in both the prevalence of AGN activity and AGN luminosity. This suggests that the level of nuclear activity depends primarily on the availability of cold gas in the nuclear regions of galaxies and that secular processes can drive the AGN activity in the majority of cases. Large scale environment and galaxy interactions only affect AGN activity in an indirect manner, by influencing the central gas supply.

  14. Star Formation Histories Across the Interacting Galaxy NGC 6872, the Largest-Known Spiral

    CERN Document Server

    Eufrasio, Rafael T; Arendt, Richard G; de Mello, Duilia F; Gadotti, Dimitri; Urrutia-Viscarra, Fernanda; de Oliveira, Claudia Mendes; Benford, Dominic

    2014-01-01

    NGC 6872, hereafter the Condor, is a large spiral galaxy that is interacting with its closest companion, the S0 galaxy IC 4970. The extent of the Condor provides an opportunity for detailed investigation of the impact of the interaction on the current star formation rate and its history across the galaxy, on the age and spatial distribution of its stellar population, and on the mechanism that drive the star formation activity. To address these issues we analyzed the far-ultraviolet (FUV) to near-infrared (near-IR) spectral energy distribution (SED) of 17, 10 kpc diameter, regions across the galaxy, and derived their star formation history, current star formation rate, and stellar population and mass. We find that most of the star formation takes place in the extended arms, with very little star formation in the central 5 kpc of the galaxy, in contrast to what was predicted from previous numerical simulations. There is a trend of increasing star formation activity with distance from the nucleus of the galaxy, ...

  15. Effects of the environment on galaxies in the Catalogue of Isolated Galaxies: physical satellites and large scale structure

    Science.gov (United States)

    Argudo-Fernández, M.; Verley, S.; Bergond, G.; Sulentic, J.; Sabater, J.; Fernández Lorenzo, M.; Espada, D.; Leon, S.; Sánchez-Expósito, S.; Santander-Vela, J. D.; Verdes-Montenegro, L.

    2014-04-01

    Context. We present a study of the 3D environment for a sample of 386 galaxies in the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973) using the Ninth Data Release of the Sloan Digital Sky Survey (SDSS-DR9). Aims: We aim to identify and quantify the effects of the satellite distribution around a sample of galaxies in the CIG, as well as the effects of the large-scale structure (LSS). Methods: To recover the physically bound galaxies we first focused on the satellites that are within the escape speed of each CIG galaxy. We also propose a more conservative method using the stacked Gaussian distribution of the velocity difference of the neighbours. The tidal strengths affecting the primary galaxy were estimated to quantify the effects of the local and LSS environments. We also defined the projected number density parameter at the fifth nearest neighbour to characterise the LSS around the CIG galaxies. Results: Out of the 386 CIG galaxies considered in this study, at least 340 (88% of the sample) have no physically linked satellite. Following the more conservative Gaussian distribution of physical satellites around the CIG galaxies leads to upper limits. Out of the 386 CIG galaxies, 327 (85% of the sample) have no physical companion within a projected distance of 0.3 Mpc. The CIG galaxies are distributed following the LSS of the local Universe, although presenting a large heterogeneity in their degree of connection with it. When present around a CIG galaxy, the effect of physically bound galaxies largely dominates (typically by more than 90%) the tidal strengths generated by the LSS. Conclusions: The CIG samples a variety of environments, from galaxies with physical satellites to galaxies without neighbours within 3 Mpc. A clear segregation appears between early-type CIG galaxies with companions and isolated late-type CIG galaxies. Isolated galaxies are in general bluer, with probably younger stellar populations and very high star formation compared with older

  16. Magnetic fields of our Galaxy on large and small scales

    CERN Document Server

    Han, Jinlin

    2007-01-01

    Magnetic fields have been observed on all scales in our Galaxy, from AU to kpc. With pulsar dispersion measures and rotation measures, we can directly measure the magnetic fields in a very large region of the Galactic disk. The results show that the large-scale magnetic fields are aligned with the spiral arms but reverse their directions many times from the inner-most arm (Norma) to the outer arm (Perseus). The Zeeman splitting measurements of masers in HII regions or star-formation regions not only show the structured fields inside clouds, but also have a clear pattern in the global Galactic distribution of all measured clouds which indicates the possible connection of the large-scale and small-scale magnetic fields.

  17. Effects on Galaxy Evolution: Pair Interactions versus Environment

    CERN Document Server

    Tonnesen, Stephanie

    2011-01-01

    In a hierarchical universe, mergers may be an important mechanism not only in increasing the mass of galaxies but also in driving the colour and morphological evolution of galaxies. We use a large sample of ~1000 simulated galaxies of stellar mass greater than 10^{9.6} solar masses (for ~4800 observations at multiple redshifts) from a high-resolution (0.46 kpc/h) cosmological simulation to determine under what circumstances being a member of a pair influences galaxy properties at z <= 0.2. We identify gravitationally bound pairs, and find a relative fraction of blue-blue (wet), red-red (dry), and blue-red (mixed) pairs that agrees with observations (Lin et al. 2010). All pairs tend to avoid the extreme environments of clusters and void centres. While pairs in groups can include galaxies that are both blue, both red, or one of each colour, in the field it is extraordinarily rare for pair galaxies to both be red. We find that, while physically bound pairs closer than 250 kpc/h tend to be bluer than the galax...

  18. The gas content of peculiar galaxies: strongly interacting systems

    CERN Document Server

    Casasola, V; Galletta, G

    2004-01-01

    A study of the gas content in 1038 interacting galaxies, essentially selected from Arp, Arp and Madore, Vorontsov-Velyaminov catalogues and some of the published literature, is presented here. The data on the interstellar medium have been extracted from a number of sources in the literature and compared with a sample of 1916 normal galaxies. The mean values for each of the different ISM tracers (FIR, 21 cm, CO lines, X-ray) have been estimated by means of survival analysis techniques, in order to take into account the presence of upper limits. From the data it appears that interacting galaxies have a higher gas content than normal ones. Galaxies classified as ellipticals have both a dust and gas content one order of magnitude higher than normal. Spirals have in most part a normal dust and HI content but an higher molecular gas mass. The X-ray luminosity also appears higher than that of normal galaxies of same morphological type, both including or excluding AGNs. We considered the alternative possibilities tha...

  19. Highly ionized gas on galaxy scales: mapping the interacting Seyfert galaxy LEDA 135736

    CERN Document Server

    Gerssen, J; Christensen, L; Bower, R G; Wild, V

    2008-01-01

    We have used the VIMOS IFU to map the properties of the Seyfert 1.9 galaxy LEDA 135736. These maps reveal a number of interesting features including: an Extended Narrow Line Region detectable out to 9 kpc, an area of intense star formation located at a projected distance of 12 kpc from the centre, an elliptical companion galaxy, and kinematic features, aligned along the long-axis of the ENLR, that are consistent with radio jet-driven mass outflow. We propose that the ENLR results from extra-planar gas ionized by the AGN, and that the AGN in turn might be triggered by interaction with the companion galaxy, which can also explain the burst of star formation and morphological features. Only about two percent of the ENLR's kinetic energy is in the mass outflow. We infer from this that the bulk of mechanical energy imparted by the jet is used to heat this gas.

  20. Seeking large-scale magnetic fields in a pure-disk dwarf galaxy NGC 2976

    CERN Document Server

    Drzazga, R T; Heald, G H; Elstner, D; Gallagher, J S

    2016-01-01

    It is still unknown how magnetic field-generation mechanisms could operate in low-mass dwarf galaxies. Here, we present a detailed study of a nearby pure-disk dwarf galaxy NGC 2976. Unlike previously observed dwarf objects, this galaxy possesses a clearly defined disk. For the purpose of our studies, we performed deep multi-frequency polarimetric observations of NGC 2976 with the VLA and Effelsberg radio telescopes. Additionally, we supplement them with re-imaged data from the WSRT-SINGS survey. The magnetic field morphology discovered in NGC 2976 consists of a southern polarized ridge. This structure does not seem to be due to just a pure large-scale dynamo process (possibly cosmic-ray driven) at work in this object, as indicated by the RM data and dynamo number calculations. Instead, the field of NGC 2976 is modified by past gravitational interactions and possibly also by ram pressure inside the M 81 galaxy group environment. The estimates of total (7 muG) and ordered (3 muG) magnetic field strengths, as we...

  1. The impact of interactions, bars, bulges, and AGN on star formation efficiency in local massive galaxies

    CERN Document Server

    Saintonge, A; Fabello, S; Wang, J; Catinella, B; Genzel, R; Gracia-Carpio, J; Kramer, C; Moran, S; Heckman, T M; Schiminovich, D; Schuster, K; Wuyts, S

    2012-01-01

    Using observations from the GASS and COLD GASS surveys and complementary data from SDSS and GALEX, we investigate the nature of variations in gas depletion time observed across the local massive galaxy population. The large and unbiased COLD GASS sample allows us to assess the relative importance of galaxy interactions, bar instabilities, morphologies and the presence of AGN in regulating star formation efficiency. Both the H2 mass fraction and depletion time vary as a function of the distance of a galaxy from the main sequence in the SFR-M* plane. The longest gas depletion times are found in below-main sequence bulge-dominated galaxies that are either gas-poor, or else on average less efficient than disk-dominated galaxy at converting into stars any cold gas they may have. We find no link between AGN and these long depletion times. The galaxies undergoing mergers or showing signs of morphological disruptions have the shortest molecular gas depletion times, while those hosting strong stellar bars have only ma...

  2. Ultraluminous X-ray Sources in Interacting Galaxies

    CERN Document Server

    Swartz, Douglas A

    2009-01-01

    I give a brief review of how X-rays from nearby galaxies are used as direct tracers of recent star formation. This leads to the conclusion that it is the most luminous point-like sources that are associated with star formation and that the majority of these are high-mass X-ray binaries.I then discuss a recent study that shows that ULXs are preferentially found in regions as young as or younger than typical HII regions in their host galaxies. Finally, I describe a new study that attempts to determine the maximum luminosity of ULXs in the local universe by searching for them in interacting galaxies where the star formation rate is high.

  3. Large-scale structure and the intrinsic alignment of galaxies

    CERN Document Server

    Blazek, Jonathan; Mandelbaum, Rachel

    2015-01-01

    Coherent alignments of galaxy shapes, often called "intrinsic alignments" (IA), are the most significant source of astrophysical uncertainty in weak lensing measurements. We develop the tidal alignment model of IA and demonstrate its success in describing observational data. We also describe a technique to separate IA from galaxy-galaxy lensing measurements. Applying this technique to luminous red galaxy lenses in the Sloan Digital Sky Survey, we constrain potential IA contamination from associated sources to be below a few percent.

  4. IRAS high resolution studies and modeling of closely interacting galaxies. Galaxy collisions: Infrared observations and analysis of numerical models. UV spectroscopy of massive young stellar populations in interacting galaxies

    Science.gov (United States)

    Lamb, Susan A.

    1993-01-01

    The Final Technical Report covering the period from 15 Aug. 1989 to 14 Aug. 1991 is presented. Areas of research included Infrared Astronomy Satellite (IRAS) high resolution studies and modeling of closely interacting galaxies; galaxy collisions: infrared observations and analysis of numerical models; and UV spectroscopy of massive young stellar populations in interacting galaxies. Both observational studies and theoretical modelling of interacting galaxies are covered. As a consequence the report is divided into two parts, one on each aspect of the overall project.

  5. Starburst in the interacting HII galaxy II Zw 40 and in non-interacting HII galaxies

    CERN Document Server

    Telles, Eduardo

    2009-01-01

    I summarize the results of our integral field spectroscopic observations of the nearby prototype of HII galaxies, II Zw 40. Observations with GMOS-IFU on GEMINI-North in the optical allowed us to make a detailed kinematic picture of the central starburst, while SINFONI with adaptive optics on the ESO-VLT gave us a near-IR view of the interplay between the ISM phases. Here, I also address the question that not all starbursts require an external trigger such as a galaxy-galaxy encounter, as it seems to be the case for a fraction of low luminosity HII galaxies. We speculate that these may form stars spontaneously like "pop-corn in a pan".

  6. Under pressure: Star clusters in the tidal debris of interacting galaxies

    Science.gov (United States)

    Mullan, Brendan Lawrence

    in many others. I compare these to the kinds of tails that host them, and the galaxies involved in their inception, and find that these broad properties of interacting galaxies I examine cannot well predict the multitude of clustered stellar progeny a tail is likely to have. However, there are indirect indications that the manner in which they form is very similar to that of ordinary galaxies across the Universe. then move to a detailed examination of the tumultuous aggregates of hydrogen gas that compose the backbones of these tails. I find strong evidence to suggest that it is fundamentally local properties of gas---i.e., on scales smaller than that of whole galaxies and tails---that determine a tidal tail's propensity for forming bright star clusters. This gas may be under relatively high pressures, which helps compress and gravitationally bind the cool, dense clouds of interstellar molecules that form the clusters. Much as lustrous diamonds are formed in compacted regions deep beneath the Earth's surface, luminous stars clusters require interstellar nurseries that are under high pressures. It would seem that this compressed gas appears preferentially in relatively young tails, before the material is dispersed and unceremoniously flung into intergalactic space. It is also frequently seen in tidal debris from the mergers of comparably massed galaxies, where the gravitational interaction and the shocks and turbulent motions it stirs into the gas is especially strong. This matches the basic, general predictions of galaxy interaction simulations well. A picture, admittedly incomplete, of how star clusters form in tidal tails therefore emerges: the formation of bright clusters depends largely on the character and amount of hydrogen gas in their local environment. These conditions are determined in part by how the galaxies interact and the ingredients they bring to the cosmic table. (Abstract shortened by UMI.)

  7. Percolation Properties of Nearby Large-Scale Structures: Every Galaxy has a Neighbour

    CERN Document Server

    Fairall, A; Pretorius, M L; Wiehahn, M; McBride, V; de Vaux, G; Woudt, P A; Fairall, Anthony

    2004-01-01

    The distribution of nearby (cz < 7500 km/s) galaxies has been explored by minimal spanning trees; allowance has been made for the drastic decrease of data with distance. The investigation finds that all galaxies are members of irregular elongated large-scale structures; there are no `field galaxies'. Based on our local large-scale structure, every galaxy appears to have a neighbouring galaxy within <100 km/s (1.4 h_{70}^{-1} Mpc) of redshift space, and thereby all galaxies are found to lie in filaments or tree configurations. Every large-scale structure appears to have a neighbouring large-scale structure within <700 km/s (10 h_{70}^{-1} Mpc), such that large-scale structures interconnect to form a continuous labyrinth.

  8. A Pipeline for Constructing a Catalog of Multi-method Models of Interacting Galaxies

    Science.gov (United States)

    Holincheck, Anthony

    Galaxies represent a fundamental unit of matter for describing the large-scale structure of the universe. One of the major processes affecting the formation and evolution of galaxies are mutual interactions. These interactions can including gravitational tidal distortion, mass transfer, and even mergers. In any hierarchical model, mergers are the key mechanism in galaxy formation and evolution. Computer simulations of interacting galaxies have evolved in the last four decades from simple restricted three-body algorithms to full n-body gravity models. These codes often included sophisticated physical mechanisms such as gas dynamics, supernova feedback, and central blackholes. As the level of complexity, and perhaps realism, increases so does the amount of computational resources needed. These advanced simulations are often used in parameter studies of interactions. They are usually only employed in an ad hoc fashion to recreate the dynamical history of specific sets of interacting galaxies. These specific models are often created with only a few dozen or at most few hundred sets of simulation parameters being attempted. This dissertation presents a prototype pipeline for modeling specific pairs of interacting galaxies in bulk. The process begins with a simple image of the current disturbed morphology and an estimate of distance to the system and mass of the galaxies. With the use of an updated restricted three-body simulation code and the help of Citizen Scientists, the pipeline is able to sample hundreds of thousands of points in parameter space for each system. Through the use of a convenient interface and innovative scoring algorithm, the pipeline aids researchers in identifying the best set of simulation parameters. This dissertation demonstrates a successful recreation of the disturbed morphologies of 62 pairs of interacting galaxies. The pipeline also provides for examining the level of convergence and uniqueness of the dynamical properties of each system. By

  9. Cosmology from large scale galaxy clustering and galaxy-galaxy lensing with Dark Energy Survey Science Verification data

    CERN Document Server

    Kwan, Juliana; Clampitt, Joseph; Blazek, Jonathan; Crocce, Martin; Jain, Bhuvnesh; Zuntz, Joe; Amara, Adam; Becker, Matthew; Bernstein, Gary; Bonnett, Christopher; DeRose, Joseph; Dodelson, Scott; Eifler, Tim; Gaztanaga, Enrique; Giannantonio, Tommaso; Gruen, Daniel; Hartley, Will; Kacprzak, Tomasz; Kirk, Donnacha; Krause, Elisabeth; MacCrann, Niall; Miquel, Ramon; Park, Youngsoo; Ross, Ashley; Rozo, Eduardo; Rykoff, Eli; Sheldon, Erin; Troxel, Michael A; Wechsler, Risa; Abbott, Tim; Abdalla, Filipe; Allam, Sahar; Benoit-Lévy, Aurélien; Brooks, David; Burke, David; Rosell, Aurelio Carnero; Kind, Matias Carrasco; Cunha, Carlos; D'Andrea, Chris; da Costa, Luiz; Desai, Shantanu; Diehl, H Thomas; Dietrich, Jörg; Doel, Peter; Evrard, August; Fernandez, Enrique; Finley, David; Flaugher, Brenna; Fosalba, Pablo; Frieman, Josh; Gerdes, David; Gruendl, Robert; Gutierrez, Gaston; Honscheid, Klaus; James, David; Jarvis, Mike; Kuehn, Kyler; Lahav, Ofer; Lima, Marcos; Maia, Marcio; Marshall, Jennifer; Martini, Paul; Melchior, Peter; Mohr, Joe; Nichol, Robert; Nord, Brian; Plazas, Andres; Reil, Kevin; Romer, Kathy; Roodman, Aaron; Sanchez, Eusebio; Scarpine, Vic; Sevilla, Ignacio; Smith, R Chris; Soares-Santos, Marcelle; Sobreira, Flavia; Suchyta, Eric; Swanson, Molly; Tarle, Gregory; Thomas, Daniel; Vikram, Vinu; Walker, Alistair

    2016-01-01

    We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 square degree contiguous patch of DES data from the Science Verification (SV) period of observations. Using large scale measurements, we constrain the matter density of the Universe as Omega_m = 0.31 +/- 0.09 and the clustering amplitude of the matter power spectrum as sigma_8 = 0.74 +/- 0.13 after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into S_8 = sigma_8(Omega_m/0.3)^{0.16} = 0.74 +/- 0.12 for our fiducial lens redshift bin at 0.35

  10. Large-eddy simulations of isolated disc galaxies with thermal and turbulent feedback

    CERN Document Server

    Braun, Harald; Niemeyer, Jens C; Almgren, Ann S

    2014-01-01

    We present a subgrid-scale model for the Multi-phase Interstellar medium, Star formation, and Turbulence (MIST) and explore its behaviour in high-resolution large-eddy simulations of isolated disc galaxies. MIST follows the evolution of a clumpy cold and a diffuse warm component of the gas within a volume element which exchange mass and energy via various cooling, heating and mixing processes. The star formation rate is dynamically computed from the state of the gas in the cold phase. An important feature of MIST is the treatment of unresolved turbulence in the two phases and its interaction with star formation and feedback by supernovae. This makes MIST a particularly suitable model for the interstellar medium in galaxy simulations. We carried out a suite of simulations varying fundamental parameters of our feedback implementation. Several observational properties of galactic star formation are reproduced in our simulations, such as an average star formation efficiency ~1%, a typical velocity dispersion arou...

  11. Dynamical Analyses of Galaxy Clusters With Large Redshift Samples

    Science.gov (United States)

    Mohr, J. J.; Richstone, D. O.; Wegner, G.

    1998-12-01

    We construct equilibrium models of galaxy orbits in five nearby galaxy clusters to study the distribution of binding mass, the nature of galaxy orbits and the kinematic differences between cluster populations of emission-line and non emission-line galaxies. We avail ourselves of 1718 galaxy redshifts (and 1203 cluster member redshifts) in this Jeans analysis; most of these redshifts are new, coming from multifiber spectroscopic runs on the MDM 2.4m with the Decaspec and queue observing on WIYN with Hydra. In addition to the spectroscopic data we have V and R band CCD mosaics (obtained with the MDM 1.3m) of the Abell region in each of these clusters. Our scientific goals include: (i) a quantitative estimate of the range of binding masses M500 consistent with the optical and X-ray data, (ii) an estimate of the typical galaxy oribital anisotropies required to make the galaxy data consistent with the NFW expectation for the cluster potential, (iii) a better understanding of the systematics inherent in the process of rescaling and ``stacking'' galaxy cluster observations, (iv) a reexamination of the recent CNOC results implying that emission-line (blue) galaxies are an equilibrium population with a more extended radial distribution than their non emission-line (red) galaxy counterparts and (v) a measure of the galaxy contribution to the cluster mass of baryons.

  12. Self-similar energetics in large clusters of galaxies

    CERN Document Server

    Miniati, Francesco

    2015-01-01

    Massive galaxy clusters are filled with a hot, turbulent and magnetized intra-cluster medium. Still forming under the action of gravitational instability, they grow in mass by accretion of supersonic flows. These flows partially dissipate into heat through a complex network of large-scale shocks [1], while residual transonic flows create giant turbulent eddies and cascades [2,3]. Turbulence heats the intra-cluster medium [4] and also amplifies magnetic energy by way of dynamo action [5-8]. However, the pattern regulating the transformation of gravitational energy into kinetic, thermal, turbulent and magnetic energies remains unknown. Here we report that the energy components of the intra-cluster medium are ordered according to a permanent hierarchy, in which the ratio of thermal to turbulent to magnetic energy densities remains virtually unaltered throughout the cluster's history, despite evolution of each individual component and the drive towards equipartition of the turbulent dynamo. This result revolves a...

  13. Effects of interaction on the properties of spiral galaxies. II. Isolated galaxies: The zero point

    Science.gov (United States)

    Márquez, I.; Moles, M.

    1999-04-01

    We analyse the properties of a sample of 22 bright isolated spiral galaxies on the basis of Johnson B,V,I images and optical rotation curves. The fraction of early morphological types in our sample of isolated galaxies (or in other samples of non-interacting spiral galaxies) appears to be smaller than in samples including interacting systems. The overall morphological aspect is regular and symmetric, but all the galaxies present non-axisymmetric components in the form of bars or rings. We find that the color indices become bluer towards the outer parts and that their central values are well correlated with the total colors. The properties of the bulges span a larger range than those of the disks, that thus are more alike between them. None of the galaxies shows a truncated, type II disk profile. It is found that the relation between surface brightness and size for the bulges, the Kormendy relation, is tighter when only isolated galaxies are considered. We find a similar relation for the disk parameters with an unprecedented low scatter. A Principal Component Analysis of the measured parameters shows that 2 eigenvectors suffice to explain more than 95 % of the total variance. These are, as found for other samples including spiral galaxies in different environmental situations, a scale parameter given by the mass or, equivalently, the luminosity or the size; and a form parameter given by the bulge to disk luminosity ratio, B/D, or, equivalently, by the gradient of the solid-body rotation region of the rotation curve, the G-parameter. We report here a tight correlation between G and B/D for our sample of isolated spirals that could be used as a new distance indicator. Based on data obtained at the 1.5m telescope of the Estacion de Observacion de Calar Alto, Instituto Geografico Nacional, which is jointly operated by the Instituto Geografico Nacional and the Consejo Superior de Investigaciones Cientificas through the Instituto de Astrofisica de Andalucia

  14. A large sample of Kohonen selected E+A (post-starburst) galaxies from the Sloan Digital Sky Survey

    Science.gov (United States)

    Meusinger, H.; Brünecke, J.; Schalldach, P.; in der Au, A.

    2017-01-01

    Context. The galaxy population in the contemporary Universe is characterised by a clear bimodality, blue galaxies with significant ongoing star formation and red galaxies with only a little. The migration between the blue and the red cloud of galaxies is an issue of active research. Post starburst (PSB) galaxies are thought to be observed in the short-lived transition phase. Aims: We aim to create a large sample of local PSB galaxies from the Sloan Digital Sky Survey (SDSS) to study their characteristic properties, particularly morphological features indicative of gravitational distortions and indications for active galactic nuclei (AGNs). Another aim is to present a tool set for an efficient search in a large database of SDSS spectra based on Kohonen self-organising maps (SOMs). Methods: We computed a huge Kohonen SOM for 106 spectra from SDSS data release 7. The SOM is made fully available, in combination with an interactive user interface, for the astronomical community. We selected a large sample of PSB galaxies taking advantage of the clustering behaviour of the SOM. The morphologies of both PSB galaxies and randomly selected galaxies from a comparison sample in SDSS Stripe 82 (S82) were inspected on deep co-added SDSS images to search for indications of gravitational distortions. We used the Portsmouth galaxy property computations to study the evolutionary stage of the PSB galaxies and archival multi-wavelength data to search for hidden AGNs. Results: We compiled a catalogue of 2665 PSB galaxies with redshifts z 3 Å and z 5 Å, significantly higher than in the comparison sample. The search for AGNs based on conventional selection criteria in the radio and MIR results in a low AGN fraction of 2-3%. We confirm an MIR excess in the mean SED of the E+A sample that may indicate hidden AGNs, though other sources are also possible. The catalogue is available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc

  15. The interacting galaxy pair KPG 390: H$\\alpha$ kinematics

    CERN Document Server

    Repetto, P; Gabbasov, R; Fuentes-Carrera, I

    2010-01-01

    In this work we present scanning Fabry-Perot H$\\alpha$ observations of the isolated interacting galaxy pair NGC 5278/79 obtained with the PUMA Fabry-Perot interferometer. We derived velocity fields and rotation curves for both galaxies. For NGC 5278 we also obtained the residual velocity map to investigate the non-circular motions, and estimated its mass by fitting the rotation curve with a disk+halo components. We test three different types of halo (pseudo-isothermal, Hernquist and Navarro Frenk White) and obtain satisfactory fits to the rotation curve for all profiles. The amount of dark matter required by pseudo-isothermal profile is about ten times smaller than, that for the other two halo distributions. Finally, our kinematical results together with the analysis of dust lanes distribution and of surface brightness profiles along the minor axis allowed us to determine univocally that both components of the interacting pair are trailing spirals.

  16. Globular Clusters at the Centre of the Fornax Cluster: Tracing Interactions Between Galaxies

    CERN Document Server

    Bassino, L P; Faifer, F R; Forte, J C; Dirsch, B; Geisler, D; Schuberth, Y

    2006-01-01

    We present the combined results of two investigations: a large-scale study of the globular cluster system (GCS) around NGC 1399, the central galaxy of the Fornax cluster, and a study of the GCSs around NGC 1374, NGC 1379 and NGC 1387, three low-luminosity early-type galaxies located close to the centre of the same cluster. In both cases, the data consist of images from the wide-field MOSAIC Imager of the CTIO 4-m telescope, obtained with Washington C and Kron-Cousins R filters, which provide good metallicity resolution. The colour distributions and radial projected densities of the GCSs are analyzed. We focus on the properties of the GCSs that trace possible interaction processes between the galaxies, such as tidal stripping of globular clusters. For the blue globular clusters, we find tails between NGC 1399 and neighbouring galaxies in the azimuthal projected distribution, and the three low-luminosity galaxies show low specific frequencies and a low proportion of blue GCs.

  17. Global Star Formation Rates and Dust Emission Over the Galaxy Interaction Sequence

    CERN Document Server

    Lanz, Lauranne; Brassington, Nicola; Smith, Howard A; Ashby, Matthew L N; da Cunha, Elisabete; Fazio, Giovanni G; Hayward, Christopher C; Hernquist, Lars; Jonsson, Patrik

    2013-01-01

    We measured and modeled the spectral energy distributions (SEDs) in 28 bands from the ultraviolet to the far-infrared (FIR) for 31 interacting galaxies in 14 systems. The sample is drawn from the Spitzer Interacting Galaxy Survey, which probes a range of galaxy interaction parameters at multiple wavelengths with an emphasis on the infrared bands. The subset presented in this paper consists of all galaxies for which FIR Herschel SPIRE observations are publicly available. Our SEDs combine the Herschel photometry with multi-wavelength data from Spitzer, GALEX, Swift UVOT, and 2MASS. While the shapes of the SEDs are broadly similar across our sample, strongly interacting galaxies typically have more mid-infrared emission relative to their near-infrared and FIR emission than weakly or moderately interacting galaxies. We modeled the full SEDs to derive host galaxy star formation rates (SFR), specific star formation rates (sSFR), stellar masses, dust temperatures, dust luminosities, and dust masses. We find increase...

  18. The formation and evolution of star clusters in interacting galaxies

    CERN Document Server

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

    2016-01-01

    Observations of globular clusters show that they have universal lognormal mass functions with a characteristic peak at $\\sim 2\\times 10^{5}\\, {\\rm{M_{\\odot}}}$, but the origin of this peaked distribution is highly debated. Here we investigate the formation and evolution of star clusters in interacting galaxies using high-resolution hydrodynamical simulations performed with two different codes in order to mitigate numerical artifacts. We find that massive star clusters in the range of $\\sim 10^{5.5} - 10^{7.5}\\, {\\rm{M_{\\odot}}}$ form preferentially in the highly-shocked regions produced by galaxy interactions. The nascent cluster-forming clouds have high gas pressures in the range of $P/k \\sim 10^8 - 10^{12}\\, \\rm{K}\\,\\rm{cm^{-3}}$, which is $\\sim 10^4 - 10^8$ times higher than the typical pressure of the interstellar medium but consistent with recent observations of a pre-super star cluster cloud in the Antennae Galaxies. Furthermore, these massive star clusters have quasi-lognormal initial mass functions wi...

  19. Effects of interactions on the radio properties of non-Seyfert galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Giuricin, G.; Mardirossian, F.; Mezzetti, M. (Trieste Univ. (Italy). Dip. di Astronomia Centro Interuniversitario Regionale per l' Astrofisica a la Cosmologia (CIRAC), Trieste (Italy)); Bertotti, G. (Center for Advanced Research in Space Optics, Trieste (Italy))

    1990-12-01

    On the basis of radiosurveys published in the literature we have compared the radio properties of samples of relatively isolated spiral galaxies with LINER- and H II-region-like nuclei (hereafter called L and H galaxies) with corresponding samples of non-Seyfert interacting galaxies, in order to explore the effects of interactions on their radio properties. Our statistical study reveals basic structural differences between the radio properties of the L, H and Seyfert galaxies, and between the effects of interactions on the radio properties of the three classes of galaxies. (author).

  20. The Evolving Physical Processes In Interacting Galaxies Traced By Their Spectral Energy Distributions

    Science.gov (United States)

    Smith, Howard

    Hernquist et al. models. SEDs for the simulations will be calculated in each case using the SUNRISE radiative transfer code. We will identify the simulation and interacting stage/age that best reproduces each observed merger TMs properties. The results will allow us to refine and test how physical parameters develop in mergers of various kinds, as well as help test the reliability of the simulation assumptions. We will in addition analyze 25 non-interacting galaxies as comparisons. We have already successfully completed the analyses suite on a subset of 31 galaxies in 14 merger groups. This initial set contained all the Keel-Kennicutt mergers for which suitable Herschel data were in the archive when the project began several years ago. Our conclusions, published in Lanz et al. (2013), demonstrate the power of the techniques to trace physical activity across the merger sequence. The conclusions, however, were limited by the small numbers. Today the available dataset is much larger and, with the end of Herschel, is in some sense complete. We propose a focused effort to extend our work to the large sample described. The much larger sample will enable us to reach much firmer statistical conclusions, and to address the processes in intermediate interaction stages across a wider range of galaxy mass-ratios and impact parameters. Our catalog of ~23-band UV-FIR photometry on these 180 (+25) galaxies will constitute a legacy contribution. Our conclusions will have application for mergers in the more distant universe. Our team is expert in the important and difficult issues of data reduction and analysis in the many bands required for this project, in modeling and using Bayesian and other methods to obtain the best fits to the observations from multi-component galaxy models, in the simulations, and in understanding physical processes in galaxies.

  1. Galaxy interactions: dark matter vs. Modified Newtonian dynamics (MOND)

    CERN Document Server

    Bílek, Michal

    2016-01-01

    (doctoral thesis of Michal Bilek, finished on June 19, 2015) MOND is an observational rule for predicting the acceleration of stars and galaxies from the distribution of the visible matter. It possibly stems from a new law of physics. I list the theoretical aspects of MOND, its achievements and problems. MOND has been tested mainly in disc galaxies so far. Its tests in elliptical galaxies are rare because the MOND effects are small for them in the parts observable by the conventional methods. In the thesis, I explain the methods and ideas I developed for testing MOND in the ellipticals using stellar shells. Moreover, the shells enable us to test MOND for stars in radial orbits for the first time. The shells are results of galactic interactions. I discuss the shell formation mechanisms and summarize the findings from shell observations and simulations. The thesis contains as yet unpublished results mainly in: 1) the introduction of Sect. 3 (the expected differences in the shell morphology in the Newtonian dyna...

  2. Comparing models of star formation simulating observed interacting galaxies

    Science.gov (United States)

    Quiroga, L. F.; Muñoz-Cuartas, J. C.; Rodrigues, I.

    2017-07-01

    In this work, we make a comparison between different models of star formation to reproduce observed interacting galaxies. We use observational data to model the evolution of a pair of galaxies undergoing a minor merger. Minor mergers represent situations weakly deviated from the equilibrium configuration but significant changes in star fomation (SF) efficiency can take place, then, minor mergers provide an unique scene to study SF in galaxies in a realistic but yet simple way. Reproducing observed systems also give us the opportunity to compare the results of the simulations with observations, which at the end can be used as probes to characterize the models of SF implemented in the comparison. In this work we compare two different star formation recipes implemented in Gadget3 and GIZMO codes. Both codes share the same numerical background, and differences arise mainly in the star formation recipe they use. We use observations from Pico dos Días and GEMINI telescopes and show how we use observational data of the interacting pair in AM2229-735 to characterize the interacting pair. Later we use this information to simulate the evolution of the system to finally reproduce the observations: Mass distribution, morphology and main features of the merger-induced star formation burst. We show that both methods manage to reproduce roughly the star formation activity. We show, through a careful study, that resolution plays a major role in the reproducibility of the system. In that sense, star formation recipe implemented in GIZMO code has shown a more robust performance. Acknowledgements: This work is supported by Colciencias, Doctorado Nacional - 617 program.

  3. The role of galaxy interaction in the SFR-M {sub *} relation: characterizing morphological properties of Herschel-selected galaxies at 0.2 < z < 1.5

    Energy Technology Data Exchange (ETDEWEB)

    Hung, Chao-Ling; Sanders, D. B.; Casey, C. M.; Lee, N.; Barnes, J. E.; Koss, M.; Larson, K. L.; Lockhart, K.; Man, A. W. S.; Mann, A. W. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Capak, P. [Spitzer Science Center, MS 314-6, California Institute of Technology, Pasadena, CA 91125 (United States); Kartaltepe, J. S. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Le Floc' h, E. [UMR AIM (CEA-UP7-CNRS), CEA-Saclay, Orme des Merisiers, bât. 709, F-91191 Gif-sur-Yvette Cedex (France); Riguccini, L. [NASA Ames Research Center, Moffett Field, CA (United States); Scoville, N. [California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Symeonidis, M., E-mail: clhung@ifa.hawaii.edu [University of Sussex, Department of Physics and Astronomy, Pevensey 2 Building, Falmer, Brighton BN1 9QH, Sussex (United Kingdom)

    2013-12-01

    Galaxy interactions/mergers have been shown to dominate the population of IR-luminous galaxies (L {sub IR} ≳ 10{sup 11.6} L {sub ☉}) in the local universe (z ≲ 0.25). Recent studies based on the relation between galaxies' star formation rates and stellar mass (the SFR-M {sub *} relation or the {sup g}alaxy main sequence{sup )} have suggested that galaxy interaction/mergers may only become significant when galaxies fall well above the galaxy main sequence. Since the typical SFR at a given M {sub *} increases with redshift, the existence of the galaxy main sequence implies that massive, IR-luminous galaxies at high z may not necessarily be driven by galaxy interactions. We examine the role of galaxy interactions in the SFR-M {sub *} relation by carrying out a morphological analysis of 2084 Herschel-selected galaxies at 0.2 < z < 1.5 in the COSMOS field. Using a detailed visual classification scheme, we show that the fraction of 'disk galaxies' decreases and the fraction of 'irregular' galaxies increases systematically with increasing L {sub IR} out to z ≲ 1.5 and z ≲ 1.0, respectively. At L {sub IR} >10{sup 11.5} L {sub ☉}, ≳ 50% of the objects show evident features of strongly interacting/merger systems, where this percentage is similar to the studies of local IR-luminous galaxies. The fraction of interacting/merger systems also systematically increases with the deviation from the SFR-M {sub *} relation, supporting the view that galaxies falling above the main sequence are more dominated by mergers than the main-sequence galaxies. Meanwhile, we find that ≳ 18% of massive IR-luminous 'main-sequence galaxies' are classified as interacting systems, where this population may not evolve through the evolutionary track predicted by a simple gas exhaustion model.

  4. 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

  5. Optical imaging for the Spitzer Survey of Stellar Structure in Galaxies. Data release and notes on interacting galaxies

    CERN Document Server

    Knapen, Johan H; Roa, Javier; Bakos, Judit; Cisternas, Mauricio; Leaman, Ryan; Szymanek, Nik

    2014-01-01

    (Abridged) The Spitzer Survey for Stellar Structure in Galaxies (S4G) and its more recently approved extension will lead to a set of 3.6 and 4.5 micron images for 2829 galaxies, which can be used to study many different aspects of the structure and evolution of local galaxies. We collected and re-processed optical images in five bands from the Sloan Digital Sky Survey for 1657 galaxies, which are publicly released with the publication of this paper. We observed, in only the g-band, an additional 111 S4G galaxies in the northern hemisphere with the 2.5 m Liverpool Telescope, so that optical imaging is released for 1768 galaxies, or for 62% of the S4G sample. We visually checked all images. We noted interactions and close companions in our optical data set and in the S4G sample, confirming them by determining the galaxies' radial velocities and magnitudes in the NASA-IPAC Extragalactic Database. We find that 17% of the S4G galaxies (21% of those brighter than 13.5 mag) have a close companion (within a radius of...

  6. Galaxy And Mass Assembly (GAMA): Trends in galaxy colours, morphology, and stellar populations with large scale structure, group, and pair environments

    CERN Document Server

    Alpaslan, Mehmet; Robotham, Aaron S G; Obreschkow, Danail; Andrae, Ellen; Cluver, Michelle; Kelvin, Lee S; Lange, Rebecca; Owers, Matt; Taylor, Edward N; Andrews, Stephen K; Bamford, Steven; Bland-Hawthorn, Joss; Brough, Sarah; Brown, Michael J I; Colless, Matthew; Davies, Luke J M; Eardley, Elizabeth; Grootes, Meiert W; Hopkins, Andrew M; Kennedy, Rebecca; Liske, Jochen; Lara-Lopez, Maritza A; Lopez-Sanchez, Angel R; Loveday, Jon; Madore, Barry F; Mahajan, Smriti; Meyer, Martin; Moffett, Amanda; Norberg, Peder; Penny, Samantha; Pimbblet, Kevin A; Popescu, Cristina C; Seibert, Mark; Tuffs, Richard

    2015-01-01

    We explore trends in galaxy properties with Mpc-scale structures using catalogues of environment and large scale structure from the Galaxy And Mass Assembly (GAMA) survey. Existing GAMA catalogues of large scale structure, group and pair membership allow us to construct galaxy stellar mass functions for different environmental types. To avoid simply extracting the known underlying correlations between galaxy properties and stellar mass, we create a mass matched sample of galaxies with stellar masses between $9.5 \\leq \\log{M_*/h^{-2} M_{\\odot}} \\leq 11$ for each environmental population. Using these samples, we show that mass normalised galaxies in different large scale environments have similar energy outputs, $u-r$ colours, luminosities, and morphologies. Extending our analysis to group and pair environments, we show galaxies that are not in groups or pairs exhibit similar characteristics to each other regardless of broader environment. For our mass controlled sample, we fail to see a strong dependence of S\\...

  7. Making Large Classes More Interactive.

    Science.gov (United States)

    Brenner, John

    2000-01-01

    Describes the method of using prompts to allow students to have more "voice" in a large class. The prompt assignment requires students to respond anonymously to a statement that concerns the chapter being discussed in the class. Discusses how the Internet has allowed more freedom with the prompts. Puts forth some student responses to the…

  8. The HI Content of Galaxies as a Function of Local Density and Large-Scale Environment

    Science.gov (United States)

    Thoreen, Henry; Cantwell, Kelly; Maloney, Erin; Cane, Thomas; Brough Morris, Theodore; Flory, Oscar; Raskin, Mark; Crone-Odekon, Mary; ALFALFA Team

    2017-01-01

    We examine the HI content of galaxies as a function of environment, based on a catalogue of 41527 galaxies that are part of the 70% complete Arecibo Legacy Fast-ALFA (ALFALFA) survey. We use nearest-neighbor methods to characterize local environment, and a modified version of the algorithm developed for the Galaxy and Mass Assembly (GAMA) survey to classify large-scale environment as group, filament, tendril, or void. We compare the HI content in these environments using statistics that include both HI detections and the upper limits on detections from ALFALFA. The large size of the sample allows to statistically compare the HI content in different environments for early-type galaxies as well as late-type galaxies. This work is supported by NSF grants AST-1211005 and AST-1637339, the Skidmore Faculty-Student Summer Research program, and the Schupf Scholars program.

  9. Detection of Large-Scale Structure in a $B<17^{m}$ Galaxy Redshift Survey

    CERN Document Server

    Ratcliffe, A; Broadbent, A J; Parker, Q A; Watson, F G; Oates, A P; Fong, R; Collins, C A

    1996-01-01

    We report on results from the Durham/UKST Galaxy Redshift Survey where we have found large scale ``cellular'' features in the galaxy distribution. These have spatial 2-point correlation function power significantly in excess of the predictions of the standard cold dark matter cosmological model^{1}, supporting the previous observational results from the APM survey^{2,3}. At smaller scales, the 1-D pairwise galaxy velocity dispersion is measured to be \\bf 387^{+96}_{-62} kms^{-1} which is also inconsistent with the prediction of the standard cold dark matter model^{1}. Finally, the survey has produced the most significant detection yet of large scale redshift space distortions due to dynamical infall of galaxies^{4}. An estimate of \\bf \\Omega^{0.6}/b = 0.55 \\pm 0.12 is obtained which is consistent either with a low density Universe or a critical density Universe where galaxies are biased tracers of the mass.

  10. Modeling the Initial Conditions of Interacting Galaxy Pairs Using Identikit

    CERN Document Server

    Mortazavi, S Alireza; Barnes, Joshua E

    2014-01-01

    We develop and test an automated technique to model the dynamics of interacting galaxy pairs. We use Identikit (Barnes & Hibbard 2009; Barnes 2011) as a tool for modeling and matching the morphology and kinematics of the interacting pairs of equal-mass galaxies. In order to reduce the effect of subjective human judgement, we automate the selection of phase-space regions used to match simulations to data, and we explore how selection of these regions affects the random uncertainties of parameters in the best-fit model. In this work, we used an independent set of GADGET SPH simulations as input data, to determine the systematic bias in the measured encounter parameters based on the known initial conditions of these simulations. We tested both cold gas and young stellar components in the GADGET simulations to explore the effect of choosing HI vs. H$\\alpha$ as the line of sight velocity tracer. We found that we can group the results into tests with good, fair, and poor convergence based on the distribution of...

  11. Physical origin of the large-scale conformity in the specific star formation rates of galaxies

    CERN Document Server

    Kauffmann, Guinevere

    2015-01-01

    Two explanations have been put forward to explain the observed conformity between the colours and specific star formation rates (SFR/$M_*$) of galaxies on large scales: 1) the formation times of their surrounding dark matter halos are correlated (commonly referred to as "assembly bias"), 2) gas is heated over large scales at early times, leading to coherent modulation of cooling and star formation between well-separated galaxies (commonly referred to as "pre-heating") . To distinguish between the pre-heating and assembly bias scenarios, we search for relics of energetic feedback events in the neighbourhood of central galaxies with different specific star formation rates. We find a significant excess of very high mass ($\\log M_* > 11.3$) galaxies out to a distance of 2.5 Mpc around low SFR/$M_*$ central galaxies compared to control samples of higher SFR/$M_*$ central galaxies with the same stellar mass and redshift. We also find that very massive galaxies in the neighbourhood of low SFR/$M_*$ galaxies have muc...

  12. Soft X-ray properties of a spectroscopically selected sample of interacting and isolated Seyfert galaxies

    Science.gov (United States)

    Pfefferkorn, F.; Boller, Th.; Rafanelli, P.

    2001-03-01

    We present a catalogue of ROSAT detected sources in the sample of spectroscopically selected Seyfert 1 and Seyfert 2 galaxies of Rafanelli et al. (\\cite{Rafanelli95}). The catalogue contains 102 Seyfert 1 and 36 Seyfert 2 galaxies. The identification is based on X-ray contour maps overlaid on optical images taken from the Digitized Sky Survey. We have derived the basic spectral and timing properties of the X-ray detected Seyfert galaxies. For Seyfert 1 galaxies a strong correlation between photon index and X-ray luminosity is detected. We confirm the presence of generally steeper X-ray continua in narrow-line Seyfert 1 galaxies (NLS1s) compared to broad-line Seyfert 1 galaxies. Seyfert 2 galaxies show photon indices similar to those of NLS1s. Whereas a tendency for an increasing X-ray luminosity with increasing interaction strength is found for Seyfert 1 galaxies, such a correlation is not found for Seyfert 2 galaxies. For Seyfert 1 galaxies we found also a strong correlation for increasing far-infrared luminosity with increasing interaction strength. Both NLS1s and Seyfert 2 galaxies show the highest values of far-infrared luminosity compared to Seyfert 1 galaxies, suggesting that NLS1s and Seyfert 2 galaxies host strong (circumnuclear) star formation. For variable Seyfert galaxies we present the X-ray light curves obtained from the ROSAT All-Sky Survey and from ROSAT PSPC and HRI pointed observations. Besides the expected strong short- and long-term X-ray variability in Seyfert 1 galaxies, we find indications for X-ray flux variations in Seyfert 2 galaxies. All overlays can be retrieved via CDS anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)} or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/368/797

  13. The nongravitational interactions of dark matter in colliding galaxy clusters.

    Science.gov (United States)

    Harvey, David; Massey, Richard; Kitching, Thomas; Taylor, Andy; Tittley, Eric

    2015-03-27

    Collisions between galaxy clusters provide a test of the nongravitational forces acting on dark matter. Dark matter's lack of deceleration in the "bullet cluster" collision constrained its self-interaction cross section σ(DM)/m dark matter) for long-ranged forces. Using the Chandra and Hubble Space Telescopes, we have now observed 72 collisions, including both major and minor mergers. Combining these measurements statistically, we detect the existence of dark mass at 7.6σ significance. The position of the dark mass has remained closely aligned within 5.8 ± 8.2 kiloparsecs of associated stars, implying a self-interaction cross section σ(DM)/m < 0.47 cm(2)/g (95% CL) and disfavoring some proposed extensions to the standard model.

  14. Radio Galaxy Zoo: host galaxies and radio morphologies for large surveys from visual inspection

    CERN Document Server

    Willett, Kyle W

    2016-01-01

    We present early results from Radio Galaxy Zoo, a web-based citizen science project for visual inspection and classification of images from all-sky radio surveys. The goals of the project are to classify individual radio sources (particularly galaxies with multiple lobes and/or complex morphologies) as well as matching the continuum radio emission to the host galaxy. Radio images come from the FIRST and ATLAS surveys, while matches to potential hosts are performed with infrared imaging from WISE and SWIRE. The first twelve months of classification yielded more than 1 million classifications of more than 60,000 sources. For images with at least 75% consensus by the volunteer classifiers, the accuracy is comparable to visual inspection by the expert science team. Based on mid-infrared colors, the hosts associated with radio emission are primarily a mixture of elliptical galaxies, QSOs, and LIRGs, which are in good agreement with previous studies. The full catalog of radio lobes and their host galaxies will meas...

  15. A large sample of Kohonen selected E+A (post-starburst) galaxies from the Sloan Digital Sky Survey

    CERN Document Server

    Meusinger, H; der Au, P Schalldach and A in

    2016-01-01

    We aim to create a large sample of local post-starburst (PSB) galaxies to study their characteristic properties, particularly morphological features indicative of gravitational distortions and indications for active galactic nuclei (AGNs). The selection is based on a huge Kohonen self-organising map (SOM) of about one million SDSS spectra. The SOM is made fully available for the astronomical community, in combination with an interactive user interface. We compiled a catalogue of 2665 PSB galaxies with redshifts z < 0.4. In the colour-mass diagram, the PSB sample is found to be clearly concentrated towards the region between the red and the blue cloud, in agreement with the idea that PSB galaxies represent the transitioning phase between actively and passively evolving galaxies. The relative frequency of morphologically distorted PSB galaxies is at least 57%, significantly higher than in a comparison sample. The search for AGNs based on conventional selection criteria in the radio and MIR results in a low A...

  16. Probing the imprint of interacting dark energy on very large scales

    CERN Document Server

    Duniya, Didam; Maartens, Roy

    2015-01-01

    The observed galaxy power spectrum acquires relativistic corrections from lightcone effects, and these corrections grow on very large scales. Future galaxy surveys in optical, infrared and radio bands will probe increasingly large wavelength modes and reach higher redshifts. In order to exploit the new data on large scales, an accurate analysis requires inclusion of the relativistic effects. This is especially the case for primordial non-Gaussianity and for extending tests of dark energy models to horizon scales. Here we investigate the latter, focusing on models where the dark energy interacts non-gravitationally with dark matter. Interaction in the dark sector can also lead to large-scale deviations in the power spectrum. If the relativistic effects are ignored, the imprint of interacting dark energy will be incorrectly identified and thus lead to a bias in constraints on interacting dark energy on very large scales.

  17. The rapid formation of a large rotating disk galaxy three billion years after the Big Bang.

    Science.gov (United States)

    Genzel, R; Tacconi, L J; Eisenhauer, F; Schreiber, N M Förster; Cimatti, A; Daddi, E; Bouché, N; Davies, R; Lehnert, M D; Lutz, D; Nesvadba, N; Verma, A; Abuter, R; Shapiro, K; Sternberg, A; Renzini, A; Kong, X; Arimoto, N; Mignoli, M

    2006-08-17

    Observations and theoretical simulations have established a framework for galaxy formation and evolution in the young Universe. Galaxies formed as baryonic gas cooled at the centres of collapsing dark-matter haloes; mergers of haloes and galaxies then led to the hierarchical build-up of galaxy mass. It remains unclear, however, over what timescales galaxies were assembled and when and how bulges and disks--the primary components of present-day galaxies--were formed. It is also puzzling that the most massive galaxies were more abundant and were forming stars more rapidly at early epochs than expected from models. Here we report high-angular-resolution observations of a representative luminous star-forming galaxy when the Universe was only 20% of its current age. A large and massive rotating protodisk is channelling gas towards a growing central stellar bulge hosting an accreting massive black hole. The high surface densities of gas, the high rate of star formation and the moderately young stellar ages suggest rapid assembly, fragmentation and conversion to stars of an initially very gas-rich protodisk, with no obvious evidence for a major merger.

  18. THE SPITZER INTERACTING GALAXIES SURVEY: A MID-INFRARED ATLAS OF STAR FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Brassington, N. J. [School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Zezas, A.; Ashby, M. L. N.; Lanz, L.; Smith, Howard A.; Willner, S. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Klein, C., E-mail: n.brassington@herts.ac.uk [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)

    2015-05-15

    The Spitzer Interacting Galaxies Survey is a sample of 103 nearby galaxies in 48 systems, selected using association likelihoods and therefore free from disturbed morphology biases. All galaxies have been observed with Infrared Array Camera and MIPS 24 μm bands from the Spitzer Space Telescope. This catalog presents the global flux densities and colors of all systems and correlations between the interacting systems and their specific star formation rate (sSFR). This sample contains a wide variety of galaxy interactions with systems ranging in mass, mass ratios, and gas-content as well as interaction strength. This study seeks to identify the process of triggering star formation in galaxy interactions, therefore, we focus on the non-active galactic nucleus spiral galaxies only. From this subset of 70 spiral galaxies we have determined that this sample has enhanced sSFR compared to a sample of non-interacting field galaxies. Through optical data we have classified each system by “interaction strength”; the strongly interacting (Stage 4) galaxies have higher sSFR values than the weakly (Stage 2) and moderately (Stage 3) interacting systems. However, the Stage 2 and 3 systems have statistically identical sSFR properties, despite the lack of optical interaction signatures exhibited by the Stage 2 galaxies. We suggest that the similarity of sSFR in these stages could be a consequence of some of these Stage 2 systems actually being post-perigalactic and having had sufficient time for their tidal features to fade to undetectable levels. This interpretation is consistent with the correlation of sSFR with separation, which we have determined to have little variation up to 100 kpc.

  19. Tidal Tails in Interacting Galaxies: Formation of Compact Stellar Structures

    CERN Document Server

    Mullan, B; Konstantopoulos, I S; Bastian, N; Chandar, R; Durrell, P R; Elmegreen, D; English, J; Gallagher, S C; Gronwall, C; Hibbard, J E; Hunsberger, S; Johnson, K E; Kepley, A; Knierman, K; Koribalski, B; Lee, K H; Maybhate, A; Palma, C; Vacca, W D

    2009-01-01

    We have used V- and I- band images from the Hubble Space Telescope (HST) to identify compact stellar clusters within the tidal tails of twelve different interacting galaxies. The seventeen tails within our sample span a physical parameter space of HI/stellar masses, tail pressure and density through their diversity of tail lengths, optical brightnesses, mass ratios, HI column densities, stage on the Toomre sequence, and tail kinematics. Our preliminary findings in this study indicate that star cluster demographics of the tidal tail environment are compatible with the current understanding of star cluster formation in quiescent systems, possibly only needing changes in certain parameters or normalization of the Schechter cluster initial mass function (CIMF) to replicate what we observe in color-magnitude diagrams and a brightest absolute magnitude -- log N plot.

  20. On the Interaction in a Quartet of Galaxies

    CERN Document Server

    Yeghiazaryan, A A; Nazaryan, T A

    2015-01-01

    We performed the Fabry-Perot scanning interferometry of the quartet of galaxies NGC 7769, 7770, 7771 and 7771A in Ha line and studied their velocity fields. We found that the rotation curve of NGC 7769 is weakly distorted. The rotation curve of NGC 7771 is strongly distorted with the tidal arms caused by direct flyby of NGC 7769 and flyby of a smaller neighbor NGC 7770. The rotation curve of NGC 7770 is significantly skewed because of the interaction with much massive NGC 7771. The rotation curves and morphological disturbances suggest that the NGC 7769 and NGC 7771 have passed the first pericenter stage, however, probably the second encounter has not happened yet.

  1. Detection of a Large Population of Ultradiffuse Galaxies in Massive Galaxy Clusters: Abell S1063 and Abell 2744

    Science.gov (United States)

    Lee, Myung Gyoon; Kang, Jisu; Lee, Jeong Hwan; Jang, In Sung

    2017-08-01

    We present the detection of a large population of ultradiffuse galaxies (UDGs) in two massive galaxy clusters, Abell S1063 at z = 0.348 and Abell 2744 at z = 0.308, based on F814W and F105W images in the Hubble Frontier Fields Program. We find 47 and 40 UDGs in Abell S1063 and Abell 2744, respectively. Color-magnitude diagrams of the UDGs show that they are mostly located at the faint end of the red sequence. From the comparison with simple stellar population models, we estimate their stellar mass to range from 108 to 109 M ⊙. Radial number density profiles of the UDGs show a turnover or a flattening in the central region at r 1013 M ⊙ with a power law, N(UDG) = {M}2001.05+/- 0.09. These results suggest that a majority of the UDGs have a dwarf galaxy origin, while only a small number of the UDGs are massive L* galaxies that failed to form a normal population of stars.

  2. Large Area Survey for z=7 Galaxies in SDF and GOODS-N: Implications for Galaxy Formation and Cosmic Reionization

    CERN Document Server

    Ouchi, Masami; Shimasaku, Kazuhiro; Ferguson, Henry C; Fall, Michael S; Ono, Yoshiaki; Kashikawa, Nobunari; Morokuma, Tomoki; Nakajima, Kimihiko; Okamura, Sadanori; Dickinson, Mark; Giavalisco, Mauro; Ohta, Kouji

    2009-01-01

    We present results of our large-area survey for z'-band dropout galaxies at z=7 in a 1568 arcmin^2 sky area covering the SDF and GOODS-N fields. Combining our ultra-deep Subaru/Suprime-Cam z'- and y-band (lambda_eff=1um) images with legacy data of Subaru and HST, we have identified 22 bright z-dropout galaxies down to y=26, one of which has a spectroscopic redshift of z=6.96 determined from Lya emission. The z=7 luminosity function (LF) yields the best-fit Schechter parameters of phi*=1.1 +2.8/-0.8 x10^(-3) Mpc^(-3), Muv*=-19.9 +/-0.7 mag, and alpha=-1.7 +/-1.3, and indicates a decrease from z=6 at the =~ 95% confidence level. This decrease is beyond the cosmic variance in our two fields, which is estimated to be a factor of ~ 3 but not larger than ~100. A comparison with the reionization models suggests either that the Universe could not be totally ionized by only galaxies at z=7, or more likely that properties of galaxies at z=7 are different from those at low redshifts having, e.g., a larger escape fractio...

  3. Cosmology from large-scale galaxy clustering and galaxy–galaxy lensing with Dark Energy Survey Science Verification data

    Energy Technology Data Exchange (ETDEWEB)

    Kwan, J.; Sánchez, C.; Clampitt, J.; Blazek, J.; Crocce, M.; Jain, B.; Zuntz, J.; Amara, A.; Becker, M. R.; Bernstein, G. M.; Bonnett, C.; DeRose, J.; Dodelson, S.; Eifler, T. F.; Gaztanaga, E.; Giannantonio, T.; Gruen, D.; Hartley, W. G.; Kacprzak, T.; Kirk, D.; Krause, E.; MacCrann, N.; Miquel, R.; Park, Y.; Ross, A. J.; Rozo, E.; Rykoff, E. S.; Sheldon, E.; Troxel, M. A.; Wechsler, R. H.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Benoit-Lévy, A.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Carrasco Kind, M.; Cunha, C. E.; D' Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Evrard, A. E.; Fernandez, E.; Finley, D. A.; Flaugher, B.; Fosalba, P.; Frieman, J.; Gerdes, D. W.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Jarvis, M.; Kuehn, K.; Lahav, O.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Martini, P.; Melchior, P.; Mohr, J. J.; Nichol, R. C.; Nord, B.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Vikram, V.; Walker, A. R.

    2016-10-05

    We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 square degree contiguous patch of DES data from the Science Verification (SV) period of observations. Using large scale measurements, we constrain the matter density of the Universe as $\\Omega_m = 0.31 \\pm 0.09$ and the clustering amplitude of the matter power spectrum as $\\sigma_8 = 0.74 +\\pm 0.13$ after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into $S_8$ = $\\sigma_8(\\Omega_m/0.3)^{0.16} = 0.74 \\pm 0.12$ for our fiducial lens redshift bin at 0.35 < z < 0.5, while $S_8 = 0.78 \\pm 0.09$ using two bins over the range 0.2 < z < 0.5. We study the robustness of the results under changes in the data vectors, modelling and systematics treatment, including photometric redshift and shear calibration uncertainties, and find consistency in the derived cosmological parameters. We show that our results are consistent with previous cosmological analyses from DES and other data sets and conclude with a joint analysis of DES angular clustering and galaxy-galaxy lensing with Planck CMB data, Baryon Accoustic Oscillations and Supernova type Ia measurements.

  4. Super-large-scale structures in the distribution of infrared galaxies

    Institute of Scientific and Technical Information of China (English)

    邓祖淦; 夏晓阳; G.Borner

    1999-01-01

    Typical scales in the distribution of IRAS galaxies with the unnormalized pair count method. Samples are those provided by QDOT redshift survey and sorted out from the IRAS faint sources catalog. Analysis is concentrated on the structures at super-large scales. The results show that statistically significant typical scales do exist in the distribution of all these samples from both 2-dimensional and 3-dimensional analyses. These scales are consistent with those found from the analyses of galaxies and clusters of galaxies by Mo et al. and also consistent with those found from analysis of quasars by Deng et al. The analysis provides additional evidence for the existence of typical scales in the large-scale structure of the universe. The existence of typical scales challenges all the existing models on the formation of galaxies and structures.

  5. SPIN ALIGNMENTS OF SPIRAL GALAXIES WITHIN THE LARGE-SCALE STRUCTURE FROM SDSS DR7

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Youcai; Yang, Xiaohu; Luo, Wentao [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030 (China); Wang, Huiyuan [Key Laboratory for Research in Galaxies and Cosmology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Wang, Lei [Purple Mountain Observatory, The Partner Group of MPI für Astronomie, 2 West Beijing Road, Nanjing 210008 (China); Mo, H. J. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States); Van den Bosch, Frank C., E-mail: yczhang@shao.ac.cn, E-mail: xyang@sjtu.edu.cn [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)

    2015-01-01

    Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 and Galaxy Zoo 2, we investigate the alignment of spin axes of spiral galaxies with their surrounding large-scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certain mass threshold. We find that the spin axes only have weak tendencies to be aligned with (or perpendicular to) the intermediate (or minor) axis of the local tidal tensor. The signal is the strongest in a cluster environment where all three eigenvalues of the local tidal tensor are positive. Compared to the alignments between halo spins and the local tidal field obtained in N-body simulations, the above observational results are in best agreement with those for the spins of inner regions of halos, suggesting that the disk material traces the angular momentum of dark matter halos in the inner regions.

  6. Large Area Lyman Alpha Survey: Finding Young Galaxies at z=4.5

    Science.gov (United States)

    Malhotra, S.; Rhoads, J.; Dey, A.; Stern, D.; Spinrad, H.

    Strong Lyα emission is a signpost of young stars and the absence of dust and thus indicates young galaxies. To find such a population of young galaxies at z=4.5 we started the Large Area Lyman Alpha survey (LALA). This survey achieves an unprecedented combination of volume and sensitivity by using narrow-band filters on a large format (36' × 36') camera on the 4 meter telescope at KPNO. The volume density and star-formation contribution of the Lyα emitters at z=4.5 is comparable to that of Lyman break galaxies. With many candidates and a few spectroscopic confirmations in hand we discuss what the properties of Lyα emitters imply for galaxy and star formation in the early universe.

  7. Large-scale HI in nearby radio galaxies : segregation in neutral gas content with radio source size

    NARCIS (Netherlands)

    Emonts, B. H. C.; Morganti, R.; Oosterloo, T. A.; van der Hulst, J. M.; van Moorsel, G.; Tadhunter, C. N.

    2007-01-01

    We present results of a study of neutral hydrogen ( HI) in a complete sample of nearby non-cluster radio galaxies. We find that radio galaxies with large amounts of extended HI (M-HI >= 109 M-circle dot) all have a compact radio source. The host galaxies of the more extended radio sources, all of Fa

  8. Large-scale environmental dependence of gas-phase metallicity in dwarf galaxies

    CERN Document Server

    Douglass, Kelly A

    2016-01-01

    We study how the cosmic environment affects galaxy evolution in the Universe by comparing the metallicities of dwarf galaxies in voids with dwarf galaxies in more dense regions. Ratios of the fluxes of emission lines, particularly those of the forbidden [OIII] and [SII] transitions, provide estimates of a region's electron temperature and number density. From these two quantities and the emission line fluxes [OII] 3727, [OIII] 4363, and [OIII] 4959,5007, we estimate the abundance of oxygen with the Direct Te method. We estimate the metallicity of 37 void dwarf galaxies and 75 dwarf galaxies in more dense regions using spectroscopic observations from the Sloan Digital Sky Survey Data Release 7, as re-processed in the MPA-JHU value-added catalog. We find very little difference between the two sets of galaxies, indicating little influence from the large-scale environment on their chemical evolution. Of particular interest are a number of extremely metal-poor dwarf galaxies that are equally abundant in both voids...

  9. RCSLenS: A new estimator for large-scale galaxy-matter correlations

    CERN Document Server

    Buddendiek, A; Hildebrandt, H; Blake, C; Choi, A; Erben, T; Heymans, C; van Waerbeke, L; Viola, M; Harnois-Deraps, J; Koens, L; Nakajima, R

    2015-01-01

    We present measurements of the galaxy bias $b$ and the galaxy-matter cross-correlation coefficient $r$ for the BOSS LOWZ luminous red galaxy sample. Using a new statistical weak lensing analysis of the Red Sequence Cluster Lensing Survey (RCSLenS) we find the bias properties of this sample to be higher than previously reported with $b=2.45^{+0.05}_{-0.05}$ and $r=1.64^{+0.17}_{-0.16}$ on scales between $3'$ and $20'$. We repeat the measurement for angular scales of $20'\\leq \\vartheta \\leq70'$, which yields $b=2.39^{+0.07}_{-0.07}$ and $r=1.24^{+0.26}_{-0.25}$. This is the first application of a data compression analysis using a complete set of discrete estimators for galaxy-galaxy lensing and galaxy clustering. As cosmological data sets grow, our new method of data compression will become increasingly important in order to interpret joint weak lensing and galaxy clustering measurements and to estimate the data covariance. In future studies this formalism can be used as a tool to study the large-scale structur...

  10. Large Molecular Gas Reservoirs in Ancestors of Milky Way-Mass Galaxies 9 Billion Years Ago

    CERN Document Server

    Papovich, Casey; Glazebrook, Karl; Quadri, Ryan; Bekiaris, Georgios; Dickinson, Mark; Finkelstein, Steven; Fisher, David; Inami, Hanae; Livermore, Rachael; Spitler, Lee; Straatman, Caroline; Tran, Kim-Vy

    2016-01-01

    The gas accretion and star-formation histories of galaxies like the Milky Way remain an outstanding problem in astrophysics. Observations show that 8 billion years ago, the progenitors to Milky Way-mass galaxies were forming stars 30 times faster than today and predicted to be rich in molecular gas, in contrast with low present-day gas fractions ($<$10%). Here we show detections of molecular gas from the CO(J=3-2) emission (rest-frame 345.8 GHz) in galaxies at redshifts z=1.2-1.3, selected to have the stellar mass and star-formation rate of the progenitors of today's Milky Way-mass galaxies. The CO emission reveals large molecular gas masses, comparable to or exceeding the galaxy stellar masses, and implying most of the baryons are in cold gas, not stars. The galaxies' total luminosities from star formation and CO luminosities yield long gas-consumption timescales. Compared to local spiral galaxies, the star-formation efficiency, estimated from the ratio of total IR luminosity to CO emission,} has remained...

  11. 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.

  12. Galaxy pairs in cosmological simulations: effects of interactions on colours and chemical abundances

    CERN Document Server

    Perez, M J; Lambas, D G; Scannapieco, C; Tissera, P B; Lambas, Diego G.; Rossi, Maria E. De; Scannapieco, Cecilia; Tissera, Patricia B.

    2006-01-01

    We perform an statistical analysis of galaxies in pairs in a Lambda-CDM scenario by using the chemical GADGET-2 of Scannapieco et al. (2005) in order to study the effects of galaxy interactions on colours and metallicities. We find that galaxy-galaxy interactions can produce a bimodal colour distribution with galaxies with significant recent star formation activity contributing mainly to blue colours. In the simulations, the colours and the fractions of recently formed stars of galaxies in pairs depend on environment more strongly than those of galaxies without a close companion, suggesting that interactions play an important role in galaxy evolution. If the metallicity of the stellar populations is used as the chemical indicator, we find that the simulated galaxies determine luminosity-metallicity and stellar mass-metallicity relations which do not depend on the presence of a close companion. However, in the case of the luminosity-metallicity relation, at a given level of enrichment, we detect a systematic d...

  13. Evaluating Large-Scale Interactive Radio Programmes

    Science.gov (United States)

    Potter, Charles; Naidoo, Gordon

    2009-01-01

    This article focuses on the challenges involved in conducting evaluations of interactive radio programmes in South Africa with large numbers of schools, teachers, and learners. It focuses on the role such large-scale evaluation has played during the South African radio learning programme's development stage, as well as during its subsequent…

  14. WISE-2MASS all-sky infrared galaxy catalog for large scale structure

    CERN Document Server

    Kovács, András

    2014-01-01

    We combine photometric information of the WISE and 2MASS infrared all-sky surveys to produce a clean galaxy sample for large-scale structure research. Adding 2MASS colors improves star-galaxy separation substantially at the expense of loosing a small fraction of the galaxies: 93% of the WISE objects within the W1<15.2 mag limit have 2MASS observation as well. We use a class of supervised machine learning algorithms, Support Vector Machines (SVM), to classify objects in our large data set. We used SDSS PhotoObj table with known star-galaxy separation for a training set on classification, and the GAMA spectroscopic survey for determining the redshift distribution of our sample. Varying the combination of photometric parameters input into our algorithm revealed that W1-J is a simple and effective star-galaxy separator, capable of producing results comparable to the multi-dimensional SVM classification. The final catalog has an estimated ~2% stellar contamination among 5 million galaxies with median redshift o...

  15. An Efficient Approach to Obtaining Large Numbers of Distant Supernova Host Galaxy Redshifts

    CERN Document Server

    Lidman, C; Sullivan, M; Myzska, J; Dobbie, P; Glazebrook, K; Mould, J; Astier, P; Balland, C; Betoule, M; Carlberg, R; Conley, A; Fouchez, D; Guy, J; Hardin, D; Hook, I; Howell, D A; Pain, R; Palanque-Delabrouille, N; Perrett, K; Pritchet, C; Regnault, N; Rich, J

    2012-01-01

    We use the wide-field capabilities of the 2dF fibre positioner and the AAOmega spectrograph on the Anglo-Australian Telescope (AAT) to obtain redshifts of galaxies that hosted supernovae during the first three years of the Supernova Legacy Survey (SNLS). With exposure times ranging from 10 to 60 ksec per galaxy, we were able to obtain redshifts for 400 host galaxies in two SNLS fields, thereby substantially increasing the total number of SNLS supernovae with host galaxy redshifts. The median redshift of the galaxies in our sample that hosted photometrically classified Type Ia supernovae (SNe Ia) is 0.77, which is 25% higher than the median redshift of spectroscopically confirmed SNe Ia in the three-year sample of the SNLS. Our results demonstrate that one can use wide-field fibre-fed multi-object spectrographs on 4m telescopes to efficiently obtain redshifts for large numbers of supernova host galaxies over the large areas of sky that will be covered by future high-redshift supernova surveys, such as the Dark...

  16. Interaction of Jets with the ISM of Radio Galaxies

    CERN Document Server

    Sutherland, R S

    2007-01-01

    We present three dimensional simulations of the interaction of a light hypersonic jet with an inhomogeneous thermal and turbulently supported disk in an elliptical galaxy, including Radio and multi-band X-ray visualisations. These simulations are applicable to the GPS/CSS phase of some extragalactic radio sources. We identify four generic phases in the evolution of such a jet with the interstellar medium. The first is a `flood and channel'' phase, dominated by complex jet interactions with the dense cloudy medium close to the nucleus. A spherical, energy driven, bubble phase follows, where the bubble is larger than the disk scale, but the jet remains fully disrupted close to the nucleus. Then in a rapid, jet break--out phase, the jet breaks free of the last obstructing dense clouds, becomes collimated and pierces the more or less spherical bubble. In the final classical phase, the jet propagates in a momentum-dominated fashion similar to jets in single component hot haloes, leading to the classical jet -- coc...

  17. Elliptical galaxies interacting with the cluster tidal field origin of the intracluster stellar population

    CERN Document Server

    Muccione, V

    2002-01-01

    With the aid of simple numerical models, we discuss a particular aspect of the interaction between stellar orbital periods inside elliptical galaxies (Es) and the parent cluster tidal field (CTF), i.e., the possibility that collisionless stellar evaporation from Es is an effective mechanism for the production of the recently discovered intracluster stellar populations (ISP). These very preliminary investigations, based on idealized galaxy density profiles (such as Ferrers density distributions) show that, over an Hubble time, the amount of stars lost by a representative galaxy may sum up to the 10% of the initial galaxy mass, a fraction in interesting agreement with observational data. The effectiveness of this mechanism is due to the fact that the galaxy oscillation periods near its equilibrium configurations in the CTF are of the same order of stellar orbital times in the external galaxy regions.

  18. ChAInGeS: The Chandra Arp Interacting Galaxies Survey

    CERN Document Server

    Smith, Beverly J; Miller, Olivia; Burleson, Jacob A; Nowak, Michael A; Struck, Curtis

    2012-01-01

    We have conducted a statistical analysis of the ultra-luminous X-ray point sources (ULXs; L(X) >= 10^39 erg/s) in a sample of galaxies selected from the Arp Atlas of Peculiar Galaxies. We find a possible enhancement of a factor of ~2-4 in the number of ULXs per blue luminosity for the strongly interacting subset. Such an enhancement would be expected if ULX production is related to star formation, as interacting galaxies tend to have enhanced star formation rates on average. For most of the Arp galaxies in our sample, the total number of ULXs compared to the far-infrared luminosity is consistent with values found earlier for spiral galaxies. This suggests that for these galaxies, ULXs trace recent star formation. However, for the most infrared-luminous galaxies, we find a deficiency of ULXs compared to the infrared luminosity. For these very infrared-luminous galaxies, AGNs may contribute to powering the far-infrared; alternatively, ULXs may be highly obscured in the X-ray in these galaxies and therefore not ...

  19. Modeling the Dynamics of Interacting Galaxy Pairs - Testing Identikit Using GADGET SPH Simulations

    Science.gov (United States)

    Mortazavi, S. Alireza; Lotz, Jennifer; Barnes, Joshua E.

    2015-01-01

    We develop and test an automated technique to model the dynamics of interacting galaxy pairs. We use Identikit (Barnes & Hibbard 2009; Barnes 2011) as a tool for modeling and matching the morphology and kinematics of the interacting pairs of similar-size galaxies. In order to reduce the effect of subjective human interference, we automate the selection of phase-space regions used to match simulations to data, and we explore how selection of these regions affects the random uncertainties of parameters in the best-fit model. In this work, we used an independent set of GADGET SPH simulations as input data, so we determined the systematic bias in the measured encounter parameters based on the known initial conditions of these simulations. We tested both cold gas and young stellar components in the GADGET simulations to explore the effect of choosing HI vs. Hα as the line of sight velocity tracer. We found that we can group the results into tests with good, fair, and poor convergence based on the distribution of parameters of models close enough to the best-fit model. For tests with good and fair convergence, we ruled out large fractions of parameter space and recovered merger stage, eccentricity, viewing angle, and pericentric distance within 2σ of the correct value. All of tests on gaseous component of prograde systems had either good or fair convergence. Retrograde systems and most of tests on young stars had poor convergence and may require constraints from regions other than the tidal tails. In this work we also present WIYN SparsePak IFU data for a few interacting galaxies, and we show the result of applying our method on this data set.

  20. The Ha Velocity Fields and Galaxy Interaction in the Quartet of Galaxies NGC 7769, 7770, 7771 and 7771A

    CERN Document Server

    Yeghiazaryan, A A; Hakobyan, A A

    2015-01-01

    The quartet of galaxies NGC 7769, 7770, 7771 and 7771A is a system of interacting galaxies. Close interaction between galaxies caused characteristic morphological features: tidal arms and bars, as well as an induced star formation. In this study, we performed the Fabry-Perot scanning interferometry of the system in Ha line and studied the velocity fields of the galaxies. We found that the rotation curve of NGC 7769 is weakly distorted. The rotation curve of NGC 7771 is strongly distorted with the tidal arms caused by direct flyby of NGC 7769 and flyby of a smaller neighbor NGC 7770. The rotation curve of NGC 7770 is significantly skewed because of the interaction with much massive NGC 7771. The rotation curves and morphological disturbances suggest that the NGC 7769 and NGC 7771 have passed the first pericenter stage, however, probably the second encounter has not happened yet. Profiles of surface brightness of NGC 7769 have a characteristic break, and profiles of color indices have a minimum at a radius of i...

  1. The SAMI galaxy survey: Galaxy Interactions and Kinematic Anomalies in Abell 119

    CERN Document Server

    Oh, Sree; Cortese, Luca; van de Sande, Jesse; Mahajan, Smriti; Jeong, Hyunjin; Sheen, Yun-Kyeong; Allen, James T; Bekki, Kenji; Bland-Hawthorn, Joss; Bloom, Jessica V; Brough, Sarah; Bryant, Julia J; Colless, Matthew; Croom, Scott M; Fogarty, L M R; Goodwin, Michael; Green, Andy; Konstantopoulos, Iraklis S; Lawrence, Jon; López-Sánchez, Á R; Lorente, Nuria P F; Medling, Anne M; Owers, Matt S; Richards, Samuel; Scott, Nicholas; Sharp, Rob; Sweet, Sarah M

    2016-01-01

    Galaxy mergers are important events that can determine the fate of a galaxy by changing its morphology, star-formation activity and mass growth. Merger systems have commonly been identified from their disturbed morphologies, and we now can employ Integral Field Spectroscopy to detect and analyze the impact of mergers on stellar kinematics as well. We visually classified galaxy morphology using deep images ($\\mu_{\\rm r} = 28\\,\\rm mag\\,\\, arcsec^{-2}$) taken by the Blanco 4-m telescope at the Cerro Tololo Inter-American Observatory. In this paper we investigate 63 bright ($M_{\\rm r}<-19.3$) spectroscopically-selected galaxies in Abell 119; of which 53 are early type and 20 galaxies show a disturbed morphology by visual inspection. A misalignment between the major axes in the photometric image and the kinematic map is conspicuous in morphologically-disturbed galaxies. Our sample is dominated by early-type galaxies, yet it shows a surprisingly tight Tully-Fisher relation except for the morphologically-disturbe...

  2. GESE: A Small UV Space Telescope to Conduct a Large Spectroscopic Survey of Z-1 Galaxies

    Science.gov (United States)

    Heap, Sara R.; Gong, Qian; Hull, Tony; Kruk, Jeffrey; Purves, Lloyd

    2013-01-01

    One of the key goals of NASA's astrophysics program is to answer the question: How did galaxies evolve into the spirals and elliptical galaxies that we see today? We describe a space mission concept called Galaxy Evolution Spectroscopic Explorer (GESE) to address this question by making a large spectroscopic survey of galaxies at a redshift, z is approximately 1 (look-back time of approximately 8 billion years). GESE is a 1.5-meter space telescope with an ultraviolet (UV) multi-object slit spectrograph that can obtain spectra of hundreds of galaxies per exposure. The spectrograph covers the spectral range, 0.2-0.4 micrometers at a spectral resolving power, R approximately 500. This observed spectral range corresponds to 0.1-0.2 micrometers as emitted by a galaxy at a redshift, z=1. The mission concept takes advantage of two new technological advances: (1) light-weighted, wide-field telescope mirrors, and (2) the Next- Generation MicroShutter Array (NG-MSA) to be used as a slit generator in the multi-object slit spectrograph.

  3. Large turbulent reservoirs of cold molecular gas around high-redshift starburst galaxies

    Science.gov (United States)

    Falgarone, E.; Zwaan, M. A.; Godard, B.; Bergin, E.; Ivison, R. J.; Andreani, P. M.; Bournaud, F.; Bussmann, R. S.; Elbaz, D.; Omont, A.; Oteo, I.; Walter, F.

    2017-08-01

    Starburst galaxies at the peak of cosmic star formation are among the most extreme star-forming engines in the Universe, producing stars over about 100 million years (ref. 2). The star-formation rates of these galaxies, which exceed 100 solar masses per year, require large reservoirs of cold molecular gas to be delivered to their cores, despite strong feedback from stars or active galactic nuclei. Consequently, starburst galaxies are ideal for studying the interplay between this feedback and the growth of a galaxy. The methylidyne cation, CH+, is a most useful molecule for such studies because it cannot form in cold gas without suprathermal energy input, so its presence indicates dissipation of mechanical energy or strong ultraviolet irradiation. Here we report the detection of CH+ (J = 1–0) emission and absorption lines in the spectra of six lensed starburst galaxies at redshifts near 2.5. This line has such a high critical density for excitation that it is emitted only in very dense gas, and is absorbed in low-density gas. We find that the CH+ emission lines, which are broader than 1,000 kilometres per second, originate in dense shock waves powered by hot galactic winds. The CH+ absorption lines reveal highly turbulent reservoirs of cool (about 100 kelvin), low-density gas, extending far (more than 10 kiloparsecs) outside the starburst galaxies (which have radii of less than 1 kiloparsec). We show that the galactic winds sustain turbulence in the 10-kiloparsec-scale environments of the galaxies, processing these environments into multiphase, gravitationally bound reservoirs. However, the mass outflow rates are found to be insufficient to balance the star-formation rates. Another mass input is therefore required for these reservoirs, which could be provided by ongoing mergers or cold-stream accretion. Our results suggest that galactic feedback, coupled jointly to turbulence and gravity, extends the starburst phase of a galaxy instead of quenching it.

  4. Constraining Gravity at Large Scales with Clusters of Galaxies

    Science.gov (United States)

    Rapetti, D.; Cataneo, M.; Schmidt, F.; Lombriser, L.; Li, B.; Mantz, A.; Allen, S.; Applegate, D.; Kelly, P.; von der Linden, A.; Morris, R. G.

    2017-01-01

    I will present the most recent constraints on f(R) modifications of gravity from the abundance of massive galaxy clusters. Our analysis self-consistently and simultaneously incorporates survey, observable-mass scaling relations, as well as weak gravitational lensing data to accurately calibrate the absolute cluster mass scale. Using this advanced cluster analysis in combination with CMB data, and other cosmological constraints, we obtain upper bounds on f(R) gravity that are about an order of magnitude tighter than those from such previous studies. The robustness of our results derives from our high quality cluster growth data out to redshifts z 0 . 5 , a tight control of systematic uncertainties, accounting for the covariance between all parameters, and the use of the full shape of the halo mass function (HMF) over the mass range of the data. Based on the current highest resolution N-body simulations, I will also describe our new modeling of the f(R) HMF. This includes novel corrections to capture key non-linear effects of the Chameleon screening mechanism that will allow us to obtain the next generation of cluster constraints on this model. DR is supported by an NPP Senior Fellowship at NASA ARC, administered by USRA under contract with NASA.

  5. The Evolution of Interacting Spiral Galaxy NGC 5194

    CERN Document Server

    Kang, Xiaoyu; Zhang, Fenghui; Cheng, Liantao; Wang, Lang

    2015-01-01

    NGC 5194 (M51a) is a grand-design spiral galaxy and undergoing interactions with its companion. Here we focus on investigating main properties of its star-formation history (SFH) by constructing a simple evolution model, which assumes that the disc builds up gradually by cold gas infall and the gas infall rate can be parameterizedly described by a Gaussian form. By comparing model predictions with the observed data, we discuss the probable range for free parameter in the model and then know more about the main properties of the evolution and SFH of M51a. We find that the model predictions are very sensitive to the free parameter and the model adopting a constant infall-peak time $t_{\\rm p}\\,=\\,7.0{\\rm Gyr}$ can reproduce most of the observed constraints of M51a. Although our model does not assume the gas infall time-scale of the inner disc is shorter than that of the outer disc, our model predictions still show that the disc of M51a forms inside-out. We find that the mean stellar age of M51a is younger than t...

  6. Escape dynamics in a binary system of interacting galaxies

    CERN Document Server

    Zotos, Euaggelos E

    2016-01-01

    The escape dynamics in an analytical gravitational model which describes the motion of stars in a binary system of interacting dwarf spheroidal galaxies is investigated in detail. We conduct a numerical analysis distinguishing between regular and chaotic orbits as well as between trapped and escaping orbits, considering only unbounded motion for several energy levels. In order to distinguish safely and with certainty between ordered and chaotic motion, we apply the Smaller ALingment Index (SALI) method. It is of particular interest to locate the escape basins through the openings around the collinear Lagrangian points $L_1$ and $L_2$ and relate them with the corresponding spatial distribution of the escape times of the orbits. Our exploration takes place both in the configuration $(x,y)$ and in the phase $(x,\\dot{x})$ space in order to elucidate the escape process as well as the overall orbital properties of the galactic system. Our numerical analysis reveals the strong dependence of the properties of the con...

  7. Galaxy Peculiar Velocities From Large-Scale Supernova Surveys as a Dark Energy Probe

    CERN Document Server

    Bhattacharya, Suman; Newman, Jeffrey A; Zentner, Andrew R

    2010-01-01

    Upcoming imaging surveys such as the Large Synoptic Survey Telescope will repeatedly scan large areas of sky and have the potential to yield million-supernova catalogs. Type Ia supernovae are excellent standard candles and will provide distance measures that suffice to detect mean pairwise velocities of their host galaxies. We show that when combining these distance measures with photometric redshifts for either the supernovae or their host galaxies, the mean pairwise velocities of the host galaxies will provide a dark energy probe which is competitive with other widely discussed methods. Adding information from this test to type Ia supernova photometric luminosity distances from the same experiment, plus the cosmic microwave background power spectrum from the Planck satellite, improves the Dark Energy Task Force Figure of Merit by a factor of 2.2. Pairwise velocity measurements require no additional observational effort beyond that required to perform the traditional supernova luminosity distance test, but m...

  8. Measuring Large-Scale Structure at z ~ 1 with the VIPERS galaxy survey

    Science.gov (United States)

    Guzzo, Luigi

    2016-10-01

    The VIMOS Public Extragalactic Redshift Survey (VIPERS) is the largest redshift survey ever conducted with the ESO telescopes. It has used the Very Large Telescope to collect nearly 100,000 redshifts from the general galaxy population at 0.5 properties and the relation of the latter to large-scale structure. This paper presents an overview of the galaxy clustering results obtained so far, together with their cosmological implications. Most of these are based on the ~ 55,000 galaxies forming the first public data release (PDR-1). As of January 2015, observations and data reduction are complete and the final data set of more than 90,000 redshifts is being validated and made ready for the final investigations.

  9. Large scale profiles of galaxies at z=0-2 studied by stacking the HSC SSP survey data

    Science.gov (United States)

    Kubo, Mariko; Ouchi, Masami; Shibuya, Takatoshi

    2017-03-01

    We are carrying out the study of the evolution of radial surface brightness profiles of galaxies from z = 0 to 2 by stacking analysis using data corrected by the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP). This will allow us to constrain the large scale average profiles of various galaxy populations at high redshift. From the stacking analysis of galaxies selected based on their photometric redshifts, we successfully detected the outer components of galaxies at z > 1 extending to at least ~80 kpc, which imply an early formation for the galaxy outskirts.

  10. On the influence of ram-pressure stripping on interacting galaxies in clusters

    CERN Document Server

    Kapferer, W; Ferrari, C; Riser, T; Schindler, S

    2008-01-01

    We investigate the influence of ram pressure on the star-formation rate and the distribution of gas and stellar matter in interacting model galaxies in clusters. To simulate the baryonic and non-baryonic components of interacting disc galaxies moving through a hot, thin medium we use a combined N-body/hydrodynamic code GADGET2 with a description for star formation based on density thresholds. Two identical model spiral galaxies on a collision trajectory with three different configurations were investigated in detail. In the first configuration the galaxies collide without the presence of an ambient medium, in the second configurations the ram pressure acts face on on the interacting galaxies and in the third configuration the ram pressure acts edge on. The ambient medium is thin ($10^{-28}$ g/cm$^3$), hot (3 keV $\\approx 3.6\\times10^7$K) and has a relative velocity of 1000 km/s, to mimic an average low ram pressure in the outskirts of galaxy clusters. The interaction velocities are comparable to galaxy intera...

  11. Simulations of ram-pressure stripping in galaxy-cluster interactions

    CERN Document Server

    Steinhauser, Dominik; Springel, Volker

    2016-01-01

    Observationally, the quenching of star-forming galaxies appears to depend both on their mass and environment. The exact cause of the environmental dependence is still poorly understood, yet semi-analytic models (SAMs) of galaxy formation need to parameterise it to reproduce observations of galaxy properties. In this work, we use hydrodynamical simulations to investigate the quenching of disk galaxies through ram-pressure stripping (RPS) as they fall into galaxy clusters with the goal of characterising the importance of this effect for the reddening of disk galaxies. Our set-up employs a live model of a galaxy cluster that interacts with infalling disk galaxies on different orbits. We use the moving-mesh code AREPO, augmented with a special refinement strategy to yield high resolution around the galaxy on its way through the cluster in a computationally efficient way. Our direct simulations differ substantially from stripping models employed in current SAMs, which in most cases overpredict the mass loss from R...

  12. Galaxy Infall by Interacting with its Environment: a Comprehensive Study of 340 Galaxy Clusters

    CERN Document Server

    Gu, Liyi; Gandhi, Poshak; Inada, Naohisa; Kawaharada, Madoka; Kodama, Tadayuki; Konami, Saori; Nakazawa, Kazuhiro; Xu, Haiguang; Makishima, Kazuo

    2016-01-01

    To study systematically the evolution on the angular extents of the galaxy, 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 with the Sloan Digital Sky Survey (SDSS) and {\\it Chandra}/{\\it 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, were 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 towards 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. We interpret that the galaxies, the ICM, and the dark matter compone...

  13. Relativistic distortions in the large-scale clustering of SDSS-III BOSS CMASS galaxies

    Science.gov (United States)

    Alam, Shadab; Zhu, Hongyu; Croft, Rupert A. C.; Ho, Shirley; Giusarma, Elena; Schneider, Donald P.

    2017-09-01

    General relativistic effects have long been predicted to subtly influence the observed large-scale structure of the universe. The current generation of galaxy redshift surveys has reached a size where detection of such effects is becoming feasible. In this paper, we report the first detection of the redshift asymmetry from the cross-correlation function of two galaxy populations that is consistent with relativistic effects. The data set is taken from the Sloan Digital Sky Survey Data Release 12 CMASS galaxy sample, and we detect the asymmetry at the 2.7σ level by applying a shell-averaged estimator to the cross-correlation function. Our measurement dominates at scales around 10 h-1 Mpc, larger than those over which the gravitational redshift profile has been recently measured in galaxy clusters, but smaller than scales for which linear perturbation theory is likely to be accurate. The detection significance varies by 0.5σ with the details of our measurement and tests for systematic effects. We have also devised two null tests to check for various survey systematics and show that both results are consistent with the null hypothesis. We measure the dipole moment of the cross-correlation function, and from this the asymmetry is also detected, at the 2.8σ level. The amplitude and scale dependence of the clustering asymmetries are approximately consistent with the expectations of general relativity and a biased galaxy population, within large uncertainties. We explore theoretical predictions using numerical simulations in a companion paper.

  14. Which processes shape stellar population gradients of massive galaxies at large radii?

    Science.gov (United States)

    Hirschmann, Michaela

    2016-08-01

    We investigate the differential impact of physical mechanisms, mergers (stellar accretion) and internal energetic phenomena, on the evolution of stellar population gradients in massive, present-day galaxies employing a set of high-resolution, cosmological zoom simulations. We demonstrate that negative metallicity and color gradients at large radii (>2Reff) originate from the accretion of metal-poor stellar systems. At larger radii, galaxies become typically more dominated by stars accreted from satellite galaxies in major and minor mergers. However, only strong galactic winds can sufficiently reduce the metallicity content of the accreted stars to realistically steepen the outer metallicity and colour gradients in agreement with present-day observations. In contrast, the gradients of the models without winds are inconsistent with observations (too flat). In the wind model, colour and metallicity gradients are significantly steeper for systems which have accreted stars in minor mergers, while galaxies with major mergers have relatively flat gradients, confirming previous results. This analysis greatly highlights the importance of both energetic processes and merger events for stellar population properties of massive galaxies at large radii. Our results are expected to significantly contribute to the interpretation of current and up-coming IFU surveys (like MaNGA and Califa), which in turn can help to better constrain still uncertain models for energetic processes in simulations.

  15. Determine the galaxy bias factors on large scales using bispectrum method

    CERN Document Server

    Guo, Hong

    2009-01-01

    We study whether the bias factors of galaxies can be unbiasedly recovered from their power spectra and bispectra. We use a set of numerical N-body simulations and construct large mock galaxy catalogs based upon the semi-analytical model of Croton et al. (2006). We measure the reduced bispectra for galaxies of different luminosity, and determine the linear and first nonlinear bias factors from their bispectra. We find that on large scales down to that of the wavenumber k=0.1h/Mpc, the bias factors b1 and b2 are nearly constant, and b1 obtained with the bispectrum method agrees very well with the expected value. The nonlinear bias factor b2 is negative, except for the most luminous galaxies with M<-23 which have a positive b2. The behavior of b2 of galaxies is consistent with the b2 mass dependence of their host halos. We show that it is essential to have an accurate estimation of the dark matter bispectrum in order to have an unbiased measurement of b1 and b2. We also test the analytical approach of incorpo...

  16. Effects of tidal interactions on the gas flows of elliptical galaxies

    CERN Document Server

    D'Ercole, A; Ciotti, L

    1999-01-01

    During a Hubble time, cluster galaxies may undergo several mutual encounters close enough to gravitationally perturb their hot, X-ray emitting gas flows. We ran several 2D, time dependent hydrodynamical models to investigate the effects of such perturbations on the gas flow inside elliptical galaxies. In particular, we studied in detail the modifications occurring in the scenario proposed by D'Ercole et al. (1989), in which the galactic interstellar medium produced by the aging galactic stellar population, is heated by SNIa at a decreasing rate. We find that, although the tidal interaction in our models lasts less than 1 Gyr, its effect extends over several Gyrs. The tidally induced turbulent flows create dense filaments which cool quickly and accrete onto the galactic center, producing large spikes in the global Lx. Once this mechanism starts, it is fed by gravity and amplified by SNIa. In cooling flow models without supernovae the amplitude of the Lx fluctuations due to the tidal interaction is substantiall...

  17. EVIDENCE FOR AN INTERACTION IN THE NEAREST STARBURSTING DWARF IRREGULAR GALAXY IC 10

    Energy Technology Data Exchange (ETDEWEB)

    Nidever, David L.; Slater, Colin T.; Bell, Eric F. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Ashley, Trisha; Simpson, Caroline E. [Department of Physics, Florida International University, Miami, FL 33199 (United States); Ott, Jürgen [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Johnson, Megan [National Radio Astronomy Observatory, Green Bank, WV 24944 (United States); Stanimirović, Snežana [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Putman, Mary [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Majewski, Steven R. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States); Jütte, Eva [Astronomisches Institut der Ruhr-Universität Bochum, Universitätsstr. 150, D-44801 Bochum (Germany); Oosterloo, Tom A. [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990-AA Dwingeloo (Netherlands); Burton, W. Butler, E-mail: dnidever@umich.edu [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States)

    2013-12-20

    Using deep 21 cm H I data from the Green Bank Telescope we have detected an ≳18.3 kpc long gaseous extension associated with the starbursting dwarf galaxy IC 10. The newly found feature stretches 1.°3 to the northwest and has a large radial velocity gradient reaching to ∼65 km s{sup –1} lower than the IC 10 systemic velocity. A region of higher column density at the end of the extension that possesses a coherent velocity gradient (∼10 km s{sup –1} across ∼26') transverse to the extension suggests rotation and may be a satellite galaxy of IC 10. The H I mass of IC 10 is 9.5 × 10{sup 7} (d/805 kpc){sup 2} M {sub ☉} and the mass of the new extension is 7.1 × 10{sup 5} (d/805 kpc){sup 2} M {sub ☉}. An IC 10-M31 orbit using known radial velocity and proper motion values for IC 10 show that the H I extension is inconsistent with the trailing portion of the orbit so that an M31-tidal or ram pressure origin seems unlikely. We argue that the most plausible explanation for the new feature is that it is the result of a recent interaction (and possible late merger) with another dwarf galaxy. This interaction could not only have triggered the origin of the recent starburst in IC 10, but could also explain the existence of previously found counter-rotating H I gas in the periphery of the IC 10 which was interpreted as originating from primordial gas infall.

  18. The Fueling Diagram: Linking Galaxy Molecular-to-Atomic Gas Ratios to Interactions and Accretion

    CERN Document Server

    Stark, David V; Wei, Lisa H; Baker, Andrew J; Leroy, Adam K; Eckert, Kathleen D; Vogel, Stuart N

    2013-01-01

    To assess how external factors such as local interactions and fresh gas accretion influence the global ISM of galaxies, we analyze the relationship between recent enhancements of central star formation and total molecular-to-atomic (H2/HI) gas ratios, using a broad sample of field galaxies spanning early-to-late type morphologies, stellar masses of 10^(7.2-11.2) Msun, and diverse stages of evolution. We find that galaxies occupy several loci in a "fueling diagram" that plots H2/HI vs. mass-corrected blue-centeredness, a metric tracing the degree to which galaxies have bluer centers than the average galaxy at their stellar mass. Spiral galaxies show a positive correlation between H2/HI and mass-corrected blue-centeredness. When combined with previous results linking mass-corrected blue-centeredness to external perturbations, this correlation suggests a link between local galaxy interactions and molecular gas inflow/replenishment. Intriguingly, E/S0 galaxies show a more complex picture: some follow the same cor...

  19. Early Science with the Large Millimeter Telescope: discovery of the 12CO(1-0) emission line in the ring galaxy VIIZw466

    Science.gov (United States)

    Wong, O. Ivy; Vega, O.; Sánchez-Argüelles, D.; Narayanan, G.; Wall, W. F.; Zwaan, M. A.; Rosa González, D.; Zeballos, M.; Bekki, K.; Mayya, Y. D.; Montaña, A.; Chung, A.

    2017-04-01

    We report an early science discovery of the 12CO(1-0) emission line in the collisional ring galaxy VII Zw466, using the Redshift Search Receiver instrument on the Large Millimeter Telescope Alfonso Serrano. The apparent molecular-to-atomic gas ratio either places the interstellar medium (ISM) of VII Zw466 in the H I-dominated regime or implies a large quantity of CO-dark molecular gas, given its high star formation rate. The molecular gas densities and star formation rate densities of VII Zw466 are consistent with the standard Kennicutt-Schmidt star formation law even though we find this galaxy to be H2-deficient. The choice of CO-to-H2 conversion factors cannot explain the apparent H2 deficiency in its entirety. Hence, we find that the collisional ring galaxy, VII Zw466, is either largely deficient in both H2 and H I or contains a large mass of CO-dark gas. A low molecular gas fraction could be due to the enhancement of feedback processes from previous episodes of star formation as a result of the star-forming ISM being confined to the ring. We conclude that collisional ring galaxy formation is an extreme form of galaxy interaction that triggers a strong galactic-wide burst of star formation that may provide immediate negative feedback towards subsequent episodes of star formation - resulting in a short-lived star formation history or, at least, the appearance of a molecular gas deficit.

  20. The Large, Oxygen-Rich Halos of Star-Forming Galaxies Are A Major Reservoir of Galactic Metals

    CERN Document Server

    Tumlinson, Jason; Werk, Jessica K; Prochaska, J Xavier; Tripp, Todd M; Weinberg, David H; Peeples, Molly S; O'Meara, John M; Oppenheimer, Benjamin D; Meiring, Joseph D; Katz, Neal S; Dave, Romeel; Ford, Amanda Brady; Sembach, Kenneth R

    2011-01-01

    The circumgalactic medium (CGM) is fed by galaxy outflows and accretion of intergalactic gas, but its mass, heavy element enrichment, and relation to galaxy properties are poorly constrained by observations. In a survey of the outskirts of 42 galaxies with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope, we detected ubiquitous, large (150 kiloparsec) halos of ionized oxygen surrounding star-forming galaxies, but we find much less ionized oxygen around galaxies with little or no star formation. This ionized CGM contains a substantial mass of heavy elements and gas, perhaps far exceeding the reservoirs of gas in the galaxies themselves. It is a basic component of nearly all star-forming galaxies that is removed or transformed during the quenching of star formation and the transition to passive evolution.

  1. The large, oxygen-rich halos of star-forming galaxies are a major reservoir of galactic metals.

    Science.gov (United States)

    Tumlinson, J; Thom, C; Werk, J K; Prochaska, J X; Tripp, T M; Weinberg, D H; Peeples, M S; O'Meara, J M; Oppenheimer, B D; Meiring, J D; Katz, N S; Davé, R; Ford, A B; Sembach, K R

    2011-11-18

    The circumgalactic medium (CGM) is fed by galaxy outflows and accretion of intergalactic gas, but its mass, heavy element enrichment, and relation to galaxy properties are poorly constrained by observations. In a survey of the outskirts of 42 galaxies with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope, we detected ubiquitous, large (150-kiloparsec) halos of ionized oxygen surrounding star-forming galaxies; we found much less ionized oxygen around galaxies with little or no star formation. This ionized CGM contains a substantial mass of heavy elements and gas, perhaps far exceeding the reservoirs of gas in the galaxies themselves. Our data indicate that it is a basic component of nearly all star-forming galaxies that is removed or transformed during the quenching of star formation and the transition to passive evolution.

  2. Graphle: Interactive exploration of large, dense graphs

    Directory of Open Access Journals (Sweden)

    Huttenhower Curtis

    2009-12-01

    Full Text Available Abstract Background A wide variety of biological data can be modeled as network structures, including experimental results (e.g. protein-protein interactions, computational predictions (e.g. functional interaction networks, or curated structures (e.g. the Gene Ontology. While several tools exist for visualizing large graphs at a global level or small graphs in detail, previous systems have generally not allowed interactive analysis of dense networks containing thousands of vertices at a level of detail useful for biologists. Investigators often wish to explore specific portions of such networks from a detailed, gene-specific perspective, and balancing this requirement with the networks' large size, complex structure, and rich metadata is a substantial computational challenge. Results Graphle is an online interface to large collections of arbitrary undirected, weighted graphs, each possibly containing tens of thousands of vertices (e.g. genes and hundreds of millions of edges (e.g. interactions. These are stored on a centralized server and accessed efficiently through an interactive Java applet. The Graphle applet allows a user to examine specific portions of a graph, retrieving the relevant neighborhood around a set of query vertices (genes. This neighborhood can then be refined and modified interactively, and the results can be saved either as publication-quality images or as raw data for further analysis. The Graphle web site currently includes several hundred biological networks representing predicted functional relationships from three heterogeneous data integration systems: S. cerevisiae data from bioPIXIE, E. coli data using MEFIT, and H. sapiens data from HEFalMp. Conclusions Graphle serves as a search and visualization engine for biological networks, which can be managed locally (simplifying collaborative data sharing and investigated remotely. The Graphle framework is freely downloadable and easily installed on new servers, allowing any

  3. Optical multiband surface photometry of a sample of Seyfert galaxies. I. Large-scale morphology and local environment analysis of matched Seyfert and inactive galaxy samples

    CERN Document Server

    Slavcheva-Mihova, L; 10.1051/0004-6361/200913243

    2010-01-01

    Parallel analysis of the large-scale morphology and local environment of matched active and control galaxy samples plays an important role in studies of the fueling of active galactic nuclei. We carry out a detailed morphological characterization of a sample of 35 Seyfert galaxies and a matched sample of inactive galaxies in order to compare the evidence of non-axisymmetric perturbation of the potential and, in the second part of this paper, to be able to perform a multicomponent photometric decomposition of the Seyfert galaxies. We constructed contour maps, BVRcIc profiles of the surface brightness, ellipticity, and position angle, as well as colour index profiles. We further used colour index images, residual images, and structure maps, which helped clarify the morphology of the galaxies. We studied the presence of close companions using literature data. By straightening out the morphological status of some of the objects, we derived an improved morphological classification and built a solid basis for a fur...

  4. Confirmation of general relativity on large scales from weak lensing and galaxy velocities

    CERN Document Server

    Reyes, Reinabelle; Seljak, Uros; Baldauf, Tobias; Gunn, James E; Lombriser, Lucas; Smith, Robert E; 10.1038/nature08857

    2010-01-01

    Although general relativity underlies modern cosmology, its applicability on cosmological length scales has yet to be stringently tested. Such a test has recently been proposed, using a quantity, EG, that combines measures of large-scale gravitational lensing, galaxy clustering and structure growth rate. The combination is insensitive to 'galaxy bias' (the difference between the clustering of visible galaxies and invisible dark matter) and is thus robust to the uncertainty in this parameter. Modified theories of gravity generally predict values of EG different from the general relativistic prediction because, in these theories, the 'gravitational slip' (the difference between the two potentials that describe perturbations in the gravitational metric) is non-zero, which leads to changes in the growth of structure and the strength of the gravitational lensing effect3. Here we report that EG = 0.39 +/- 0.06 on length scales of tens of megaparsecs, in agreement with the general relativistic prediction of EG $\\app...

  5. In the Wake of Dark Giants: New Signatures of Dark Matter Self Interactions in Equal Mass Mergers of Galaxy Clusters

    CERN Document Server

    Kim, Stacy Y; Wittman, David

    2016-01-01

    Merging galaxy clusters have been touted as one of the best probes for constraining self-interacting dark matter, but few simulations exist to back up this claim. We simulate equal mass mergers of 10$^{15}$ M$_\\odot$ halos, like the El Gordo and Sausage clusters, with cosmologically-motivated halo and merger parameters, and with velocity-independent dark-matter self-interactions. Although the standard lore for merging clusters is that self-interactions lead to large separations between the galaxy and dark-matter distributions, we find that maximal galaxy-dark matter offsets of $\\lesssim~20$~kpc form for a self-interaction cross section of $\\sigma_\\text{SI}/m_\\chi$ = 1 cm$^2$/g. This is an order of magnitude smaller than those measured in observed equal mass and near equal mass mergers, and is likely to be even smaller for lower-mass systems. While competitive cross-section constraints are thus unlikely to emerge from offsets, we find other signatures of self-interactions which are more promising. Intriguingly...

  6. The Effect of Large-Scale Structure on the SDSS Galaxy Three-Point Correlation Function

    CERN Document Server

    Nichol, R C; Blanton, M; Brinkmann, J; Connolly, A J; Csabai, I; Gardner, J P; Gray, A J; Jain, B; Kayo, I; Kulkarni, G; Marin, F; Miller, C J; Moore, A W; Pope, A; Pun, J; Schneider, D; Schneider, J; Sheth, R K; Suto, Y; Szalay, A S; Szapudi, I; Wechsler, R H; Zehavi, I

    2006-01-01

    We present measurements of the normalised redshift-space three-point correlation function (Q_z) of galaxies from the Sloan Digital Sky Survey (SDSS) main galaxy sample. We have applied our "npt" algorithm to both a volume-limited (36738 galaxies) and magnitude-limited sample (134741 galaxies) of SDSS galaxies, and find consistent results between the two samples, thus confirming the weak luminosity dependence of Q_z recently seen by other authors. We compare our results to other Q_z measurements in the literature and find it to be consistent within the full jack-knife error estimates. However, we find these errors are significantly increased by the presence of the ``Sloan Great Wall'' (at z ~ 0.08) within these two SDSS datasets, which changes the 3-point correlation function (3PCF) by 70% on large scales (s>=10h^-1 Mpc). If we exclude this supercluster, our observed Q_z is in better agreement with that obtained from the 2dFGRS by other authors, thus demonstrating the sensitivity of these higher-order correlat...

  7. Discovery of Large Molecular Gas Reservoirs in Post-Starburst Galaxies

    CERN Document Server

    French, K Decker; Zabludoff, Ann; Narayanan, Desika; Shirley, Yancy; Walter, Fabian; Smith, John-David; Tremonti, Christy A

    2015-01-01

    Post-starburst (or "E+A") galaxies are characterized by low H$\\alpha$ emission and strong Balmer absorption, suggesting a recent starburst, but little current star formation. Although many of these galaxies show evidence of recent mergers, the mechanism for ending the starburst is not yet understood. To study the fate of the molecular gas, we search for CO (1-0) and (2-1) emission with the IRAM 30m and SMT 10m telescopes in 32 nearby ($0.01galaxies drawn from the Sloan Digital Sky Survey. We detect CO in 17 (53%). Using CO as a tracer for molecular hydrogen, and a Galactic conversion factor, we obtain molecular gas masses of $M(H_2)=10^{8.6}$-$10^{9.8} M_\\odot$ and molecular gas mass to stellar mass fractions of $\\sim10^{-2}$-$10^{-0.5}$, comparable to those of star-forming galaxies. The large amounts of molecular gas rule out complete gas consumption, expulsion, or starvation as the primary mechanism that ends the starburst in these galaxies. The upper limits on $M(H_2)$ for th...

  8. A Multifrequency Study of Five Large Radio Galaxies

    Indian Academy of Sciences (India)

    A. Pirya; S. Nandi; D. J. Saikia; C. Konar; M. Singh

    2011-12-01

    We present the results of GMRT and VLA observations of five large radio sources over a wide frequency range to investigate their structural and spectral asymmetries. The hot-spot brightness ratios suggest intrinsic source asymmetries, while the spectral indices show evidence of re-acceleration of particles.

  9. Large-scale galaxy distribution in the Las Campanas Redshift Survey

    Science.gov (United States)

    Doroshkevich, A. G.; Tucker, D. L.; Fong, R.; Turchaninov, V.; Lin, H.

    2001-04-01

    We make use of three-dimensional clustering analysis, inertia tensor methods, and the minimal spanning tree technique to estimate some physical and statistical characteristics of the large-scale galaxy distribution and, in particular, of the sample of overdense regions seen in the Las Campanas Redshift Survey (LCRS). Our investigation provides additional evidence for a network of structures found in our core sampling analysis of the LCRS: a system of rich sheet-like structures, which in turn surround large underdense regions criss-crossed by a variety of filamentary structures. We find that the overdense regions contain ~40-50 per cent of LCRS galaxies and have proper sizes similar to those of nearby superclusters. The formation of such structures can be roughly described as a non-linear compression of protowalls of typical cross-sectional size ~20-25h-1Mpc this scale is ~5 times the conventional value for the onset of non-linear clustering - to wit, r0, the autocorrelation length for galaxies. The comparison with available simulations and theoretical estimates shows that the formation of structure elements with parameters similar to those observed is presently possible only in low-density cosmological models, Ωmh~0.2-0.3, with a suitable large-scale bias between galaxies and dark matter.

  10. Interaction Between Flow Elements in Large Enclosures

    DEFF Research Database (Denmark)

    Heiselberg, Per

    In this paper experiments in a scale model are used as a first attempt to investigate how different flow elements such as supply air jets, thermal plumes and free convection flows interact with each other in a large enclosure, if the path of each individual flow element changes and if this influe......In this paper experiments in a scale model are used as a first attempt to investigate how different flow elements such as supply air jets, thermal plumes and free convection flows interact with each other in a large enclosure, if the path of each individual flow element changes...... and if this influences the overall air flow pattern in the enclosure. The main emphasis has been put on the pathways of chilled free air jets and whether the convective flows from both distributed and concentrated heat sources affect the pathway of the jet and the air flow pattern in the enclosure as a function...

  11. Evidence for tidal interaction and merger as the origin of galaxy morphology evolution in compact groups

    CERN Document Server

    Coziol, R

    2007-01-01

    We present the results of a morphological study based on NIR images of 25 galaxies, with different levels of nuclear activity, in 8 Compact Groups of Galaxies (CGs). We perform independently two different analysis: a isophotal study and a study of morphological asymmetries. The results yielded by the two analysis are highly consistent. For the first time, it is possible to show that deviations from pure ellipses are produced by inhomogeneous stellar mass distributions related to galaxy interactions and mergers. We find evidence of mass asymmetries in 74% of the galaxies in our sample. In 59% of these cases, the asymmetries come in pairs, and are consistent with tidal effects produced by the proximity of companion galaxies. The symmetric galaxies are generally small in size or mass, inactive, and have an early-type morphology. In 20% of the galaxies we find evidence for cannibalism. In 36% of the early-type galaxies the color gradient is positive (blue nucleus) or flat. Summing up these results, as much as 52%...

  12. Interacting on and around Large Displays

    DEFF Research Database (Denmark)

    Markussen, Anders

    of content that reside outside the display boundaries, taking advantage of users’ perceived location of off-screen content. Off-Limits was found to provide significant benefits over touch-based interaction. The results show that an extension of interactions beyond the boundaries of the display can increase......), a previously successfully text entry method for touch- and pen-based input, to work as a technique for mid-air text entry. With a text entry rate of 20.6 WPM after 10 sessions of text entry, the mid-air WGK provided faster text entry rates than previously evaluated methods for mid-air text entry. An improved....... To improve understanding of the differences between input modalities for large displays, the mid-air WGK was compared to a touch-based functionally equivalent WGK. The touch-based keyboard was found to be significantly faster than the mid-air WGK, indicating that touch based interaction may be preferable...

  13. Interaction effects on galaxy pairs with Gemini/GMOS- I: Electron density

    CERN Document Server

    Krabbe, A C; Dors, O L; Pastoriza, M G; Winge, C; Hagele, G F; Cardaci, M V; Rodrigues, I

    2013-01-01

    We present an observational study about the impacts of the interactions in the electron density of \\ion{H}{ii} regions located in 7 systems of interacting galaxies. The data consist of long-slit spectra in the range 4400-7300 A, obtained with the Gemini Multi-Object Spectrograph at Gemini South (GMOS). The electron density was determined using the ratio of emission lines [SII]6716/6731. Our results indicate that the electron density estimates obtained of HII regions from our sample of interacting galaxies are systematically higher than those derived for isolated galaxies. The mean electron density values of interacting galaxies are in the range of $N_{\\rm e}=24-532$\\,$ \\rm cm^{-3}$, while those obtained for isolated galaxies are in the range of $N_{\\rm e}=40-137\\: \\rm cm^{-3}$. Comparing the observed emission lines with predictions of photoionization models, we verified that almost all the \\ion{H}{ii} regions of the galaxies AM\\,1054A, AM\\,2058B, and AM\\,2306B, have emission lines excited by shock gas. For th...

  14. First detection of GeV emission from an ultraluminous infrared galaxy Arp 220 with the Fermi Large Area Telescope

    CERN Document Server

    Peng, Fang-Kun; Liu, Ruo-Yu; Tang, Qing-Wen; Wang, Jun-Feng

    2016-01-01

    Cosmic rays (CRs) in starburst galaxies produce high energy gamma-rays by colliding with the dense interstellar medium. Arp 220 is the nearest ultra luminous infrared galaxy (ULIRG) that has star-formation at extreme levels, so it has long been predicted to emit high-energy gamma-rays. However, no evidence of gamma-ray emission was found despite intense efforts of search. Here we report the discovery of high-energy gamma-ray emission above 200 MeV from Arp 220 at a confidence level of $\\sim 6.3 \\sigma $ using 7.5 years of \\textsl {Fermi} Large Area Telescope observation. The gamma-ray emission shows no significant variability over the observation period and it obeys the quasi-linear scaling relation between the gamma-ray luminosity and total infrared luminosity for star-forming galaxies, suggesting that these gamma-rays arise from CR interactions. As the high density gas makes Arp 220 an ideal CR calorimeter, the gamma-ray luminosity can be used to measure the efficiency of powering CRs by supernova remnants ...

  15. Are luminous radio-loud active galactic nuclei triggered by galaxy interactions?

    CERN Document Server

    Almeida, C Ramos; Tadhunter, C; Pérez-González, P G; Barro, G; Inskip, K J; Morganti, R; Holt, J; Dicken, D

    2011-01-01

    We present the results of a comparison between the optical morphologies of a complete sample of 46 southern 2Jy radio galaxies at intermediate redshifts (0.05galaxies: 55 ellipticals at redshifts z<0.01 from the Observations of Bright Ellipticals at Yale (OBEY) survey, and 107 early-type galaxies at redshifts 0.2galaxy interactions in the triggering of powerful radio galaxies (PRGs). We find that a significant fraction of quiescent ellipticals at low and intermediate redshifts show evidence for disturbed morphologies at relatively high surface brightness levels, which are likely the result of past or on-going galaxy interactions. However, the morphological features detected in the galaxy hosts of the PRGs (e.g. tidal tails, shells, bridges, etc.) are up to 2 magnitudes brighter than those present in their quiescent counterparts. Indeed, if...

  16. Galaxy interactions in compact groups - II. Abundance and kinematic anomalies in HCG 91c

    Science.gov (United States)

    Vogt, Frédéric P. A.; Dopita, Michael A.; Borthakur, Sanchayeeta; Verdes-Montenegro, Lourdes; Heckman, Timothy M.; Yun, Min S.; Chambers, Kenneth C.

    2015-07-01

    Galaxies in Hickson Compact Group 91 (HCG 91) were observed with the WiFeS integral field spectrograph as part of our ongoing campaign targeting the ionized gas physics and kinematics inside star-forming members of compact groups. Here, we report the discovery of H II regions with abundance and kinematic offsets in the otherwise unremarkable star-forming spiral HCG 91c. The optical emission line analysis of this galaxy reveals that at least three H II regions harbour an oxygen abundance ˜0.15 dex lower than expected from their immediate surroundings and from the abundance gradient present in the inner regions of HCG 91c. The same star-forming regions are also associated with a small kinematic offset in the form of a lag of 5-10 km s-1 with respect to the local circular rotation of the gas. H I observations of HCG 91 from the Very Large Array and broad-band optical images from Pan-STARRS (Panoramic Survey Telescope And Rapid Response System) suggest that HCG 91c is caught early in its interaction with the other members of HCG 91. We discuss different scenarios to explain the origin of the peculiar star-forming regions detected with WiFeS, and show that evidence points towards infalling and collapsing extraplanar gas clouds at the disc-halo interface, possibly as a consequence of long-range gravitational perturbations of HCG 91c from the other group members. As such, HCG 91c provides evidence that some of the perturbations possibly associated with the early phase of galaxy evolution in compact groups impact the star-forming disc locally, and on sub-kpc scales.

  17. Spin alignments of spiral galaxies within the large-scale structure from SDSS DR7

    CERN Document Server

    Zhang, Youcai; Wang, Huiyuan; Wang, Lei; Luo, Wentao; Mo, H J; Bosch, Frank C van den

    2014-01-01

    Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) and Galaxy Zoo 2 (GZ2), we investigate the alignment of spin axes of spiral galaxies with their surrounding large scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certain mass threshold. We find that the spin axes of only have weak tendency to be aligned with (or perpendicular to) the intermediate (or minor) axis of the local tidal tensor. The signal is the strongest in a \\cluster environment where all the three eigenvalues of the local tidal tensor are positive. Compared to the alignments between halo spins and local tidal field obtained in N-body simulations, the above observational results are in best agreement with those for the spins of inner regions of halos, suggesting that the disk material traces the angular momentum of dark matter halos in the inner regions.

  18. Galaxy Bias and Halo-Occupation Numbers from Large-Scale Clustering

    CERN Document Server

    Sefusatti, E; Sefusatti, Emiliano; Scoccimarro, Roman

    2005-01-01

    We show that current surveys have at least as much signal to noise in higher-order statistics as in the power spectrum at weakly nonlinear scales. We discuss how one can use this information to determine the mean of the galaxy halo occupation distribution (HOD) using only large-scale information, through galaxy bias parameters determined from the galaxy bispectrum and trispectrum. After introducing an averaged, reasonably fast to evaluate, trispectrum estimator, we show that the expected errors on linear and quadratic bias parameters can be reduced by at least 20-40%. Also, the inclusion of the trispectrum information, which is sensitive to "three-dimensionality" of structures, helps significantly in constraining the mass dependence of the HOD mean. Our approach depends only on adequate modeling of the abundance and large-scale clustering of halos and thus is independent of details of how galaxies are distributed within halos. This provides a consistency check on the traditional approach of using two-point st...

  19. What shapes stellar metallicity gradients of massive galaxies at large radii?

    Science.gov (United States)

    Hirschmann, Michaela

    2017-03-01

    We investigate the differential impact of physical mechanisms, mergers and internal energetic phenomena, on the evolution of stellar metallicity gradients in massive, present-day galaxies employing sets of high-resolution, cosmological zoom simulations. We demonstrate that negative metallicity gradients at large radii (>2Reff) originate from the accretion of metal-poor stellar systems. At larger radii, galaxies become typically more dominated by stars accreted from satellite galaxies in major and minor mergers. However, only strong galactic, stellar-driven winds can sufficiently reduce the metallicity content of the accreted stars to realistically steepen the outer metallicity gradients in agreement with observations. In contrast, the gradients of the models without winds are inconsistent with observations. Moreover, we discuss the impact of additional AGN feedback. This analysis greatly highlights the importance of both energetic processes and merger events for stellar population properties of massive galaxies at large radii. Our results are expected to significantly contribute to the interpretation of current and up-coming IFU surveys (e.g. MaNGA, CALIFA).

  20. Galaxy Interactions in Compact Groups II: abundance and kinematic anomalies in HCG 91c

    CERN Document Server

    Vogt, F P A; Borthakur, S; Verdes-Montenegro, L; Heckman, T M; Yun, M S; Chambers, K C

    2015-01-01

    Galaxies in Hickson Compact Group 91 (HCG 91) were observed with the WiFeS integral field spectrograph as part of our ongoing campaign targeting the ionized gas physics and kinematics inside star forming members of compact groups. Here, we report the discovery of HII regions with abundance and kinematic offsets in the otherwise unremarkable star forming spiral HCG 91c. The optical emission line analysis of this galaxy reveals that at least three HII regions harbor an oxygen abundance ~0.15 dex lower than expected from their immediate surroundings and from the abundance gradient present in the inner regions of HCG 91c. The same star forming regions are also associated with a small kinematic offset in the form of a lag of 5-10 km/s with respect to the local circular rotation of the gas. HI observations of HCG 91 from the Very Large Array and broadband optical images from Pan-STARRS suggest that HCG 91c is caught early in its interaction with the other members of HCG 91. We discuss different scenarios to explain...

  1. Evidence for an Interaction in the Nearest Starbursting Dwarf Irregular Galaxy IC 10

    CERN Document Server

    Nidever, David L; Slater, Colin T; Ott, Juergen; Johnson, Megan; Bell, Eric F; Stanimirovic, Snezana; Putman, Mary; Majewski, Steven R; Simpson, Caroline E; Juette, Eva; Oosterloo, Tom A; Burton, W Butler

    2013-01-01

    Using deep 21-cm HI data from the Green Bank Telescope we have detected an ~18.3 kpc-long gaseous extension associated with the starbursting dwarf galaxy IC 10. The newly-found feature stretches 1.3 deg to the northwest and has a large radial velocity gradient reaching to ~65 km/s lower than the IC 10 systemic velocity. A region of higher column density at the end of the extension that possesses a coherent velocity gradient (~10 km/s across ~26 arcmin) transverse to the extension suggests rotation and may be a satellite galaxy of IC 10. The HI mass of IC 10 is 9.5x10^7 (d/805 kpc)^2 Msun and the mass of the new extension is 7.1x10^5 (d/805 kpc)^2 Msun. An IC 10-M31 orbit using known radial velocity and proper motion values for IC 10 show that the HI extension is inconsistent with the trailing portion of the orbit so that an M31-tidal or ram pressure origin seems unlikely. We argue that the most plausible explanation for the new feature is that it is the result of a recent interaction (and possible late merger...

  2. The large scale dust distribution in the inner galaxy

    Science.gov (United States)

    Hauser, M. G.; Dwek, E.; Gezari, D.; Silverberg, R.; Kelsall, T.; Stier, M.; Cheung, L.

    1983-01-01

    Initial results are presented from a new large-scale survey of the first quadrant of the galactic plane at wavelengths of 160, 260, and 300 microns. The submillimeter wavelength emission, interpreted as thermal radiation by dust grains, reveals an optically thin disk of angular width about 0.09 deg (FWHM) with a mean dust temperature of 23 K and significant variation of the dust mass column density. Comparison of the dust column density with the gas column density inferred from CO survey data shows a striking spatial correlation. The mean luminosity per hydrogen atom is found to be 2.5 x 10 to the -30th W/H, implying a radiant energy density in the vicinity of the dust an order of magnitude larger than in the solar neighborhood. The data favor dust in molecular clouds as the dominant submillimeter radiation source.

  3. Large-scale BAO signatures of the smallest galaxies

    CERN Document Server

    Dalal, Neal; Seljak, Uros

    2010-01-01

    Recent work has shown that at high redshift, the relative velocity between dark matter and baryonic gas is typically supersonic. This relative velocity suppresses the formation of the earliest baryonic structures like minihalos, and the suppression is modulated on large scales. This effect imprints a characteristic shape in the clustering power spectrum of the earliest structures, with significant power on 100 Mpc scales featuring highly pronounced baryon acoustic oscillations. The amplitude of these oscillations is orders of magnitude larger at z=20 than previously expected. This characteristic signature can allow us to distinguish the effects of minihalos on intergalactic gas at times preceding and during reionization. We illustrate this effect with the example of 21 cm emission and absorption from redshifts during and before reionization. This effect can potentially allow us to probe physics on kpc scales using observations on 100 Mpc scales. We present sensitivity forecasts for FAST and Arecibo. Depending...

  4. IRAS F02044+0957 radio source in interacting system of galaxies

    CERN Document Server

    Verkhodanov, O V; Mujica, R; Valdés, J R; Trushkin, S A

    2001-01-01

    The steep spectrum of IRAS F02044+0957 was obtained with the RATAN-600 radio telescope at four frequencies. Optical spectroscopy of the system components, was carried out with the 2.1m telescope of the Guillermo Haro Observatory. Observational data allow us to conclude that this object is a pair of interacting galaxies, a LINER and a HII galaxy, at $z=0.093$.

  5. Kinematics in the Interacting, Star-Forming Galaxies NGC 3395/3396 and NGC 3991/3994/3995

    Science.gov (United States)

    Weistrop, Donna; Nelson, Charles H.

    1999-01-01

    It has been suggested that induced star formation is more sensitive to galaxy dynamics than to local phenomena and that enhanced star formation is found in galaxies with disturbed velocity structures. We are studying the stellar populations of several UV-bright, interacting galaxies to try to understand the detailed star formation process in these systems. We present preliminary results of an investigation of the kinematics of star-forming regions in the interacting systems NGC 3395/3396 and NGC 3991/3994/3995. Regions of powerful star formation are observed throughout these galaxies. The observatation will be used to investigate rotation curves in the galaxies and motion in the tidal tails.

  6. Large-scale BAO signatures of the smallest galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Dalal, Neal; Pen, Ue-Li [Canadian Institute for Theoretical Astrophyics, University of Toronto, 60 St. George St., Toronto, Ontario M5S 3H8 (Canada); Seljak, Uros, E-mail: neal@cita.utoronto.ca, E-mail: pen@cita.utoronto.ca, E-mail: useljak@berkeley.edu [Physics Department and Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)

    2010-11-01

    Recent work has shown that at high redshift, the relative velocity between dark matter and baryonic gas is typically supersonic. This relative velocity suppresses the formation of the earliest baryonic structures like minihalos, and the suppression is modulated on large scales. This effect imprints a characteristic shape in the clustering power spectrum of the earliest structures, with significant power on ∼ 100 Mpc scales featuring highly pronounced baryon acoustic oscillations. The amplitude of these oscillations is orders of magnitude larger at z ∼ 20 than previously expected. This characteristic signature can allow us to distinguish the effects of minihalos on intergalactic gas at times preceding and during reionization. We illustrate this effect with the example of 21 cm emission and absorption from redshifts during and before reionization. This effect can potentially allow us to probe physics on kpc scales using observations on 100 Mpc scales. We present sensitivity forecasts for FAST and Arecibo. Depending on parameters, this enhanced structure may be detectable by Arecibo at z ∼ 15−20, and with appropriate instrumentation FAST could measure the BAO power spectrum with high precision. In principle, this effect could also pose a serious challenge for efforts to constrain dark energy using observations of the BAO feature at low redshift.

  7. Tidal Dwarf Galaxies, Accretion Tails, and `Beads on a String' in the `Spirals, Bridges, and Tails' Interacting Galaxy Survey

    CERN Document Server

    Smith, Beverly J; Struck, Curtis; Hancock, Mark; Hurlock, Sabrina

    2009-01-01

    We have used the GALEX ultraviolet telescope to study stellar populations and star formation morphology in a well-defined sample of more than three dozen nearby optically-selected pre-merger interacting galaxy pairs. We have combined the GALEX NUV and FUV images with broadband optical maps from the Sloan Digitized Sky Survey to investigate the ages and extinctions of the tidal features and the disks. We have identified a few new candidate tidal dwarf galaxies in this sample, as well as other interesting morphologies such as accretion tails, `beads on a string', and `hinge clumps'. In only a few cases are strong tidal features seen in HI maps but not in GALEX.

  8. Cosmic ray propagation and interactions in the Galaxy

    CERN Document Server

    Zirakashvili, V N

    2014-01-01

    Cosmic ray propagation in the Galaxy is shortly reviewed. In particular we consider the self-consistent models of CR propagation. In these models CR streaming instability driven by CR anisotropy results in the Alfv\\'enic turbulence which in turn determines the scattering and diffusion of particles.

  9. The GALAXY Classroom: An Interactive, Thematic Approach to Literacy Instruction.

    Science.gov (United States)

    Lewison, Mitzi

    The GALAXY Classroom, developed as a nation-wide reform effort, was designed to make a significant positive difference in the educational lives of elementary school students who have traditionally been labeled "at-risk." As part of a 2-year demonstration and research phase, 39 elementary schools across the United States (and one school…

  10. Metallicity gradients and newly created star-forming systems in interacting galaxies

    Science.gov (United States)

    Mendes de Oliveira, Claudia L.

    2015-08-01

    Interactions play an extremely important role in the evolution of galaxies, changing their morphologies and kinematics. Galaxy collisions may result in the formation of intergalactic star-forming objects, such as HII regions, young clusters and/or tidal dwarf galaxies. Several studies have found a wealth of newly created objects in interacting systems. We will exemplify the problems and challenges in this field and will describe observations of the interacting group NGC 6845, which contains four bright galaxies, two of which have extended tidal tails. We obtained Gemini/GMOS spectra for 28 of the regions located in the galaxies and in the tails. All regions in the latter are star-forming objects according to their line ratios, with ages younger than 10 Myr. A super luminous star forming complex is found in the brightest member of the group, NGC 6845A. Its luminosity reveals a star formation density of 0.19 solar masses, per year, per kpc^2, suggesting that this object is a localized starburst. We derived the gas-phase metallicity gradients across NGC 6845A and its two tails and we find that these are shallower than those for isolated galaxies. We speculate that the observed metallicity gradient may be related to one or more of the following mechanisms: (1) interaction induced inflow of fresh gas to the galaxy center, as seen in simulations, which is expected to dilute the metallicity of the central burst, (2) the formation of young metal-rich star forming regions in the tidal tails, which were born out of enriched gas expelled from the central regions of the system during the interaction and (3) the incremental growth of metals accumulated over time, due to the successful generations of star forming regions along the tails. Finally we will describe our plans to do a search for such objects on Halpha images that will soon be available for 17.5k degrees of the sky, with the A-PLUS survey.

  11. Star Formation and AGN Activity in Interacting Galaxies: A Near-UV Perspective

    CERN Document Server

    Scott, Caroline

    2013-01-01

    We study nearby galaxies in close pairs to study the key factors affecting star formation and AGN activity triggered during galaxy interactions. Close pairs are selected from the Sloan Digital Sky Survey assuming a projected separation of $<$30kpc and recessional velocity difference $<$500km s$^{-1}$. Near-ultraviolet (NUV) fluxes from GALEX are used to estimate specific star formation rates (SSFRs). We find a factor of $\\sim$5.3 increase in SSFR for low mass (10$^{8}-10^{11}$M$_{\\odot}$) close pair galaxies and a factor of $\\sim$2.1 increase in SSFR for high mass mass (10$^{11}-10^{13}$M$_{\\odot}$) close pairs compared to the general galaxy population. Considering galaxies of all masses, we find a factor of $\\sim$1.8 enhancement in SSFR for close pairs in field environments compared to non-pairs, with no significant increase for pairs in group and cluster environments. A modest decrease of a factor of $\\sim$1.4 is found in the Seyfert fraction in close pair galaxies when compared to isolated galaxies, ...

  12. Early Science with the Large Millimeter Telescope: Dust constraints in a z~9.6 galaxy

    CERN Document Server

    Zavala, J A; Aretxaga, I; Wilson, G W; Hughes, D H; Montaña, A; Dunlop, J S; Pope, A; Sánchez-Argüelles, D; Yun, M S; Zeballos, M

    2015-01-01

    Recent observations with the GISMO 2 mm camera revealed a detection 8" away from the lensed galaxy MACS1149-JD1 at z=9.6. Within the 17.5" FWHM GISMO beam, this detection is consistent with the position of the high-redshift galaxy and therefore, if confirmed, this object could be claimed to be the youngest galaxy producing significant quantities of dust. We present higher resolution (8.5") observations of this system taken with the AzTEC 1.1 mm camera mounted on the Large Millimeter Telescope Alfonso Serrano. Dust continuum emission at the position of MACS1149-JD1 is not detected with an r.m.s. of 0.17 mJy/beam. However, we find a detection ~ 11" away from MACS1149-JD1, still within the GISMO beam which is consistent with an association to the GISMO source. Combining the AzTEC and GISMO photometry, together with Herschel ancillary data, we derive a z_phot= 0.7-1.6 for the dusty galaxy. We conclude therefore that the GISMO and AzTEC detections are not associated with MACS1149-JD1. From the non-detection of MAC...

  13. Large-Scale Structure Formation: from the first non-linear objects to massive galaxy clusters

    CERN Document Server

    Planelles, S; Bykov, A M

    2014-01-01

    The large-scale structure of the Universe formed from initially small perturbations in the cosmic density field, leading to galaxy clusters with up to 10^15 Msun at the present day. Here, we review the formation of structures in the Universe, considering the first primordial galaxies and the most massive galaxy clusters as extreme cases of structure formation where fundamental processes such as gravity, turbulence, cooling and feedback are particularly relevant. The first non-linear objects in the Universe formed in dark matter halos with 10^5-10^8 Msun at redshifts 10-30, leading to the first stars and massive black holes. At later stages, larger scales became non-linear, leading to the formation of galaxy clusters, the most massive objects in the Universe. We describe here their formation via gravitational processes, including the self-similar scaling relations, as well as the observed deviations from such self-similarity and the related non-gravitational physics (cooling, stellar feedback, AGN). While on i...

  14. Large-Scale Asymmetry of Rotation Curves in Lopsided Spiral Galaxies

    CERN Document Server

    Jog, C J

    2002-01-01

    Many spiral galaxies show a large-scale asymmetry with a cos\\phi dependence in their rotation curves as well as in their morphology, such as M101 and NGC 628. We show that both these features can be explained by the response of a galactic disk to an imposed lopsided halo potential. A perturbation potential of 5 % is deduced for the morphologically lopsided galaxies in the Rix & Zaritsky (1995) sample. This is shown to result in a difference of 10 % or about 20-30 kms^{-1} in the rotation velocity on the two sides of the major axis. Interestingly, the observed isophotal asymmetry in a typical spiral galaxy is not much smaller and it results in a velocity asymmetry of 7 % or about 14-21 kms^{-1} . Hence, we predict that most galaxies show a fairly significant rotational asymmetry. The rotation velocity is shown to be maximum along the elongated isophote - in agreement with the observations along the SW in M101, while it is minimum along the opposite direction. This result leads to the distinctive asymmetric...

  15. Spectroscopic Confirmation of the Existence of Large, Diffuse Galaxies in the Coma Cluster

    CERN Document Server

    van Dokkum, Pieter; Abraham, Roberto; Brodie, Jean; Conroy, Charlie; Geha, Marla; Merritt, Allison; Villaume, Alexa; Zhang, Jielai

    2015-01-01

    We recently identified a population of low surface brightness objects in the field of the z=0.023 Coma cluster, using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these "ultra-diffuse galaxies" (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of cz=6280 +- 120 km/s is within the 1 sigma velocity dispersion of the Coma cluster. The galaxy has an effective radius of 4.3 +- 0.3 kpc and a Sersic index of 0.89 +- 0.06, as measured from Keck imaging. We find no indications of tidal tails or other distortions, at least out to a radius of ~2 r_e. We show that UDGs are located in a previously sparsely populated region of the size - magnitude plane of quiescent stellar systems, as they are ~6 magnitudes fainter than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent galax...

  16. THE IMPACT OF INTERACTIONS, BARS, BULGES, AND ACTIVE GALACTIC NUCLEI ON STAR FORMATION EFFICIENCY IN LOCAL MASSIVE GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Saintonge, Amelie; Fabello, Silvia; Wang Jing; Catinella, Barbara [Max-Planck Institut fuer Astrophysik, D-85741 Garching (Germany); Tacconi, Linda J.; Genzel, Reinhard; Gracia-Carpio, Javier; Wuyts, Stijn [Max-Planck Institut fuer extraterrestrische Physik, D-85741 Garching (Germany); Kramer, Carsten [Instituto Radioastronomia Milimetrica, Av. Divina Pastora 7, Nucleo Central, E-18012 Granada (Spain); Moran, Sean; Heckman, Timothy M. [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Schiminovich, David [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Schuster, Karl [Institut de Radioastronomie Millimetrique, 300 Rue de la piscine, F-38406 St Martin d' Heres (France)

    2012-10-20

    Using atomic and molecular gas observations from the GASS and COLD GASS surveys and complementary optical/UV data from the Sloan Digital Sky Survey and the Galaxy Evolution Explorer, we investigate the nature of the variations in the molecular gas depletion time observed across the local massive galaxy population. The large and unbiased COLD GASS sample allows us for the first time to statistically assess the relative importance of galaxy interactions, bar instabilities, morphologies, and the presence of active galactic nuclei (AGNs) in regulating star formation efficiency. We find that both the H{sub 2} mass fraction and depletion time vary as a function of the distance of a galaxy from the main sequence traced by star-forming galaxies in the SFR-M {sub *} plane. The longest gas depletion times are found in below-main-sequence bulge-dominated galaxies ({mu}{sub *} >5 Multiplication-Sign 10{sup 8} M {sub Sun} kpc{sup -2}, C > 2.6) that are either gas-poor (M{sub H{sub 2}}/M {sub *} <1.5%) or else on average less efficient by a factor of {approx}2 than disk-dominated galaxies at converting into stars any cold gas they may have. We find no link between the presence of AGNs and these long depletion times. In the regime where galaxies are disk-dominated and gas-rich, the galaxies undergoing mergers or showing signs of morphological disruptions have the shortest molecular gas depletion times, while those hosting strong stellar bars have only marginally higher global star formation efficiencies as compared to matched control samples. Our interpretation is that the molecular gas depletion time variations are caused by changes in the ratio between the gas mass traced by the CO(1-0) observations and the gas mass in high-density star-forming cores (as traced by observations of, e.g., HCN(1-0)). While interactions, mergers, and bar instabilities can locally increase pressure and raise the ratio of efficiently star-forming gas to CO-detected gas (therefore lowering the CO

  17. A Pipeline for Constructing Optimized N-Body Models of Interacting Galaxies

    Science.gov (United States)

    Harvey, Allen S., Jr.

    Galaxies form the building blocks of our understanding of a hierarchical evolution of the universe. Galaxies interact with other galaxies by impacting each other's gravitational fields, exchanging mass, spurring star formation, and even by merging. As sky surveys continue to capture images of interacting galaxies as they were in a snapshot of time so long ago, simulations of their evolution are needed to understand how they have arrived at their observed state. Restricted three-body simulations have advanced to produce realistic gravitational potentials to rapidly model interacting galaxies. Much research has been conducted to advance the creation and convergence of these models to obtain good matches to observed galaxies. Unfortunately, these models lack the physics for rich and realistic tidal features, gas dynamics, stellar black holes, and star formation, among others, that necessitate the use of higher fidelity models, such as N-Body gravity methods. The parameters describing the interacting galaxies from a restricted three-body simulation can be backwards integrated to estimate reasonable initial parameters for the galaxies well before their observed state. However, the backwards and forward integration in time of these simulations must be tuned by carefully choosing a tuning scalar to capture the dynamical friction of the interacting galaxies. This dissertation presents a prototype pipeline to link computationally efficient restricted three-body simulations of galaxy interactions to full, high resolution N-Body simulations. The software iterates between both classes of simulations to converge on the best match to an observed galaxy merger state. The system begins with a state vector from a merger at its peri-center as determined by the restricted three-body simulation code, SPAM, with an uncertain value for a dynamical friction scalar. The pipeline uses this vector to backwards integrate another SPAMmodel that systematically varies a scalar for dynamical

  18. Galaxy Pairs in cosmological simulations: Effects of interactions on star formation

    CERN Document Server

    Perez, M J; Lambas, D G; Scannapieco, C; Tissera, Patricia B.; Lambas, Diego G.; Scannapieco, Cecilia

    2005-01-01

    We carried out a statistical analysis of galaxy pairs in hydrodynamical Lambda-CDM simulations. We focused on the triggering of star formation by interactions and analysed the enhancement of star formation activity in terms of orbital parameters. By comparing to a suitable sample of simulated galaxies without a nearby companion, we find that close encounters (r<30 kpc/h) may effectively induce star formation. However, our results suggest that the stability properties of systems and the spatial proximity are both relevant factors in the process of triggering star formation by tidal interactions. In order to assess the effects of projection and spurious pairs in observational samples, we also constructed and analysed samples of pairs of galaxies in the simulations obtained in projection. We found a good agreement with observational results with a threshold at rp ~ 25 kpc/h for interactions to effectively enhance star formation activity. For pairs within rp < 100 kpc/h, we estimated a ~27% contamination by...

  19. VIPERS: An Unprecedented View of Galaxies and Large-Scale Structure Halfway Back in the Life of the Universe

    CERN Document Server

    Guzzo, L; Adami, C; Arnouts, S; Bel, J; Bolzonella, M; Bottini, D; Branchini, E; Burden, A; Cappi, A; Coupon, J; Cucciati, O; Davidzon, I; de la Torre, S; De Lucia, G; Di Porto, C; Franzetti, P; Fritz, A; Fumana, M; Garilli, B; Granett, B R; Guennou, L; Ilbert, O; Iovino, A; Krywult, J; Brun, V Le; Fèvre, O Le; Maccagni, D; Malek, K; Marchetti, A; Marinoni, C; Marulli, F; McCracken, H J; Mellier, Y; Moscardini, L; Nichol, R C; Paioro, L; Peacock, J A; Percival, W J; Phleps, S; Polletta, M; Pollo, A; Schlagenhaufer, H; Scodeggio, M; Solarz, A; Tasca, L A M; Tojeiro, R; Vergani, D; Wolk, M; Zamorani, G; Zanichelli, A

    2013-01-01

    The VIMOS Public Extragalactic Redshift Survey (VIPERS) is an ongoing ESO Large Programme to map in detail the large-scale distribution of galaxies at 0.5 < z <1.2. With a combination of volume and sampling density that is unique for these redshifts, it focuses on measuring galaxy clustering and related cosmological quantities as part of the grand challenge of understanding the origin of cosmic acceleration. VIPERS has also been designed to guarantee a broader legacy, allowing detailed investigations of the properties and evolutionary trends of z~1 galaxies. The survey strategy exploits the specific advantages of the VIMOS spectrograph at the VLT, aiming at a final sample of nearly 100,000 galaxy redshifts to iAB = 22.5 mag, which represents the largest redshift survey ever performed with ESO telescopes. In this introductory article we describe the survey construction, together with early results based on a first sample of ~55,000 galaxies.

  20. DISCOVERY OF A DISSOCIATIVE GALAXY CLUSTER MERGER WITH LARGE PHYSICAL SEPARATION

    Energy Technology Data Exchange (ETDEWEB)

    Dawson, William A.; Wittman, David; Jee, M. James; Gee, Perry; Tyson, J. Anthony; Schmidt, Samuel; Thorman, Paul; Bradac, Marusa; Lemaux, Brian [Department of Physics, University of California, Davis, One Shields Av., Davis, CA 95616 (United States); Hughes, John P. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019 (United States); Miyazaki, Satoshi; Utsumi, Yousuke [Department of Astronomical Science, The Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Margoniner, Vera E., E-mail: wadawson@ucdavis.edu [Department of Physics and Astronomy, California State University, Sacramento, 6000 J Street Sacramento, CA 95819 (United States)

    2012-03-10

    We present DLSCL J0916.2+2951 (z = 0.53), a newly discovered major cluster merger in which the collisional cluster gas has become dissociated from the collisionless galaxies and dark matter (DM). We identified the cluster using optical and weak-lensing observations as part of the Deep Lens Survey. Our follow-up observations with Keck, Subaru, Hubble Space Telescope, and Chandra show that the cluster is a dissociative merger and constrain the DM self-interaction cross-section {sigma}{sub DM} m{sup -1}{sub DM} {approx}< 7 cm{sup 2} g{sup -1}. The system is observed at least 0.7 {+-} 0.2 Gyr since first pass-through, thus providing a picture of cluster mergers 2-5 times further progressed than similar systems observed to date. This improved temporal leverage has implications for our understanding of merging clusters and their impact on galaxy evolution.

  1. A deep Large Binocular Telescope view of the Canes Venatici I dwarf galaxy

    CERN Document Server

    Martin, Nicolas F; De Jong, Jelte T A; Rix, Hans-Walter; Bell, Eric F; Sand, David J; Hill, John M; Kochanek, Christopher S; Thompson, David; Burwitz, Vadim; Giallongo, Emanuele; Ragazzoni, Roberto; Diolaiti, Emiliano; Gasparo, Federico; Grazian, Andrea; Pedichini, Fernando; Bechtold, Jill

    2007-01-01

    We present the first deep color-magnitude diagram of the Canes Venatici I (CVnI) dwarf galaxy from observations with the wide field Large Binocular Camera of the Large Binocular Telescope. Reaching down to the main-sequence turnoff of the oldest stars, it reveals a dichotomy in the stellar populations of CVnI: it harbors an old (>~ 10 Gyr), metal-poor ([Fe/H] ~ -2.0) and spatially extended population along with a much younger (~1.4-2.0 Gyr), 0.5 dex more metal-rich, and spatially more concentrated population. These young stars are also offset by ~100 pc to the East of the center of the galaxy. The data suggest that this young population should be identified with the kinematically cold stellar component found by Ibata et al. (2006). CVnI therefore follows the behavior of the other remote MW dwarf spheroidals which all contain intermediate age and/or young populations: a complex star formation history is possible in extremely low-mass galaxies.

  2. Confirmation of general relativity on large scales from weak lensing and galaxy velocities.

    Science.gov (United States)

    Reyes, Reinabelle; Mandelbaum, Rachel; Seljak, Uros; Baldauf, Tobias; Gunn, James E; Lombriser, Lucas; Smith, Robert E

    2010-03-11

    Although general relativity underlies modern cosmology, its applicability on cosmological length scales has yet to be stringently tested. Such a test has recently been proposed, using a quantity, E(G), that combines measures of large-scale gravitational lensing, galaxy clustering and structure growth rate. The combination is insensitive to 'galaxy bias' (the difference between the clustering of visible galaxies and invisible dark matter) and is thus robust to the uncertainty in this parameter. Modified theories of gravity generally predict values of E(G) different from the general relativistic prediction because, in these theories, the 'gravitational slip' (the difference between the two potentials that describe perturbations in the gravitational metric) is non-zero, which leads to changes in the growth of structure and the strength of the gravitational lensing effect. Here we report that E(G) = 0.39 +/- 0.06 on length scales of tens of megaparsecs, in agreement with the general relativistic prediction of E(G) approximately 0.4. The measured value excludes a model within the tensor-vector-scalar gravity theory, which modifies both Newtonian and Einstein gravity. However, the relatively large uncertainty still permits models within f(R) theory, which is an extension of general relativity. A fivefold decrease in uncertainty is needed to rule out these models.

  3. Large-scale CMB anisotropies wrinkles in the Galaxy rather than in time

    CERN Document Server

    López-Corredoira, M

    2000-01-01

    This paper presents strong evidence for the Galactic, rather than cosmological, nature of the large-scale anisotropies in the microwave background radiation, or at least the greater part of them, in form of the dependence of their amplitude on Galactic latitude. What have hitherto been called wrinkles in time in the light of the first COBE-DMR data and claimed to mark the discovery of the primordial seeds from which our present-day Universe has grown could more appropriately be named wrinkles in the interstellar medium of our Galaxy in the light of the present analysis, which uses the same data as those used by Smoot et al. This implies that present models of Galaxy formation and many parts of the standard cosmology are not correct.

  4. Approximate Bayesian Computation in Large Scale Structure: constraining the galaxy-halo connection

    CERN Document Server

    Hahn, ChangHoon; Walsh, Kilian; Hearin, Andrew P; Hogg, David W; Cambpell, Duncan

    2016-01-01

    The standard approaches to Bayesian parameter inference in large scale structure (LSS) assume a Gaussian functional form (chi-squared form) for the likelihood. They are also typically restricted to measurements such as the two point correlation function. Likelihood free inferences such as Approximate Bayesian Computation (ABC) make inference possible without assuming any functional form for the likelihood, thereby relaxing the assumptions and restrictions of the standard approach. Instead it relies on a forward generative model of the data and a metric for measuring the distance between the model and data. In this work, we demonstrate that ABC is feasible for LSS parameter inference by using it to constrain parameters of the halo occupation distribution (HOD) model for populating dark matter halos with galaxies. Using specific implementation of ABC supplemented with Population Monte Carlo importance sampling, a generative forward model using HOD, and a distance metric based on galaxy number density, two-point...

  5. Large-Scale Structures Behind the Southern Milky Way from Observations of Partially Obscured Galaxies

    CERN Document Server

    Kraan-Korteweg, R C; Henning, P A

    1996-01-01

    We report here on extragalactic large-scale structures uncovered by a deep optical survey for galaxies behind the southern Milky Way. Systematic visual inspection of the ESO/SRC-survey revealed over 10000 previously unknown galaxies in the region 265 ~ 2500 km/s connecting to the Hydra and Antlia clusters, a shallow extended supercluster in Vela (~ 6000km/s), and a nearby (4882 km/s), very massive (M ~ 2-5 10^15 Msun), rich Coma-like cluster which seems to constitute the previously unidentified center of the Great Attractor. The innermost part of the Milky Way where the foreground obscuration in the blue is 5mag, respectively HI-column densities greater than 6 10^21 / cm^2 remains fully opaque. In this approximately 8 degrees wide strip, the forthcoming blind HI-survey with the multi-beam system at Parkes will provide the only tool to unveil this part of the extragalactic sky.

  6. Large interactive database: design and implementation

    Science.gov (United States)

    Peralta-Fabi, Ricardo; Peralta, Alejandro; Vicente, Esau; Prado, Jorge M.; Diaz, C.

    1992-04-01

    A database system is being integrated in order to store and interactively retrieve information from a several hundred Gbytes optical memory. The low cost, high reliability requirements for the development and maintenance phase of the system suggested a modular design based on a network server, optical server, and some 40 (80386 based) viewing consoles with touch screens, but no keyboard or other controls since they are exposed to use by the general public. Optical disks store graphics, video, stills, text, animation, and audio which are accessed through hypertext and interactive graphics while a somewhat simple expert analyzes and records data on various aspects of the user, such as general interests, common questions, sociological-educational, background, etc. This information is in turn used to adapt several parameters of information display: rate of flow, language style, number and type of control buttons, degree of detail, and others. The large quantity of video, still images, and different graphics formats, has made it necessary to optimize the information contained via reduction of colors/resolution, compression techniques, and recursive use of a basic set of displays and video segments. The paper presents the design in some detail, with general examples of system capabilities, growth, and applications.

  7. Quiescent Galaxies in the 3D-HST Survey: Spectroscopic Confirmation of a Large Number of Galaxies With Relatively Old Stellar Populations at z Approx. 2

    Science.gov (United States)

    Tease, Katherine Whitaker; vanDokkum, Pieter G.; Brammer, Gabriel; Momcheva, Ivelina; Skelton, Rosalind; Franx, Marijin; Kriek, Mariska; Labbe, Ivo; Fumagalli, Mattia; Lundgren, Britt F.; Nelson, Erica J.; Patel, Shannon G.; Rix, Hans-Walter

    2013-01-01

    Quiescent galaxies at z approx. 2 have been identified in large numbers based on rest-frame colors, but only a small number of these galaxies have been spectroscopically confirmed to show that their rest-frame optical spectra show either strong Balmer or metal absorption lines. Here, we median stack the rest-frame optical spectra for 171 photometrically quiescent galaxies at 1.4 populations already existed when the universe was approx. 3 Gyr old, and that rest-frame color selection techniques can efficiently select them. We find an average age of 1.3+0.10.3 Gyr when fitting a simple stellar population to the entire stack. We confirm our previous result from medium-band photometry that the stellar age varies with the colors of quiescent galaxies: the reddest 80 of galaxies are dominated by metal lines and have a relatively old mean age of 1.6+0.50.4 Gyr, whereas the bluest (and brightest) galaxies have strong Balmer lines and a spectroscopic age of 0.9+0.20.1 Gyr. Although the spectrum is dominated by an evolved stellar population, we also find [O iii] and H emission. Interestingly, this emission is more centrally concentrated than the continuum with LOiii = 1.7+/- 0.3 x 10(exp 40) erg/s, indicating residual central star formation or nuclear activity.

  8. A large Hα survey of star formation in relaxed and merging galaxy cluster environments at z ∼ 0.15-0.3

    Science.gov (United States)

    Stroe, Andra; Sobral, David; Paulino-Afonso, Ana; Alegre, Lara; Calhau, João; Santos, Sergio; van Weeren, Reinout

    2017-03-01

    We present the first results from the largest Hα survey of star formation and active galactic nucleus activity in galaxy clusters. Using nine different narrow-band filters, we select >3000 Hα emitters within 19 clusters and their larger scale environment over a total volume of 1.3 × 105 Mpc3. The sample includes both relaxed and merging clusters, covering the 0.15-0.31 redshift range and spanning from 5 × 1014 to 30 × 1014 M⊙. We find that the Hα luminosity function for merging clusters has a higher characteristic density ϕ* compared to relaxed clusters. ϕ* drops from cluster core to cluster outskirts for both merging and relaxed clusters, with the merging cluster values ∼0.3 dex higher at each projected radius. The characteristic luminosity L* drops over the 0.5-2.0 Mpc distance from the cluster centre for merging clusters and increases for relaxed objects. Among disturbed objects, clusters hosting large-scale shock waves (traced by radio relics) are overdense in Hα emitters compared to those with turbulence in their intracluster medium (traced by radio haloes). We speculate that the increase in star formation activity in disturbed, young, massive galaxy clusters can be triggered by interactions between gas-rich galaxies, shocks and/or the intracluster medium, as well as accretion of filaments and galaxy groups. Our results indicate that disturbed clusters represent vastly different environments for galaxy evolution compared to relaxed clusters or average field environments.

  9. Interacting galaxies: co-rotating and counter-rotating systems with tidal tails

    CERN Document Server

    Mesa, Valeria; Alonso, Sol; Coldwell, Georgina; Lambas, Diego G

    2013-01-01

    We analyse interacting galaxy pairs with evidence of tidal features in the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7). The pairs were selected within $z<0.1$ by requiring a projected separation $r_p < 50 \\kpc$ and relative radial velocity $\\Delta V < 500 \\kms$. We complete spectroscopic pairs using galaxies with photometric redshifts considering $\\Delta V_{phot} < 6800 \\kms$, taking into account the mean photometric redshift uncertainty. We classify by visual inspection pairs of spirals into co-rotating and counter-rotating systems. For a subsample of non-AGN galaxies, counter-rotating pairs have larger star formation rates, and a higher fraction of young, star-forming galaxies. These effects are enhanced by restricting to $r_p < 12 \\kpc$. The distributions of $C$, $D_n(4000)$ and $(M_u-M_r)$ for AGN galaxies show that counter-rotating hosts have bluer colours and younger stellar population than the co-rotating galaxies although the relative fractions of Seyfert, Liner, Composite and Am...

  10. Newtonian limit of scalar-tensor theories and galactic dynamics: isolated and interacting galaxies

    CERN Document Server

    Cervantes-Cota, J L; Gabbasov, R; Klapp, J

    2007-01-01

    We use the Newtonian limit of a general scalar-tensor theory around a background field to study astrophysical effects. The gravitational theory modifies the standard Newtonian potential by adding a Yukawa term to it, which is quantified by two theoretical parameters: $\\lambda$, the lenghtscale of the gravitational interaction and its strength, $\\alpha$. Within this formalism we firstly present a numerical study on the formation of bars in isolated galaxies. We have found for positive $\\alpha$ that the modified gravity destabilizes the galactic discs and leads to rapid bar formation in isolated galaxies. Values of $\\lambda$ in the range $\\approx 8$ -- 14 kpc produce strongest bars in isolated models. Then, we extent this work by considering tidal effects due to interacting galaxies. We send two spirals to collide and study the bar properties of the remnant. We characterize the bar kinematical properties in terms of our parameters ($\\lambda, \\alpha$).

  11. The warped galaxy MKN 306 in the interacting system MKN 305/306

    Science.gov (United States)

    Kollatschny, W.; Dietrich, M.

    1990-07-01

    Optical images and spectra of the interacting galaxy system Mkn 305/306 are presented. Both galaxies have a disturbed morphology, and they show spectra with starburst or poststarburst characteristics as a result of mutual tidal interaction. Mkn 306 is shaped like an integral sign with two strong symmetrical central emission regions. The morphology, the velocity structure, and the optical spectra demonstrate that the galaxy Mkn 306 is seen nearly edge-on with a very strong warp of the stellar disk. The extreme degree of this optical distortion is comparable only with the strongest radio warps so far known; but these radio warps show only the H I gas distribution in the outer galactic regions and not the stellar distribution.

  12. APOSTL: An Interactive Galaxy Pipeline for Reproducible Analysis of Affinity Proteomics Data.

    Science.gov (United States)

    Kuenzi, Brent M; Borne, Adam L; Li, Jiannong; Haura, Eric B; Eschrich, Steven A; Koomen, John M; Rix, Uwe; Stewart, Paul A

    2016-12-02

    With continuously increasing scale and depth of coverage in affinity proteomics (AP-MS) data, the analysis and visualization is becoming more challenging. A number of tools have been developed to identify high-confidence interactions; however, a cohesive and intuitive pipeline for analysis and visualization is still needed. Here we present Automated Processing of SAINT Templated Layouts (APOSTL), a freely available Galaxy-integrated software suite and analysis pipeline for reproducible, interactive analysis of AP-MS data. APOSTL contains a number of tools woven together using Galaxy workflows, which are intuitive for the user to move from raw data to publication-quality figures within a single interface. APOSTL is an evolving software project with the potential to customize individual analyses with additional Galaxy tools and widgets using the R web application framework, Shiny. The source code, data, and documentation are freely available from GitHub ( https://github.com/bornea/APOSTL ) and other sources.

  13. Interacting galaxies: corotating and counter-rotating systems with tidal tails

    Science.gov (United States)

    Mesa, Valeria; Duplancic, Fernanda; Alonso, Sol; Coldwell, Georgina; Lambas, Diego G.

    2014-02-01

    We analyse interacting galaxy pairs with evidence of tidal features in the Sloan Digital Sky Survey Data Release 7. The pairs were selected within z visual inspection pairs of spirals into corotating and counter-rotating systems. For a subsample of non-active galactic nucleus (non-AGN) galaxies, counter-rotating pairs have larger star formation rates and a higher fraction of young, star-forming galaxies. These effects are enhanced by restricting to rp Composite and Ambiguous AGN are similar. Also, counter-rotating hosts have more powerful AGN as revealed by enhanced Lum[O III] values. The number of corotating systems is approximately twice the number of counter-rotating pairs which could be owed to a more rapid evolution of counter-rotating systems, besides possible different initial conditions of these interacting pairs.

  14. The isolated interacting galaxy pair NGC 5426/27 (Arp 271)

    CERN Document Server

    Fuentes-Carrera, I; Amram, P; Dultzin-Hacyan, D; Cruz-Gonzalez, I; Salo, H; Laurikainen, E; Bernal, A; Ambrocio-Cruz, P; Le Coarer, E

    2003-01-01

    We present H alpha observations of the isolated interacting galaxy pair NGC 5426/27 using the scanning Fabry-Perot interferometer PUMA. The velocity field, various kinematical parameters and rotation curve for each galaxy were derived. The FWHM map and the residual velocities map were also computed to study the role of non-circular motions of the gas. Most of these motions can be associated with the presence of spiral arms and structure such as central bars. We found a small bar-like structure in NGC 5426, a distorted velocity field for NGC 5427 and a bridge-like feature between both galaxies which seems to be associated with NGC 5426. Using the observed rotation curves, a range of possible masses was computed for each galaxy. These were compared with the orbital mass of the pair derived from the relative motion of the participants. The rotation curve of each galaxy was also used to fit different mass distribution models considering the most common theoretical dark halo models. An analysis of the interaction ...

  15. VLA HI Imaging of the LARS+eLARS Galaxies: Tidally Interacting Systems

    Science.gov (United States)

    Reilly, Bridget; Eisner, Brian Andrew; Cannon, John M.; Hayes, Matthew; Melinder, Jens; Östlin, Göran; Pardy, Stephen; LARS Team

    2017-01-01

    The Lyman Alpha Reference Sample (LARS) and its extension (eLARS) form the most comprehensive effort to date to study the details of Lyman Alpha radiative transfer in galaxies. Direct imaging of Lyman Alpha emission from the Hubble Space Telescope is supplemented by a wealth of multi-wavelength observations designed to probe the complex processes that contribute to the escape or destruction of Lyman Alpha photons as they resonantly scatter in the neutral ISM. The 42 LARS+eLARS galaxies span a range of physical properties, including mass and star formation rate. A companion poster presents VLA HI imaging of 32 LARS+eLARS galaxies. In this work, we present new VLA D-configuration HI imaging of selected LARS+eLARS galaxies that are well-resolved or tidally interacting. HI column density and velocity field images are compared to SDSS imaging. We interpret the results in the context of tidal interactions shifting the HI gas out of resonance and increasing the likelihood of Lyman Alpha photons escaping the galaxy.

  16. A Multiwavelength View of Star Formation in Interacting Galaxies in the Pavo Group

    CERN Document Server

    Machacek, M; Jones, C; Forman, W R; Bastian, N

    2008-01-01

    We combine Spitzer IRAC mid-infrared (MIR) and Chandra X-ray observations of the dominant galaxies NGC6872 and NGC6876 in the Pavo group with archival optical and HI data to study interaction-induced star formation. In spiral galaxy NGC6872, 8.0 and 5.8 micron nonstellar emission having colors consistent with polycyclic aromatic hydrocarbons (PAHs) is concentrated in clumps in three regions: in a 5 kpc radius outer ring about the center of the spiral galaxy, in a bridge of emission connecting NGC6872's northern spiral arm to IC4970, and along the full extent of NGC6872's tidal arms. PAH emission is correlated with young star clusters and dense HI regions. We find no strong differences in the MIR colors of star-forming regions in the spiral galaxy NGC6872 as a function of position relative to the tidally interacting companion galaxy IC4970. We find 11 very luminous X-ray sources (>~ (0.5 - 5) x 10^{39} ergs/s) clustered to the southwest in NGC6872, near bright star-forming regions. In NGC6872's tidal features,...

  17. Discovery of a transparent sightline at {\\rho} < 20 kpc from an interacting pair of galaxies

    CERN Document Server

    Johnson, Sean D; Mulchaey, John S; Tripp, Todd M; Prochaska, J Xavier; Werk, Jessica K

    2013-01-01

    We report the discovery of a transparent sightline at projected distances of {\\rho} < 20 kpc to an interacting pair of mature galaxies at z = 0.12. The sightline of the UV-bright quasar PG1522+101 at z = 1.328 passes at {\\rho} = 11.5 kpc from the higher-mass galaxy (M_* = 10^10.6 M_Sun) and {\\rho} = 20.4 kpc from the lower-mass one (M_* = 10^10.0 M_Sun). The two galaxies are separated by 9 kpc in projected distance and 30 km/s in line-of-sight velocity. Deep optical images reveal tidal features indicative of close interactions. Despite the small projected distances, the quasar sightline shows little absorption associated with the galaxy pair with a total HI column density it no greater than log N(HI) = 13.65. This limiting HI column density is already two orders-of-magnitude less than what is expected from previous halo gas studies. In addition, we detect no heavy-element absorption features associated with the galaxy pair with 3-{\\sigma} limits of log N(MgII) < 12.2 and log N(OVI) < 13.7. The probab...

  18. The large-scale 3-point correlation function of the SDSS BOSS DR12 CMASS galaxies

    CERN Document Server

    Slepian, Zachary; Beutler, Florian; Cuesta, Antonio J; Ge, Jian; Gil-Marín, Héctor; Ho, Shirley; Kitaura, Franciso-Shu; McBride, Cameron K; Nichol, Robert C; Percival, Will J; Rodríguez-Torres, Sergio; Ross, Ashley J; Scoccimarro, Román; Seo, Hee-Jong; Tinker, Jeremy; Tojeiro, Rita; Vargas-Magaña, Mariana

    2015-01-01

    We report a measurement of the large-scale 3-point correlation function of galaxies using the largest dataset for this purpose to date, 777, 202 Luminous Red Galaxies in the Sloan Digital Sky Survey Baryon Acoustic Oscillation Spectroscopic Survey (SDSS BOSS) DR12 CMASS sample. This work exploits the novel algorithm of Slepian & Eisenstein (2015b) to compute the multipole moments of the 3PCF in $\\mathcal{O}(N^2)$ time, with $N$ the number of galaxies. Leading-order perturbation theory models the data well in a compressed basis where one triangle side is integrated out. We also present an accurate and computationally efficient means of estimating the covariance matrix. With these techniques the redshift-space linear and non-linear bias are measured, with 2.6% precision on the former if $\\sigma_8$ is fixed. The data also indicates a $2.8\\sigma$ preference for the BAO, confirming the presence of BAO in the 3-point function.

  19. Large-Scale Fluctuations in the Number Density of Galaxies in Independent Surveys of Deep Fields

    CERN Document Server

    Shirokov, S I; Baryshev, Yu V; Gorokhov, V L

    2016-01-01

    New arguments supporting the reality of large-scale fluctuations in the density of the visible matter in deep galaxy surveys are presented. A statistical analysis of the radial distributions of galaxies in the COSMOS and HDF-N deep fields is presented. Independent spectral and photometric surveys exist for each field, carried out in different wavelength ranges and using different observing methods. Catalogs of photometric redshifts in the optical (COSMOS-Zphot) and infrared (UltraVISTA) were used for the COSMOS field in the redshift interval $0.1 < z < 3.5$, as well as the zCOSMOS (10kZ) spectroscopic survey and the XMM-COSMOS and ALHAMBRA-F4 photometric redshift surveys. The HDFN-Zphot and ALHAMBRA-F5 catalogs of photometric redshifts were used for the HDF-N field. The Pearson correlation coefficient for the fluctuations in the numbers of galaxies obtained for independent surveys of the same deep field reaches $R = 0.70 \\pm 0.16$. The presence of this positive correlation supports the reality of fluctu...

  20. Missing baryons traced by the galaxy luminosity density in the large-scale WHIM filaments

    CERN Document Server

    Nevalainen, J; Liivamägi, L J; Branchini, E; Roncarelli, M; Giocoli, C; Heinämäki, P; Saar, E; Tamm, A; Finoguenov, A; Nurmi, P; Bonamente, M

    2015-01-01

    We propose a new approach to the missing baryons problem. Building on the common assumption that the missing baryons are in the form of the Warm Hot Intergalactic Medium (WHIM), we further assumed here that the galaxy luminosity density can be used as a tracer of the WHIM. The latter assumption is supported by our finding of a significant correlation between the WHIM density and the galaxy luminosity density in the hydrodynamical simulations of Cui et al. (2012). We further found that the fraction of the gas mass in the WHIM phase is substantially (by a factor of $\\sim$1.6) higher within the large scale galactic filaments, i.e. $\\sim$70\\%, compared to the average in the full simulation volume of $\\sim$0.1\\,Gpc$^3$. The relation between the WHIM overdensity and the galaxy luminosity overdensity within the galactic filaments is consistent with linear: $\\delta_{\\rm whim}\\,=\\,0.7\\,\\pm\\,0.1\\,\\times\\,\\delta_\\mathrm{LD}^{0.9 \\pm 0.2}$. We applied our procedure to the line of sight to the blazar H2356-309 and found e...

  1. Approximate Bayesian computation in large-scale structure: constraining the galaxy-halo connection

    Science.gov (United States)

    Hahn, ChangHoon; Vakili, Mohammadjavad; Walsh, Kilian; Hearin, Andrew P.; Hogg, David W.; Campbell, Duncan

    2017-08-01

    Standard approaches to Bayesian parameter inference in large-scale structure assume a Gaussian functional form (chi-squared form) for the likelihood. This assumption, in detail, cannot be correct. Likelihood free inferences such as approximate Bayesian computation (ABC) relax these restrictions and make inference possible without making any assumptions on the likelihood. Instead ABC relies on a forward generative model of the data and a metric for measuring the distance between the model and data. In this work, we demonstrate that ABC is feasible for LSS parameter inference by using it to constrain parameters of the halo occupation distribution (HOD) model for populating dark matter haloes with galaxies. Using specific implementation of ABC supplemented with population Monte Carlo importance sampling, a generative forward model using HOD and a distance metric based on galaxy number density, two-point correlation function and galaxy group multiplicity function, we constrain the HOD parameters of mock observation generated from selected 'true' HOD parameters. The parameter constraints we obtain from ABC are consistent with the 'true' HOD parameters, demonstrating that ABC can be reliably used for parameter inference in LSS. Furthermore, we compare our ABC constraints to constraints we obtain using a pseudo-likelihood function of Gaussian form with MCMC and find consistent HOD parameter constraints. Ultimately, our results suggest that ABC can and should be applied in parameter inference for LSS analyses.

  2. A Catalog of Faint Interacting Galaxies in Pairs and Groups: Erratum

    Science.gov (United States)

    de Mello, Duilia F.; Infante, Leopoldo; Menanteau, Felipe

    In the paper ``A Catalog of Faint Interacting Galaxies in Pairs and Groups'' by Duília F. de Mello, Leopoldo Infante, and Felipe Menanteau (ApJS, 108, 99 [1997]), a correction should be made to Table 2. No sextet was found in this survey. The total number of groups is 29.

  3. An investigation of the luminosity-metallicity relation for a large sample of low-metallicity emission-line galaxies

    CERN Document Server

    Guseva, N G; Meyer, H T; Izotov, Yu I; Fricke, K J

    2009-01-01

    (abridged) We present 8.2m VLT spectroscopic observations of 28 HII regions in 16 emission-line galaxies and 3.6m ESO telescope spectroscopic observations of 38 HII regions in 28 emission-line galaxies. These emission-line galaxies were selected mainly from the Data Release 6 (DR6) of the Sloan Digital Sky Survey (SDSS) as metal-deficient galaxy candidates. We collect photometric and high-quality spectroscopic data for a large uniform sample of star forming galaxies including new observations. Our aim is to study the luminosity-metallicity (L-Z) relation for nearby galaxies, especially at its low-metallicity end and compare it with that for higher-redshift galaxies. From our new observations we find that the oxygen abundance in 61 out of the 66 HII regions of our sample ranges from 12+logO/H=7.05 to 8.22. Our sample includes 27 new galaxies with 12+logO/HMg>-20) and nearly 2 dex in its oxygen abundance (7.0<12+logO/H<8.8), allowing us to probe the L-Z relation in the nearby universe down to the lowest c...

  4. Direct observational evidence for a large transient galaxy population in groups at 0.85

    CERN Document Server

    Balogh, Michael L; Wilman, David J; Finoguenov, Alexis; Parker, Laura C; Connelly, Jennifer L; Mulchaey, John S; Bower, Richard G; Tanaka, Masayuki; Giodini, Stefania

    2010-01-01

    (abridged) We introduce our survey of galaxy groups at 0.8515 members. The dynamical mass estimates are in good agreement with the masses estimated from the X-ray luminosity, with most of the groups having 131E10.1 Msun, and for blue galaxies we sample masses as low as Mstar=1E8.8 Msun. Like lower-redshift groups, these systems are dominated by red galaxies, at all stellar masses Mstar>1E10.1 Msun. Few group galaxies inhabit the ``blue cloud'' that dominates the surrounding field; instead, we find a large and possibly distinct population of galaxies with intermediate colours. The ``green valley'' that exists at low redshift is instead well-populated in these groups, containing ~30 per cent of galaxies. These do not appear to be exceptionally dusty galaxies, and about half show prominent Balmer-absorption lines. Furthermore, their HST morphologies appear to be intermediate between those of red-sequence and blue-cloud galaxies of the same stellar mass. We postulate that these are a transi ent population, migrat...

  5. MUSE 3D Spectroscopy and Kinematics of the GPS Radio Galaxy PKS 1934-63: Interaction, Recently Triggered AGN and Star Formation

    CERN Document Server

    Roche, Nathan; Lagos, Patricio; Papaderos, Polychronis; Silva, Marckelson; Cardoso, Leandro S M; Gomes, Jean Michel

    2016-01-01

    We observe the radio galaxy PKS 1934-63 (at $z=0.1825$) using MUSE (Multi Unit Spectroscopic Explorer) on the Very Large Telescope (VLT). The radio source is GigaHertz Peaked Spectrum and compact (0.13 kpc), implying an early stage of evolution ($\\leq 10^4$ yr). Our data show an interacting pair of galaxies, projected separation 9.1 kpc, velocity difference $\\Delta(v)=216$ km $\\rm s^{-1}$. The larger galaxy is a $\\rm M_{*}\\simeq 10^{11}M_{\\odot}$ spheroidal with the emission-line spectrum of a high-excitation young radio AGN, e.g. strong [OI]6300 and [OIII]5007. Emission-line ratios indicate a large contribution to the line luminosity from high-velocity shocks ($\\simeq 550$ km $\\rm s^{-1}$) . The companion is a non-AGN disk galaxy, with extended $\\rm H\\alpha$ emission from which its star-formation rate is estimated as $\\rm 0.61~M_{\\odot}yr^{-1}$. Both galaxies show rotational velocity gradients in $\\rm H\\alpha$ and other lines, with the interaction being prograde-prograde. The SE-NW velocity gradient of the A...

  6. Cosmic-ray Propagation and Interactions in the Galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Strong, Andrew W.; /Garching, Max Planck Inst., MPE; Moskalenko, Igor V.; /Stanford U., HEPL /KIPAC, Menlo Park; Ptuskin, Vladimir S.; /Troitsk, IZMIRAN

    2007-01-22

    We survey the theory and experimental tests for the propagation of cosmic rays in the Galaxy up to energies of 10{sup 15} eV. A guide to the previous reviews and essential literature is given, followed by an exposition of basic principles. The basic ideas of cosmic-ray propagation are described, and the physical origin of its processes are explained. The various techniques for computing the observational consequences of the theory are described and contrasted. These include analytical and numerical techniques. We present the comparison of models with data including direct and indirect--especially gamma-ray--observations, and indicate what we can learn about cosmic-ray propagation. Some particular important topics including electrons and antiparticles are chosen for discussion.

  7. A New Hydrodynamic Model for Numerical Simulation of Interacting Galaxies on Intel Xeon Phi Supercomputers

    Science.gov (United States)

    Kulikov, Igor; Chernykh, Igor; Tutukov, Alexander

    2016-05-01

    This paper presents a new hydrodynamic model of interacting galaxies based on the joint solution of multicomponent hydrodynamic equations, first moments of the collisionless Boltzmann equation and the Poisson equation for gravity. Using this model, it is possible to formulate a unified numerical method for solving hyperbolic equations. This numerical method has been implemented for hybrid supercomputers with Intel Xeon Phi accelerators. The collision of spiral and disk galaxies considering the star formation process, supernova feedback and molecular hydrogen formation is shown as a simulation result.

  8. Properties of Molecular Gas in Galaxies in Early and Mid Stage of the Interaction: I. Distribution of Molecular Gas

    CERN Document Server

    Kaneko, Hiroyuki; Iono, Daisuke; Tamura, Yoichi; Tosaki, Tomoka; Nakanishi, Koichiro; Sawada, Tsuyoshi

    2012-01-01

    We present the results of 12CO(J = 1-0) mapping observations toward four interacting galaxies in early and mid stages of the interaction to understand the behavior of molecular gas in galaxy-galaxy interaction. The observations were carried out using the 45-m telescope at Nobeyama Radio Observatory (NRO). We compared our CO total flux to those previously obtained with single-dish observations and found that there are no discrepancy between them. Applying a typical CO-H2 conversion factor, all constituent galaxies have molecular gas mass more than 10^9 M_sun. Comparisons to HI, Ks and tracers of SF such as Halpha, FUV, 8 um and 24 um revealed that the distribution of molecular gas in interacting galaxies in the early stage of the interaction differs from atomic gas, stars and star-forming regions. These differences are not explained without the result of the interaction. Central concentration of molecular gas of interacting galaxies in the early stage of the interaction is lower than that of isolated galaxies,...

  9. Models of galaxy collisions in Stephan's quintet and other interacting systems

    Science.gov (United States)

    Hwang, Jeong-Sun

    2010-12-01

    This dissertation describes numerical studies of three interacting galaxy systems. First, hydrodynamical models of the collisions in the famous compact galaxy group, Stephan's Quintet, were constructed to investigate the dynamical interaction history and evolution of the intergalactic gas. It has been found that with a sequence of two-at-a-time collisions, most of the major morphological and kinematical features of the group were well reproduced in the models. The models suggest the two long tails extending from NGC 7319 toward NGC 7320c may be formed simultaneously from a strong collisional encounter between the two galaxies, resulting in a thinner and denser inner tail than the outer one. The tails then also run parallel to each other as observed. The model results support the idea that the group-wide shock detected in multi-wavelength observations between NGC 7319 and 7318b and the starburst region north of NGC 7318b are triggered by the current high-speed collision between NGC 7318b and the intergalactic gas. It is expected that other compact groups containing rich extended features like Stephan's Quintet can be modeled in similar ways, and that sequences of two-at-a-time collisions will be the general rule. The second set of hydrodynamical simulations were performed to model the peculiar galaxy pair, Arp 285. This system possesses a series of star-forming complexes in an unusual tail-like feature extending out perpendicular to the disk of the northern galaxy. Several conceptual ideas for the origin of the tail-like feature were examined. The models suggest that the bridge material falling into the gravitational potential of the northern disk overshoots the disk; as more bridge material streams into the region, compression drives star formation. This work on star-formation in the pile-up region can be extended to the studies of the formation of tidal dwarf galaxies or globular clusters. Thirdly, the development of spiral waves was studied with numerical models

  10. The spatial distribution of ultra diffuse galaxies within large scale structures

    CERN Document Server

    Roman, Javier

    2016-01-01

    Taking advantage of the Sloan Digital Sky Survey Stripe82, we have explored the spatial distribution of ultra diffuse galaxies (UDGs) within an area of 8x8 Mpc^2 centered around the galaxy cluster Abell 168 (z=0.045). This intermediate massive cluster (sigma=550 km/s) is surrounded by a complex large scale structure, rich in filaments and groups. This allows us to probe the large scale distribution of UDGs and address the question whether the infalling structures fed the cluster with new UDGs. We find that UDGs are located within the large scale structures that comprise the Abell 168 overdensity. Approximately 42% of the UDGs analysed inhabit the cluster region: ~7+-3% in the core and ~35+-7% in the outskirts whereas the remaining UDGs are found outside the main overdensity: ~19+-5% in groups and ~40% in filaments. UDGs structural properties gradually change from the lowest to the densest regions with a decrease of their stellar mass by a factor of ~1.5, an increase of their Sersic index n by a factor of ~1.2...

  11. The SLUGGS Survey: stellar kinematics, kinemetry and trends at large radii in 25 early-type galaxies

    CERN Document Server

    Foster, Caroline; Roediger, Joel; Brodie, Jean P; Forbes, Duncan A; Kartha, Sreeja S; Pota, Vincenzo; Romanowsky, Aaron J; Spitler, Lee R; Strader, Jay; Usher, Christopher; Arnold, Jacob A

    2015-01-01

    Due to longer dynamical timescales, the outskirts of early-type galaxies retain the footprint of their formation and assembly. Under the popular two-phase galaxy formation scenario, an initial in-situ phase of star formation is followed by minor merging and accretion of ex-situ stars leading to the expectation of observable transitions in the kinematics and stellar populations on large scales. However, observing the faint galactic outskirts is challenging, often leaving the transition unexplored. The large scale, spatially-resolved stellar kinematic data from the SAGES Legacy Unifying Galaxies and GlobularS (SLUGGS) survey are ideal for detecting kinematic transitions. We present kinematic maps out to 2.6 effective radii on average, kinemetry profiles, measurement of kinematic twists and misalignments, and the average outer intrinsic shape of 25 SLUGGS galaxies. We find good overall agreement in the kinematic maps and kinemetry radial profiles with literature. We are able to confirm significant radial modulat...

  12. Quiescent Galaxies in the 3D-HST Survey: Spectroscopic Confirmation of a Large Number of Galaxies with Relatively Old Stellar Populations at z~2

    CERN Document Server

    Whitaker, Katherine E; Brammer, Gabriel; Momcheva, Ivelina G; Skelton, Rosalind; Franx, Marijn; Kriek, Mariska; Labbe, Ivo; Fumagalli, Mattia; Lundgren, Britt F; Nelson, Erica J; Patel, Shannon G; Rix, Hans-Walter

    2013-01-01

    Quiescent galaxies at z~2 have been identified in large numbers based on rest-frame colors, but only a small number of these galaxies have been spectroscopically confirmed to show that their rest-frame optical spectra show either strong Balmer or metal absorption lines. Here, we median stack the rest-frame optical spectra for 171 photometrically-quiescent galaxies at 1.4 < z < 2.2 from the 3D-HST grism survey. In addition to Hbeta (4861A), we unambiguously identify metal absorption lines in the stacked spectrum, including the G-band (4304A), Mg I (5175A), and Na I (5894A). This finding demonstrates that galaxies with relatively old stellar populations already existed when the universe was ~3 Gyr old, and that rest-frame color selection techniques can efficiently select them. We find an average age of 1.3^0.1_0.3 Gyr when fitting a simple stellar population to the entire stack. We confirm our previous result from medium-band photometry that the stellar age varies with the colors of quiescent galaxies: th...

  13. Interaction effects on galaxy pairs with Gemini/GMOS- III: stellar population synthesis

    Science.gov (United States)

    Krabbe, A. C.; Rosa, D. A.; Pastoriza, M. G.; Hägele, G. F.; Cardaci, M. V.; Dors, O. L., Jr.; Winge, C.

    2017-05-01

    We present an observational study of the impacts of interactions on the stellar population in a sample of galaxy pairs. Long-slit spectra in the wavelength range 3440-7300 Å obtained with the Gemini Multi-Object Spectrograph (GMOS) at Gemini South for 15 galaxies in nine close pairs were used. The spatial distributions of the stellar population contributions were obtained using the stellar population synthesis code starlight. Taking into account the different contributions to the emitted light, we found that most of the galaxies in our sample are dominated by young/intermediate stellar populations. This result differs from the one derived for isolated galaxies, where the old stellar population dominates the disc surface brightness. We interpreted such different behaviour as being due to the effect of gas inflows along the discs of interacting galaxies on the star formation over a time-scale of the order of about 2 Gyr. We also found that, in general, the secondary galaxy of a pair has a higher contribution from the young stellar population than the primary one. We compared the estimated values of stellar and nebular extinction derived from the synthesis method and the Hα/Hβ emission-line ratio, finding that nebular extinctions are systematically higher than stellar ones by about a factor of 2. We did not find any correlation between nebular and stellar metallicities. Neither did we find a correlation between stellar metallicities and ages, while a positive correlation between nebular metallicities and stellar ages was obtained, with older regions being the most metal-rich.

  14. A low-frequency study of two asymmetric large radio galaxies

    CERN Document Server

    Pirya, A; Saikia, D J; Singh, M

    2012-01-01

    We present the results of multifrequency observations of two asymmetric, Mpc-scale radio sources with the Giant Metrewave Radio Telescope (GMRT) and the Very Large Array (VLA). The radio luminosity of these two sources, J1211+743 and J1918+742, are in the Fanaroff-Riley class II (FRII) range, but have diffuse radio components on one side of the galaxy while the opposite component appears edge-brightened with a prominent hot-spot. Although the absence of a hot-spot is reminiscent of FRI radio galaxies, suggesting a hybrid morphology, the radio jet facing the diffuse lobe in J1211+743 is similar to those in FRII radio sources, and it is important to consider these aspects as well while classifying these sources in the FR scheme. The observed asymmetries in these Mpc-scale sources are likely to be largely intrinsic rather than being due to the effects of orientation and relativistic motion. The formation of a diffuse lobe facing the radio jet in J1211+743 is possibly due to the jet being highly dissipative. The ...

  15. Probing Dark Energy with Baryonic Acoustic Oscillations from Future Large Galaxy Redshift Surveys

    CERN Document Server

    Eisenstein, D J

    2003-01-01

    We show that the measurement of the baryonic acoustic oscillations in large high redshift galaxy surveys offers a precision route to the measurement of dark energy. The cosmic microwave background provides the scale of the oscillations as a standard ruler that can be measured in the clustering of galaxies, thereby yielding the Hubble parameter and angular diameter distance as a function of redshift. This, in turn, enables one to probe dark energy. We use a Fisher matrix formalism to study the statistical errors for redshift surveys up to z=3 and report errors on cosmography while marginalizing over a large number of cosmological parameters including a time-dependent equation of state. With redshifts surveys combined with cosmic microwave background satellite data, we achieve errors of 0.037 on Omega_x, 0.10 on w(z=0.8), and 0.28 on dw(z)/dz for cosmological constant model. Models with less negative w(z) permit tighter constraints. We test and discuss the dependence of performance on redshift, survey condition...

  16. Automated Kinematic Modelling of Warped Galaxy Discs in Large Hi Surveys: 3D Tilted Ring Fitting of HI Emission Cubes

    CERN Document Server

    Kamphuis, P; Oh, S- H; Spekkens, K; Urbancic, N; Serra, P; Koribalski, B S; Dettmar, R -J

    2015-01-01

    Kinematical parameterisations of disc galaxies, employing emission line observations, are indispensable tools for studying the formation and evolution of galaxies. Future large-scale HI surveys will resolve the discs of many thousands of galaxies, allowing a statistical analysis of their disc and halo kinematics, mass distribution and dark matter content. Here we present an automated procedure which fits tilted-ring models to Hi data cubes of individual, well-resolved galaxies. The method builds on the 3D Tilted Ring Fitting Code (TiRiFiC) and is called FAT (Fully Automated TiRiFiC). To assess the accuracy of the code we apply it to a set of 52 artificial galaxies and 25 real galaxies from the Local Volume HI Survey (LVHIS). Using LVHIS data, we compare our 3D modelling to the 2D modelling methods DiskFit and rotcur. A conservative result is that FAT accurately models the kinematics and the morphologies of galaxies with an extent of eight beams across the major axis in the inclination range 20$^{\\circ}$-90$^{...

  17. A case study for a tidal interaction between dwarf galaxies in UGC 6741

    CERN Document Server

    Paudel, Sanjaya; Ree, C H

    2015-01-01

    We present a case study of the tidal interaction between low mass, star-forming, galaxies initially found exploring the Sloan Digital Sky Survey (SDSS) images and further analyzed with SDSS spectroscopy and UV GALEX photometry. With a luminosity of M$_{r}$ = $-$17.7 mag and exhibiting a prominent tidal filament, UGC 6741 appears as a scale down version of massive gas--rich interacting systems and mergers.The stellar disk of the smaller companion, UGC 6741_B, which is three times less massive, has likely been already destroyed. Both galaxies, which are connected by a 15 kpc long stellar bridge, have a similar oxygen abundance of 12+log(O/H)$\\sim$8.3. Several knots of star-forming regions are identified along the bridge, some with masses exceeding $\\sim$10$^{7}$ M$_{\\sun}$. The most compact of them, which are unresolved, may evolve into globular clusters or Ultra Compact Dwarf galaxies (UCDs). This would be the first time progenitors of such objects are detected in mergers involving dwarf galaxies. UGC 6741 has...

  18. A large difference in the progenitor masses of active and passive galaxies in the EAGLE simulation

    Science.gov (United States)

    Clauwens, Bart; Franx, Marijn; Schaye, Joop

    2016-11-01

    Cumulative number density matching of galaxies is a method to observationally connect descendent galaxies to their typical main progenitors at higher redshifts and thereby to assess the evolution of galaxy properties. The accuracy of this method is limited due to galaxy merging and scatter in the stellar mass growth history of individual galaxies. Behroozi et al. have introduced a refinement of the method, based on abundance matching of observed galaxies to the Bolshoi dark matter-only simulation. The EAGLE cosmological hydrosimulation is well suited to test this method, because it reproduces the observed evolution of the galaxy stellar mass function and the passive fraction. We find agreement with the Behroozi et al. method for the complete sample of main progenitors of z = 0 galaxies, but we also find a strong dependence on the current star formation rate. Passive galaxies with a stellar mass up to 1010.75 M⊙ have a completely different median mass history than active galaxies of the same mass. This difference persists if we only select central galaxies. This means that the cumulative number density method should be applied separately to active and passive galaxies. Even then, the typical main progenitor of a z = 0 galaxy already spans two orders of magnitude in stellar mass at z = 2.

  19. Clustering large number of extragalactic spectra of galaxies and quasars through canopies

    CERN Document Server

    De, Tuli; Chattopadhyay, Asis Kumar

    2013-01-01

    Cluster analysis is the distribution of objects into different groups or more precisely the partitioning of a data set into subsets (clusters) so that the data in subsets share some common trait according to some distance measure. Unlike classi cation, in clustering one has to rst decide the optimum number of clusters and then assign the objects into different clusters. Solution of such problems for a large number of high dimensional data points is quite complicated and most of the existing algorithms will not perform properly. In the present work a new clustering technique applicable to large data set has been used to cluster the spectra of 702248 galaxies and quasars having 1540 points in wavelength range imposed by the instrument. The proposed technique has successfully discovered ve clusters from this 702248X1540 data matrix.

  20. Modeling the large-scale redshift-space 3-point correlation function of galaxies

    CERN Document Server

    Slepian, Zachary

    2016-01-01

    We present a configuration-space model of the large-scale galaxy 3-point correlation function (3PCF) based on leading-order perturbation theory and including redshift space distortions (RSD). This model should be useful in extracting distance-scale information from the 3PCF via the Baryon Acoustic Oscillation (BAO) method. We include the first redshift-space treatment of biasing by the baryon-dark matter relative velocity. Overall, on large scales the effect of RSD is primarily a renormalization of the 3PCF that is roughly independent of both physical scale and triangle opening angle; for our adopted $\\Omega_{\\rm m}$ and bias values, the rescaling is a factor of $\\sim 1.8$. We also present an efficient scheme for computing 3PCF predictions from our model, important for allowing fast exploration of the space of cosmological parameters in future analyses.

  1. Large-scale 3D galaxy correlation function and non-Gaussianity

    Energy Technology Data Exchange (ETDEWEB)

    Raccanelli, Alvise; Doré, Olivier [Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA 91109 (United States); Bertacca, Daniele; Maartens, Roy, E-mail: alvise@caltech.edu, E-mail: daniele.bertacca@gmail.com, E-mail: Olivier.P.Dore@jpl.nasa.gov, E-mail: roy.maartens@gmail.com [Physics Department, University of the Western Cape, Cape Town 7535 (South Africa)

    2014-08-01

    We investigate the properties of the 2-point galaxy correlation function at very large scales, including all geometric and local relativistic effects --- wide-angle effects, redshift space distortions, Doppler terms and Sachs-Wolfe type terms in the gravitational potentials. The general three-dimensional correlation function has a nonzero dipole and octupole, in addition to the even multipoles of the flat-sky limit. We study how corrections due to primordial non-Gaussianity and General Relativity affect the multipolar expansion, and we show that they are of similar magnitude (when f{sub NL} is small), so that a relativistic approach is needed. Furthermore, we look at how large-scale corrections depend on the model for the growth rate in the context of modified gravity, and we discuss how a modified growth can affect the non-Gaussian signal in the multipoles.

  2. ISO observations of the interacting galaxy Markarian 297: with the powerful supernova remnant 1982aa

    CERN Document Server

    Metcalfe, L; Burgdorf, M; Clavel, J; Coia, D; Delaney, M; Gallais, P; Hanlon, L; Laureijs, R; Leech, K; McBreen, B; O'Halloran, B; Smith, N

    2005-01-01

    Markarian (Mkn) 297 is a complex system with two interacting galaxies. Observations were made with ISO using ISOCAM, ISOPHOT and LWS. We present ISOCAM maps at 6.7, 7.7, 12 and 14.3 microns which, with PHT-S spectrometry of the central interacting region, probe the dust obscured star formation and dust properties. ISOCAM reveals that the strongest emission region in the four MIR bands is completely unremarkable at visible and near-IR (e.g. 2MASS) wavelengths, and does not coincide with the nuclear region of either colliding galaxy. It shares this striking characteristic with the overlap region of the colliding galaxies in the Antennae (NGC 4038, 4039), the intragroup region of Stephan's Quintet, and IC 694 in the interacting system Arp 299. At 15 microns, the hidden source in Mkn 297 is, respectively, 14.6 and 3.8 times more luminous than the hidden sources in the Antennae (NGC 4038/4039) and Stephan's Quintet. Numerical simulations indicate that we see the Mkn 297 interaction about 1.5 x 10e8 years after the...

  3. Spatial periodicity of galaxy number counts from Fourier analysis of the large scale surveys of galaxies in the Universe

    CERN Document Server

    Hartnett, John G

    2007-01-01

    A Fourier analysis has been carried out on the galaxy number count as a function of redshift, the $N$-$z$ relation, calculated from redshift data of both the Sloan Digital Sky Survey (SDSS) and the 2dF Galaxy Redshift Survey (2dF GRS). Regardless of the interpretation of those redshifts, the results indicate that galaxies have preferred periodic redshifts. This is the \\textit{picket-fence} structure observed by some. Application of the Hubble law, at low redshift, results in galaxies preferentially located on concentric shells with periodic spacings. This analysis finds significant redshift spacings of $\\Delta z =$ 0.0102, 0.0246, and 0.0448 in the SDSS and strong agreement with the results from 2dF GRS. The combined results from both surveys indicate regular real space spacings of $44.0 \\pm 2.5$ $Mpc$, $102 \\pm 8$ $Mpc$ and $176 \\pm 29$ $Mpc$, for an assumed Hubble's constant $H_0 = 72 km s^{-1} Mpc^{-1}$. These results indicate that it is a real effect and not some observational artifact. The effect is sign...

  4. In the wake of dark giants: new signatures of dark matter self-interactions in equal-mass mergers of galaxy clusters

    Science.gov (United States)

    Kim, Stacy Y.; Peter, Annika H. G.; Wittman, David

    2017-08-01

    Merging galaxy clusters have been touted as one of the best probes for constraining self-interacting dark matter, but few simulations exist to back up this claim. We simulate equal-mass mergers of 1015 M⊙ haloes, like the El Gordo and Sausage clusters, with cosmologically motivated halo and merger parameters, and with velocity-independent dark-matter self-interactions. Although the standard lore for merging clusters is that self-interactions lead to large separations between the galaxy and dark-matter distributions, we find that maximal galaxy-dark matter offsets of ≲20 kpc form for a self-interaction cross-section of σSI/mχ = 1 cm2 g-1. This is an order of magnitude smaller than those measured in observed equal-mass and near-equal-mass mergers, and is likely to be even smaller for lower mass systems. While competitive cross-section constraints are thus unlikely to emerge from offsets, we find other signatures of self-interactions that are more promising. Intriguingly, we find that after dark-matter haloes coalesce, the collisionless galaxies [and especially the brightest cluster galaxy (BCG)] oscillate around the centre of the merger remnant on stable orbits of 100 kpc for σSI/mχ = 1 cm2 g-1 for at least several Gyr, well after the clusters have relaxed. If BCG miscentring in relaxed clusters remains a robust prediction of self-interacting dark matter under the addition of gas physics, substructure, merger mass ratios (e.g. 10:1 like the Bullet Cluster) and complex cosmological merger histories, the observed BCG offsets may constrain σSI/mχ to ≲0.1 cm2 g-1 - the tightest constraint yet.

  5. Detected Galaxies and Large Scale Structure in the Arecibo L-band Feed Array Zone of Avoidance Survey (ALFAZOA)

    Science.gov (United States)

    Henning, Patricia A.; Sanchez-Barrantes, Monica; McIntyre, Travis; Minchin, Robert F.; Momjian, Emmanuel; Butcher, Zhon; Rosenberg, Jessica L.; Schneider, Stephen E.; Staveley-Smith, Lister; van Driel, Wim; Ramatsoku, Mpati; Koribalski, Baerbel; Spears, Brady

    2017-01-01

    While large, systematic redshift surveys of galaxies have been conducted for decades, lack of information behind the Milky Way (the Zone of Avoidance) contributes uncertainty to our picture of dynamics in the local universe. Controversy persists for the dipole calculated from galaxy and redshift surveys compared to the CMB. Depth in redshift space is an issue, as is incomplete sky mapping, even of supposed all sky redshifts surveys. For instance, the wide-angle 2MASS Redshift Survey retains a gap of 5-8 deg around the Galactic plane. Fortunately, there is no ZOA at 21cm, except for velocities occupied by the Galaxy. This long-wavelength spectral line passes unimpeded through dust, and is unaffected by stellar confusion. With immediate redshift determination, a 21-cm survey produces a 3-dimensional map of the distribution of obscured galaxies which contain HI. It traces large-scale structure right across the Galactic Plane, and identifies obscured mass overdensities relevant to flow-field studies.ALFAZOA is a blind HI survey for galaxies behind the Milky Way covering more than 1000 square degrees of the Arecibo sky. It proceeds in two phases: shallow (completed) and deep (ongoing). The shallow survey (rms ~5-7 mJy) mapped the region within Galactic longitude l = 30 - 75 deg, and latitude b = -10 to +10 deg, detecting several hundred galaxies to about 12,000 km/s, tracing large-scale structure across the plane. The deep survey (rms ~1 mJy), in both the inner (Galactic longitude 30 - 75 deg and latitude plus/minus 2 deg) and outer (longitude 175 - 207 deg and latitude = +1 to -2 deg) Galaxy is ongoing, with detections reaching to 18,000 km/s. Analysis of detections to date, and large-scale structure mapped, will be presented.

  6. Wide and deep near-UV (360nm) galaxy counts and the extragalactic background light with the Large Binocular Camera

    CERN Document Server

    Grazian, A; Giallongo, E; Gallozzi, S; Fontanot, F; Fontana, A; Testa, V; Ragazzoni, R; Baruffolo, A; Beccari, G; Diolaiti, E; Di Paola, A; Farinato, J; Gasparo, F; Gentile, G; Green, R; Hill, J; Kuhn, O; Pasian, F; Pedichini, F; Radovich, M; Smareglia, R; Speziali, R; Thompson, D; Wagner, R M

    2009-01-01

    Deep multicolour surveys are the main tool to explore the formation and evolution of the faint galaxies which are beyond the spectroscopic limit with the present technology. The photometric properties of these faint galaxies are usually compared with current renditions of semianalytical models to provide constraints on the fundamental physical processes involved in galaxy formation and evolution, namely the mass assembly and the star formation. Galaxy counts over large sky areas in the near-UV band are important because they are difficult to obtain given the low efficiency of near-UV instrumentation, even at 8m class telescopes. A large instrumental field of view helps in minimizing the biases due to the cosmic variance. We have obtained deep images in the 360nm U band provided by the blue channel of the Large Binocular Camera at the prime focus of the Large Binocular Telescope. We have derived over an area of ~0.4 sq. deg. the galaxy number counts down to U=27 in the Vega system (corresponding to U=27.86 in ...

  7. Horizon Run 4 Simulation: Coupled Evolution of Galaxies and Large-scale Structures of the Universe

    CERN Document Server

    Kim, Juhan; L'Huillier, Benjamin; Hong, Sungwook E

    2015-01-01

    The Horizon Run 4 is a cosmological $N$-body simulation designed for the study of coupled evolution between galaxies and large-scale structures of the Universe, and for the test of galaxy formation models. Using $6300^3$ gravitating particles in a cubic box of $L_{\\rm box} = 3150 ~h^{-1}{\\rm Mpc}$, we build a dense forest of halo merger trees to trace the halo merger history with a halo mass resolution scale down to $M_s = 2.7 \\times 10^{11} h^{-1}{\\rm M_\\odot}$. We build a set of particle and halo data, which can serve as testbeds for comparison of cosmological models and gravitational theories with observations. We find that the FoF halo mass function shows a substantial deviation from the universal form with tangible redshift evolution of amplitude and shape. At higher redshifts, the amplitude of the mass function is lower, and the functional form is shifted toward larger values of $\\ln (1/\\sigma)$. We also find that the baryonic acoustic oscillation feature in the two-point correlation function of mock ga...

  8. COLDz: Karl G. Jansky Very Large Array discovery of a gas-rich galaxy in COSMOS

    CERN Document Server

    Lentati, L; Carilli, C L; Riechers, D; Capak, P; Walter, F; Aravena, M; da Cunha, E; Hodge, J A; Ivison, R J; Smail, I; Sharon, C; Daddi, E; Decarli, R; Dickinson, M; Sargent, M; Scoville, N; Smolcic, V

    2014-01-01

    The broad spectral bandwidth at mm and cm-wavelengths provided by the recent upgrades to the Karl G. Jansky Very Large Array (VLA) has made it possible to conduct unbiased searches for molecular CO line emission at redshifts, z > 1.31. We present the discovery of a gas-rich, star-forming galaxy at z = 2.48, through the detection of CO(1-0) line emission in the COLDz survey, through a sensitive, Ka-band (31 to 39 GHz) VLA survey of a 6.5 square arcminute region of the COSMOS field. We argue that the broad line (FWHM ~570 +/- 80 km/s) is most likely to be CO(1-0) at z=2.48, as the integrated emission is spatially coincident with an infrared-detected galaxy with a photometric redshift estimate of z = 3.2 +/- 0.4. The CO(1-0) line luminosity is L'_CO = (2.2 +/- 0.3) x 10^{10} K km/s pc^2, suggesting a cold molecular gas mass of M_gas ~ (2 - 8)x10^{10}M_solar depending on the assumed value of the molecular gas mass to CO luminosity ratio alpha_CO. The estimated infrared luminosity from the (rest-frame) far-infrare...

  9. A Stacked Analysis of Brightest Cluster Galaxies Observed with the Fermi Large Area Telescope

    CERN Document Server

    Dutson, K L; Edge, A C; Hinton, J A; Hogan, M T

    2012-01-01

    We present the results of a search for high-energy gamma-ray emission from a large sample of galaxy clusters sharing the properties of three existing Fermi-LAT detections (in Perseus, Virgo and Abell 3392), namely a powerful radio source within their brightest cluster galaxy (BCG). From a parent, X-ray flux-limited sample of clusters, we select 114 systems with a core-dominated BCG radio flux above 50 or 75 mJy, stacking data from the first 45 months of the Fermi mission, to determine statistical limits on the gamma-ray fluxes of the ensemble of candidate sources. For a >300 MeV selection, the distribution of detection significance across the sample is consistent with that across control samples for significances 4 sigma signals which are not associated with previously identified gamma-ray emission. Modelling of the data in these fields results in the detection of four non-2FGL Fermi sources, though none appear to be unambiguously associated with the BCG candidate. A search at energies >3 GeV hints at emissio...

  10. Large-scale variations of the dust optical properties in the Galaxy

    CERN Document Server

    Cambresy, L; Beichman, C A

    2005-01-01

    We present an analysis of the dust optical properties at large scale, for the whole galactic anticenter hemisphere. We used the 2MASS Extended Source Catalog to obtain the total reddening on each galaxy line of sight and we compared this value to the IRAS 100 microns surface brightness converted to extinction by Schlegel et al (1998). We performed a careful examination and correction of the possible systematic effects resulting from foreground star contamination, redshift contribution and galaxy selection bias. We also evaluated the contribution of dust temperature variations and interstellar clumpiness to our method. The correlation of the near-infrared extinction to the far-infrared optical depth shows a discrepancy for visual extinction greater than 1 mag with a ratio A_V(FIR) / A_V(gal) = 1.31 +- 0.06. We attribute this result to the presence of fluffy/composite grains characterized by an enhanced far--infrared emissivity. Our analysis, applied to half of the sky, provides new insights on the dust grains ...

  11. Dark matter constraints from observations of 25 Milky Way satellite galaxies with the Fermi Large Area Telescope

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M.; et al.

    2014-02-11

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma-ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in gamma rays, and we present gamma-ray flux upper limits between 500 MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the the annihilation of dark matter particles with masses between 2 GeV and 10 TeV into prototypical Standard Model channels. We find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse gamma-ray background modeling, and assumed dark matter density profile.

  12. Dark Matter Constraints from Observations of 25 Milky Way Satellite Galaxies with the Fermi Large Area Telescope

    CERN Document Server

    :,; Albert, A; Anderson, B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Bissaldi, E; Bloom, E D; Bonamente, E; Bouvier, A; Brandt, T J; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caragiulo, M; Caraveo, P A; Cecchi, C; Charles, E; Chekhtman, A; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; D'Ammando, F; de Angelis, A; Dermer, C D; Digel, S W; Silva, E do Couto e; Drell, P S; Drlica-Wagner, A; Essig, R; Favuzzi, C; Ferrara, E C; Franckowiak, A; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Giglietto, N; Giroletti, M; Godfrey, G; Gomez-Vargas, G A; Grenier, I A; Guiriec,; Gustafsson, M; Hayashida, M; Hays, E; Hewitt, J; Hughes, R E; Jogler, T; Kamae, T; Knödlseder, J; Kocevski, D; Kuss, M; Larsson,; Latronico, L; Garde, M Llena; Longo, F; Loparco, F; Lovellette, M N; Lubrano, P; Martinez, G; Mayer, M; Mazziotta, M N; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nemmen, R; Nuss, E; Ohsugi, T; Orlando, E; Ormes, J F; Perkins, J S; Piron, F; Pivato, G; Porter, T A; Rainò, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Ritz, S; Sànchez-Conde, M; Sehgal, N; Sgrò, C; Siskind, E J; Spinelli, P; Strigari, L; Suson, D J; Tajima, H; Takahashi, H; Thayer, J B; Tibaldo, L; Tinivella, M; Torres, D F; Uchiyama, Y; Usher, T L; Vandenbroucke, J; Vianello, G; Vitale, V; Werner, M; Winer, B L; Wood, K S; Wood, M; Zaharijas, G; Zimmer, S

    2013-01-01

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma-ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in gamma rays, and we present gamma-ray flux upper limits between 500 MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the the annihilation of dark matter particles with masses between 2 GeV and 10 TeV into prototypical Standard Model channels. W...

  13. Dark Matter Constraints from Observations of 25 Milky Way Satellite Galaxies with the Fermi Large Area Telescope

    Science.gov (United States)

    Ackermann, M.; Albert, A.; Anderson, B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Bloom, E. D.; Bonamente, E.; Bouvier, A.; Brandt, T. J.; Hays, E.; Perkins, J. S.

    2013-01-01

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in gamma rays, and we present gamma ray flux upper limits between 500MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the annihilation of dark matter particles with masses between 2 GeV and 10TeV into prototypical standard model channels. We find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse gamma ray background modeling, and assumed dark matter density profile.

  14. TiNy Titans: The Role of Dwarf-Dwarf Interactions in the Evolution of Low Mass Galaxies

    CERN Document Server

    Stierwalt, S; Patton, D; Johnson, K; Kallivayalil, N; Putman, M; Privon, G; Ross, G

    2014-01-01

    We introduce TiNy Titans (TNT), the first systematic study of star formation and the subsequent processing of the interstellar medium in interacting dwarf galaxies. Here we present the first results from a multiwavelength observational program based on a sample of 104 dwarf galaxy pairs selected from a range of environments within the SDSS and caught in various stages of interaction. The TNT dwarf pairs span mass ratios of M1/M2 100 A, occur in 20% of TNT dwarf pairs, regardless of environment, compared to only 6-8% of matched unpaired dwarfs. Starbursts can be triggered throughout the merger (out to large pair separations) and not just approaching coalescence. Despite their enhanced star formation, most TNT dwarf pairs have similar gas fractions relative to unpaired dwarfs. Thus, there may be significant reservoirs of diffuse, non-starforming gas surrounding the dwarf pairs or the gas consumption timescales may be long in the starburst phase. The only TNT dwarf pairs with low gas fractions (fgas <0.4) and...

  15. Kinematic classifications of local interacting galaxies: implications for the merger/disk classifications at high-z

    CERN Document Server

    Hung, Chao-Ling; Yuan, Tiantian; Larson, Kirsten L; Casey, Caitlin M; Smith, Howard A; Sanders, D B; Kewley, Lisa J; Hayward, Christopher C

    2015-01-01

    The classification of galaxy mergers and isolated disks is key for understanding the relative importance of galaxy interactions and secular evolution during the assembly of galaxies. The kinematic properties of galaxies as traced by emission lines have been used to suggest the existence of a significant population of high-z star-forming galaxies consistent with isolated rotating disks. However, recent studies have cautioned that post-coalescence mergers may also display disk-like kinematics. To further investigate the robustness of merger/disk classifications based on kinematic properties, we carry out a systematic classification of 24 local (U)LIRGs spanning a range of galaxy morphologies: from isolated spiral galaxies, ongoing interacting systems, to fully merged remnants. We artificially redshift the WiFeS observations of these local (U)LIRGs to z=1.5 to make a realistic comparison with observations at high-z, and also to ensure that all galaxies have the same spatial sampling of ~900 pc. Using both kineme...

  16. Signatures of Interstellar-Intracluster Medium Interactions Spiral Galaxy Rotation Curves in Abell 2029

    CERN Document Server

    Dale, D A; Dale, Daniel A.; Uson, Juan M.

    2000-01-01

    We investigate the rich cluster Abell 2029 (z~0.08) using optical imaging and long-slit spectral observations of 52 disk galaxies distributed throughout the cluster field. No strong emission-line galaxies are present within ~400 kpc of the cluster center, a region largely dominated by the similarly-shaped X-ray and low surface brightness optical envelopes centered on the giant cD galaxy. However, two-thirds of the galaxies observed outside the cluster core exhibit line emission. H-alpha rotation curves of 14 cluster members are used in conjunction with a deep I band image to study the environmental dependence of the Tully-Fisher relation. The Tully-Fisher zero-point of Abell 2029 matches that of clusters at lower redshifts, although we do observe a relatively larger scatter about the Tully-Fisher relation. We do not observe any systematic variation in the data with projected distance to the cluster center: we see no environmental dependence of Tully-Fisher residuals, R-I color, H-alpha equivalent width, and t...

  17. Constraints on dark matter annihilation in clusters of galaxies with the Fermi large area telescope

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M.; Ajello, M.; Allafort, A.; Bechtol, K.; Blandford, R.D.; Bloom, E.D.; Borgland, A.W.; Bouvier, A.; Buehler, R. [W.W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d' Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brandt, T.J. [Centre d' Étude Spatiale des Rayonnements, CNRS/UPS, BP 44346, F-30128 Toulouse Cedex 4 (France); Brigida, M. [Dipartimento di Fisica ' ' M. Merlin' ' dell' Università e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P., E-mail: tesla@ucolick.org, E-mail: profumo@scipp.ucsc.edu [Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, Palaiseau (France); and others

    2010-05-01

    Nearby clusters and groups of galaxies are potentially bright sources of high-energy gamma-ray emission resulting from the pair-annihilation of dark matter particles. However, no significant gamma-ray emission has been detected so far from clusters in the first 11 months of observations with the Fermi Large Area Telescope. We interpret this non-detection in terms of constraints on dark matter particle properties. In particular for leptonic annihilation final states and particle masses greater than ∼ 200 GeV, gamma-ray emission from inverse Compton scattering of CMB photons is expected to dominate the dark matter annihilation signal from clusters, and our gamma-ray limits exclude large regions of the parameter space that would give a good fit to the recent anomalous Pamela and Fermi-LAT electron-positron measurements. We also present constraints on the annihilation of more standard dark matter candidates, such as the lightest neutralino of supersymmetric models. The constraints are particularly strong when including the fact that clusters are known to contain substructure at least on galaxy scales, increasing the expected gamma-ray flux by a factor of ∼ 5 over a smooth-halo assumption. We also explore the effect of uncertainties in cluster dark matter density profiles, finding a systematic uncertainty in the constraints of roughly a factor of two, but similar overall conclusions. In this work, we focus on deriving limits on dark matter models; a more general consideration of the Fermi-LAT data on clusters and clusters as gamma-ray sources is forthcoming.

  18. The technicolor "big picture" of black hole evolution: Multiwavelength views of AGN, galaxies, and large-scale structures

    Science.gov (United States)

    Hickox, Ryan C.

    2016-08-01

    Large multiwavelength extragalactic surveys have revolutionized our understanding of the cosmic evolution of supermassive black holes (SMBHs). I will discuss recent results on the host galaxies and clustering of AGN selected using a range of techniques from the radio to the hard X-ray wavebands, including data from the NuSTAR and WISE space observatories. I will show that relatively small dark matter halos hosting star-forming galaxies are connected with rapid but highly variable black hole growth that is often heavily obscured. In contrast, massive halos hosting passive galaxies are associated with slower, mechanically-dominated modes of black hole growth. I will conclude by discussing new analysis techniques for measuring AGN clustering and look to the future of large-scale extragalactic surveys.

  19. A large difference in the progenitor masses of active and passive galaxies in the EAGLE simulation

    CERN Document Server

    Clauwens, Bart; Schaye, Joop

    2016-01-01

    Cumulative number density matching of galaxies is a method to observationally connect descendent galaxies to their typical main progenitors at higher redshifts and thereby to assess the evolution of galaxy properties. The accuracy of this method is limited due to galaxy merging and scatter in the stellar mass growth history of individual galaxies. Behroozi et al. (2013) have introduced a refinement of the method, based on abundance matching of observed galaxies to the Bolshoi dark-matter-only simulation. The EAGLE cosmological hydro-simulation is well suited to test this method, because it reproduces the observed evolution of the galaxy stellar mass function and has a representative sample of passive/active galaxies. We find agreement with the Behroozi et al. (2013) method for the complete sample of main progenitors of z = 0 galaxies, but we also find a strong dependence on the current star formation rate. Passive galaxies with a stellar mass up to 10^10.75 Msun have a completely different median mass history...

  20. $\\rm{H}\\alpha$ Velocity Fields and Galaxy Interaction in the Quartet of Galaxies NGC 7769, 7770, 7771 and 7771A

    Indian Academy of Sciences (India)

    A. A. Yeghiazaryan; T. A. Nazaryan; A. A. Hakobyan

    2016-03-01

    The quartet of galaxies NGC 7769, 7770, 7771 and 7771A is a system of interacting galaxies. Close interaction between galaxies caused characteristic morphological features: tidal arms and bars, as well as an induced star formation. In this study, we performed the Fabry–Perot scanning interferometry of the system in $\\rm{H}\\alpha$ line and studied the velocity fields of the galaxies. We found that the rotation curve of NGC 7769 is weakly distorted. The rotation curve of NGC 7771 is strongly distorted with the tidal arms caused by direct flyby of NGC 7769 and flyby of a smaller neighbor NGC 7770. The rotation curve of NGC 7770 is significantly skewed because of the interaction with the much massive NGC 7771. The rotation curves and morphological disturbances suggest that the NGC 7769 and NGC 7771 have passed the first pericenter stage, however, probably the second encounter has not happened yet. Profiles of surface brightness of NGC 7769 have a characteristic break, and profiles of color indices have a minimum at a radius of intensive star formation induced by the interaction with NGC 7771.

  1. An interaction scenario of the galaxy pair NGC 3893/96 (KPG 302): A single passage?

    Energy Technology Data Exchange (ETDEWEB)

    Gabbasov, R. F.; Rosado, M. [Instituto de Astronomía, Universidad Nacional Autónoma de Mexico (UNAM), A.P. 70-264,04510 México D.F. (Mexico); Klapp, J., E-mail: ruslan.gabb@gmail.com [Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca S/N, La Marquesa, Ocoyoacac, 52750 Estado de México (Mexico)

    2014-05-20

    Using the data obtained previously from Fabry-Perot interferometry, we study the orbital characteristics of the interacting pair of galaxies KPG 302 with the aim to estimate a possible interaction history, the conditions necessary for the spiral arm formation, and initial satellite mass. We found by performing N-body/smoothed particle hydrodynamics simulations of the interaction that a single passage can produce a grand design spiral pattern in less than 1 Gyr. Although we reproduce most of the features with the single passage, the required satellite to host mass ratio should be ∼1:5, which is not confirmed by the dynamical mass estimate made from the measured rotation curve. We conclude that a more realistic interaction scenario would require several passages in order to explain the mass ratio discrepancy.

  2. An interaction scenario of the galaxy pair NGC 3893/96 (KPG 302). A single passage?

    CERN Document Server

    Gabbasov, R F; Klapp, J

    2014-01-01

    Using the data obtained previously from Fabry-Perot interferometry, we study the orbital characteristics of the interacting pair of galaxies KPG 302 with the aim to estimate a possible interaction history, the conditions necessary for the spiral arms formation and initial satellite mass. We found by performing N-body/SPH simulations of the interaction that a single passage can produce a grand design spiral pattern in less than 1 Gyr. Althought we reproduce most of the features with the single passage, the required satellite to host mass ratio should be 1:5, which is not confirmed with the dynamical mass estimate made from the measured rotation curve. We conclude that a more realistic interaction scenario would require several passages in order to explain the mass ratio discrepancy.

  3. SDSS-III Baryon Oscillation Spectroscopic Survey Data Release 12: galaxy target selection and large scale structure catalogues

    CERN Document Server

    Reid, Beth; Padmanabhan, Nikhil; Percival, Will J; Tinker, Jeremy; Tojeiro, Rita; White, Martin; Eisenstein, Daniel J; Maraston, Claudia; Ross, Ashley J; Sanchez, Ariel G; Schlegel, David; Sheldon, Erin; Strauss, Michael A; Thomas, Daniel; Wake, David; Beutler, Florian; Bizyaev, Dmitry; Bolton, Adam S; Brownstein, Joel R; Chuang, Chia-Hsun; Dawson, Kyle; Harding, Paul; Kitaura, Francisco-Shu; Leauthaud, Alexie; Masters, Karen; McBride, Cameron K; More, Surhud; Olmstead, Matthew D; Oravetz, Daniel; Nuza, Sebastian E; Pan, Kaike; Parejko, John; Pforr, Janine; Prada, Francisco; Rodriguez-Torres, Sergio; Salazar-Albornoz, Salvador; Samushia, Lado; Schneider, Donald P; Scoccola, Claudia G; Simmons, Audrey; Vargas-Magana, Mariana

    2015-01-01

    The Baryon Oscillation Spectroscopic Survey (BOSS), part of the Sloan Digital Sky Survey (SDSS) III project, has provided the largest survey of galaxy redshifts available to date, in terms of both the number of galaxy redshifts measured by a single survey, and the effective cosmological volume covered. Key to analysing the clustering of these data to provide cosmological measurements is understanding the detailed properties of this sample. Potential issues include variations in the target catalogue caused by changes either in the targeting algorithm or properties of the data used, the pattern of spectroscopic observations, the spatial distribution of targets for which redshifts were not obtained, and variations in the target sky density due to observational systematics. We document here the target selection algorithms used to create the galaxy samples that comprise BOSS. We also present the algorithms used to create large scale structure catalogues for the final Data Release (DR12) samples and the associated ...

  4. The Axis of Opportunity: The Large-Scale Correlation of Elliptical Galaxies

    OpenAIRE

    Longo, Michael J.

    2007-01-01

    This paper has been withdrawn by the author due to the discovery of a serious bias resulting from the systematic dimming of galaxies with larger ellipticities away from the North Galactic Pole. Thus the conclusion that there is a special axis along which the elliptical galaxies tend to be aligned is incorrect.

  5. Spatially resolved stellar, dust and gas properties of the post-interacting Whirlpool Galaxy system

    CERN Document Server

    Cooper, Erin Mentuch; Foyle, Kelly; Bendo, George; Koda, Jin; Baes, Marten; Boquien, Médéric; Boselli, Alessandro; Ciesla, Laure; Cooray, Asantha; Eales, Steve; Galametz, Maud; Lebouteiller, Vianney; Parkin, Tara; Roussel, Hélène; Sauvage, Marc; Spinoglio, Luigi; Smith, Matthew W L

    2012-01-01

    Using infrared imaging from the Herschel Space Observatory, observed as part of the VNGS, we investigate the spatially resolved dust properties of the interacting Whirlpool galaxy system (NGC 5194 and NGC 5195), on physical scales of 1 kpc. Spectral energy distribution modelling of the new infrared images in combination with archival optical, near- through mid-infrared images confirms that both galaxies underwent a burst of star formation ~370-480 Myr ago and provides spatially resolved maps of the stellar and dust mass surface densities. The resulting average dust-to-stellar mass ratios are comparable to other spiral and spheroidal galaxies studied with Herschel, with NGC 5194 at log M(dust)/M(star)= -2.5+/-0.2 and NGC 5195 at log M(dust)/M(star)= -3.5+/-0.3. The dust-to-stellar mass ratio is constant across NGC 5194 suggesting the stellar and dust components are coupled. In contrast, the mass ratio increases with radius in NGC 5195 with decreasing stellar mass density. Archival mass surface density maps of ...

  6. Large Scale Structure Setting the Stage for the Galaxy Formation Saga

    CERN Document Server

    Van de Weygaert, R

    1998-01-01

    Over the past three decades the established view of a nearly homogeneuous, featureless Universe on scales larger than a few Megaparsec has been completely overhauled. In particular through the advent of ever larger galaxy redshift surveys we were revealed a galaxy distribution displaying an intriguing cellular pattern in which filamentary and wall-like structures, as well as huge regions devoid of galaxies, are amongst the most conspicuous morphological elements. In this contribution we will provide an overview of the present observational state of affairs concerning the distribution of galaxies and the structure traced out by the matter distribution in our Universe. In conjunction with the insight on the dynamics of the structure formation process obtained through the mapping of the peculiar velocities of galaxies in our local Universe and the information on the embryonic circumstances that prevailed at the epoch of Recombination yielded by the various Cosmic Microwave Background experiments, we seek to arri...

  7. IRAS galaxies and the large-scale structure in the CfA slice

    Science.gov (United States)

    Babul, Arif; Postman, Marc

    1990-01-01

    The spatial distributions of the IRAS and the optical galaxies in the first CfA slice are compared. The IRAS galaxies are generally less clustered than optical ones, but their distribution is essentially identical to that of late-type optical galaxies. The discrepancy between the clustering properties of the IRAS and optical samples in the CfA slice region is found to be entirely due to the paucity of IRAS galaxies in the core of the Coma cluster. The spatial distributions of the IRAS and the optical galaxies, both late and early types, outside the dense core of the Coma cluster are entirely consistent with each other. This conflicts with the prediction of the linear biasing scenario.

  8. Spacecraft charging and plasma interaction implications for large space systems

    Science.gov (United States)

    Miller, E.; Stauber, M.; Rossi, M.; Fischbein, W.

    1978-01-01

    Specific discharge mechanisms, plasma interactions, and scale effects associated with very large spacecraft are studied. The large area, low density character, and extensive use of non-conducting materials is thought to have a major impact on the performance and survivability of many large space systems.

  9. THE FIRST DETECTION OF GeV EMISSION FROM AN ULTRALUMINOUS INFRARED GALAXY: Arp 220 AS SEEN WITH THE FERMI LARGE AREA TELESCOPE

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Fang-Kun; Wang, Xiang-Yu [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Liu, Ruo-Yu [Max-Planck-Institut für Kernphysik, D-69117 Heidelberg (Germany); Tang, Qing-Wen [School of Science, Nanchang University, Nanchang 330031 (China); Wang, Jun-Feng, E-mail: xywang@nju.edu.cn [Department of Astronomy and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005 (China)

    2016-04-20

    Cosmic rays (CRs) in starburst galaxies produce high-energy gamma-rays by colliding with the dense interstellar medium. Arp 220 is the nearest ultraluminous infrared galaxy that has star formation at extreme levels, so it has long been predicted to emit high-energy gamma-rays. However, no evidence of gamma-ray emission was found despite intense search efforts. Here we report the discovery of high-energy gamma-ray emission above 200 MeV from Arp 220 at a confidence level of ∼6.3σ using 7.5 years of Fermi Large Area Telescope observations. The gamma-ray emission shows no significant variability over the observation period and it is consistent with the quasi-linear scaling relation between the gamma-ray luminosity and total infrared luminosity for star-forming galaxies, suggesting that these gamma-rays arise from CR interactions. As the high-density medium of Arp 220 makes it an ideal CR calorimeter, the gamma-ray luminosity can be used to measure the efficiency of powering CRs by supernova (SN) remnants given a known supernova rate in Arp 220. We find that this efficiency is about 4.2 ± 2.6% for CRs above 1 GeV.

  10. Connections between galaxy mergers and Starburst: evidence from local Universe

    CERN Document Server

    Luo, Wentao; Zhang, Youcai

    2014-01-01

    Major mergers and interactions between gas-rich galaxies with comparable masses are thought to be the main triggers of starburst. In this work, we study, for a large stellar mass range, the interaction rate of the starburst galaxies in the local universe. We focus independently on central and satellite star forming galaxies extracted from the Sloan Digital Sky Survey. Here the starburst galaxies are selected in the star formation rate (SFR) stellar mass plane with SFR five times larger than the median value found for "star forming" galaxies of the same stellar mass. Through visual inspection of their images together with close companions determined using spectroscopic redshifts, we find that ~50% of the "starburst" populations show evident merger features, i.e., tidal tails, bridges between galaxies, double cores and close companions. In contrast, in the control sample we selected from the normal star forming galaxies, only ~19% of galaxies are associated with evident mergers. The interaction rates may increa...

  11. Physical Galaxy Pairs and Their Effects on Star Formation

    CERN Document Server

    Selim, I M; Bendary, R

    2014-01-01

    We present 776 truly physical galaxy pairs, 569 of them are close pairs and 208 false pairs from Karachentsev (1972) and Reduzzi & Rampazzo (1995) catalogues, which contains 1012 galaxy pairs. Also we carried out star formation activity through the far-infrared emission (FIR) in physical (truly) interacting galaxies in some galaxy pairs and compared them with projection (optical) interacting galaxy pairs. We focused on the triggering of star formation by interactions and analyzed the enhancement of star formation activity in terms of truly physical galaxy pairs. The large fraction of star formation activity is probably due to the activity in the exchange of matter between the truly companions. The star formation rate (SFR) of galaxies in truly galaxy pairs is found to be more enhanced than the apparent pairs.

  12. A new GPU-accelerated hydrodynamical code for numerical simulation of interacting galaxies

    CERN Document Server

    Igor, Kulikov

    2013-01-01

    In this paper a new scalable hydrodynamic code GPUPEGAS (GPU-accelerated PErformance Gas Astrophysic Simulation) for simulation of interacting galaxies is proposed. The code is based on combination of Godunov method as well as on the original implementation of FlIC method, specially adapted for GPU-implementation. Fast Fourier Transform is used for Poisson equation solution in GPUPEGAS. Software implementation of the above methods was tested on classical gas dynamics problems, new Aksenov's test and classical gravitational gas dynamics problems. Collisionless hydrodynamic approach was used for modelling of stars and dark matter. The scalability of GPUPEGAS computational accelerators is shown.

  13. SHIELD II: AGC 198507 - An Extremely Rare Low-Mass Galaxy Interaction?

    Science.gov (United States)

    Nikolina Borg Stevens, Karin; Cannon, John M.; McNichols, Andrew; McQuinn, Kristen B.; Teich, Yaron; SHIELD II Team

    2016-01-01

    The "Survey of HI in Extremely Low-mass Dwarfs II" ("SHIELD II") is a multiwavelength, legacy-class observational campaign that is facilitating the study of both internal and global evolutionary processes in low-mass dwarf galaxies discovered by the Arecibo Legacy Fast ALFA (ALFALFA) survey. New HST imaging of one of these sample galaxies, AGC 198507, has revealed it to be a very rare interacting system; to our knowledge this is one of only a few known interactions in this extreme mass range. WSRT imaging indicates that the bulk of the HI is associated with the more luminous AGC 198507, while low surface brightness gas extends toward and coincides with the less luminous companion, which is separated by roughly 1.5 kpc from AGC 198507. Here we present new VLA B configuration HI imaging that allows us to localize the HI gas, to examine the rotational dynamics of AGC 198507, and to study the nature of star formation in this unique low-mass interacting system.Support for this work was provided by NSF grant AST-1211683 to JMC at Macalester College, and by NASA through grant GO-13750 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555.

  14. Evidence for a Large Stellar Bar in the LSB Galaxy UGC 7321

    CERN Document Server

    Pohlen, M; Lütticke, R; Dettmar, R J

    2003-01-01

    Late-type spiral galaxies are thought to be the dynamically simplest type of disk galaxies and our understanding of their properties plays a key role in the galaxy formation and evolution scenarios. The low surface brightness (LSB) galaxy UGC 7321, a nearby, isolated, ``superthin'' edge-on galaxy, is an ideal object to study those purely disk dominated bulge-less galaxies. Although late type spirals are believed to exhibit the simplest possible structure, even prior observations showed deviations from a pure single component exponential disk in the case of UGC 7321. We present for the first time photometric evidence for peanut-shaped outer isophotes from a deep optical (R-band) image of UGC 7321. Observations and dynamical modeling suggest that boxy/peanut-shaped (b/p) bulges in general form through the buckling instability in bars of the parent galaxy disks. Together with recent HI observations supporting the presence of a stellar bar in UGC 7321 this could be the earliest known case of the buckling process ...

  15. Herschel Inventory of The Agents of Galaxy Evolution (HERITAGE): the Large Magellanic Cloud dust

    CERN Document Server

    Meixner, M; Hony, S; Roman-Duval, J; Robitaille, T; Panuzzo, P; Sauvage, M; Gordon, K; Engelbracht, C; Misselt, K; Okumura, K; Beck, T; Bernard, J -P; Bolatto, A; Bot, C; Boyer, M; Bracker, S; Carlson, L R; Clayton, G C; Chen, C -H R; Churchwell, E; Fukui, Y; Galametz, M; Hora, J L; Hughes, A; Indebetouw, R; Israel, F P; Kawamura, A; Kemper, F; Kim, S; Kwon, E; Lawton, B; Li, A; Long, K S; Marengo, M; Madden, S C; Matsuura, M; Oliveira, J M; Onishi, T; Otsuka, M; Paradis, D; Poglitsch, A; Riebel, D; Reach, W T; Rubio, M; Sargent, B; Sewiło, M; Simon, J D; Skibba, R; Smith, L J; Srinivasan, S; Tielens, A G G M; van Loon, J Th; Whitney, B; Woods, P M

    2010-01-01

    The HERschel Inventory of The Agents of Galaxy Evolution (HERITAGE) of the Magellanic Clouds will use dust emission to investigate the life cycle of matter in both the Large and Small Magellanic Clouds (LMC and SMC). Using the Herschel Space Observatory's PACS and SPIRE photometry cameras, we imaged a 2x8 square degree strip through the LMC, at a position angle of ~22.5 degrees as part of the science demonstration phase of the Herschel mission. We present the data in all 5 Herschel bands: PACS 100 and 160 {\\mu}m and SPIRE 250, 350 and 500 {\\mu}m. We present two dust models that both adequately fit the spectral energy distribution for the entire strip and both reveal that the SPIRE 500 {\\mu}m emission is in excess of the models by 6 to 17%. The SPIRE emission follows the distribution of the dust mass, which is derived from the model. The PAH-to-dust mass (f_PAH) image of the strip reveals a possible enhancement in the LMC bar in agreement with previous work. We compare the gas mass distribution derived from th...

  16. A large CO and HCN line survey of Luminous Infrared Galaxies

    CERN Document Server

    Papadopoulos, P P; Van der Werf, P P; M"uehle, S; Isaak, K; Gao, Y; Papadopoulos, Padelis P.; Greve, Thomas R.; Werf, Paul van der; M\\"uehle, Stefanie; Isaak, Kate; Gao, Yu

    2007-01-01

    A large CO, HCN multi-transition survey of 30 Luminous Infrared Galaxies ($\\rm L_{IR}>10^{11} L_{\\odot}$) is nearing completion with the James Clerk Maxwell Telescope (JCMT) on Mauna Kea (Hawaii), and the IRAM 30-meter telescope at Pico Veleta (Spain). The CO J=1--0, 2--1, 3--2, 4--3,6--5, $ ^{13}$CO J=2--1, HCN J=1--0, 3--2, 4--3 observations, resulting from $\\sim 250$ hours of JCMT, $\\sim 100$ hours of 30-m observing time and data from the literature constitute {\\it the largest extragalactic molecular line survey to date}, and can be used to address a wide range of issues and eventually allow the construction of reliable Spectral Line Energy Distributions (SLEDs) for the molecular gas in local starbursts. First results suggest that: a) HCN and HCO$^+$ J=1--0 line luminosities can be poor mass estimators of dense molecular gas ($\\rm n\\geq 10^4 cm^{-3}$) unless their excitation is accounted for, b) CO cooling of such gas in ULIRGs may be comparable to that of the CII line at $\\rm 158 \\mu m$, and c) low excita...

  17. Luminosity and surface brightness distribution of K-band galaxies from the UKIDSS Large Area Survey

    CERN Document Server

    Smith, Anthony J; Cross, Nicholas J G

    2008-01-01

    We present luminosity and surface brightness distributions of 36,663 galaxies with K-band photometry from the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS), Data Release 3 and optical photometry from Data Release 5 of the Sloan Digital Sky Survey (SDSS). Various features and limitations of the new UKIDSS data are examined, such as a problem affecting Petrosian magnitudes of extended sources. Selection limits in K- and r-band magnitude, K-band surface brightness and K-band radius are included explicitly in the 1/Vmax estimation of the space density and luminosity function. The bivariate brightness distribution in K-band absolute magnitude and surface brightness is presented and found to display a clear luminosity-surface brightness correlation that flattens at high luminosity and broadens at low luminosity, consistent with similar analyses at optical wavelengths. Best fitting Schechter function parameters for the K-band luminosity function are found to be M*-5log h=-23.17 +/- 0.04, alpha=-0.8...

  18. Understanding Giant Radio Galaxy J1420-0545: Large-Scale Morphology, Environment, and Energetics

    CERN Document Server

    Machalski, J; Stawarz, L; Koziel-Wierzbowska, D

    2011-01-01

    In this paper we consider the possibility that the structure of the largest radio galaxy J1420-0545 is formed by a restarted rather than a primary jet activity. This hypothesis is motivated by the unusual morphological properties of the source, suggesting almost ballistic propagation of powerful jets in a particularly low-density environment. New radio observations of J1420-0545 confirm its morphology consisting of only two narrow lobes; no trace of any outer low-density cavity due to the previous jet activity is therefore detected. Different model fits performed using the newly accessed radio data imply relatively young age of the source, its exceptionally high expansion velocity, large jet kinetic power, and confirm particularly low-density environment. We find that it is possible to choose a realistic set of the model parameters for which the hypothetical outer lobes of J1420-0545 are old enough so that their expected radio surface brightness is substantially below the rms noise level of the available radi...

  19. Large Scale Impact of the Cosmological Population of Expanding Radio Galaxies

    CERN Document Server

    Barai, Paramita

    2008-01-01

    We seek to compute the fraction of the volume of the Universe filled by expanding cocoons of the cosmological population of radio galaxies over the Hubble time as well as the magnetic field infused by them, in order to assess their importance in the cosmic evolution of the Universe. Using N-body $\\Lambda$CDM simulations, radio galaxies distributed according to the observed radio luminosity function are allowed to evolve in a cosmological volume as using well defined prescriptions for their expansion. We find that the radio galaxies permeate $10 - 30%$ of the total volume with $\\sim 10^{-8}$ G magnetic field by the present epoch.

  20. Large-Scale Outer Rings of Early-type Disk Galaxies

    CERN Document Server

    Kostiuk, Irina P

    2015-01-01

    We have searched for presence of current star formation in outer stellar rings of early-type disk (S0-Sb) galaxies by inspecting a representative sample of nearby galaxies with rings from the recent Spitzer catalog ARRAKIS (Comeron et al. 2014). We have found that regular rings (of R-type) reveal young stellar population with the age of less than 200~Myr in about half of all the cases, while in the pseudorings (open rings, R'), which inhabit only spiral galaxies, current star formation proceeds almost always.

  1. The Interactive Lecture: Teaching and Learning Technologies for Large Classrooms

    OpenAIRE

    2005-01-01

    Conventional lectures in large classrooms are connected to fundamental didactic problems due to a lack of interactivity and feedback opportunities. In an interactive lecture each student is equipped with a light-weight, mobile device that can be used to interact with the lecturer during the lesson, thus creating an additional channel of communication. These devices support new teaching and learning paradigms such as participatory simulations. In this paper, we present our experiences with the...

  2. Collision Induced Galaxy Formation

    CERN Document Server

    Balland, C; Schäffer, R

    1997-01-01

    We present a semi-analytical model in which galaxy collisions and strong tidal interactions, both in the field and during the collapse phase of groups and clusters help determine galaxy morphology. From a semi-analytical analysis based on simulation results of tidal collisions (Aguilar & White 1985), we propose simple rules for energy exchanges during collisions that allow to discriminate between different Hubble types: efficient collisions result in the disruption of disks and substantial star formation, leading to the formation of elliptical galaxies; inefficient collisions allow a large gas reservoir to survive and form disks. Assuming that galaxy formation proceeds in a Omega_0=1 Cold Dark Matter universe, the model both reproduces a number of observations and makes predictions, among which are the redshifts of formation of the different Hubble types in the field. When the model is normalized to the present day abundance of X-ray clusters, the amount of energy exchange needed to produce elliptical gal...

  3. Game theory in the death galaxy: interaction of cancer and stromal cells in tumour microenvironment.

    Science.gov (United States)

    Wu, Amy; Liao, David; Tlsty, Thea D; Sturm, James C; Austin, Robert H

    2014-08-06

    Preventing relapse is the major challenge to effective therapy in cancer. Within the tumour, stromal (ST) cells play an important role in cancer progression and the emergence of drug resistance. During cancer treatment, the fitness of cancer cells can be enhanced by ST cells because their molecular signalling interaction delays the drug-induced apoptosis of cancer cells. On the other hand, competition among cancer and ST cells for space or resources should not be ignored. We explore the population dynamics of multiple myeloma (MM) versus bone marrow ST cells by using an experimental microecology that we call the death galaxy, with a stable drug gradient and connected microhabitats. Evolutionary game theory is a quantitative way to capture the frequency-dependent nature of interactive populations. Therefore, we use evolutionary game theory to model the populations in the death galaxy with the gradients of pay-offs and successfully predict the future densities of MM and ST cells. We discuss the possible clinical use of such analysis for predicting cancer progression.

  4. Large Scale Structure in Absorption: Gas within and around Galaxy Voids

    CERN Document Server

    Tejos, Nicolas; Crighton, Neil H M; Theuns, Tom; Altay, Gabriel; Finn, Charles W

    2012-01-01

    We investigate the properties of the HI Ly-a absorption systems (Ly-a forest) within and around galaxy voids at z99% c.l.) of Ly-a systems at the edges of galaxy voids with respect to a random distribution, on ~5 h^{-1} Mpc scales. We find no significant difference in the number of systems inside voids with respect to the random expectation. We report differences between both column density (N_{HI}) and Doppler parameter (b_{HI}) distributions of Ly-a systems found inside and at the edge of galaxy voids at the >98% and >90% c.l. respectively. Low density environments (voids) have smaller values for both N_{HI} and b_{HI} than higher density ones (edges of voids). These trends are theoretically expected and also found in GIMIC, a state-of-the-art hydrodynamical simulation. Our findings are consistent with a scenario of at least three types of Ly-alpha: (1) containing embedded galaxies and so directly correlated with galaxies (referred as `halo-like'), (2) correlated with galaxies only because they lie in the s...

  5. The non-gravitational interactions of dark matter in colliding galaxy clusters

    CERN Document Server

    Harvey, David; Kitching, Thomas; Taylor, Andy; Tittley, Eric

    2015-01-01

    Collisions between galaxy clusters provide a test of the non-gravitational forces acting on dark matter. Dark matter's lack of deceleration in the `bullet cluster collision' constrained its self-interaction cross-section \\sigma_DM/m < 1.25cm2/g (68% confidence limit) for long-ranged forces. Using the Chandra and Hubble Space Telescopes we have now observed 72 collisions, including both `major' and `minor' mergers. Combining these measurements statistically, we detect the existence of dark mass at 7.6\\sigma significance. The position of the dark mass has remained closely aligned within 5.8+/-8.2 kpc of associated stars: implying a self-interaction cross-section \\sigma_DM/m < 0.47 cm2/g (95% CL) and disfavoring some proposed extensions to the standard model.

  6. Next Generation Very Large Array Memo No. 8 Science Working Group 3: Galaxy Assembly through Cosmic Time

    CERN Document Server

    Casey, Caitlin M; Lacy, Mark; Hales, Christopher A; Barger, Amy; Narayanan, Desika; Carilli, Chris; Alatalo, Katherine; da Cunha, Elisabete; Emonts, Bjorn; Ivison, Rob; Kimball, Amy; Kohno, Kotaro; Murphy, Eric; Riechers, Dominik; Sargent, Mark; Walter, Fabian

    2015-01-01

    The Next-Generation Very Large Array (ngVLA) will be critical for understanding how galaxies are built and evolve at the earliest epochs. The sensitivity and frequency coverage will allow for the detection of cold gas and dust in `normal' distant galaxies, including the low-J transitions of molecular gas tracers such as CO, HNC, and HCO+; synchrotron and free-free continuum emission; and even the exciting possibility of thermal dust emission at the highest (z~7) redshifts. In particular, by enabling the total molecular gas reservoirs to be traced to unprecedented sensitivities across a huge range of epochs simultaneously -- something no other radio or submillimeter facility will be capable of -- the detection of the crucial low-J transitions of CO in a diverse body of galaxies will be the cornerstone of ngVLA's contribution to high-redshift galaxy evolution science. The ultra-wide bandwidths will allow a complete sampling of radio SEDs, as well as the detection of emission lines necessary for spectroscopic co...

  7. Magnetic fields in spiral galaxies

    Science.gov (United States)

    Beck, Rainer

    2015-12-01

    Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 \\upmu G) and in central starburst regions (50-100 \\upmu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 \\upmu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.—Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edge-on galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young galaxies and their dynamical importance during galaxy evolution, will be studied with

  8. Large and small-scale structures and the dust energy balance problem in spiral galaxies

    CERN Document Server

    Saftly, W; De Geyter, G; Camps, P; Renaud, F; Guedes, J; De Looze, I

    2015-01-01

    The interstellar dust content in galaxies can be traced in extinction at optical wavelengths, or in emission in the far-infrared. Several studies have found that radiative transfer models that successfully explain the optical extinction in edge-on spiral galaxies generally underestimate the observed FIR/submm fluxes by a factor of about three. In order to investigate this so-called dust energy balance problem, we use two Milky Way-like galaxies produced by high-resolution hydrodynamical simulations. We create mock optical edge-on views of these simulated galaxies (using the radiative transfer code SKIRT), and we then fit the parameters of a basic spiral galaxy model to these images (using the fitting code FitSKIRT). The basic model includes smooth axisymmetric distributions along a S\\'ersic bulge and exponential disc for the stars, and a second exponential disc for the dust. We find that the dust mass recovered by the fitted models is about three times smaller than the known dust mass of the hydrodynamical in...

  9. The galaxy hosts and large-scale environments of short-hard (gamma)-ray bursts

    Energy Technology Data Exchange (ETDEWEB)

    Prochaska, J X; Bloom, J S; Chen, H; Foley, R J; Perley, D A; Ramirez-Ruiz, E; Granot, J; Lee, W H; Pooley, D; Alatalo, K; Hurley, K; Cooper, M C; Dupree, A K; Gerke, B F; Hansen, B S; Kalirai, J S; Newman, J A; Rich, R M; Richer, H; Stanford, S A; Stern, D; van Breugel, W

    2006-04-07

    The nature of the progenitors of short duration, hard spectrum, gamma-ray bursts (GRBs) has remained a mystery. Even with the recent localizations of four short-hard GRBs, no transient emission has been found at long wavelengths that directly constrains the progenitor nature. Instead, as was the case in studying the different morphological subclasses of supernovae and the progenitors of long-duration GRBs, we suggest that the progenitors of short bursts can be meaningfully constrained by the environment in which the bursts occur. Here we present the discovery spectra of the galaxies that hosted three short-hard GRBs and the spectrum of a fourth host. The results indicate that these environments, both at the galaxy scale and galaxy-cluster scale, differ substantially from those of long-soft GRBs. The spatial offset of three bursts from old and massive galaxy hosts strongly favors an origin from the merger of compact stellar remnants, such as double neutron stars or a neutron-star black hole binary. The star-forming host of another GRB provides confirmation that, like supernovae of Type Ia, the progenitors of short-hard bursts are created in all galaxy types. This indicates a class of progenitors with a wide distribution of delay times between formation and explosion.

  10. LYα FOREST TOMOGRAPHY FROM BACKGROUND GALAXIES: THE FIRST MEGAPARSEC-RESOLUTION LARGE-SCALE STRUCTURE MAP AT z > 2

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Khee-Gan; Hennawi, Joseph F.; Eilers, Anna-Christina [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Stark, Casey; White, Martin [Department of Astronomy, University of California at Berkeley, B-20 Hearst Field Annex 3411, Berkeley, CA 94720 (United States); Prochaska, J. Xavier [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Schlegel, David J. [University of California Observatories, Lick Observatory, 1156 High Street, Santa Cruz, CA 95064 (United States); Arinyo-i-Prats, Andreu [Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Martí Franquès 1, E-08028 Barcelona (Spain); Suzuki, Nao [Kavli Institute for the Physics and Mathematics of the Universe (IPMU), The University of Tokyo, Kashiwano-ha 5-1-5, Kashiwa-shi, Chiba (Japan); Croft, Rupert A. C. [Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Caputi, Karina I. [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700-AV Groningen (Netherlands); Cassata, Paolo [Instituto de Fisica y Astronomia, Facultad de Ciencias, Universidad de Valparaiso, Av. Gran Bretana 1111, Casilla 5030, Valparaiso (Chile); Ilbert, Olivier; Le Brun, Vincent; Le Fèvre, Olivier [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Garilli, Bianca [INAF-IASF, Via Bassini 15, I-20133, Milano (Italy); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Maccagni, Dario [INAF-Osservatorio Astronomico di Bologna, Via Ranzani,1, I-40127 Bologna (Italy); Nugent, Peter, E-mail: lee@mpia.de [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); and others

    2014-11-01

    We present the first observations of foreground Lyα forest absorption from high-redshift galaxies, targeting 24 star-forming galaxies (SFGs) with z ∼ 2.3-2.8 within a 5' × 14' region of the COSMOS field. The transverse sightline separation is ∼2 h {sup –1} Mpc comoving, allowing us to create a tomographic reconstruction of the three-dimensional (3D) Lyα forest absorption field over the redshift range 2.20 ≤ z ≤ 2.45. The resulting map covers 6 h {sup –1} Mpc × 14 h {sup –1} Mpc in the transverse plane and 230 h {sup –1} Mpc along the line of sight with a spatial resolution of ≈3.5 h {sup –1} Mpc, and is the first high-fidelity map of a large-scale structure on ∼Mpc scales at z > 2. Our map reveals significant structures with ≳ 10 h {sup –1} Mpc extent, including several spanning the entire transverse breadth, providing qualitative evidence for the filamentary structures predicted to exist in the high-redshift cosmic web. Simulated reconstructions with the same sightline sampling, spectral resolution, and signal-to-noise ratio recover the salient structures present in the underlying 3D absorption fields. Using data from other surveys, we identified 18 galaxies with known redshifts coeval with our map volume, enabling a direct comparison with our tomographic map. This shows that galaxies preferentially occupy high-density regions, in qualitative agreement with the same comparison applied to simulations. Our results establish the feasibility of the CLAMATO survey, which aims to obtain Lyα forest spectra for ∼1000 SFGs over ∼1 deg{sup 2} of the COSMOS field, in order to map out the intergalactic medium large-scale structure at (z) ∼ 2.3 over a large volume (100 h {sup –1} Mpc){sup 3}.

  11. A mid-IR study of Hickson Compact Groups I : Probing the Effects of Environment in Galaxy Interactions

    CERN Document Server

    Bitsakis, T; Le Floc'h, E; Diaz-Santos, T; Slater, S K; Xilouris, E; Haynes, M P

    2010-01-01

    Hickson Compact Groups (HCGs) are among the densest galaxy environments of the local universe. To examine the effects of the environment on the infrared properties of these systems, we present an analysis of Spitzer and ISO mid-infrared imaging as well as deep ground based near-infrared imaging of 14 HCGs containing a total of 69 galaxies. Based on mid-infrared color diagnostics we identify the galaxies which appear to host an active nucleus, while using a suite of templates, we fit the complete infrared spectral energy distribution for each group member. We compare our estimates of galaxy mass, star formation rate, total infrared luminosities, and specific star formation rates (sSFR) for our HCG sample, to samples of isolated galaxies and interacting pairs and find that overall there is no discernible difference among them. However, HCGs which can be considered as dynamically "old", host late-type galaxies with a slightly lower sSFR than the one found in dynamically "young" groups. This could be attributed t...

  12. Chandra Observations of the Interacting Galaxies NGC 3395/3396 (Arp 270)

    CERN Document Server

    Brassington, N J; Ponman, T J

    2005-01-01

    In this paper we present the results of a 20 ks high resolution Chandra X-ray observation of the peculiar galaxy pair NGC 3395/3396, a system at a very early stage of merging, and less evolved than the famous Antennae and Mice merging systems. Previously unpublished ROSAT HRI data are also presented. The point source population and the hot diffuse gas in this system are investigated, and compared with other merging galaxy pairs. 16 X-ray point sources are detected in Arp 270, 7 of which are classified as ULXs (Lx > 10^39 erg/s). From spectral fits and the age of the system it seems likely that these are predominantly high mass X-ray binaries. The diffuse gas emits at a global temperature of ~0.5 keV, consistent with temperatures observed in other interacting systems, and we see no evidence of the starburst-driven hot gaseous outflows seen in more evolved systems such as The Mice and The Antennae. It is likely that these features are absent from Arp 270 as the gas has had insufficient time to break out of the ...

  13. Dynamical evolution of topology of large-scale structure. [in distribution of galaxies

    Science.gov (United States)

    Park, Changbom; Gott, J. R., III

    1991-01-01

    The nonlinear effects of statistical biasing and gravitational evolution on the genus are studied. The biased galaxy subset is picked for the first time by actually identifying galaxy-sized peaks above a fixed threshold in the initial conditions, and their subsequent evolution is followed. It is found that in the standard cold dark matter (CDM) model the statistical biasing in the locations of galaxies produces asymmetry in the genus curve and coupling with gravitational evolution gives rise to a shift in the genus curve to the left in moderately nonlinear regimes. Gravitational evolution alone reduces the amplitude of the genus curve due to strong phase correlations in the density field and also produces asymmetry in the curve. Results on the genus of the mass density field for both CDM and hot dark matter models are consistent with previous work by Melott, Weinberg, and Gott (1987).

  14. A Novel Method to Automatically Detect and Measure the Ages of Star Clusters in Nearby Galaxies: Application to the Large Magellanic Cloud

    Science.gov (United States)

    Bitsakis, T.; Bonfini, P.; González-Lópezlira, R. A.; Ramírez-Siordia, V. H.; Bruzual, G.; Charlot, S.; Maravelias, G.; Zaritsky, D.

    2017-08-01

    We present our new, fully automated method to detect and measure the ages of star clusters in nearby galaxies, where individual stars can be resolved. The method relies purely on statistical analysis of observations and Monte-Carlo simulations to define stellar overdensities in the data. It decontaminates the cluster color-magnitude diagrams and, using a revised version of the Bayesian isochrone fitting code of Ramírez-Siordia et al., estimates the ages of the clusters. Comparisons of our estimates with those from other surveys show the superiority of our method to extract and measure the ages of star clusters, even in the most crowded fields. An application of our method is shown for the high-resolution, multiband imaging of the Large Magellanic Cloud. We detect 4850 clusters in the 7 deg2 we surveyed, 3451 of which have not been reported before. Our findings suggest multiple epochs of star cluster formation, with the most probable occurring ˜310 Myr ago. Several of these events are consistent with the epochs of the interactions among the Large and Small Magellanic Clouds, and the Galaxy, as predicted by N-body numerical simulations. Finally, the spatially resolved star cluster formation history may suggest an inside-out cluster formation scenario throughout the LMC, for the past 1 Gyr.

  15. Testing gravity on large scales. The skewness of the galaxy distribution at z~1

    CERN Document Server

    Marinoni, C; Cappi, A; Le Fèvre, O; Mazure, A; Meneux, B; Pollo, A; Iovino, A; McCracken, H J; Scaramella, R; De la Torre, S; Virey, J M; Bottini, D; Garilli, B; Le Brun, V; MacCagni, D; Picat, J P; Scodeggio, M; Tresse, L; Vettolani, G; Zanichelli, A; Adami, C; Arnouts, S; Bardelli, S; Bolzonella, M; Charlot, S; Ciliegi, P; Contini, T; Foucaud, S; Franzetti, P; Gavignaud, I; Ilbert, O; Lamareille, F; Marano, B; Mathez, G; Merighi, R; Paltani, S; Pellò, R; Pozzetti, L; Radovich, M; Vergani, D; Zamorani, G; Zucca, E; Abbas, U; Bondi, M; Bongiorno, A; Brinchmann, J; Buzzi, A; Cucciati, O; de Ravel, L; Gregorini, L; Mellier, Y; Merluzzi, P; Pérez-Montero, E; Taxil, P; Temporin, S; Walcher, C J

    2008-01-01

    We study the evolution of the low-order moments of the galaxy overdensity distribution over the redshift interval 0.7galaxy biasing to avoid disagreement between theory and observations.

  16. Dark and luminous matter in the NGC 3992 group of galaxies, I. The large barred spiral NGC 3992

    CERN Document Server

    Bottema, R; Bottema, Roelof; Verheijen, Marc A.W.

    2002-01-01

    Detailed neutral hydrogen observations have been obtained of the large barred spiral galaxy NGC 3992 and its three small companion galaxies, UGC 6923, UGC 6940, and UGC 6969. For the main galaxy, the HI distribution is regular with a low level radial extension outside the stellar disc. However, at exactly the region of the bar, there is a pronounced central HI hole in the gas distribution. Likely gas has been transported inwards by the bar and because of the emptyness of the hole no large accretion events can have happened in recent galactic times. The gas kinematics is very regular and it is demonstrated that the influence of the bar potential on the velocity field is negligible. A precise and extended rotation curve has been derived showing some distinct features which can be explained by the non-exponential radial light distribution of NGC 3992. The decomposition of the rotation curve gives a slight preference for a sub maximal disc, though a range of disc contributions, up to a maximum disc situation fits...

  17. The NGC 1614 Interacting Galaxy: Molecular Gas Feeding a "Ring of Fire"

    CERN Document Server

    König, S; Muller, S; Beswick, R J; Gallagher, J S

    2013-01-01

    Minor mergers frequently occur between giant and gas-rich low mass galaxies and can provide significant amounts of interstellar matter to refuel star formation and power AGN in the giant systems. Major starbursts and/or AGN result when fresh gas is transported and compressed in the central regions of the giant galaxy. This is the situation in NGC1614, whose molecular medium we explore at half arcsecond angular resolution through our observations of 12CO(2-1) emission using the SMA. We compare our maps with optical and Pa alpha, HST and high angular resolution radio continuum images to study the relationships between dense molecular gas and the starburst region. The most intense CO emission occurs in a partial ring with ~230pc radius around the center, with an extension to the north-west into the dust lane that contains diffuse molecular gas. We resolve 10 GMAs in the ring which has an integrated molecular mass of ~8x10^8M_sun. Our observations filter out a large part of the CO(1-0) emission mapped at shorter ...

  18. Massive star formation in Wolf-Rayet galaxies. V: Star formation rates, masses and the importance of galaxy interactions

    CERN Document Server

    Lopez-Sanchez, Angel R

    2010-01-01

    (Abridged) We have performed a comprehensive analysis of a sample of 20 starburst galaxies, most of them classified as Wolf-Rayet galaxies. In this paper, the last of the series, we analyze the global properties of our galaxy sample using multiwavelength data (X-ray, FUV, optical, NIR, FIR, and radio). The agreement between our Ha-based SFR and those provided by indicators at other wavelengths is remarkable, but we consider that the new Ha-based calibration provided by Calzetti et al. (2007) should be preferred over older calibrations. The FUV-based SFR provides a powerful tool to analyze the star-formation activity in both global and local scales independently to the Ha emission. We provide empirical relationships between the ionized gas mass, neutral gas mass, dust mass, stellar mass, and dynamical mass with the B-luminosity. Although all mass estimations increase with increasing luminosity, we find important deviations to the general trend in some objects, that seem to be consequence of their particular ev...

  19. JSPAM: A restricted three-body code for simulating interacting galaxies

    Science.gov (United States)

    Wallin, J. F.; Holincheck, A. J.; Harvey, A.

    2016-07-01

    Restricted three-body codes have a proven ability to recreate much of the disturbed morphology of actual interacting galaxies. As more sophisticated n-body models were developed and computer speed increased, restricted three-body codes fell out of favor. However, their supporting role for performing wide searches of parameter space when fitting orbits to real systems demonstrates a continuing need for their use. Here we present the model and algorithm used in the JSPAM code. A precursor of this code was originally described in 1990, and was called SPAM. We have recently updated the software with an alternate potential and a treatment of dynamical friction to more closely mimic the results from n-body tree codes. The code is released publicly for use under the terms of the Academic Free License ("AFL") v. 3.0 and has been added to the Astrophysics Source Code Library.

  20. JSPAM: A restricted three-body code for simulating interacting galaxies

    CERN Document Server

    Wallin, John; Harvey, Allen

    2015-01-01

    Restricted three-body codes have a proven ability to recreate much of the disturbed morphology of actual interacting galaxies. As more sophisticated n-body models were developed and computer speed increased, restricted three-body codes fell out of favor. However, their supporting role for performing wide searches of parameter space when fitting orbits to real systems demonstrates a continuing need for their use. Here we present the model and algorithm used in the JSPAM code. A precursor of this code was originally described in 1990, and was called SPAM. We have recently updated the software with an alternate potential and a treatment of dynamical friction to more closely mimic the results from n-body tree codes. The code is released publicly for use under the terms of the Academic Free License (AFL) v.3.0 and has been added to the Astrophysics Source Code Library.

  1. The relation between bar formation, galaxy luminosity, and environment

    CERN Document Server

    Corsini, E M; Sanchez-Janssen, R; Aguerri, J A L; Zarattini, S

    2013-01-01

    We derive the bar fraction in three different environments ranging from the field to Virgo and Coma clusters, covering an unprecedentedly large range of galaxy luminosities (or, equivalently, stellar masses). We confirm that the fraction of barred galaxies strongly depends on galaxy luminosity. We also show that the difference between the bar fraction distributions as a function of galaxy luminosity (and mass) in the field and Coma cluster are statistically significant, with Virgo being an intermediate case. We interpret this result as a variation of the effect of environment on bar formation depending on galaxy luminosity. We speculate that brighter disk galaxies are stable enough against interactions to keep their cold structure, thus, the interactions are able to trigger bar formation. For fainter galaxies the interactions become strong enough to heat up the disks inhibiting bar formation and even destroying the disks. Finally, we point out that the controversy regarding whether the bar fraction depends on...

  2. Large-scale structure and galaxy motions in the Leo/Cancer constellations

    CERN Document Server

    Karachentsev, Igor D; Karachentseva, Valentina E

    2015-01-01

    In the region of the sky limited by the coordinates RA$=7.0^h...12.0^h$, Dec$=0^\\circ...+20^\\circ$ and extending from the Virgo Cluster to the South Pole of the Local Supercluster, we consider the data on the galaxies with radial velocities $V_{LG}\\lesssim 2000$ km/s. For 290 among them, we determine individual distances and peculiar velocities. In this region, known as the local velocity anomaly zone, there are 23 groups and 20 pairs of galaxies for which the estimates of virial/orbital masses are obtained. A nearby group around NGC3379 = Leo I and NGC3627 as well as the Local Group show the motion from the Local Void in the direction of Leo cloud with a characteristic velocity of about 400 km/s. Another rich group of galaxies around NGC3607 reveals peculiar velocity of about -420 km/s in the frame of reference related with the cosmic background radiation. A peculiar scattered association of dwarf galaxies Gemini Flock at a distance of 8 Mpc has the radial velocity dispersion of only 20 km/s and the size of ...

  3. ALMA Reveals Large Molecular Gas Reservoirs in Ancestors of Milky Way-Mass Galaxies at z=1.2-1.3

    Science.gov (United States)

    Papovich, Casey J.; Labbe, Ivo; Glazebrook, Karl; Quadri, Ryan; Bekiaris, Georgios; Dickinson, Mark; Finkelstein, Steven L.; Fisher, David B.; Inami, Hanae; Livermore, Rachael C.; Spitler, Lee; Straatman, Caroline; Tran, Kim-Vy

    2017-01-01

    The gas accretion and star-formation histories of galaxies like the Milky Way remain an outstanding problem in astrophysics. Observations show that 8 billion years ago, at redshifts z > 1, the progenitors to Milky Way-mass galaxies were forming stars 30 times faster than today and predicted to be rich in molecular gas, in contrast with low present-day gas fractions (ALMA Band 4 observations, we detected the molecular gas using the CO(J=3-2) emission (rest-frame 345.8 GHz) in a sample of galaxies at redshifts z=1.2-1.3, selected to have the stellar mass (Log M*/M⊙ =10.2) and star-formation rate (SFR = 20 M⊙ yr-1) of the main progenitors of today's Milky Way-mass galaxies at this epoch. We show that with relatively short ALMA integrations, we now probe efficiently the CO luminosities of z > 1 star-forming galaxies a factor two lower than was possible previously. The CO emission from these galaxies reveals large molecular gas reservoirs, with a ratio of molecular-gas mass-to-stellar mass of ~100%, indicating most of the baryons are in cold gas, not stars. The ratio of the galaxies' total luminosity from star formation to CO luminosity corresponds to long gas-consumption timescales. Compared to local spiral galaxies, the star-formation efficiency, estimated from the ratio of total IR luminosity to CO emission, has remained nearly constant since redshift z=1.2, despite the order of magnitude decrease in gas fraction, consistent with results for more massive and more luminous galaxies at this epoch. This implies that the the physical processes that determine the rate at which gas cools to form stars in distant galaxies appear to be similar to that in local galaxies.

  4. 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 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 formation as well as a classical accretion disc.

  5. Large Binocular Telescope and Sptizer Spectroscopy of Star-forming Galaxies at 1 Extinction and Star Formation Rate Indicators

    Science.gov (United States)

    Rujopakarn, W.; Rieke, G. H.; Papovich, C. J.; Weiner, B. J.; Rigby, Jane; Rex, M.; Bian, F.; Kuhn, O. P.; Thompson, D.

    2012-01-01

    We present spectroscopic observations in the rest-frame optical and near- to mid-infrared wavelengths of four gravitationally lensed infrared (IR) luminous star-forming galaxies at redshift 1 extinction, Av, of these systems, as well as testing star formation rate (SFR) indicators against the SFR measured by fitting spectral energy distributions to far-IR photometry. Our galaxies occupy a range of Av from 0 to 5.9 mag, larger than previously known for a similar range of IR luminosities at these redshifts. Thus, estimates of SFR even at z 2 must take careful count of extinction in the most IR luminous galaxies.We also measure extinction by comparing SFR estimates from optical emission lines with those from far- IR measurements. The comparison of results from these two independent methods indicates a large variety of dust distribution scenarios at 1 extinction, the Ha SFR indicator underestimates the SFR; the size of the necessary correction depends on the IR luminosity and dust distribution scenario. Individual SFR estimates based on the 6.2µm polycyclic aromatic hydrocarbon emission line luminosity do not show a systematic discrepancy with extinction, although a considerable, 0.2 dex, scatter is observed.

  6. Large gas reservoirs and free-free emission in two lensed star-forming galaxies at z=2.7

    CERN Document Server

    Aravena, M; Aguirre, J E; Ashby, M L N; Benson, B A; Bothwell, M; Brodwin, M; Carlstrom, J E; Chapman, S C; Crawford, T M; de Breuck, C; Fassnacht, C D; Gonzalez, A H; Greve, T R; Gullberg, B; Hezaveh, Y; Holder, G P; Holzapfel, W L; Keisler, R; Malkan, M; Marrone, D P; McIntyre, V; Reichardt, C L; Sharon, K; Spilker, J S; Stalder, B; Stark, A A; Vieira, J D; Weiss, A

    2013-01-01

    We report the detection of CO(1-0) line emission in the bright, lensed star-forming galaxies SPT-S 233227-5358.5 (z=2.73) and SPT-S 053816-5030.8 (z=2.78), using the Australia Telescope Compact Array (ATCA). Both galaxies were discovered in a large-area millimeter survey with the South Pole Telescope (SPT) and found to be gravitationally lensed by intervening structures. The measured CO intensities imply galaxies with molecular gas masses of (3.2 \\pm 0.5)x10^10 (mu/15)^{-1}(X_CO/0.8) M_sun and (1.7 \\pm 0.3)x10^10 (mu/20)^{-1}(X_CO/0.8) M_sun, and gas depletion timescales of 4.9x10^7 (X_CO/0.8) yr and 2.6x10^7 (X_CO/0.8) yr, respectively, where mu corresponds to the lens magnification and X_CO is the CO luminosity to gas mass conversion factor. In the case of SPT-S 053816-5030.8, we also obtained significant detections of the rest-frame 115.7 and 132.4 GHz radio continuum. Based on the radio to infrared spectral energy distribution and an assumed synchrotron spectral index, we find that 42 \\pm 10 % and 55 \\pm ...

  7. Testing gravity on large scales by combining weak lensing with galaxy clustering using CFHTLenS and BOSS CMASS

    CERN Document Server

    Alam, Shadab; More, Surhud; Ho, Shirley; Mandelbaum, Rachel

    2016-01-01

    We measure a combination of gravitational lensing, galaxy clustering, and redshift-space distortions called $E_G$. The quantity $E_G$ probes both parts of metric potential and is insensitive to galaxy bias and $\\sigma_8$. These properties make it an attractive statistic to test $\\Lambda$CDM, General Relativity and its alternate theories. We have combined CMASS DR11 with CFHTLenS and recent measurements of $\\beta$ from RSD analysis, and find $E_G(z = 0.57) = 0.42 \\pm 0.056$, an 13\\% measurement in agreement with the prediction of general relativity $E_G(z = 0.57) = 0.396 \\pm 0.011$ using the Planck 2015 cosmological parameters. We have corrected our measurement for various observational and theoretical systematics. Our measurement is consistent with the first measurement of $E_G$ using CMB lensing in place of galaxy lensing (Pullen et. al. 2015a) at small scales, but shows 2.8$\\sigma$ tension when compared with their final results including large scales. This analysis with future surveys will provide improved ...

  8. An Extreme Metallicity, Large-Scale Outflow from a Star-Forming Galaxy at z ~ 0.4

    CERN Document Server

    Muzahid, Sowgat; Churchil, Christopher W; Charlton, Jane C; Nielsen, Nikole M; Mathes, Nigel L; Trujillo-Gomez, Sebastian

    2015-01-01

    We present a detailed analysis of a large-scale galactic outflow in the CGM of a massive (M_h ~ 10^12.5 Msun), star-forming (6.9 Msun/yr), sub-L* (0.5 L_B*) galaxy at z=0.39853 that exhibits a wealth of metal-line absorption in the spectra of the background quasar Q 0122-003 at an impact parameter of 163 kpc. The galaxy inclination angle (i=63 degree) and the azimuthal angle (Phi=73 degree) imply that the QSO sightline is passing through the projected minor-axis of the galaxy. The absorption system shows a multiphase, multicomponent structure with ultra-strong, wide velocity spread OVI (logN = 15.16\\pm0.04, V_{90} = 419 km/s) and NV (logN = 14.69\\pm0.07, V_{90} = 285 km/s) lines that are extremely rare in the literature. The highly ionized absorption components are well explained as arising in a low density (10^{-4.2} cm^{-3}), diffuse (10 kpc), cool (10^4 K) photoionized gas with a super-solar metallicity ([X/H] > 0.3). From the observed narrowness of the Lyb profile, the non-detection of SIV absorption, and...

  9. The Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS): Survey design, data catalogue and GAMA/WiggleZ spectroscopy

    CERN Document Server

    Ching, John H Y; Croom, Scott M; Johnston, Helen M; Pracy, Michael B; Couch, Warrick J; Hopkins, A M; Jurek, Russell J; Pimbblet, K A

    2016-01-01

    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 roughly 800 square degrees 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 i_mod < 20.5 in Sloan Digital Sky Survey (SDSS) images. Both galaxies and 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 5,000 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% of the LARGESS spectroscopic sample are radio AGN (median redshift z = 0.44), and 15% are ne...

  10. Testing gravity on large scales by combining weak lensing with galaxy clustering using CFHTLenS and BOSS CMASS

    Science.gov (United States)

    Alam, Shadab; Miyatake, Hironao; More, Surhud; Ho, Shirley; Mandelbaum, Rachel

    2017-03-01

    We measure a combination of gravitational lensing, galaxy clustering and redshift-space distortions (RSDs) called EG. The quantity EG probes both parts of metric potential and is insensitive to galaxy bias and σ8. These properties make it an attractive statistic to test lambda cold dark matter, general relativity and its alternate theories. We have combined CMASS Data Release 11 with CFHTLenS and recent measurements of β from RSD analysis, and find EG(z = 0.57) = 0.42 ± 0.056, a 13 per cent measurement in agreement with the prediction of general relativity EG(z = 0.57) = 0.396 ± 0.011 using the Planck 2015 cosmological parameters. We have corrected our measurement for various observational and theoretical systematics. Our measurement is consistent with the first measurement of EG using cosmic microwave background lensing in place of galaxy lensing at small scales, but shows 2.8σ tension when compared with their final results including large scales. This analysis with future surveys will provide improved statistical error and better control over systematics to test general relativity and its alternate theories.

  11. The properties of a large volume-limited sample of face-on low surface brightness disk galaxies

    Institute of Scientific and Technical Information of China (English)

    Guo-Hu Zhong; Yan-Chun Liang; Feng-Shan Liu; Francois Hammer; Karen Disseau; Li-Cai Deng

    2012-01-01

    We select a large volume-limited sample of low surface brightness galaxies (LSBGs,2021) to investigate in detail their statistical properties and their differences from high surface brightness galaxies (HSBGs,3639).The distributions of stellar masses of LSBGs and HSBGs are nearly the same and they have the same median values.Thus this volume-limited sample has good completeness and is further removed from the effect of stellar masses on their other properties when we compare LSBGs to HSBGs.We found that LSBGs tend to have lower stellar metallicities and lower effective dust attenuations,indicating that they have lower dust than HSBGs.The LSBGs have relatively higher stellar mass-to-light ratios,higher gas fractions,lower star forming rates (SFRs),and lower specific SFRs than HSBGs.Moreover,with the decreasing surface brightness,gas fraction increases,but the SFRs and specific SFRs decrease rapidly for the sample galaxies.This could mean that the star formation histories between LSBGs and HSBGs are different,and HSBGs may have stronger star forming activities than LSBGs.

  12. Chemical tagging with APOGEE: discovery of a large population of N-rich stars in the inner Galaxy

    Science.gov (United States)

    Schiavon, Ricardo P.; Zamora, Olga; Carrera, Ricardo; Lucatello, Sara; Robin, A. C.; Ness, Melissa; Martell, Sarah L.; Smith, Verne V.; García-Hernández, D. A.; Manchado, Arturo; Schönrich, Ralph; Bastian, Nate; Chiappini, Cristina; Shetrone, Matthew; Mackereth, J. Ted; Williams, Rob A.; Mészáros, Szabolcs; Allende Prieto, Carlos; Anders, Friedrich; Bizyaev, Dmitry; Beers, Timothy C.; Chojnowski, S. Drew; Cunha, Katia; Epstein, Courtney; Frinchaboy, Peter M.; García Pérez, Ana E.; Hearty, Fred R.; Holtzman, Jon A.; Johnson, Jennifer A.; Kinemuchi, Karen; Majewski, Steven R.; Muna, Demitri; Nidever, David L.; Nguyen, Duy Cuong; O'Connell, Robert W.; Oravetz, Daniel; Pan, Kaike; Pinsonneault, Marc; Schneider, Donald P.; Schultheis, Matthias; Simmons, Audrey; Skrutskie, Michael F.; Sobeck, Jennifer; Wilson, John C.; Zasowski, Gail

    2017-02-01

    Formation of globular clusters (GCs), the Galactic bulge, or galaxy bulges in general is an important unsolved problem in Galactic astronomy. Homogeneous infrared observations of large samples of stars belonging to GCs and the Galactic bulge field are one of the best ways to study these problems. We report the discovery by APOGEE (Apache Point Observatory Galactic Evolution Experiment) of a population of field stars in the inner Galaxy with abundances of N, C, and Al that are typically found in GC stars. The newly discovered stars have high [N/Fe], which is correlated with [Al/Fe] and anticorrelated with [C/Fe]. They are homogeneously distributed across, and kinematically indistinguishable from, other field stars within the same volume. Their metallicity distribution is seemingly unimodal, peaking at [Fe/H] ˜ -1, thus being in disagreement with that of the Galactic GC system. Our results can be understood in terms of different scenarios. N-rich stars could be former members of dissolved GCs, in which case the mass in destroyed GCs exceeds that of the surviving GC system by a factor of ˜8. In that scenario, the total mass contained in so-called `first-generation' stars cannot be larger than that in `second-generation' stars by more than a factor of ˜9 and was certainly smaller. Conversely, our results may imply the absence of a mandatory genetic link between `second-generation' stars and GCs. Last, but not least, N-rich stars could be the oldest stars in the Galaxy, the by-products of chemical enrichment by the first stellar generations formed in the heart of the Galaxy.

  13. Next Generation Very Large Array Memo No. 7 Science Working Group 2: "Galaxy Ecosystems": The Matter Cycle in and Around Galaxies

    CERN Document Server

    Leroy, Adam K; Armus, Lee; Brogan, Crystal; Meyer, Jennifer Donovan; Evans, Aaron; Hunter, Todd; Johnson, Kelsey; Koda, Jin; Meier, David S; Menten, Karl; Mills, Elizabeth; Momjian, Emmanuel; Ott, Juergen; Owen, Frazer; Reid, Mark; Rosolowsky, Erik; Schinnerer, Eva; Scoville, Nicholas; Spekkens, Kristine; van Zee, Liese; Wong, Tony

    2015-01-01

    This white paper discusses how a "next-generation" Very Large Array (ngVLA) operating in the frequency range 1-116 GHz could be a groundbreaking tool to study the detailed astrophysics of the "matter cycle" in the Milky Way and other galaxies. If optimized for high brightness sensitivity, the ngVLA would bring detailed microwave spectroscopy and modeling of the full radio spectral energy distribution into regular use as survey tools at resolutions of 0.1- 1 arcseconds. This wavelength range includes powerful diagnostics of density, excitation, and chemistry in the cold ISM, as well as multiple tracers of the rate of recent star formation, the magnetic field, shocks, and properties of the ionized ISM. We highlight design considerations that would make this facility revolutionary in this area, the foremost of which is a large amount of collecting area on ~km-length baselines. We also emphasize the strong case for harnessing the large proposed collecting area of the ngVLA for very long baseline applications as p...

  14. Large-radius bipolaron and the polaron-polaron interaction

    Energy Technology Data Exchange (ETDEWEB)

    Kashirina, N I [Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, Kiev (Ukraine); Lakhno, Viktor D [Institute of Mathematical Problems of Biology, Russian Academy of Sciences, Pushchino, Moscow region (Russian Federation)

    2010-08-09

    Research on the polaron-polaron interaction and the theory of large-radius bipolarons are reviewed. The difference between the two-center and one-center continuum bipolaron models in isotropic and anisotropic crystals is discussed. It is shown that the inclusion of electron-electron correlations can significantly reduce the bipolaron and D{sup -}-center energies as well as the energies of exchange-bound pairs of shallow hydrogen-like centers. The two-center bipolaron configuration corresponds to a shallow secondary minimum and is unstable. The phonon-mediated exchange interaction between Pekar polarons has an antiferromagnetic nature and exceeds the ferromagnetic interaction due to the Coulomb interaction of electrons localized in polaron potential wells. The possibility that the superfluidity of bipolarons can give rise to high-temperature superconductivity is discussed and problems related to the Wigner crystallization of a polaron gas are examined. (reviews of topical problems)

  15. Orbits of Massive Satellite Galaxies: I. A Close Look at the Large Magellanic Cloud and a New Orbital History for M33

    CERN Document Server

    Patel, Ekta; Sohn, Tony

    2016-01-01

    The Milky Way (MW) and M31 both harbor massive satellite galaxies, the Large Magellanic Cloud (LMC) and M33, which may comprise up to 10 per cent of their host's total mass. Massive satellites can change the orbital barycentre of the host-satellite system by tens of kiloparsecs and are cosmologically expected to harbor dwarf satellite galaxies of their own. Assessing the impact of these effects depends crucially on the orbital histories of the LMC and M33. Here, we revisit the dynamics of the MW-LMC system and present the first detailed analysis of the M31-M33 system utilizing high precision proper motions and statistics from the dark matter-only Illustris cosmological simulation. With the latest Hubble Space Telescope proper motion measurements of M31, we reliably constrain M33's interaction history with its host. In particular, like the LMC, M33 is either on its first passage (t_{inf} =2x10^12 Msun), it is on a long period orbit of about 6 Gyr. Cosmological analogs of the LMC and M33 identified in Illustris...

  16. Comparison of the Large Scale Clustering in the APM and the EDSGC Galaxy Surveys

    CERN Document Server

    Szapudi, I; Szapudi, István

    1997-01-01

    Clustering statistics are compared in the Automatic Plate Machine (APM) and the Edinburgh/Durham Southern Galaxy Catalogue (EDSGC) angular galaxy surveys. Both surveys were independently constructed from scans of the same adjacent UK IIIa--J Schmidt photographic plates with the APM and COSMOS microdensitometers, respectively. The comparison of these catalogs is a rare practical opportunity to study systematic errors, which cannot be achieved via simulations or theoretical methods. On intermediate scales, $0.1^\\circ < \\theta < 0.5^\\circ$, we find good agreement for the cumulants or reduced moments of counts in cells up to sixth order. On larger scales there is a small disagreement due to edge effects in the EDSGC, which covers a smaller area. On smaller scales, we find a significant disagreement that can only be attributed to differences in the construction of the surveys, most likely the dissimilar deblending of crowded fields. The overall agreement of the APM and EDSGC is encouraging, and shows that th...

  17. An analytical dynamo solution for large-scale magnetic fields of galaxies

    CERN Document Server

    Chamandy, Luke

    2016-01-01

    We present an effectively global analytical asymptotic galactic dynamo solution for the regular magnetic field of an axisymmetric thin disc in the saturated state. This solution is constructed by combining two well-known types of local galactic dynamo solution, parameterized by the disc radius. Namely, the critical (zero growth) solution obtained by treating the dynamo equation as a perturbed diffusion equation is normalized using a non-linear solution that makes use of the `no-$z$' approximation and the dynamical $\\alpha$-quenching non-linearity. This overall solution is found to be reasonably accurate when compared with detailed numerical solutions. It is thus potentially useful as a tool for predicting observational signatures of magnetic fields of galaxies. In particular, such solutions could be painted onto galaxies in cosmological simulations to enable the construction of synthetic polarized synchrotron and Faraday rotation measure (RM) datasets. Further, we explore the properties of our numerical solut...

  18. Large-scale clustering of galaxies in the CfA Redshift Survey

    Science.gov (United States)

    Vogeley, Michael S.; Park, Changbom; Geller, Margaret J.; Huchra, John P.

    1992-01-01

    The power spectrum of the galaxy distribution in the Center for Astrophysics Redshift Survey (de Lapparent et al., 1986; Geller and Huchra, 1989; and Huchra et al., 1992) is measured up to wavelengths of 200/h Mpc. Results are compared with several cosmological simulations with Gaussian initial conditions. It is shown that the power spectrum of the standard CDM model is inconsistent with the observed power spectrum at the 99 percent confidence level.

  19. Minor Mergers or Progenitor Bias? The Stellar Ages of Small and Large Quenched Galaxies

    Science.gov (United States)

    Fagioli, Martina; Carollo, C. Marcella; Renzini, Alvio; Lilly, Simon J.; Onodera, Masato; Tacchella, Sandro

    2016-11-01

    We investigate the origin of the evolution of the population-averaged size of quenched galaxies (QGs) through a spectroscopic analysis of their stellar ages. This evolution has been claimed to arise from either the size growth of individual galaxies through a sequence of dry minor mergers, or the addition of larger, newly quenched galaxies to the pre-existing population (i.e., a progenitor bias effect). We use the 20k zCOSMOS-bright spectroscopic survey to select bona fide QGs at 0.2 < z < 0.8. We stack their spectra in bins of redshift, stellar mass, and size to compute stellar population parameters through fits to the rest-frame optical spectra and Lick indices. The size-age relation differs below and above ˜1011 M ⊙: at 10.5\\lt {log} {M}* /{M}⊙ \\lt 11, at all redshifts the stellar populations of the largest galaxies are younger than those of the smaller counterparts, indicating progenitor bias as the main driver of the average size evolution. In contrast, at higher masses, there is no clear size-age trend, supporting a substantial role of dry mergers in increasing with cosmic time the sizes of these most massive QGs. The [α/Fe] abundance ratios of QGs are (i) above-solar over the entire redshift range of our analysis, hinting at universally short timescales for the buildup of the stellar populations of QGs, and (ii) similar at all masses and sizes, suggesting similar (short) timescales for the whole QG population—and strengthening the role of mergers in the buildup of the most massive QGs in the universe.

  20. THE ROLE OF GALAXY INTERACTION IN ENVIRONMENTAL DEPENDENCE OF THE STAR FORMATION ACTIVITY AT z {approx_equal} 1.2

    Energy Technology Data Exchange (ETDEWEB)

    Ideue, Y. [Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama 790-8577 (Japan); Taniguchi, Y.; Shioya, Y.; Kajisawa, M. [Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho, Matsuyama 790-8577 (Japan); Nagao, T. [The Hakubi Project, Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto 606-8302 (Japan); Trump, J. R. [UCO/Lick, UC Santa Cruz, Santa Cruz, CA 95064 (United States); Vergani, D. [INAF-Osservatorio Astronomico di Bolona, Via Ranzani 1, I-40127 Bologna (Italy); Iovino, A. [INSF-Osservatorio Astronomico di Brera, Via Brera 28, I-20159 Milano (Italy); Koekemoer, A. M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Le Fevre, O. [Laboratoire d' Astrophysique de Marseile, CNRS-Universite d' Aix-Marseille, 38 rue Frederic Joliot Curie, F-13388 Marseille (France); Ilbert, O. [Observatoriore de Marseille-Provence, Pole de I' Etoile Site de Chiateau-Gombert, 38 rue Frederic Joliot-Curie, 13388 Marseille Cedex 13 (France); Scoville, N. Z., E-mail: ideue@cosmos.phys.sci.ehime-u.ac.jp [Department of Astronomy, MS 105-24, California Institute of Technology, Pasadena, CA 91125 (United States)

    2012-03-01

    In order to understand environmental effects on star formation in high-redshift galaxies, we investigate the physical relationships between the star formation activity, stellar mass, and environment for z {approx_equal} 1.2 galaxies in the 2 deg{sup 2} COSMOS field. We estimate star formation using the [O II]{lambda}3727 emission line and environment from the local galaxy density. Our analysis shows that for massive galaxies (M{sub *} {approx}> 10{sup 10} M{sub Sun }), the fraction of [O II] emitters in high-density environments ({Sigma}{sub 10th} {approx}> 3.9 Mpc{sup -2}) is 1.7 {+-} 0.4 times higher than in low-density environments ({Sigma}{sub 10th} {approx}< 1.5 Mpc{sup -2}), while the [O II] emitter fraction does not depend on environment for low-mass M{sub *} {approx}< 10{sup 10} M{sub Sun} galaxies. In order to understand what drives these trends, we investigate the role of companion galaxies in our sample. We find that the fraction of [O II] emitters in galaxies with companions is 2.4 {+-} 0.5 times as high as that in galaxies without companions at M{sub *} {approx}> 10{sup 10} M{sub Sun }. In addition, massive galaxies are more likely to have companions in high-density environments. However, although the number of star-forming galaxies increases for massive galaxies with close companions and in dense environments, the average star formation rate of star-forming galaxies at a given mass is independent of environment and the presence/absence of a close companion. These results suggest that interactions and/or mergers in a high-density environment could induce star formation in massive galaxies at z {approx} 1.2, increasing the fraction of star-forming galaxies with M{sub *} {approx}> 10{sup 10} M{sub Sun }.

  1. DISCOVERY OF MASSIVE, MOSTLY STAR FORMATION QUENCHED GALAXIES WITH EXTREMELY LARGE Lyα EQUIVALENT WIDTHS AT z ∼ 3

    Energy Technology Data Exchange (ETDEWEB)

    Taniguchi, Yoshiaki; Kajisawa, Masaru; Kobayashi, Masakazu A. R.; Nagao, Tohru; Shioya, Yasuhiro [Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho, Matsuyama 790-8577 (Japan); Scoville, Nick Z.; Capak, Peter L. [Department of Astronomy, California Institute of Technology, MS 105-24, Pasadena, CA 91125 (United States); Sanders, David B. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Toft, Sune [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Mariesvej 30, DK-2100 Copenhagen (Denmark); McCracken, Henry J. [Institut d’Astrophysique de Paris, UMR7095 CNRS, Université Pierre et Marie Curie, 98 bis Boulevard Arago, F-75014 Paris (France); Le Fèvre, Olivier; Tasca, Lidia; Ilbert, Olivier [Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille), UMR 7326, F-13388 Marseille (France); Sheth, Kartik [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Renzini, Alvio [Dipartimento di Astronomia, Universita di Padova, vicolo dell’Osservatorio 2, I-35122 Padua (Italy); Lilly, Simon; Carollo, Marcella; Kovač, Katarina [Department of Physics, ETH Zurich, 8093 Zurich (Switzerland); Schinnerer, Eva, E-mail: tani@cosmos.phys.sci.ehime-u.ac.jp [MPI for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); and others

    2015-08-10

    We report a discovery of six massive galaxies with both extremely large Lyα equivalent widths (EWs) and evolved stellar populations at z ∼ 3. These MAssive Extremely STrong Lyα emitting Objects (MAESTLOs) have been discovered in our large-volume systematic survey for strong Lyα emitters (LAEs) with 12 optical intermediate-band data taken with Subaru/Suprime-Cam in the COSMOS field. Based on the spectral energy distribution fitting analysis for these LAEs, it is found that these MAESTLOs have (1) large rest-frame EWs of EW{sub 0} (Lyα) ∼ 100–300 Å, (2) M{sub ⋆} ∼ 10{sup 10.5}–10{sup 11.1} M{sub ⊙}, and (3) relatively low specific star formation rates of SFR/M{sub ⋆} ∼ 0.03–1 Gyr{sup −1}. Three of the six MAESTLOs have extended Lyα emission with a radius of several kiloparsecs, although they show very compact morphology in the HST/ACS images, which correspond to the rest-frame UV continuum. Since the MAESTLOs do not show any evidence for active galactic nuclei, the observed extended Lyα emission is likely to be caused by a star formation process including the superwind activity. We suggest that this new class of LAEs, MAESTLOs, provides a missing link from star-forming to passively evolving galaxies at the peak era of the cosmic star formation history.

  2. Tidal Interaction as the origin of early-type dwarf galaxies in group environment

    CERN Document Server

    Paudel, Sanjaya

    2014-01-01

    We present a sample of dwarf galaxies that suffer ongoing disruption by the tidal force of nearby massive galaxies. Analysing structural and stellar population properties using the archival imaging and spectroscopic data from the Sloan Digital Sky Survey (SDSS), we find that they are likely a `smoking gun' example of the formation of early-type dwarf galaxies (dEs) in the galaxy group environment through the tidal stirring. Inner cores of these galaxies are fairly intact and the observed light profiles are well fitted with the Sersic functions, while the tidally stretched stellar halos are prominent in the outer parts. They are all located within the 50 kpc sky-projected distance from the center of host galaxies and no dwarf galaxies have relative line-of-sight velocity larger than 205 km/s to their hosts. We derive the Composite Stellar Population (CSP) properties these galaxies by fitting the SDSS optical spectra to a multiple-burst composite stellar population model. We find that these galaxies accumulate ...

  3. VIPERS: Unveiling the Combined Evolution of Galaxies and Large Scale Structure at 0.5≤z ≤1.2

    Science.gov (United States)

    Iovino, A.; Vipers Team

    2016-10-01

    The VIMOS Public Extragalactic Redshift Survey (VIPERS) is the largest redshift survey ever conducted with the ESO telescopes. It has used the Very Large Telescope to collect nearly 100,000 redshifts from the general galaxy population at 0.5≤ z ≤1.2. With a combination of volume and sampling density that is unique for these redshifts, VIPERS allows statistical measurements of galaxy clustering and related cosmological quantities to be obtained on an equal footing with classic results from local redshift surveys. At the same time, the broad selection function and ancillary photometric data provide detailed information on the physical properties of the galaxy population and their relation to large-scale structure. This talk presents an overview of the results obtained so far, mostly based on the ˜ 55,000 galaxies forming the first public data release (PDR-1).

  4. Growing Galaxies Gently

    Science.gov (United States)

    2010-10-01

    New observations from ESO's Very Large Telescope have, for the first time, provided direct evidence that young galaxies can grow by sucking in the cool gas around them and using it as fuel for the formation of many new stars. In the first few billion years after the Big Bang the mass of a typical galaxy increased dramatically and understanding why this happened is one of the hottest problems in modern astrophysics. The results appear in the 14 October issue of the journal Nature. The first galaxies formed well before the Universe was one billion years old and were much smaller than the giant systems - including the Milky Way - that we see today. So somehow the average galaxy size has increased as the Universe has evolved. Galaxies often collide and then merge to form larger systems and this process is certainly an important growth mechanism. However, an additional, gentler way has been proposed. A European team of astronomers has used ESO's Very Large Telescope to test this very different idea - that young galaxies can also grow by sucking in cool streams of the hydrogen and helium gas that filled the early Universe and forming new stars from this primitive material. Just as a commercial company can expand either by merging with other companies, or by hiring more staff, young galaxies could perhaps also grow in two different ways - by merging with other galaxies or by accreting material. The team leader, Giovanni Cresci (Osservatorio Astrofisico di Arcetri) says: "The new results from the VLT are the first direct evidence that the accretion of pristine gas really happened and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe." The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day. Theories of galaxy formation and evolution may have to be re-written. The group began by selecting three very distant galaxies to see if they could find evidence

  5. Interactive histology of large-scale biomedical image stacks.

    Science.gov (United States)

    Jeong, Won-Ki; Schneider, Jens; Turney, Stephen G; Faulkner-Jones, Beverly E; Meyer, Dominik; Westermann, Rüdiger; Reid, R Clay; Lichtman, Jeff; Pfister, Hanspeter

    2010-01-01

    Histology is the study of the structure of biological tissue using microscopy techniques. As digital imaging technology advances, high resolution microscopy of large tissue volumes is becoming feasible; however, new interactive tools are needed to explore and analyze the enormous datasets. In this paper we present a visualization framework that specifically targets interactive examination of arbitrarily large image stacks. Our framework is built upon two core techniques: display-aware processing and GPU-accelerated texture compression. With display-aware processing, only the currently visible image tiles are fetched and aligned on-the-fly, reducing memory bandwidth and minimizing the need for time-consuming global pre-processing. Our novel texture compression scheme for GPUs is tailored for quick browsing of image stacks. We evaluate the usability of our viewer for two histology applications: digital pathology and visualization of neural structure at nanoscale-resolution in serial electron micrographs.

  6. Star Clusters in the Tidal Tails of Interacting Galaxies: Cluster Populations Across a Variety of Tail Environments

    CERN Document Server

    Mullan, B; Kepley, A A; Lee, K H; Charlton, J C; Knierman, K; Bastian, N; Chandar, R; Durrell, P R; Elmegreen, D; English, J; Gallagher, S C; Gronwall, C; Hibbard, J E; Hunsberger, S; Johnson, K E; Maybhate, A; Palma, C; Trancho, G; Vacca, W D

    2011-01-01

    We have searched for compact stellar structures within 17 tidal tails in 13 different interacting galaxies using F606W- and F814W- band images from the Wide Field Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST). The sample of tidal tails includes a diverse population of optical properties, merging galaxy mass ratios, HI content, and ages. Combining our tail sample with Knierman et al. (2003), we find evidence of star clusters formed in situ with Mv < -8.5 and V-I < 2.0 in 10 of 23 tidal tails; we are able to identify cluster candidates to Mv = -6.5 in the closest tails. Three tails offer clear examples of "beads on a string" star formation morphology in V-I color maps. Two tails present both tidal dwarf galaxy (TDG) candidates and cluster candidates. Statistical diagnostics indicate that clusters in tidal tails may be drawn from the same power-law luminosity functions (with logarithmic slopes ~ -2 - -2.5) found in quiescent spiral galaxies and the interiors of interacting systems. We find...

  7. Flow mapping and multivariate visualization of large spatial interaction data.

    Science.gov (United States)

    Guo, Diansheng

    2009-01-01

    Spatial interactions (or flows), such as population migration and disease spread, naturally form a weighted location-to-location network (graph). Such geographically embedded networks (graphs) are usually very large. For example, the county-to-county migration data in the U.S. has thousands of counties and about a million migration paths. Moreover, many variables are associated with each flow, such as the number of migrants for different age groups, income levels, and occupations. It is a challenging task to visualize such data and discover network structures, multivariate relations, and their geographic patterns simultaneously. This paper addresses these challenges by developing an integrated interactive visualization framework that consists three coupled components: (1) a spatially constrained graph partitioning method that can construct a hierarchy of geographical regions (communities), where there are more flows or connections within regions than across regions; (2) a multivariate clustering and visualization method to detect and present multivariate patterns in the aggregated region-to-region flows; and (3) a highly interactive flow mapping component to map both flow and multivariate patterns in the geographic space, at different hierarchical levels. The proposed approach can process relatively large data sets and effectively discover and visualize major flow structures and multivariate relations at the same time. User interactions are supported to facilitate the understanding of both an overview and detailed patterns.

  8. Topology of Large-Scale Structures of Galaxies in two Dimensions—Systematic Effects

    Science.gov (United States)

    Appleby, Stephen; Park, Changbom; Hong, Sungwook E.; Kim, Juhan

    2017-02-01

    We study the two-dimensional topology of galactic distribution when projected onto two-dimensional spherical shells. Using the latest Horizon Run 4 simulation data, we construct the genus of the two-dimensional field and consider how this statistic is affected by late-time nonlinear effects—principally gravitational collapse and redshift space distortion (RSD). We also consider systematic and numerical artifacts, such as shot noise, galaxy bias, and finite pixel effects. We model the systematics using a Hermite polynomial expansion and perform a comprehensive analysis of known effects on the two-dimensional genus, with a view toward using the statistic for cosmological parameter estimation. We find that the finite pixel effect is dominated by an amplitude drop and can be made less than 1% by adopting pixels smaller than 1/3 of the angular smoothing length. Nonlinear gravitational evolution introduces time-dependent coefficients of the zeroth, first, and second Hermite polynomials, but the genus amplitude changes by less than 1% between z = 1 and z = 0 for smoothing scales {R}{{G}}> 9 {Mpc}/{{h}}. Non-zero terms are measured up to third order in the Hermite polynomial expansion when studying RSD. Differences in the shapes of the genus curves in real and redshift space are small when we adopt thick redshift shells, but the amplitude change remains a significant ∼ { O }(10 % ) effect. The combined effects of galaxy biasing and shot noise produce systematic effects up to the second Hermite polynomial. It is shown that, when sampling, the use of galaxy mass cuts significantly reduces the effect of shot noise relative to random sampling.

  9. Dendroscope: An interactive viewer for large phylogenetic trees

    Directory of Open Access Journals (Sweden)

    Franz Markus

    2007-11-01

    Full Text Available Abstract Background Research in evolution requires software for visualizing and editing phylogenetic trees, for increasingly very large datasets, such as arise in expression analysis or metagenomics, for example. It would be desirable to have a program that provides these services in an effcient and user-friendly way, and that can be easily installed and run on all major operating systems. Although a large number of tree visualization tools are freely available, some as a part of more comprehensive analysis packages, all have drawbacks in one or more domains. They either lack some of the standard tree visualization techniques or basic graphics and editing features, or they are restricted to small trees containing only tens of thousands of taxa. Moreover, many programs are diffcult to install or are not available for all common operating systems. Results We have developed a new program, Dendroscope, for the interactive visualization and navigation of phylogenetic trees. The program provides all standard tree visualizations and is optimized to run interactively on trees containing hundreds of thousands of taxa. The program provides tree editing and graphics export capabilities. To support the inspection of large trees, Dendroscope offers a magnification tool. The software is written in Java 1.4 and installers are provided for Linux/Unix, MacOS X and Windows XP. Conclusion Dendroscope is a user-friendly program for visualizing and navigating phylogenetic trees, for both small and large datasets.

  10. An analytical dynamo solution for large-scale magnetic fields of galaxies

    Science.gov (United States)

    Chamandy, Luke

    2016-11-01

    We present an effectively global analytical asymptotic galactic dynamo solution for the regular magnetic field of an axisymmetric thin disc in the saturated state. This solution is constructed by combining two well-known types of local galactic dynamo solution, parametrized by the disc radius. Namely, the critical (zero growth) solution obtained by treating the dynamo equation as a perturbed diffusion equation is normalized using a non-linear solution that makes use of the `no-z' approximation and the dynamical α-quenching non-linearity. This overall solution is found to be reasonably accurate when compared with detailed numerical solutions. It is thus potentially useful as a tool for predicting observational signatures of magnetic fields of galaxies. In particular, such solutions could be painted on to galaxies in cosmological simulations to enable the construction of synthetic polarized synchrotron and Faraday rotation measure data sets. Further, we explore the properties of our numerical solutions, and their dependence on certain parameter values. We illustrate and assess the degree to which numerical solutions based on various levels of approximation, common in the dynamo literature, agree with one another.

  11. Self-interacting Dark Matter Benchmarks

    OpenAIRE

    Kaplinghat, M.; Tulin, S.; Yu, H-B

    2017-01-01

    Dark matter self-interactions have important implications for the distributions of dark matter in the Universe, from dwarf galaxies to galaxy clusters. We present benchmark models that illustrate characteristic features of dark matter that is self-interacting through a new light mediator. These models have self-interactions large enough to change dark matter densities in the centers of galaxies in accord with observations, while remaining compatible with large-scale structur...

  12. ARCHITECTURAL LARGE CONSTRUCTED ENVIRONMENT. MODELING AND INTERACTION USING DYNAMIC SIMULATIONS

    Directory of Open Access Journals (Sweden)

    P. Fiamma

    2012-09-01

    Full Text Available How to use for the architectural design, the simulation coming from a large size data model? The topic is related to the phase coming usually after the acquisition of the data, during the construction of the model and especially after, when designers must have an interaction with the simulation, in order to develop and verify their idea. In the case of study, the concept of interaction includes the concept of real time "flows". The work develops contents and results that can be part of the large debate about the current connection between "architecture" and "movement". The focus of the work, is to realize a collaborative and participative virtual environment on which different specialist actors, client and final users can share knowledge, targets and constraints to better gain the aimed result. The goal is to have used a dynamic micro simulation digital resource that allows all the actors to explore the model in powerful and realistic way and to have a new type of interaction in a complex architectural scenario. On the one hand, the work represents a base of knowledge that can be implemented more and more; on the other hand the work represents a dealt to understand the large constructed architecture simulation as a way of life, a way of being in time and space. The architectural design before, and the architectural fact after, both happen in a sort of "Spatial Analysis System". The way is open to offer to this "system", knowledge and theories, that can support architectural design work for every application and scale. We think that the presented work represents a dealt to understand the large constructed architecture simulation as a way of life, a way of being in time and space. Architecture like a spatial configuration, that can be reconfigurable too through designing.

  13. The evolution of superluminous supernova LSQ14mo and its interacting host galaxy system

    CERN Document Server

    Chen, T -W; Smartt, S J; Mazzali, P A; Yates, R M; Moriya, T J; Inserra, C; Langer, N; Kruehler, T; Pan, Y -C; Kotak, R; Galbany, L; Schady, P; Wiseman, P; Greiner, J; Schulze, S; Man, A W S; Jerkstrand, A; Smith, K W; Dennefeld, M; Baltay, C; Bolmer, J; Kankare, E; Knust, F; Maguire, K; Rabinowitz, D; Rostami, S; Sullivan, M; Young, D R

    2016-01-01

    We present and analyse an extensive dataset of the superluminous supernova LSQ14mo (z = 0.256), consisting of a multi-colour lightcurve from -30 d to +70 d in the rest-frame and a series of 6 spectra from PESSTO covering -7 d to +50 d. This is among the densest spectroscopic coverage, and best-constrained rising lightcurve, for a fast-declining hydrogen-poor superluminous supernova. The bolometric lightcurve can be reproduced with a millisecond magnetar model with ~ 4 M_sol ejecta mass, and the temperature and velocity evolution is also suggestive of a magnetar as the power source. Spectral modelling indicates that the SN ejected ~ 6 M_sol of CO-rich material with a kinetic energy of ~ 7 x 10^51 erg, and suggests a partially thermalised additional source of luminosity between -2 d and +22 d. This may be due to interaction with a shell of material originating from pre-explosion mass loss. We further present a detailed analysis of the host galaxy system of LSQ14mo. PESSTO and GROND imaging show three spatially ...

  14. HST Observations of the Interacting Galaxies NGC 2207 and IC 2163

    CERN Document Server

    Elmegreen, B G; Struck, C; Elmegreen, D M; Brinks, E; Thomasson, M; Klaric, M; Levay, Z G; English, J; Frattare, L M; Bond, H E; Christian, C A; Hamilton, F; Noll, K S

    2000-01-01

    Hubble Space Telescope images of the galaxies NGC 2207 and IC 2163 show star formation and dust structures in a system that has experienced a recent grazing encounter. Tidal forces from NGC 2207 compressed and elongated the disk of IC 2163, forming an oval ridge of star formation. Gas flowing away from this ridge has thin parallel dust filaments transverse to the direction of motion. Numerical models suggest that the filaments come from flocculent spiral arms that were present before the interaction. A dust lane at the outer edge of the tidal tail is a shock front where the flow abruptly changes direction. A spiral arm of NGC 2207 that is backlit by IC 2163 is seen to contain several parallel, knotty filaments that are probably shock fronts in a density wave. Blue clusters of star formation inside these dust lanes show density wave triggering by local gravitational collapse. Spiral arms inside the oval of IC 2163 could be the result of ILR-related orbits in the tidal potential that formed the oval. Their pres...

  15. Detection of infalling hydrogen in transfer between the interacting galaxies NGC 5426 and NGC 5427

    CERN Document Server

    Font, Joan; Rosado, Margarita; Epinat, Benoît; Fathi, Kambiz; Hernandez, Olivier; Carignan, Claude; Gutiérrez, Leonel; Relaño, Monica; Blasco-Herrera, Javier; Fuentes-Carrera, Isaura

    2011-01-01

    Using velocity tagging we have detected hydrogen from NGC 5426 falling onto its interacting partner NGC 5427. Our observations, with the GHaFaS Fabry-Perot spectrometer, produced maps of the two galaxies in Halpha surface brightness and radial velocity. We found emission with the range of velocities associated with NGC 5426 along lines of sight apparently emanating from NGC 5427, superposed on the velocity map of the latter. After excluding instrumental effects we assign the anomalous emission to gas pulled from NGC 5426 during its passage close to NGC 5427. Its distribution, more intense between the arms and just outside the disk of NGC 5427, and weak, or absent, in the arms, suggests that the infalling gas is behind the disk., ionized by Lyman continuum photons escaping from NGC 5427. Modeling this, we estimate the distances of these gas clouds- behind the plane: a few hundred pc to a few kpc. We also estimate the mass of the infalling (ionized plus neutral) gas, finding an infall rate of 10 solar masses pe...

  16. Studying the spatially resolved Schmidt-Kennicutt law in interacting galaxies: the case of Arp 158

    CERN Document Server

    Boquien, Médéric; Duc, Pierre-Alain; Braine, Jonathan; Bournaud, Frédéric; Brinks, Elias; Charmandaris, Vassilis

    2011-01-01

    Recent studies have shown that star formation in mergers does not seem to follow the same Schmidt-Kennicutt (KS) relation as in spiral disks, presenting a higher star formation rate (SFR) for a given gas column density. In this paper we study why and how different models of star formation arise. To do so we examine the process of star formation in the interacting system Arp 158 and its tidal debris. We perform an analysis of the properties of specific regions of interest in Arp 158 using observations tracing the atomic and the molecular gas, star formation, the stellar populations as well as optical spectroscopy to determine their exact nature. We also fit their spectral energy distribution with an evolutionary synthesis code. Finally, we compare star formation in these objects to star formation in the disks of spiral galaxies and mergers. Abundant molecular gas is found throughout the system and the tidal tails appear to have many young stars compared to their old stellar content. One of the nuclei is domina...

  17. Uncovering the deeply embedded AGN activity in the nuclear regions of the interacting galaxy Arp299

    CERN Document Server

    Alonso-Herrero, A; Esquej, P; Gonzalez-Martin, O; Pereira-Santaella, M; Almeida, C Ramos; Levenson, N A; Packham, C; Ramos, A Asensio; Mason, R E; Espinosa, J M Rodriguez; Alvarez, C; Colina, L; Aretxaga, I; Diaz-Santos, T; Perlman, E; Telesco, C M

    2013-01-01

    We present mid-infrared (MIR) 8-13micron spectroscopy of the nuclear regions of the interacting galaxy Arp299 (IC694+NGC3690) obtained with CanariCam (CC) on the 10.4m Gran Telescopio Canarias (GTC). The high angular resolution (~0.3-0.6arcsec) of the data allows us to probe nuclear physical scales between 60 and 120pc, which is a factor of 10 improvement over previous MIR spectroscopic observations of this system. The GTC/CC spectroscopy displays evidence of deeply embedded Active Galactic Nucleus (AGN) activity in both nuclei. The GTC/CC nuclear spectrum of NGC3690/Arp299-B1 can be explained as emission from AGN-heated dust in a clumpy torus with both a high covering factor and high extinction along the line of sight. The estimated bolometric luminosity of the AGN in NGC3690 is 3.2(+/-0.6)x10^44 erg/s. The nuclear GTC/CC spectrum of IC694/Arp299-A shows 11.3micron polycyclic aromatic hydrocarbon (PAH) emission stemming from a deeply embedded (A_V~24mag) region of less than 120pc in size. There is also a con...

  18. Lyα-emitting galaxies as a probe of reionization: large-scale bubble morphology and small-scale absorbers

    Science.gov (United States)

    Kakiichi, Koki; Dijkstra, Mark; Ciardi, Benedetta; Graziani, Luca

    2016-12-01

    The visibility of Lyα-emitting galaxies during the Epoch of Reionization is controlled by both diffuse H I patches in large-scale bubble morphology and small-scale absorbers. To investigate their impacts on Lyα transfer, we apply a novel combination of analytic modelling and cosmological hydrodynamical, radiative transfer simulations to three reionization models: (i) the `bubble' model, where only diffuse H I outside ionized bubbles is present; (ii) the `web' model, where H I exists only in overdense self-shielded gas; and (iii) the hybrid `web-bubble' model. The three models can explain the observed Lyα luminosity function equally well, but with very different H I fractions. This confirms a degeneracy between the ionization topology of the intergalactic medium (IGM) and the H I fraction inferred from Lyα surveys. We highlight the importance of the clustering of small-scale absorbers around galaxies. A combined analysis of the Lyα luminosity function and the Lyα fraction can break this degeneracy and provide constraints on the reionization history and its topology. Constraints can be improved by analysing the full MUV-dependent redshift evolution of the Lyα fraction of Lyman break galaxies. We find that the IGM-transmission probability distribution function is unimodal for bubble models and bimodal in web models. Comparing our models to observations, we infer that the neutral fraction at z ˜ 7 is likely to be of the order of tens of per cent when interpreted with bubble or web-bubble models, with a conservative lower limit ˜1 per cent when interpreted with web models.

  19. Lyα-Emitting Galaxies as a Probe of Reionization: Large-Scale Bubble Morphology and Small-Scale Absorbers

    Science.gov (United States)

    Kakiichi, Koki; Dijkstra, Mark; Ciardi, Benedetta; Graziani, Luca

    2016-09-01

    The visibility of Lyα emitting galaxies during the Epoch of Reionization is controlled by both diffuse H I patches in large-scale bubble morphology and small-scale absorbers. To investigate their impacts on Lyα transfer, we apply a novel combination of analytic modelling and cosmological hydrodynamical, radiative transfer simulations to three reionization models: (i) the `bubble' model, where only diffuse H I outside ionized bubbles is present; (ii) the `web' model, where H I exists only in overdense self-shielded gas; and (iii) the hybrid `web-bubble' model. The three models can explain the observed Lyα luminosity function equally well, but with very different H I fractions. This confirms a degeneracy between the ionization topology of the intergalactic medium (IGM) and the H I fraction inferred from Lyα surveys. We highlight the importance of the clustering of small-scale absorbers around galaxies. A combined analysis of the Lyα luminosity function and the Lyα fraction can break this degeneracy and provide constraints on the reionization history and its topology. Constraints can be improved by analyzing the full MUV-dependent redshift evolution of the Lyα fraction of Lyman break galaxies. We find that the IGM-transmission probability distribution function is unimodal for bubble models and bimodal in web models. Comparing our models to observations, we infer that the neutral fraction at z ˜ 7 is likely to be of order of tens of per cent when interpreted with bubble or web-bubble models, with a conservative lower limit ˜1% when interpreted with web models.

  20. Statistical assessment of the relation between the inferred morphological type and the emission-line activity type of a large sample of galaxies

    Science.gov (United States)

    Ortega-Minakata, R. A.; Torres-Papaqui, J. P.; Andernach, H.; Islas-Islas, J. M.

    2014-05-01

    We quantify the statistical evidence of the relation between the inferred morphology and the emission-line activity type of galaxies for a large sample of galaxies. We compare the distribution of the inferred morphologies of galaxies of different dominant activity types, showing that the difference in the median morphological type between the samples of different activity types is significant. We also test the significance of the difference in the mean morphological type between all the activity-type samples using an ANOVA model with a modified Tukey test that takes into account heteroscedasticity and the unequal sample sizes. We show this test in the form of simultaneous confidence intervals for all pairwise comparisons of the mean morphological types of the samples. Using this test, scarcely applied in astronomy, we conclude that there are statistically significant differences in the inferred morphologies of galaxies of different dominant activity types.

  1. LiveGantt: Interactively Visualizing a Large Manufacturing Schedule.

    Science.gov (United States)

    Jo, Jaemin; Huh, Jaeseok; Park, Jonghun; Kim, Bohyoung; Seo, Jinwook

    2014-12-01

    In this paper, we introduce LiveGantt as a novel interactive schedule visualization tool that helps users explore highly-concurrent large schedules from various perspectives. Although a Gantt chart is the most common approach to illustrate schedules, currently available Gantt chart visualization tools suffer from limited scalability and lack of interactions. LiveGantt is built with newly designed algorithms and interactions to improve conventional charts with better scalability, explorability, and reschedulability. It employs resource reordering and task aggregation to display the schedules in a scalable way. LiveGantt provides four coordinated views and filtering techniques to help users explore and interact with the schedules in more flexible ways. In addition, LiveGantt is equipped with an efficient rescheduler to allow users to instantaneously modify their schedules based on their scheduling experience in the fields. To assess the usefulness of the application of LiveGantt, we conducted a case study on manufacturing schedule data with four industrial engineering researchers. Participants not only grasped an overview of a schedule but also explored the schedule from multiple perspectives to make enhancements.

  2. Giant radio galaxies and cosmic web

    Science.gov (United States)

    Heinämäki, Pekka

    2016-10-01

    Giant radio galaxies create the welldistinguishable class of sources.These sources are characterized with edge-brightened radio lobes withhighly collimated radio jets and large linear sizes which make themthe largest individual structures in the Universe. They are also knownto be hosted by elliptical/disturbed host galaxies and avoid clustersand high galaxy density regions. Because of GRG, large linear sizeslobes extend well beyond the interstellar media and host galaxyhalo the evolution of the radio lobes may depend on interactionwith this environment. Using our method to extract filamentarystructure of the galaxies in our local universe we study whetherradio lobe properties in some giant radio galaxies are determinedon an interaction of this filament ambient.

  3. The large scale gas and dust distribution in the galaxy: Implications for star formation

    Science.gov (United States)

    Sodroski, T. J.; Dwek, E.; Hauser, M. G.; Kerr, F. J.

    1987-01-01

    Infrared Astronomy Observations are presented for the diffuse infrared (IR) emissions from the galactic plane at wavelengths of 60 and 100 microns and the total far infrared intensity and its longitudinal variations in the disk were derived. Using available CO, 5 GHz radio-continuum, and HI data, the IR luminosity per hydrogen mass and the ingrared excess (IRE) ratio in the Galaxy were derived. The longitudinal profiles of the 60 and 100 micron emission were linearly decomposed into three components that are associated with molecular (H2), neutral (HI), and ionized (HII) phases in the interstellar medium (ISM), and the relevant dust properties were derived in each phase. Implications of the findings for various models of the diffuse IR emisison and for star formation in the galactic disk are discussed.

  4. The interaction between radio lobes and hot gas in the nearby radio galaxies 3C285 and 3C442A

    CERN Document Server

    Hardcastle, M J; Worrall, D M; Croston, J H; Evans, D A; Birkinshaw, M; Murray, S S

    2007-01-01

    We present Chandra observations of two nearby radio galaxies in group environments, 3C285 and 3C442A. The host galaxies of both sources are involved in mergers with nearby massive galaxies, and the hot gas in the systems is extended along lines joining the interacting galaxies. Both sources show strong evidence for interactions between the radio lobes and the asymmetrical hot gas. We argue that the structure in the hot gas is independent of the existence of the radio lobes in these systems, and argue that hot gas shaped by an ongoing massive galaxy merger may play an important role in the dynamics of radio lobes in other objects. For 3C442A, our observations show that gas is being driven out of both members of the host interacting galaxy pair, and the implied constraints on galaxy velocities are consistent with mildly supersonic motions with respect to the group-scale hot gas. The previously known filamentary radio structure in the center of 3C442A may be a result of the interaction between hot gas expelled f...

  5. Interactive View-Dependent Rendering of Large Isosurfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gregorski, B; Duchaineau, M; Lindstrom, P; Pascucci, V; Joy, K I

    2002-11-19

    We present an algorithm for interactively extracting and rendering isosurfaces of large volume datasets in a view-dependent fashion. A recursive tetrahedral mesh refinement scheme, based on longest edge bisection, is used to hierarchically decompose the data into a multiresolution structure. This data structure allows fast extraction of arbitrary isosurfaces to within user specified view-dependent error bounds. A data layout scheme based on hierarchical space filling curves provides access to the data in a cache coherent manner that follows the data access pattern indicated by the mesh refinement.

  6. Quenched Large Deviations for Interacting Diffusions in Random Media

    Science.gov (United States)

    Luçon, Eric

    2017-03-01

    The aim of the paper is to establish a large deviation principle (LDP) for the empirical measure of mean-field interacting diffusions in a random environment. The point is to derive such a result once the environment has been frozen (quenched model). The main theorem states that a LDP holds for every sequence of environment satisfying appropriate convergence condition, with a rate function that does not depend on the disorder and is different from the rate function in the averaged model. Similar results concerning the empirical flow and local empirical measures are provided.

  7. The role of interactions in triggering bars, spiral arms and AGN in disk galaxies

    Science.gov (United States)

    Nair, Preethi; Ellison, Sara L.; Patton, David R.

    2016-01-01

    The role of secular structures like bars, rings and spiral arms in triggering star formation and AGN activity in disk galaxies are not well understood. In addition, the mechanisms which create and destroy these structures are not well characterized. Mergers are considered to be one of the main mechanisms which can trigger bars in massive disk galaxies. Using a sample of ~8000 close pair galaxies at 0.02 MaNGA will help to place stronger constraints on the role of these structures in triggering star formation and AGN.

  8. Fermi Large Area Telescope Detection of Extended Gamma-Ray Emission from the Radio Galaxy Fornax A

    CERN Document Server

    ,

    2016-01-01

    We report the Fermi Large Area Telescope detection of extended gamma-ray emission from the lobes of the radio galaxy Fornax A using 6.1 years of Pass 8 data. After Centaurus A, this is now the second example of an extended gamma-ray source attributed to a radio galaxy. Both an extended flat disk morphology and a morphology following the extended radio lobes were preferred over a point-source description, and the core contribution was constrained to be 100 MeV gamma-ray emission established, we model the source broadband emission considering currently available total lobe radio and millimeter flux measurements, as well as X-ray detections attributed to inverse Compton (IC) emission off the cosmic microwave background (CMB). Unlike the Centaurus A case, we find that a leptonic model involving IC scattering of CMB and extragalactic background light (EBL) photons underpredicts the gamma-ray fluxes by factors of about ~ 2 - 3, depending on the EBL model adopted. An additional gamma-ray spectral component is thus ...

  9. The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater

    Science.gov (United States)

    Torrealba, G.; Koposov, S. E.; Belokurov, V.; Irwin, M.

    2016-07-01

    We announce the discovery of the Crater 2 dwarf galaxy, identified in imaging data of the VLT Survey Telescope ATLAS survey. Given its half-light radius of ˜1100 pc, Crater 2 is the fourth largest satellite of the Milky Way, surpassed only by the Large Magellanic Cloud, Small Magellanic Cloud and the Sgr dwarf. With a total luminosity of MV ≈ -8, this galaxy is also one of the lowest surface brightness dwarfs. Falling under the nominal detection boundary of 30 mag arcsec-2, it compares in nebulosity to the recently discovered Tuc 2 and Tuc IV and UMa II. Crater 2 is located ˜120 kpc from the Sun and appears to be aligned in 3D with the enigmatic globular cluster Crater, the pair of ultrafaint dwarfs Leo IV and Leo V and the classical dwarf Leo II. We argue that such arrangement is probably not accidental and, in fact, can be viewed as the evidence for the accretion of the Crater-Leo group.

  10. Chemical tagging with APOGEE: Discovery of a large population of N-rich stars in the inner Galaxy

    CERN Document Server

    Schiavon, Ricardo P; Carrera, Ricardo; Lucatello, Sara; Robin, A C; Ness, Melissa; Martell, Sarah L; Smith, Verne V; Hernandez, D A Garcia; Manchado, Arturo; Schoenrich, Ralph; Bastian, Nate; Chiappini, Cristina; Shetrone, Matthew; Mackereth, J Ted; Williams, Rob A; Meszaros, Szabolcs; Prieto, Carlos Allende; Anders, Friedrich; Bizyaev, Dmitry; Beers, Timothy C; Chojnowski, S Drew; Cunha, Katia; Epstein, Courtney; Frinchaboy, Peter M; Perez, Ana E Garcia; Hearty, Fred R; Holtzman, Jon A; Johnson, Jennifer A; Kinemuchi, Karen; Majewski, Steven R; Muna, Demitri; Nidever, David L; Nguyen, Duy Cuong; O'Connell, Robert W; Oravetz, Daniel; Pan, Kaike; Pinsonneault, Marc; Schneider, Donald P; Schultheis, Matthias; Simmons, Audrey; Skrutskie, Michael F; Sobeck, Jennifer; Wilson, John C; Zasowski, Gail

    2016-01-01

    Formation of globular clusters (GCs), the Galactic bulge, or galaxy bulges in general, are important unsolved problems in Galactic astronomy. Homogeneous infrared observations of large samples of stars belonging to GCs and the Galactic bulge field are one of the best ways to study these problems. We report the discovery by APOGEE of a population of field stars in the inner Galaxy with abundances of N, C, and Al that are typically found in GC stars. The newly discovered stars have high [N/Fe], which is correlated with [Al/Fe] and anti-correlated with [C/Fe]. They are homogeneously distributed across, and kinematically indistinguishable from, other field stars in the same volume. Their metallicity distribution is seemingly unimodal, peaking at [Fe/H]~-1, thus being in disagreement with that of the Galactic GC system. Our results can be understood in terms of different scenarios. N-rich stars could be former members of dissolved GCs, in which case the mass in destroyed GCs exceeds that of the surviving GC system...

  11. Fire-on-fire interactions in three large wilderness areas

    Science.gov (United States)

    Teske, Casey C.

    Current knowledge about wildfire occurrence is not complete. Fire researchers and managers hold the assumption that previous wildfires affect subsequent wildfires; however, research regarding the interactions of large wildfires at their common boundaries is missing from the literature. This research focuses on understanding the influence of previous large wildfires on subsequent large wildfires in three wilderness areas: The Greater Bob Marshall, the Selway-Bitterroot, and the Frank Church. Data from the Monitoring Trends in Burn Severity (MTBS) project, which mapped large wildfires in the western United States occurring since 1984, are used for the research. The combination of using wilderness areas and remotely sensed images allows an objective and consistent analysis of fire-on-fire interaction that is extensive in both time and space. Standardized methods for analyzing fire interactions do not currently exist, therefore methods were developed, tested, and refined to describe, quantify, and compare once-burned and re-burned locations within a subset of ten fires in terms of size, location, timing between fires, and severity. These methods were then used to address the question of whether re-burns occur within each of the three wilderness areas. Edge and re-burn characteristics were also derived and quantified. Results were statistically and empirically compared to randomized fire intersections and to published fire history research for each area. Although a low proportion of each study area burns or re-burns, when a new fire encounters a previous fire it re-burns onto the previously burned area approximately 80% of the time. Current large wildfires are behaving in a typical fashion, although on some landscapes the amount of re-burn is not different from what would be expected due to chance. Lastly, the complexity of the post-fire landscape was assessed using texture metrics. Pre-fire and post-fire landscapes were shown to be different, with post-fire landscapes

  12. An ALMA survey of submillimetre galaxies in the COSMOS field: The extent of the radio-emitting region revealed by 3 GHz imaging with the Very Large Array

    Science.gov (United States)

    Miettinen, O.; Novak, M.; Smolčić, V.; Delvecchio, I.; Aravena, M.; Brisbin, D.; Karim, A.; Murphy, E. J.; Schinnerer, E.; Albrecht, M.; Aussel, H.; Bertoldi, F.; Capak, P. L.; Casey, C. M.; Civano, F.; Hayward, C. C.; Herrera Ruiz, N.; Ilbert, O.; Jiang, C.; Laigle, C.; Le Fèvre, O.; Magnelli, B.; Marchesi, S.; McCracken, H. J.; Middelberg, E.; Muñoz Arancibia, A. M.; Navarrete, F.; Padilla, N. D.; Riechers, D. A.; Salvato, M.; Scott, K. S.; Sheth, K.; Tasca, L. A. M.; Bondi, M.; Zamorani, G.

    2017-06-01

    Context. The observed spatial scale of the radio continuum emission from star-forming galaxies can be used to investigate the spatial extent of active star formation, constrain the importance of cosmic-ray transport, and examine the effects of galaxy interactions. Aims: We determine the radio size distribution of a large sample of 152 submillimetre galaxies (SMGs) in the COSMOS field that were pre-selected at 1.1 mm, and later detected with the Atacama Large Millimetre/submillimetre Array (ALMA) in the observed-frame 1.3 mm dust continuum emission at a signal-to-noise ratio (S/N) of ≥5. Methods: We used the deep, subarcsecond-resolution (1σ = 2.3μJy beam-1;.̋75) centimetre radio continuum observations taken by the Karl G. Jansky Very Large Array (VLA)-COSMOS 3 GHz Large Project. Results: One hundred and fifteen of the 152 target SMGs (76% ± 7%) were found to have a 3 GHz counterpart (≥ 4.2σ), which renders the radio detection rate notably high. The median value of the deconvolved major axis full width at half maximum (FWHM) size at 3 GHz is derived to be 0.̋59 ± 0.̋05 , or 4.6 ± 0.4 kpc in physical units, where the median redshift of the sources is z = 2.23 ± 0.13 (23% are spectroscopic and 77% are photometric values). The radio sizes are roughly log-normally distributed, and they show no evolutionary trend with redshift, or difference between different galaxy morphologies. We also derived the spectral indices between 1.4 and 3 GHz, and 3 GHz brightness temperatures for the sources, and the median values were found to be α1.4 GHz3 GHz = -0.67 (Sν ∝ να) and TB = 12.6 ± 2 K. Three of the target SMGs, which are also detected with the Very Long Baseline Array (VLBA) at 1.4 GHz (AzTEC/C24b, 61, and 77a), show clearly higher brightness temperatures than the typical values, reaching TB(3 GHz) > 104.03 K for AzTEC/C61. Conclusions: The derived median radio spectral index agrees with a value expected for optically thin non-thermal synchrotron radiation

  13. The disruption of nearby galaxies by the Milky Way

    CERN Document Server

    Putman, M E; Staveley-Smith, L; Banks, G D; Barnes, D G; Bhathal, R; Disney, M J; Ekers, R D; Freeman, K C; Haynes, R F; Henning, P; Jerjen, H; Kilborn, V A; Koribalski, B S; Knezek, P M; Malin, D F; Mould, J R; Oosterloo, T A; Price, R M; Ryder, S D; Sadler, E M; Stewart, I W; Stootman, F; Vaile, R A; Webster, R L; Wright, A E

    1998-01-01

    Interactions between galaxies are common and are an important factor in determining their physical properties such as position along the Hubble sequence and star-formation rate. There are many possible galaxy interaction mechanisms, including merging, ram-pressure stripping, gas compression, gravitational interaction and cluster tides. The relative importance of these mechanisms is often not clear, as their strength depends on poorly known parameters such as the density, extent and nature of the massive dark halos that surround galaxies. A nearby example of a galaxy interaction where the mechanism is controversial is that between our own Galaxy and two of its neighbours -- the Large and Small Magellanic Clouds. Here we present the first results of a new HI survey which provides a spectacular view of this interaction. In addition to the previously known Magellanic Stream, which trails 100 degrees behind the Clouds, the new data reveal a counter-stream which lies in the opposite direction and leads the motion o...

  14. HiPiler: Visual Exploration of Large Genome Interaction Matrices with Interactive Small Multiples.

    Science.gov (United States)

    Lekschas, Fritz; Bach, Benjamin; Kerpedjiev, Peter; Gehlenborg, Nils; Pfister, Hanspeter

    2017-08-29

    This paper presents an interactive visualization interface-HiPiler-for the exploration and visualization of regions-of-interest in large genome interaction matrices. Genome interaction matrices approximate the physical distance of pairs of regions on the genome to each other and can contain up to 3 million rows and columns with many sparse regions. Regions of interest (ROIs) can be defined, e.g., by sets of adjacent rows and columns, or by specific visual patterns in the matrix. However, traditional matrix aggregation or pan-and-zoom interfaces fail in supporting search, inspection, and comparison of ROIs in such large matrices. In HiPiler, ROIs are first-class objects, represented as thumbnail-like "snippets". Snippets can be interactively explored and grouped or laid out automatically in scatterplots, or through dimension reduction methods. Snippets are linked to the entire navigable genome interaction matrix through brushing and linking. The design of HiPiler is based on a series of semi-structured interviews with 10 domain experts involved in the analysis and interpretation of genome interaction matrices. We describe six exploration tasks that are crucial for analysis of interaction matrices and demonstrate how HiPiler supports these tasks. We report on a user study with a series of data exploration sessions with domain experts to assess the usability of HiPiler as well as to demonstrate respective findings in the data.

  15. Chandra Observations of the Components of Clusters, Groups, and Galaxies and their Interactions

    CERN Document Server

    Forman, W; Markevitch, M L; Vikhlinin, A A; Churazov, E

    2001-01-01

    We discuss two themes from Chandra observations of galaxies, groups, and clusters. First, we review the merging process as seen through the high angular resolution of Chandra. We present examples of sharp, edge-like surface brightness structures ``cold fronts'', the boundaries of the remaining cores of merger components and the Chandra observations of CL0657, the first clear example of a strong cluster merger shock. In addition to reviewing already published work, we present observations of the cold front around the elliptical galaxy NGC1404 which is infalling into the Fornax cluster and we discuss multiple ``edges'' in ZW3146. Second, we review the effects of relativistic, radio-emitting plasmas or ``bubbles'', inflated by active galactic nuclei, on the hot X-ray emitting gaseous atmospheres in galaxies and clusters. We review published work and also discuss the unusual X-ray structures surrounding the galaxies NGC4636 and NGC507.

  16. The impact of galaxy interactions on AGN activity in zCOSMOS

    CERN Document Server

    Silverman, J D; Jahnke, K; Andrae, R; Lilly, S; Elvis, M; Civano, F; Mainieri, V; Vignali, C; Zamorani, G; Nair, P; Fevre, O Le; de Ravel, L; Bardelli, S; Bongiorno, A; Bolzonella, M; Brusa, M; Cappelluti, N; Cappi, A; Caputi, K; Carollo, C M; Contini, T; Coppa, G; Cucciati, O; de la Torre, S; Franzetti, P; Garilli, B; Halliday, C; Hasinger, G; Iovino, A; Knobel, C; koekemoer, A; Kovac, K; Lamareille, F; Borgne, J -F Le; Brun, V Le; Maier, C; Mignoli, M; Pello, R; Montero, E Perez; Ricciardelli, E; Peng, Y; Scodeggio, M; Tanaka, M; Tasca, L; Tresse, L; Vergani, D; Zucca, E; Comastri, A; Finoguenov, A; Fu, H; Gilli, R; Hao, H; Ho, L; Salvato, M

    2011-01-01

    Close encounters between galaxies are expected to be a viable mechanism, as predicted by numerical simulations, by which accretion onto supermassive black holes can be initiated. To test this scenario, we construct a sample of 562 galaxies (M*>2.5x10^10 M_sun) in kinematic pairs over the redshift range 0.25 2x10^42 erg s^-1) detected by Chandra. We find a higher fraction of AGN in galaxies in pairs relative to isolated galaxies of similar stellar mass. Our result is primarily due to an enhancement of AGN activity, by a factor of 1.9 (observed) and 2.6 (intrinsic), for galaxies in pairs of projected separation less than 75 kpc and line-of-sight velocity offset less than 500 km s^-1. This study demonstrates that close kinematic pairs are conducive environments for black hole growth either indicating a causal physical connection or an inherent relation, such as, to enhanced star formation. In the Appendix, we describe a method to estimate the intrinsic fractions of galaxies (either in pairs or the field) hosting...

  17. CALIFA Spectroscopy of the Interacting Galaxy NGC 5394 (Arp 84): Starbursts, Enhanced [NII]6584 and Signs of Outflows and Shocks

    CERN Document Server

    Roche, Nathan; Gomes, Jean Michel; Papaderos, Polychronis; Lagos, Patricio; Sanchez, Sebastian F

    2015-01-01

    We investigate the spiral galaxy NGC 5394, which is strongly interacting with the larger spiral NGC 5395 (the pair is Arp 84), using optical integral-field spectroscopy from the CALIFA survey. Spatially-resolved equivalent-widths, emission-line ratios and kinematics reveal many features related to the interaction, which has reshaped the galaxy. $\\rm H\\alpha$ maps (with other diagnostic emission lines) show a concentrated central ($r<1$ kpc) starburst and three less luminous star-forming regions (one knot far out in the northern arm), and we estimate the dust-corrected total star-formation rate as 3.39 $\\rm M_{\\odot}yr^{-1}$. However, much of the galaxy, especially the outer tidal arms, has a post-starburst spectrum, evidence of a more extensive episode of star-formation a few $\\times 10^8$ yr ago, triggered by the previous perigalacticon. The $\\rm [NII]6584/H\\alpha$ ratio is high in the nucleus, reaching 0.63 at the centre, which we interpret as related to high electron density ($n_e\\simeq 750$ $\\rm cm^{-3...

  18. Tidal interaction vs. ram pressure stripping effects as seen in X-rays. Hot gas in group and cluster galaxies

    CERN Document Server

    Wezgowiec, M; Ehle, M; Chyzy, K T; Urbanik, M; Braine, J; Soida, M

    2012-01-01

    The hot intracluster/intragroup medium (ICM/IGM) and a high galaxy density can lead to perturbations of the galactic interstellar medium (ISM) due to ram pressure and/or tidal interaction effects. In radio polarimetry observations, both phenomena may manifest similar features. X-ray data can help to determine the real origin of the perturbation. We analyse the distribution and physical properties of the hot gas in the Virgo cluster spiral galaxies NGC 4254 and NGC 4569, which indicate that the cluster environment has had a significant influence on their properties. By performing both spatial and spectral analyses of X-ray data, we try to distinguish between two major phenomena: tidal and ram pressure interactions. We compare our findings with the case of NGC 2276, in which a shock was reported, by analysing XMM-Newton X-ray data for this galaxy. We use archival XMM-Newton observations of NGC 4254, NGC 4569, and NGC 2276. Maps of the soft diffuse emission in the energy band 0.2 - 1 keV are obtained. For the th...

  19. Searching for Dark Matter Annihilation from Milky Way Dwarf Spheroidal Galaxies with Six Years of Fermi Large Area Telescope Data.

    Science.gov (United States)

    Ackermann, M; Albert, A; Anderson, B; Atwood, W B; Baldini, L; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Bissaldi, E; Blandford, R D; Bloom, E D; Bonino, R; Bottacini, E; Brandt, T J; Bregeon, J; Bruel, P; Buehler, R; Caliandro, G A; Cameron, R A; Caputo, R; Caragiulo, M; Caraveo, P A; Cecchi, C; Charles, E; Chekhtman, A; Chiang, J; Chiaro, G; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cuoco, A; Cutini, S; D'Ammando, F; de Angelis, A; de Palma, F; Desiante, R; Digel, S W; Di Venere, L; Drell, P S; Drlica-Wagner, A; Essig, R; Favuzzi, C; Fegan, S J; Ferrara, E C; Focke, W B; Franckowiak, A; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Gomez-Vargas, G A; Grenier, I A; Guiriec, S; Gustafsson, M; Hays, E; Hewitt, J W; Horan, D; Jogler, T; Jóhannesson, G; Kuss, M; Larsson, S; Latronico, L; Li, J; Li, L; Llena Garde, M; Longo, F; Loparco, F; Lubrano, P; Malyshev, D; Mayer, M; Mazziotta, M N; McEnery, J E; Meyer, M; Michelson, P F; Mizuno, T; Moiseev, A A; Monzani, M E; Morselli, A; Murgia, S; Nuss, E; Ohsugi, T; Orienti, M; Orlando, E; Ormes, J F; Paneque, D; Perkins, J S; Pesce-Rollins, M; Piron, F; Pivato, G; Porter, T A; Rainò, S; Rando, R; Razzano, M; Reimer, A; Reimer, O; Ritz, S; Sánchez-Conde, M; Schulz, A; Sehgal, N; Sgrò, C; Siskind, E J; Spada, F; Spandre, G; Spinelli, P; Strigari, L; Tajima, H; Takahashi, H; Thayer, J B; Tibaldo, L; Torres, D F; Troja, E; Vianello, G; Werner, M; Winer, B L; Wood, K S; Wood, M; Zaharijas, G; Zimmer, S

    2015-12-04

    The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some of the most dark matter (DM) dominated objects known. We report on γ-ray observations of Milky Way dSphs based on six years of Fermi Large Area Telescope data processed with the new Pass8 event-level analysis. None of the dSphs are significantly detected in γ rays, and we present upper limits on the DM annihilation cross section from a combined analysis of 15 dSphs. These constraints are among the strongest and most robust to date and lie below the canonical thermal relic cross section for DM of mass ≲100  GeV annihilating via quark and τ-lepton channels.

  20. Kinematic alignment of non-interacting CALIFA galaxies: Quantifying the impact of bars on stellar and ionised gas velocity field orientations

    CERN Document Server

    Barrera-Ballesteros, J K; García-Lorenzo, B; van de Ven, G; Aguerri, J A L; Mendez-Abreu, J; Spekkens, K; Sánchez, S F; Husemann, B; Mast, D; García-Benito, R; Iglesias-Paramo, J; del Olmo, A; Márquez, I; Masegosa, J; Kehrig, C; Marino, R A; Verdes-Montenegro, L; Ziegler, B; MacIntosh, D H; Bland-Hawthorn, J; Walcher, C J

    2014-01-01

    We present 80 stellar and ionised gas velocity maps from the Calar Alto Legacy Integral Field Area (CALIFA) survey in order to characterize the kinematic orientation of non-interacting galaxies. The study of galaxies in isolation is a key step towards understanding how fast-external processes, such as major mergers, affect kinematic properties in galaxies. We derived the global and individual (projected approaching and receding sides) kinematic position angles (PAs) for both the stellar and ionised gas line-of-sight velocity distributions. When compared to the photometric PA, we find that morpho-kinematic differences are smaller than 22 degrees in 90% of the sample for both components; internal kinematic misalignments are generally smaller than 16 degrees. We find a tight relation between the global stellar and ionised gas kinematic PA consistent with circular-flow pattern motions in both components. This relation also holds generally in barred galaxies across the bar and galaxy disk scales. Our findings sugg...

  1. High star formation rates in turbulent atomic-dominated gas in the interacting galaxies IC 2163 and NGC 2207

    CERN Document Server

    Elmegreen, Bruce G; Bournaud, Frederic; Elmegreen, Debra Meloy; Struck, Curtis; Brinks, Elias; Juneau, Stephanie

    2016-01-01

    CO observations of the interacting galaxies IC 2163 and NGC 2207 are combined with HI, Halpha and 24 microns to study the star formation rate (SFR) surface density as a function of the gas surface density. More than half of the high SFR regions are HI dominated. When compared to other galaxies, these HI-dominated regions have excess SFRs relative to their molecular gas surface densities but normal SFRs relative to their total gas surface densities. The HI-dominated regions are mostly located in the outer part of NGC 2207, where the HI velocity dispersion is high, 40 - 50 km/s. We suggest that the star-forming clouds in these regions have envelopes at lower densities than normal, making them predominantly atomic, and cores at higher densities than normal because of the high turbulent Mach numbers. This is consistent with theoretical predictions of a flattening in the density probability distribution function for compressive, high Mach number turbulence.

  2. Orbits of massive satellite galaxies - I. A close look at the Large Magellanic Cloud and a new orbital history for M33

    Science.gov (United States)

    Patel, Ekta; Besla, Gurtina; Sohn, Sangmo Tony

    2017-02-01

    The Milky Way (MW) and M31 both harbour massive satellite galaxies, the Large Magellanic Cloud (LMC) and M33, which may comprise up to 10 per cent of their host's total mass. Massive satellites can change the orbital barycentre of the host-satellite system by tens of kiloparsec and are cosmologically expected to harbour dwarf satellite galaxies of their own. Assessing the impact of these effects crucially depends on the orbital histories of the LMC and M33. Here, we revisit the dynamics of the MW-LMC system and present the first detailed analysis of the M31-M33 system utilizing high-precision proper motions and statistics from the dark-matter-only Illustris cosmological simulation. With the latest Hubble Space Telescope proper motion measurements of M31, we reliably constrain M33's interaction history with its host. In particular, like the LMC, M33 is either on its first passage (tinf picture and provide further insight about their host masses. We conclude that, cosmologically, massive satellites such as the LMC and M33 are likely completing their first orbits about their hosts. We also find that the orbital energies of such analogues prefer an MW halo mass ˜1.5 × 1012 M⊙ and an M31 halo mass ≥1.5 × 1012 M⊙. Despite conventional wisdom, we conclude it is highly improbable that M33 made a close (<100 kpc) approach to M31 recently (tperi < 3 Gyr ago). Such orbits are rare (<1 per cent) within the 4σ error space allowed by observations. This conclusion cannot be explained by perturbative effects through four-body encounters amongst the MW, M31, M33, and the LMC. This surprising result implies that we must search for a new explanation for M33's strongly warped gas and stellar discs.

  3. Long way to go: how outflows from large galaxies propagate through the hot halo gas

    CERN Document Server

    Sarkar, Kartick Chandra; Sharma, Prateek; Shchekinov, Yuri

    2014-01-01

    Abridged Abstract: Using hydrodynamic simulations, we study the mass loss rate due to supernova-driven outflows from Milky Way type disk galaxies. Our goal is to relate the wind mass loss rates at different radii and times, and the central star formation rate (SFR). In particular, we study the role of the often-neglected extended halo gas. We find that the time averaged mass loss rate at inner radii scales roughly linearly with the star formation rate ($\\dot{M} \\propto {\\rm SFR}^{0.75}$), and that the mass loading factor at the virial radius is roughly half its value at the inner radii. The temperature distribution of the outflowing material in the very inner region ($\\sim $10 kpc) is found to be bimodal in nature , peaking at $10^5$ K and $10^{6.5}$ K, responsible for optical and X-ray emission, respectively. The contribution of cold/warm gas with temperature $\\le 10^{5.5}$ K to the outflow rate within 10 kpc is $\\approx 0.3\\hbox{--}0.5$. This helps us to connect the warm mass loading factor ($\\eta_{3e5}$, e...

  4. The Large-Scale Observational Signatures of Low-Mass Galaxies During Reionization

    CERN Document Server

    Dixon, Keri L; Mellema, Garrelt; Ahn, Kyungjin; Shapiro, Paul R

    2015-01-01

    Observations of the epoch of reionization give us clues about the nature and evolution of the sources of ionizing photons, or early stars and galaxies. We present a new suite of structure formation and radiative transfer simulations from the PRACE4LOFAR project designed to investigate whether the mechanism of radiative feedback, or the suppression of star formation in ionized regions from UV radiation, can be inferred from these observations. Our source halo mass extends down to $10^8 M_\\odot$, with sources in the mass range $10^8$ to $10^9 M_\\odot$ expected to be particularly susceptible to feedback from ionizing radiation, and we vary the aggressiveness and nature of this suppression. Not only do we have four distinct source models, we also include two box sizes (67 Mpc and 349 Mpc), each with two grid resolutions. This suite of simulations allows us to investigate the robustness of our results. All of our simulations are broadly consistent with the observed electron-scattering optical depth of the cosmic m...

  5. Probe combination in large galaxy surveys : Application of Fisher information and Shannon entropy to weak lensing

    CERN Document Server

    Carron, Julien; Lilly, Simon

    2011-01-01

    This paper is aimed at developing a better understanding of the structure of the information that in contained in galaxy surveys, so as to find optimal ways to combine observables from such surveys. We first show how Jaynes' Maximal Entropy Principle allows us, in the general case, to express the Fisher information content of data sets in terms of the curvature of the Shannon entropy surface with respect to the relevant observables. This allows us to understand the Fisher information content of a data set, once a physical model is specified, independently of the specific way that the data will be processed, and without any assumptions of Gaussianity. This includes as a special case the standard Fisher matrix prescriptions for Gaussian variables widely used in the cosmological community, for instance for power spectra extraction. As an application of this approach, we evaluate the prospects of a joint analysis of weak lensing tracers up to second order in the shapes distortions, in the case that the noise in e...

  6. The Influence of the Large-scale Environment on Galaxy Property%大尺度环境对星系性质的影响∗

    Institute of Scientific and Technical Information of China (English)

    魏玉清; 王蕾; 戴才萍

    2016-01-01

    星系的恒星形成性质及其随环境变化的规律对理解星系的形成与演化有着重要作用。不同的研究团组根据Sloan巡天(SDSS)数据分析星系物理性质及星系所在的大尺度环境。分别利用了来自Tempel等的纤维结构(filament)编目和来自Wang等的大尺度结构分类的星系编目,并考虑了星系形态、高低局域密度环境、中心(卫星)星系影响,发现星系的性质和星系所在大尺度环境相关:不同大尺度环境对漩涡星系和卫星星系的SSFR (specific star formation rate)和SFR (star formation rate)都有显著影响,但对椭圆星系和中心星系的影响很小,且低局域密度区域的星系比在高局域密度区域中的星系对不同大尺度环境更敏感,即使在相同星系质量的情况下上述结论依然成立,此外来自Tempel等的编目的统计与来自Wang等的在SSFR分布上并不完全一致。%The properties of star formation in galaxies and their dependence on environment play an important role in understanding the formation and evolution of galaxies. Using the galaxy sample of the Sloan Digital Sky Survey (SDSS), different groups have studied the physical property and the large-scale environment of galaxies. Here we use the filament catalog from Tempel et al. and classified galaxies catalog from Wang et al., considering the affect of shape of galaxies, high and low local density envi-ronment, and central (satellite) galaxies. It is found that the properties of galaxies and the large-scale environment are related: the SSFR (specific star formation rate) and SFR (star formation rate) strongly depend on large-scale environment only for spiral galaxies and satellite galaxies, but this dependence is very weak for elliptical galaxies and the central galaxies, and the influence of large-scale environment on galaxies in low density region is more sensitive than that in high density region. The above conclu-sion remains valid even for

  7. Les galaxies

    Science.gov (United States)

    Combes, Francoise

    2016-08-01

    Considerable progress has been made on galaxy formation and evolution in recent years, and new issues. The old Hubble classification according to the tuning fork of spirals, lenticulars and ellipticals, is still useful but has given place to the red sequence, the blue cloud and the green valley, showing a real bimodality of types between star forming galaxies (blue) and quenched ones (red). Large surveys have shown that stellar mass and environment density are the two main factors of the evolution from blue to red sequences. Evolution is followed directly with redshift through a look-back time of more than 12 billion years. The most distant galaxy at z=11. has already a stellar mass of a billion suns. In an apparent anti-hierarchical scenario, the most massive galaxies form stars early on, while essentially dwarf galaxies are actively star-formers now. This downsizing feature also applies to the growth of super-massive black holes at the heart of each bulgy galaxy. The feedback from active nuclei is essential to explain the distribution of mass in galaxies, and in particular to explain why the fraction of baryonic matter is so low, lower by more than a factor 5 than the baryonic fraction of the Universe. New instruments just entering in operation, like MUSE and ALMA, provide a new and rich data flow, which is developed in this series of articles.

  8. The role of 3-D interactive visualization in blind surveys of HI in galaxies

    CERN Document Server

    Punzo, D; Roerdink, J B T M; Oosterloo, T A; Ramatsoku, M; Verheijen, M A W

    2015-01-01

    Upcoming HI surveys will deliver large datasets, and automated processing using the full 3-D information (two positional dimensions and one spectral dimension) to find and characterize HI objects is imperative. In this context, visualization is an essential tool for enabling qualitative and quantitative human control on an automated source finding and analysis pipeline. We discuss how Visual Analytics, the combination of automated data processing and human reasoning, creativity and intuition, supported by interactive visualization, enables flexible and fast interaction with the 3-D data, helping the astronomer to deal with the analysis of complex sources. 3-D visualization, coupled to modeling, provides additional capabilities helping the discovery and analysis of subtle structures in the 3-D domain. The requirements for a fully interactive visualization tool are: coupled 1-D/2-D/3-D visualization, quantitative and comparative capabilities, combined with supervised semi-automated analysis. Moreover, the sourc...

  9. Active galaxies in a complete sample of isolated galaxies

    OpenAIRE

    Sabater, J.; Leon, S.; Verdes-Montenegro, L.; Bergond, G.; Carpio, J.; Combes, F.; Espada, D.; Garc??a, E.; Huchtmeier, W.; Lisenfeld, Ute; Santander-Vela, J. D.; Sulentic, J.; Verley, S.

    2006-01-01

    Galaxy evolution depends strongly on the environment, in particular, galaxy-galaxy interaction can induce nuclear activity by removing angular momentum from the gas so feeding the central black hole. Hence a higher rate of nuclear activity is expected in interacting galaxies. Different studies of this topic lead to contradictory results. Some works conclude that galaxies hosting an active galactic nuclei (AGN) have a higher rate of companions than non active ones. On the other hand other stud...

  10. Study of Milli-Jansky Seyfert Galaxies with Strong Forbidden High-Ionization Lines Using the Very Large Array Survey Images

    CERN Document Server

    Lal, Dharam V

    2016-01-01

    We study the radio properties at 1.4 GHz of Seyfert galaxies with strong forbidden high-ionization lines (FHILs), selected from the Sloan Digital Sky Survey - a large-sized sample containing nearly equal proportion of diverse range of Seyfert galaxies showing similar redshift distributions compiled by Gelbord et al. (2009) using the Very Large Array survey images. The radio detection rate is low, 49%, which is lower than the detection rate of several other known Seyfert galaxy samples. These galaxies show low star formation rates and the radio emission is dominated by the active nucleus with $\\le$10% contribution from thermal emission, and possibly, none show evidence for relativistic beaming. The radio detection rate, distributions of radio power, and correlations between radio power and line luminosities or X-ray luminosity for narrow-line Seyfert 1 (NLS1), Seyfert 1 and Seyfert 2 galaxies are consistent with the predictions of the unified scheme hypothesis. Using correlation between radio and [O\\,III]\\,$\\l...

  11. Merging Galaxies Create a Binary Quasar

    Science.gov (United States)

    2010-02-01

    Astronomers have found the first clear evidence of a binary quasar within a pair of actively merging galaxies. Quasars are the extremely bright centers of galaxies surrounding super-massive black holes, and binary quasars are pairs of quasars bound together by gravity. Binary quasars, like other quasars, are thought to be the product of galaxy mergers. Until now, however, binary quasars have not been seen in galaxies that are unambiguously in the act of merging. But images of a new binary quasar from the Carnegie Institution's Magellan telescope in Chile show two distinct galaxies with "tails" produced by tidal forces from their mutual gravitational attraction. "This is really the first case in which you see two separate galaxies, both with quasars, that are clearly interacting," says Carnegie astronomer John Mulchaey who made observations crucial to understanding the galaxy merger. Most, if not all, large galaxies, such as our galaxy the Milky Way, host super-massive black holes at their centers. Because galaxies regularly interact and merge, astronomers have assumed that binary super-massive black holes have been common in the Universe, especially during its early history. Black holes can only be detected as quasars when they are actively accreting matter, a process that releases vast amounts of energy. A leading theory is that galaxy mergers trigger accretion, creating quasars in both galaxies. Because most such mergers would have happened in the distant past, binary quasars and their associated galaxies are very far away and therefore difficult for most telescopes to resolve. The binary quasar, labeled SDSS J1254+0846, was initially detected by the Sloan Digital Sky Survey, a large scale astronomical survey of galaxies and over 120,000 quasars. Further observations by Paul Green of the Harvard-Smithsonian Center for Astrophysics and colleagues* using NASA's Chandra's X-ray Observatory and telescopes at Kitt Peak National Observatory in Arizona and Palomar

  12. Interaction effects on galaxy pairs with Gemini/GMOS- II: Oxygen abundance gradients

    CERN Document Server

    Rosa, D A; Krabbe, A C; Hagele, G F; Cardaci, M V; Pastoriza, M G; Rodrigues, I; Winge, C

    2014-01-01

    In this paper we derived oxygen abundance gradients from HII regions located in eleven galaxies in eight systems of close pairs. Long-slit spectra in the range 4400-7300A were obtained with the Gemini Multi-Object Spec- trograph at Gemini South (GMOS). Spatial profiles of oxygen abundance in the gaseous phase along galaxy disks were obtained using calibrations based on strong emission-lines (N2 and O3N2). We found oxygen gradients signifi- cantly flatter for all the studied galaxies than those in typical isolated spiral galaxies. Four objects in our sample, AM1219A, AM1256B, AM 2030A and AM2030B, show a clear break in the oxygen abundance at galactocentric radius R/R25 between 0.2 and 0.5. For AM1219A and AM1256B we found negative slopes for the inner gradients, and for AM2030B we found a positive one. In all these three cases they show a flatter behaviour to the outskirts of the galaxies. For AM2030A, we found a positive-slope outer gradient while the inner one is almost compatible with a flat behaviour. A d...

  13. The effects of UV photometry and binary interactions on photometric redshift and galaxy morphology

    CERN Document Server

    Zhang, F; Li, L; Shan, H; Zhang, Y

    2010-01-01

    Using the Hyperz code and a template spectral library which consists of 4 observed galaxy spectra from Coleman, Wu & Weedman (CWW, 1980) and 8 spectral families built with evolutionary population synthesis models, we present photometric redshift estimates (photo-z) for a spectroscopic sample of 6,531 galaxies, and morphologies for a morphological sample of 1,502 bright galaxies. All galaxies are matched with the SDSS DR7 and GALEX DR4. The inclusion of Fuv or Nuv or both photometry decreases the number of catastrophic identifications (CIs, |z_phot -z_spec| > 1.0). If CIs are removed, the inclusion of both Fuv and Nuv photometry mainly increases the number of non-CIs in the low redshift, g-r 14 regions. Moreover, BIs mainly affect the determinations of E and S0 types. Nuv -u = 1.94 and 5.77-1.47(u-r) = Fuv discriminators can be used as morphology selection indicators. These two criteria have comparable reliability and completeness for selecting early- and late-type galaxies to C=2.6 criterion and higher c...

  14. Cosmic Collisions The Hubble Atlas of Merging Galaxies

    CERN Document Server

    Christensen, Lars Lindberg; Martin, Davide

    2009-01-01

    Lars Lindberg Christensen, Raquel Yumi Shida & Davide De Martin Cosmic Collisions: The Hubble Atlas of Merging Galaxies Like majestic ships in the grandest night, galaxies can slip ever closer until their mutual gravitational interaction begins to mold them into intricate figures that are finally, and irreversibly, woven together. It is an immense cosmic dance, choreographed by gravity. Cosmic Collisions contains a hundred new, many thus far unpublished, images of colliding galaxies from the NASA/ESA Hubble Space Telescope. It is believed that many present-day galaxies, including the Milky Way, were assembled from such a coalescence of smaller galaxies, occurring over billions of years. Triggered by the colossal and violent interaction between the galaxies, stars form from large clouds of gas in firework bursts, creating brilliant blue star clusters. The importance of these cosmic encounters reaches far beyond the stunning Hubble images. They may, in fact, be among the most important processes that shape ...

  15. X-shaped radio galaxies as observational evidence for the interaction of supermassive binary black holes and accretion disk at pc scale

    CERN Document Server

    Liu, F K

    2004-01-01

    A supermassive black hole binary may form during galaxy mergering. we investigate the interaction of the supermassive binary black holes (SMBBHs) and an accretion disk and show that the detected X-shaped structure in some FRII radio galaxies may be due to the interaction-realignment of inclined binary and accretion disk occurred within the pc scale of the galaxy center. We compare in detail the model and observations and show that the configuration is consistent very well with the observations of X-shaped radio sources. X-shaped radio feature form only in FRII radio sources due to the strong interaction between the binary and a standard disk, while the absence of X-shaped FRI radio galaxies is due to that the interaction between the binary and the radiatively inefficient accretion flow in FRI radio sources is negligible. It is suggested that the binary would keep misaligned with the outer disk for most of the life time of FRII radio galaxies and the orientation of jet in most FRII radio galaxies distributes r...

  16. Discovery of Massive, Mostly Star-formation Quenched Galaxies with Extremely Large Lyman-alpha Equivalent Widths at z ~ 3

    CERN Document Server

    Taniguchi, Yoshiaki; Kobayashi, Masakazu A R; Nagao, Tohru; Shioya, Yasuhiro; Scoville, Nick Z; Sanders, David B; Capak, Peter L; Koekemoer, Anton M; Toft, Sune; McCracken, Henry J; Fevre, Olivier Le; Tasca, Lidia; Sheth, Kartik; Renzini, Alvio; Lilly, Simon; Carollo, Marcella; Kovac, Katarina; Ilbert, Olivier; Schinnerer, Eva; Fu, Hai; Tresse, Laurence; Griffiths, Richard E; Civano, Francesca

    2015-01-01

    We report a discovery of 6 massive galaxies with both extremely large Lya equivalent width and evolved stellar population at z ~ 3. These MAssive Extremely STrong Lya emitting Objects (MAESTLOs) have been discovered in our large-volume systematic survey for strong Lya emitters (LAEs) with twelve optical intermediate-band data taken with Subaru/Suprime-Cam in the COSMOS field. Based on the SED fitting analysis for these LAEs, it is found that these MAESTLOs have (1) large rest-frame equivalent width of EW_0(Lya) ~ 100--300 A, (2) M_star ~ 10^10.5--10^11.1 M_sun, and (3) relatively low specific star formation rates of SFR/M_star ~ 0.03--1 Gyr^-1. Three of the 6 MAESTLOs have extended Ly$\\alpha$ emission with a radius of several kpc although they show very compact morphology in the HST/ACS images, which correspond to the rest-frame UV continuum. Since the MAESTLOs do not show any evidence for AGNs, the observed extended Lya emission is likely to be caused by star formation process including the superwind activit...

  17. GSH 91.5+2-114: A large HI shell in the outer part of the Galaxy

    CERN Document Server

    Cichowolski, Silvina

    2010-01-01

    GSH91.5+2-114 is a large HI shell located in the outer Galaxy at a kinematic distance of about 15 kpc. It was first identified in the Canadian Galactic Plane Survey (CGPS) by Pineault et al. (2002) as being possibly associated with objects possessing infrared colors which indicates strong stellar winds. The HI shell has no obvious continuum counterpart in the CGPS radio images at 408 and 1420 MHz or in the IRAS images. We found no evidence for early-type massive stars, most likely as a result of the large extinction that is expected for this large distance. An analysis of the energetics and of the main physical parameters of the HI shell shows that this shell is likely the result of the combined action of the stellar winds and supernova explosions of many stars. We investigate whether a number of slightly extended regions characterized by a thermal radio continuum and located near the periphery of the HI shell could be the result of star formation triggered by the expanding shell.

  18. HI Recycling Formation of Tidal Dwarf Galaxies

    CERN Document Server

    Duc, P A; Duc, Pierre-Alain; Brinks, Elias

    2000-01-01

    Galactic collisions trigger a number of phenomena, such as transportation inward of gas from distances of up to kiloparsecs from the center of a galaxy to the nuclear region, fuelling a central starburst or nuclear activity. The inverse process, the ejection of material into the intergalactic medium by tidal forces, is another important aspect and can be studied especially well through detailed HI observations of interacting systems which have shown that a large fraction of the gaseous component of colliding galaxies can be expelled. Part of this tidal debris might fall back, be dispersed throughout the intergalactic medium or recondense to form a new generation of galaxies: the so-called tidal dwarf galaxies. The latter are nearby examples of galaxies in formation. The properties of these recycled objects are reviewed here and different ways to identify them are reviewed.

  19. Comparative internal kinematics of the HII regions in interacting and isolated galaxies: implications for massive star formation modes

    CERN Document Server

    Zaragoza-Cardiel, Javier; Font, Joan; García-Lorenzo, Begoña; Camps-Fariña, Artemi; Fathi, Kambiz; James, Philip A; Erroz-Ferrer, Santiago; Barrera-Ballesteros, Jorge; Cisternas, Mauricio

    2015-01-01

    We have observed 10 interacting galaxy pairs using the Fabry-Perot interferometer GH$\\alpha$FaS (Galaxy H$\\alpha$ Fabry-Perot system) on the $4.2\\rm{m}$ William Herschel Telescope (WHT) at the Observatorio del Roque de los Muchachos, La Palma. We present here the H$\\alpha$ surface brightness, velocity and velocity dispersion maps for the 10 systems we have not previously observed using this technique, as well as the physical properties (sizes, H$\\alpha$ luminosities and velocity dispersion) of 1259 HII regions from the full sample. We also derive the physical properties of 1054 HII regions in a sample of 28 isolated galaxies observed with the same instrument in order to compare the two populations of HII regions. We find a population of the brightest HII regions for which the scaling relations, for example the relation between the H$\\alpha$ luminosity and the radius, are clearly distinct from the relations for the regions of lower luminosity. The regions in this bright population are more frequent in the inte...

  20. An extremely optically dim tidal feature in the gas-rich interacting galaxy group NGC 871/NGC 876/NGC 877

    CERN Document Server

    Lee-Waddell, K; Cuillandre, J -C; Cannon, J; Haynes, M P; Sick, J; Chandra, P; Patra, N; Stierwalt, S; Giovanelli, R

    2014-01-01

    We present GMRT HI observations and deep CFHT MegaCam optical images of the gas-rich interacting galaxy group NGC 871/NGC 876/NGC 877 (hereafter NGC 871/6/7). Our high-resolution data sets provide a census of the HI and stellar properties of the detected gas-rich group members. In addition to a handful of spiral, irregular and dwarf galaxies, this group harbours an intriguing HI feature, AGC 749170, that has a gas mass of ~10^9.3 M_sol, a dynamical-to-gas mass ratio of ~1 (assuming the cloud is rotating and in dynamical equilibrium) and no optical counterpart in previous imaging. Our observations have revealed a faint feature in the CFHT g'- and r'-bands; if it is physically associated with AGC 749170, the latter has M/L_g > 1000 M_sol/L_sol as well as a higher metallicity (estimated using photometric colours) and a significantly younger stellar population than the other low-mass gas-rich group members. These properties, as well as its spectral and spatial location with respect to its suspected parent galaxie...

  1. X-rays associated with the jet-cloud interacting radio galaxy 3C 277.3 (Coma A): implications for energy deposition

    CERN Document Server

    Worrall, D M; Young, A J

    2016-01-01

    We report the discovery with Chandra of X-ray-emitting gas associated with the jet-cloud interaction in the radio galaxy 3C 277.3 (Coma A), a source that falls in the most important power range for radio-mode feedback in the Universe. This hot gas, heated by the jet, dominates the mass of the cloud which is responsible for an extreme projected deflection of the kpc-scale radio jet. Highly absorbed X-ray emission from the nucleus of 3C 277.3 confirms that the jet lies close to the plane of the sky and so has a large intrinsic deflection. We detect group gas on the scale of the radio lobes, and see X-ray cavities coincident with the brightest radio emission, with the lobes embraced by X-ray enhancements that we argue are the result of shocks. The anti-correlation between the locations of X-ray arms and H$\\alpha$-emitting filaments that are believed to have originated from a merger with one or more gas-rich galaxies suggests that shocks advancing around the lobe are inhibited by the dense colder material. Synchr...

  2. Early Science with the Large Millimeter Telescope: Detection of Dust Emission in Multiple Images of a Normal Galaxy at z > 4 Lensed by a Frontier Fields Cluster

    Science.gov (United States)

    Pope, Alexandra; Montaña, Alfredo; Battisti, Andrew; Limousin, Marceau; Marchesini, Danilo; Wilson, Grant W.; Alberts, Stacey; Aretxaga, Itziar; Avila-Reese, Vladimir; Ramón Bermejo-Climent, José; Brammer, Gabriel; Bravo-Alfaro, Hector; Calzetti, Daniela; Chary, Ranga-Ram; Cybulski, Ryan; Giavalisco, Mauro; Hughes, David; Kado-Fong, Erin; Keller, Erica; Kirkpatrick, Allison; Labbe, Ivo; Lange-Vagle, Daniel; Lowenthal, James; Murphy, Eric; Oesch, Pascal; Rosa Gonzalez, Daniel; Sánchez-Argüelles, David; Shipley, Heath; Stefanon, Mauro; Vega, Olga; Whitaker, Katherine; Williams, Christina C.; Yun, Min; Zavala, Jorge A.; Zeballos, Milagros

    2017-04-01

    We directly detect dust emission in an optically detected, multiply imaged galaxy lensed by the Frontier Fields cluster MACSJ0717.5+3745. We detect two images of the same galaxy at 1.1 mm with the AzTEC camera on the Large Millimeter Telescope leaving no ambiguity in the counterpart identification. This galaxy, MACS0717_Az9, is at z > 4 and the strong lensing model (μ = 7.5) allows us to calculate an intrinsic IR luminosity of 9.7 × 1010 L ⊙ and an obscured star formation rate of 14.6 ± 4.5 M ⊙ yr‑1. The unobscured star formation rate from the UV is only 4.1 ± 0.3 M ⊙ yr‑1, which means the total star formation rate (18.7 ± 4.5 M ⊙ yr‑1) is dominated (75%–80%) by the obscured component. With an intrinsic stellar mass of only 6.9 × 109 M ⊙, MACS0717_Az9 is one of only a handful of z > 4 galaxies at these lower masses that is detected in dust emission. This galaxy lies close to the estimated star formation sequence at this epoch. However, it does not lie on the dust obscuration relation (IRX-β) for local starburst galaxies and is instead consistent with the Small Magellanic Cloud attenuation law. This remarkable lower mass galaxy, showing signs of both low metallicity and high dust content, may challenge our picture of dust production in the early universe.

  3. The Sloan Lens ACS Survey. I. A Large Spectroscopically Selected Sample of Massive Early-Type Lens Galaxies

    Science.gov (United States)

    Bolton, Adam S.; Burles, Scott; Koopmans, Leon V. E.; Treu, Tommaso; Moustakas, Leonidas A.

    2006-01-01

    The Sloan Lens ACS (SLACS) Survey is an efficient Hubble Space Telescope (HST) Snapshot imaging survey for new galaxy-scale strong gravitational lenses. The targeted lens candidates are selected spectroscopically from the Sloan Digital Sky Survey (SDSS) database of galaxy spectra for having multiple nebular emission lines at a redshift significantly higher than that of the SDSS target galaxy. The SLACS survey is optimized to detect bright early-type lens galaxies with faint lensed sources in order to increase the sample of known gravitational lenses suitable for detailed lensing, photometric, and dynamical modeling. In this paper, the first in a series on the current results of our HST Cycle 13 imaging survey, we present a catalog of 19 newly discovered gravitational lenses, along with nine other observed candidate systems that are either possible lenses, nonlenses, or nondetections. The survey efficiency is thus >=68%. We also present Gemini 8 m and Magellan 6.5 m integral-field spectroscopic data for nine of the SLACS targets, which further support the lensing interpretation. A new method for the effective subtraction of foreground galaxy images to reveal faint background features is presented. We show that the SLACS lens galaxies have colors and ellipticities typical of the spectroscopic parent sample from which they are drawn (SDSS luminous red galaxies and quiescent MAIN sample galaxies), but are somewhat brighter and more centrally concentrated. Several explanations for the latter bias are suggested. The SLACS survey provides the first statistically significant and homogeneously selected sample of bright early-type lens galaxies, furnishing a powerful probe of the structure of early-type galaxies within the half-light radius. The high confirmation rate of lenses in the SLACS survey suggests consideration of spectroscopic lens discovery as an explicit science goal of future spectroscopic galaxy surveys.

  4. Constraining the Baryon-Dark Matter Relative Velocity with the Large-Scale 3-Point Correlation Function of the SDSS BOSS DR12 CMASS Galaxies

    CERN Document Server

    Slepian, Zachary; Blazek, Jonathan A; Brownstein, Joel R; Chuang, Chia-Hsun; Gil-Marín, Héctor; Ho, Shirley; Kitaura, Francisco-Shu; McEwen, Joseph E; Percival, Will J; Ross, Ashley J; Rossi, Graziano; Seo, Hee-Jong; Slosar, Anže; Vargas-Magaña, Mariana

    2016-01-01

    We search for a galaxy clustering bias due to a modulation of galaxy number with the baryon-dark matter relative velocity resulting from recombination-era physics. We find no detected signal and place the constraint $b_v < 0.01$ on the relative velocity bias for the CMASS galaxies. This bias is an important potential systematic of Baryon Acoustic Oscillation (BAO) method measurements of the cosmic distance scale using the 2-point clustering. Our limit on the relative velocity bias indicates a systematic shift of no more than $0.3\\%$ rms in the distance scale inferred from the BAO feature in the BOSS 2-point clustering, well below the $1\\%$ statistical error of this measurement. This constraint is the most stringent currently available and has important implications for the ability of upcoming large-scale structure surveys such as DESI to self-protect against the relative velocity as a possible systematic.

  5. Extended X-ray emission from non-thermal sources in the COSMOS field: A detailed study of a large radio galaxy at z=1.168

    CERN Document Server

    Jelic, Vibor; Finoguenov, Alexis; Tanaka, Masayuki; Civano, Francesca; Schinnerer, Eva; Cappelluti, Nico; Koekemoer, Anton

    2012-01-01

    X-ray selected galaxy group samples are usually generated by searching for extended X- ray sources that reflect the thermal radiation of the intragroup medium. On the other hand, large radio galaxies that regularly occupy galaxy groups also emit in the X-ray window, and their contribution to X-ray selected group samples is still not well understood. In order to investigate their relative importance, we have carried out a systematic search for non-thermal extended X-ray sources in the COSMOS field. Based on the morphological coincidence of X-ray and radio extensions, out of 60 radio galaxies, and \\sim 300 extended X-ray sources, we find only one candidate where the observed extended X-ray emission arises from non- thermal processes related to radio galaxies. We present a detailed analysis of this source, and its environment. Our results yield that external Inverse Compton emission of the lobes is the dominant process that generates the observed X-ray emission of our extended X-ray candidate, with a minor contr...

  6. Laser-plasma interactions in large gas-filled hohlraums

    Energy Technology Data Exchange (ETDEWEB)

    Turner, R.E.; Powers, L.V.; Berger, R.L. [and others

    1996-06-01

    Indirect-drive targets planned for the National Ignition Facility (NIF) laser consist of spherical fuel capsules enclosed in cylindrical Au hohlraums. Laser beams, arranged in cylindrical rings, heat the inside of the Au wall to produce x rays that in turn heat and implode the capsule to produce fusion conditions in the fuel. Detailed calculations show that adequate implosion symmetry can be maintained by filling the hohlraum interior with low-density, low-Z gases. The plasma produced from the heated gas provides sufficient pressure to keep the radiating Au surface from expanding excessively. As the laser heats this gas, the gas becomes a relatively uniform plasma with small gradients in velocity and density. Such long-scale-length plasmas can be ideal mediums for stimulated Brillouin Scattering (SBS). SBS can reflect a large fraction of the incident laser light before it is absorbed by the hohlraum; therefore, it is undesirable in an inertial confinement fusion target. To examine the importance of SBS in NIF targets, the authors used Nova to measure SBS from hohlraums with plasma conditions similar to those predicted for high-gain NIF targets. The plasmas differ from the more familiar exploding foil or solid targets as follows: they are hot (3 keV); they have high electron densities (n{sub e}=10{sup 21}cm{sup {minus}3}); and they are nearly stationary, confined within an Au cylinder, and uniform over large distances (>2 mm). These hohlraums have <3% peak SBS backscatter for an interaction beam with intensities of 1-4 x 10{sup 15} W/cm{sup 2}, a laser wavelength of 0.351{micro}m, f/4 or f/8 focusing optics, and a variety of beam smoothing implementations. Based on these conditions the authors conclude that SBS does not appear to be a problem for NIF targets.

  7. Formation of periodic galaxy peaks from primeval perturbations with resonance interaction

    Institute of Scientific and Technical Information of China (English)

    李晓卿; 张航

    1995-01-01

    The nonlinear development and evolution of fluctuations in the oscillation universe are investigated on the basis of three-wave process. It is shown that the perturbed fluctuations undergo some spatial modulation on the scale λ, which might be identified as the observed period in space of galaxy peaks.

  8. The Sloan Lens ACS Survey. I. A large spectroscopically selected sample of massive early-type lens galaxies

    NARCIS (Netherlands)

    Bolton, AS; Burles, S; Koopmans, LVE; Treu, T; Moustakas, LA

    2006-01-01

    The Sloan Lens ACS (SLACS) Survey is an efficient Hubble Space Telescope (HST) Snapshot imaging survey for new galaxy-scale strong gravitational lenses. The targeted lens candidates are selected spectroscopically from the Sloan Digital Sky Survey (SDSS) database of galaxy spectra for having multiple

  9. The Sloan Lens ACS Survey. I. A large spectroscopically selected sample of massive early-type lens galaxies

    NARCIS (Netherlands)

    Bolton, AS; Burles, S; Koopmans, LVE; Treu, T; Moustakas, LA

    2006-01-01

    The Sloan Lens ACS (SLACS) Survey is an efficient Hubble Space Telescope (HST) Snapshot imaging survey for new galaxy-scale strong gravitational lenses. The targeted lens candidates are selected spectroscopically from the Sloan Digital Sky Survey (SDSS) database of galaxy spectra for having multiple

  10. The Large-Scale Environment of Dynamical Young Clusters of Galaxies

    OpenAIRE

    Plionis, M.; Basilakos, S.

    2001-01-01

    We investigate whether the dynamical status of clusters is related to the large-scale structure of the Universe. We find that cluster substructure is strongly correlated with the tendency of clusters to be aligned with their nearest neighbour and in general with the nearby clusters that belong to the same supercluster. Furthermore, dynamically young clusters are more clustered than the overall cluster population. These are strong indications that clusters develop in a hierarchical fashion by ...

  11. The effects of assembly bias on cosmological inference from galaxy-galaxy lensing and galaxy clusters

    CERN Document Server

    McEwen, Joseph E

    2016-01-01

    The combination of galaxy-galaxy lensing (GGL) and galaxy clustering is a promising route to measuring the amplitude of matter clustering and testing modified gravity theories of cosmic acceleration. Halo occupation distribution (HOD) modeling can extend the approach down to nonlinear scales, but galaxy assembly bias could introduce systematic errors by causing the HOD to vary with large scale environment at fixed halo mass. We investigate this problem using the mock galaxy catalogs created by Hearin & Watson (2013, HW13), which exhibit significant assembly bias because galaxy luminosity is tied to halo peak circular velocity and galaxy colour is tied to halo formation time. The preferential placement of galaxies (especially red galaxies) in older halos affects the cutoff of the mean occupation function $\\langle N_\\text{cen}(M_\\text{min}) \\rangle$ for central galaxies, with halos in overdense regions more likely to host galaxies. The effect of assembly bias on the satellite galaxy HOD is minimal. We intro...

  12. The New Numerical Galaxy Catalog (ν2GC): An updated semi-analytic model of galaxy and active galactic nucleus formation with large cosmological N-body simulations

    Science.gov (United States)

    Makiya, Ryu; Enoki, Motohiro; Ishiyama, Tomoaki; Kobayashi, Masakazu A. R.; Nagashima, Masahiro; Okamoto, Takashi; Okoshi, Katsuya; Oogi, Taira; Shirakata, Hikari

    2016-04-01

    We present a new cosmological galaxy formation model, ν2GC, as an updated version of our previous model νGC. We adopt the so-called "semi-analytic" approach, in which the formation history of dark matter halos is computed by N-body simulations, while the baryon physics such as gas cooling, star formation, and supernova feedback are simply modeled by phenomenological equations. Major updates of the model are as follows: (1) the merger trees of dark matter halos are constructed in state-of-the-art N-body simulations, (2) we introduce the formation and evolution process of supermassive black holes and the suppression of gas cooling due to active galactic nucleus (AGN) activity, (3) we include heating of the intergalactic gas by the cosmic UV background, and (4) we tune some free parameters related to the astrophysical processes using a Markov chain Monte Carlo method. Our N-body simulations of dark matter halos have unprecedented box size and mass resolution (the largest simulation contains 550 billion particles in a 1.12 Gpc h-1 box), enabling the study of much smaller and rarer objects. The model was tuned to fit the luminosity functions of local galaxies and mass function of neutral hydrogen. Local observations, such as the Tully-Fisher relation, the size-magnitude relation of spiral galaxies, and the scaling relation between the bulge mass and black hole mass were well reproduced by the model. Moreover, the model also reproduced well the cosmic star formation history and redshift evolution of rest-frame K-band luminosity functions. The numerical catalog of the simulated galaxies and AGNs is publicly available on the web.

  13. Morphology of galaxies

    CERN Document Server

    Wadadekar, Yogesh

    2012-01-01

    The study of the morphology of galaxies is important in order to understand the formation and evolution of galaxies and their sub-components as a function of luminosity, environment, and star-formation and galaxy assembly over cosmic time. Disentangling the many variables that affect galaxy evolution and morphology, requires large galaxy samples and automated ways to measure morphology. The advent of large digital sky surveys, with unprecedented depth and resolution, coupled with sophisticated quantitative methods for morphology measurement are providing new insights in this fast evolving field of astronomical research.

  14. Pre-existing dwarfs, tidal knots and a tidal dwarf galaxy: an unbiased HI study of the gas-rich interacting galaxy group NGC 3166/9

    CERN Document Server

    Lee-Waddell, Karen; Haynes, Martha P; Stierwalt, Sabrina; Chengalur, Jayaram; Chandra, Poonam; Giovanelli, Riccardo

    2012-01-01

    We present Arecibo Legacy Fast ALFA (ALFALFA) and follow-up Giant Metrewave Radio Telescope (GMRT) HI observations of the gas-rich interacting group NGC 3166/9. The sensitive ALFALFA data provide a complete census of HI-bearing systems in the group while the high-resolution GMRT data elucidate their origin, enabling one of the first unbiased physical studies of gas-rich dwarf companions and the subsequent identification of second generation, tidal dwarf galaxies in a nearby group. The ALFALFA maps reveal an extended HI envelope around the NGC 3166/9 group core, which we mosaic at higher resolution using six GMRT pointings spanning ~1 square degree. A thorough search of the GMRT datacube reveals eight low-mass objects with gas masses ranging from 4x10^7 to 3x10^8 M_sol and total dynamical masses up to 1.4x10^9 M_sol. A comparison of the HI fluxes measured from the GMRT data to those measured in the ALFALFA data suggests that a significant fraction (~60%) of the HI is smoothly distributed on scales greater than...

  15. The growth of the central region by acquisition of counter-rotating gas in star-forming galaxies

    CERN Document Server

    Chen, Yan-Mei; Tremonti, Christy A; Bershady, Matt; Merrifield, Michael; Emsellem, Eric; Jin, Yi-Fei; Huang, Song; Fu, Hai; Wake, David A; Bundy, Kevin; Stark, David; Lin, Lihwai; Argudo-Fernandez, Maria; Bergmann, Thaisa Storchi; Bizyaev, Dmitry; Brownstein, Joel; Bureau, Martin; Chisholm, John; Drory, Niv; Guo, Qi; Hao, Lei; Hu, Jian; Li, Cheng; Li, Ran; Lopes, Alexandre Roman; Pan, Kai-Ke; Riffel, Rogemar A; Thomas, Daniel; Wang, Lan; Westfall, Kyle; Yan, Ren-Bin

    2016-01-01

    Galaxies grow through both internal and external processes. In about 10% of nearby red galaxies with little star formation, gas and stars are counter-rotating, demonstrating the importance of external gas acquisition in these galaxies. However, systematic studies of such phenomena in blue, star-forming galaxies are rare, leaving uncertain the role of external gas acquisition in driving evolution of blue galaxies. Based on new measurements with integral field spectroscopy of a large representative galaxy sample, we find an appreciable fraction of counter-rotators among blue galaxies (9 out of 489 galaxies). The central regions of blue counter-rotators show younger stellar populations and more intense, ongoing star formation than their outer parts, indicating ongoing growth of the central regions. The result offers observational evidence that the acquisition of external gas in blue galaxies is possible; the interaction with pre-existing gas funnels the gas into nuclear regions (< 1 kpc) to form new stars.

  16. IBAR: Interacting boson model calculations for large system sizes

    Science.gov (United States)

    Casperson, R. J.

    2012-04-01

    Scaling the system size of the interacting boson model-1 (IBM-1) into the realm of hundreds of bosons has many interesting applications in the field of nuclear structure, most notably quantum phase transitions in nuclei. We introduce IBAR, a new software package for calculating the eigenvalues and eigenvectors of the IBM-1 Hamiltonian, for large numbers of bosons. Energies and wavefunctions of the nuclear states, as well as transition strengths between them, are calculated using these values. Numerical errors in the recursive calculation of reduced matrix elements of the d-boson creation operator are reduced by using an arbitrary precision mathematical library. This software has been tested for up to 1000 bosons using comparisons to analytic expressions. Comparisons have also been made to the code PHINT for smaller system sizes. Catalogue identifier: AELI_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AELI_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License version 3 No. of lines in distributed program, including test data, etc.: 28 734 No. of bytes in distributed program, including test data, etc.: 4 104 467 Distribution format: tar.gz Programming language: C++ Computer: Any computer system with a C++ compiler Operating system: Tested under Linux RAM: 150 MB for 1000 boson calculations with angular momenta of up to L=4 Classification: 17.18, 17.20 External routines: ARPACK (http://www.caam.rice.edu/software/ARPACK/) Nature of problem: Construction and diagonalization of large Hamiltonian matrices, using reduced matrix elements of the d-boson creation operator. Solution method: Reduced matrix elements of the d-boson creation operator have been stored in data files at machine precision, after being recursively calculated with higher than machine precision. The Hamiltonian matrix is calculated and diagonalized, and the requested transition strengths are calculated

  17. Lyman-Alpha Emitting Galaxies as a Probe of Reionization: Large-Scale Bubble Morphology and Small-Scale Absorbers

    CERN Document Server

    Kakiichi, Koki; Ciardi, Benedetta; Graziani, Luca

    2015-01-01

    The visibility of LyA emitting galaxies during the Epoch of Reionization is controlled by both diffuse HI patches in large-scale bubble morphology and small-scale absorbers. To investigate the impact on LyA photons, we apply a novel combination of analytic and numerical calculations to three scenarios: (i) the `bubble' model, where only diffuse HI outside ionized bubbles is present; (ii) the `web' model, where HI exists only in overdense self-shielded gas; and (iii) the more realistic 'web-bubble' model, which contains both. Our analysis confirms that there is a degeneracy between the ionization structure of the intergalactic medium (IGM) and the HI fraction inferred from LyA surveys, as the three models suppress LyA flux equally with very different HI fractions. We argue that a joint analysis of the LyA luminosity function and the rest-frame equivalent width distribution/LyA fraction can break this degeneracy and provide constraints on the reionization history and its topology. We further show that constrain...

  18. Spitzer Survey of the Large Magellanic Cloud, Surveying the Agents of a Galaxy's Evolution (SAGE) I : Overview and Initial Results

    CERN Document Server

    Meixner, M; Indebetouw, R; Hora, J L; Whitney, B; Blum, R; Reach, W; Bernard, J P; Meade, M; Babler, B; Engelbracht, C W; Misselt, K; Vijh, U; Leitherer, C; Cohen, M; Churchwell, E B; Boulanger, F; Frogel, J A; Fukui, Y; Gallagher, J; Gorjian, V; Harris, J; Kelly, D; Kawamura, A; Kim, S Y; Latter, W B; Madden, S; Markwick-Kemper, C; Mizuno, A; Mizuno, N; Mould, J; Nota, A; Oey, M S; Olsen, K; Onishi, T; Paladini, R; Panagia, N; Perez-Gonzalez, P; Shibai, H; Shuji, S; Smith, L; Staveley-Smith, L; Tielens, A G G M; Ueta, T; Van Dyk, S D; Volk, K; Werner, M; Zaritsky, D; Meixner, Margaret; Gordon, Karl D.; Indebetouw, Remy; Hora, Joseph L.; Whitney, Barbara; Blum, Robert; Reach, William; Bernard, Jean-Philippe; Meade, Marilyn; Babler, Brian; Engelbracht, Charles W.; For, Bi-Qing; Misselt, Karl; Vijh, Uma; Leitherer, Claus; Cohen, Martin; Churchwell, Ed B.; Boulanger, Francois; Frogel, Jay A.; Fukui, Yasuo; Gallagher, Jay; Gorjian, Varoujan; Harris, Jason; Kelly, Douglas; Kawamura, Akiko; Kim, SoYoung; Latter, William B.; Madden, Suzanne; Markwick-Kemper, Ciska; Mizuno, Akira; Mizuno, Norikazu; Mould, Jeremy; Nota, Antonella; Olsen, Knut; Onishi, Toshikazu; Paladini, Roberta; Panagia, Nino; Perez-Gonzalez, Pablo; Shibai, Hiroshi; Shuji, Sato; Smith, Linda; Staveley-Smith, Lister; Ueta, Toshiya; Dyk, Schuyler Van; Volk, Kevin; Werner, Michael; Zaritsky, Dennis

    2006-01-01

    We are performing a uniform and unbiased, ~7x7 degrees imaging survey of the Large Magellanic Cloud (LMC), using the IRAC and MIPS instruments on board the Spitzer Space Telescope in order to survey the agents of a galaxy's evolution (SAGE), the interstellar medium (ISM) and stars in the LMC. The detection of diffuse ISM with column densities >1.2x10^21 H cm^-2 permits detailed studies of dust processes in the ISM. SAGE's point source sensitivity enables a complete census of newly formed stars with masses >3 solar masses that will determine the current star formation rate in the LMC. SAGE's detection of evolved stars with mass loss rates >1x10^-8 solar masses per year will quantify the rate at which evolved stars inject mass into the ISM of the LMC. The observing strategy includes two epochs in 2005, separated by three months, that both mitigate instrumental artifacts and constrain source variability. The SAGE data are non-proprietary. The data processing includes IRAC and MIPS pipelines and a database for mi...

  19. Mapping Large-Scale Gaseous Outflows in Ultraluminous Infrared Galaxies with Keck II ESI Spectra: Spatial Extent of the Outflow

    CERN Document Server

    Martin, C L

    2006-01-01

    The kinematics of neutral gas and warm ionized gas have been mapped in one-dimension across ultraluminous starburst galaxies using interstellar absorption and emission lines, in Keck II ESI spectra. Blue-shifted absorption is found along more of the slit than anticipated, exceeding scales of 15 kpc across several systems. The large velocity gradient measured across some of these outflows is inconsistent with a flow diverging from the central starburst -- angular momentum conservation reduces the rotational velocity of an outflow as it expands. More widespread star formation, likely triggered by the merger, probably drives these outflows, although some models suggest the collision itself could generate a wind by shock heating interstellar gas throughout the disk. Young mergers with separated nuclei present the highest outflow masses, due mainly to the larger area over which the cool gas can be detected. In a typical ULIG, the mass carried by the cool phase of the outflow is around 10^8Msun, or a few percent of...

  20. Molecular gas in spiral galaxies a new warm phase at large galactocentric distances?

    CERN Document Server

    Papadopoulos, P P; Viti, S

    2002-01-01

    There is now strong evidence suggesting that the 12CO J = 1-0 transition, widely used to trace H2 gas, significantly underestimates its mass in metal-poor regions. In spiral disks such regions are found in large galactocentric distances where we show that any unaccounted H2 gas phase is likely to be diffuse (~5-20 cm^-3) and warmer (T(kin) ~ 50-100 K) than the cool (T(kin) ~ 15-20 K) CO-luminous one. Moreover we find that a high value of the H2 formation rate on grains, suggested by recent observational work, can compensate for the reduction of the available grain surface in the metal-poor part of typical galactic disks and thus enhance this CO-poor H2 component which may be contributing significantly to the mass and pressure of spiral disks beyond their optical radius.

  1. The influence of non-minimally coupled scalar fields on the dynamics of interacting galaxies

    CERN Document Server

    Gabbasov, R F; Cervantes-Cota, J L; Klapp, J

    2009-01-01

    We study bar formation in galactic disks as a consequence of the collision of two spiral galaxies under the influence of a potential which is obtained from the Newtonian limit of a scalar--tensor theory of gravity. We found that dynamical effects depend on parameters ($\\alpha$, $\\lambda$) of the theory. In particular, we observe that the bar is shorter for weaker tidal perturbations, which in turn corresponds to smaller values of $\\lambda$ used in our numerical experiments.

  2. Galaxy Interactions in Compact Groups I : The Galactic Winds of HCG16

    CERN Document Server

    Vogt, Frédéric P A; Kewley, Lisa J

    2013-01-01

    Using the WiFeS integral field spectrograph, we have undertaken a series of observations of star-forming galaxies in Compact Groups. In this first paper dedicated to the project, we present the analysis of the spiral galaxy NGC838, a member of the Hickson Compact Group 16, and of its galactic wind. Our observations reveal that the wind forms an asymmetric, bipolar, rotating structure, powered by a nuclear starburst. Emission line ratio diagnostics indicate that photoionization is the dominant excitation mechanism at the base of the wind. Mixing from slow shocks (up to 20%) increases further out along the outflow axis. The asymmetry of the wind is most likely caused by one of the two lobes of the wind bubble bursting out of its HI envelope, as indicated by line ratios and radial velocity maps. The characteristics of this galactic wind suggest that it is caught early (a few Myr) in the wind evolution sequence. The wind is also quite different to the galactic wind in the partner galaxy NGC839 which contains a sy...

  3. The large-scale structure of the halo of the Andromeda galaxy. I. Global stellar density, morphology and metallicity properties

    Energy Technology Data Exchange (ETDEWEB)

    Ibata, Rodrigo A.; Martin, Nicolas F. [Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de lUniversité, F-67000 Strasbourg (France); Lewis, Geraint F. [Institute of Astronomy, School of Physics A28, University of Sydney, NSW 2006 (Australia); McConnachie, Alan W. [NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7 (Canada); Irwin, Michael J. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Ferguson, Annette M. N.; Bernard, Edouard J.; Peñarrubia, Jorge [Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Babul, Arif; Navarro, Julio [Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, British Columbia V8P 5C2 (Canada); Chapman, Scott C. [Department of Physics and Atmospheric Science, Dalhousie University, 6310 Coburg Road, Halifax NS B3H 4R2 (Canada); Collins, Michelle [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Fardal, Mark [University of Massachusetts, Department of Astronomy, LGRT 619-E, 710 North Pleasant Street, Amherst, MA 01003-9305 (United States); Mackey, A. D. [RSAA, The Australian National University, Mount Stromlo Observatory, Cotter Road, Weston Creek ACT 2611 (Australia); Rich, R. Michael [Department of Physics and Astronomy, University of California, Los Angeles, PAB, 430 Portola Plaza, Los Angeles, CA 90095-1547 (United States); Tanvir, Nial [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Widrow, Lawrence, E-mail: rodrigo.ibata@astro.unistra.fr [Department of Physics, Engineering Physics, and Astronomy Queen' s University, Kingston, Ontario K7L 3N6 (Canada)

    2014-01-10

    We present an analysis of the large-scale structure of the halo of the Andromeda galaxy, based on the Pan-Andromeda Archeological Survey (PAndAS), currently the most complete map of resolved stellar populations in any galactic halo. Despite the presence of copious substructures, the global halo populations follow closely power-law profiles that become steeper with increasing metallicity. We divide the sample into stream-like populations and a smooth halo component (defined as the population that cannot be resolved into spatially distinct substructures with PAndAS). Fitting a three-dimensional halo model reveals that the most metal-poor populations ([Fe/H]<−1.7) are distributed approximately spherically (slightly prolate with ellipticity c/a = 1.09 ± 0.03), with only a relatively small fraction residing in discernible stream-like structures (f {sub stream} = 42%). The sphericity of the ancient smooth component strongly hints that the dark matter halo is also approximately spherical. More metal-rich populations contain higher fractions of stars in streams, with f {sub stream} becoming as high as 86% for [Fe/H]>−0.6. The space density of the smooth metal-poor component has a global power-law slope of γ = –3.08 ± 0.07, and a non-parametric fit shows that the slope remains nearly constant from 30 kpc to ∼300 kpc. The total stellar mass in the halo at distances beyond 2° is ∼1.1 × 10{sup 10} M {sub ☉}, while that of the smooth component is ∼3 × 10{sup 9} M {sub ☉}. Extrapolating into the inner galaxy, the total stellar mass of the smooth halo is plausibly ∼8 × 10{sup 9} M {sub ☉}. We detect a substantial metallicity gradient, which declines from ([Fe/H]) = –0.7 at R = 30 kpc to ([Fe/H]) = –1.5 at R = 150 kpc for the full sample, with the smooth halo being ∼0.2 dex more metal poor than the full sample at each radius. While qualitatively in line with expectations from cosmological simulations, these observations are of great importance as

  4. Ring galaxies as the cradle for ULXs

    Science.gov (United States)

    Wolter, Anna

    2015-08-01

    Ring galaxies are unique laboratories where the effects of galaxy interactions can be studied and the final stages of stellar evolution investigated. They are characterized by high star formation rates (SFR) and low metallicity, which favours the formation of high mass remnants. The few ring galaxies for which high resolution X-ray data are available show enhanced X-ray emission, and large numbers of Ultraluminous X-ray sources (ULXs). Due to the peculiar morphology of ring galaxies, detected point sources in the ring are very likely to be physically associated with the galaxy, reducing the problem of contamination from spurious sources which affects other samples. However the evidence in the X-ray band is based on a very scanty sample of four galaxies.In order to find an unbiased sample with which to compare these findings, we have selected all the peculiar galaxies labelled as collisional rings with a spectroscopic redshift z<0.02 from the Arp & Madore `Catalogue of southern peculiar galaxies and associations'. This selection produces a sample of 12 galaxies which we have observed with Chandra and XMM-Newton. We will discuss the results of these observations and support for current models that propose low metallicity environments as the ideal cradle for ULXs. We will compare the results from this statistically selected sample with those from brighter and known ring galaxies in order to asses the likelihood to find IMBHs due to collision events. We will address the presence of other signs of interaction, from high SFR to multiwavelenght morphology and spectra (eg. IR, Halpha..).

  5. Microfluidic large scale integration of viral-host interaction analysis.

    Science.gov (United States)

    Ben-Ari, Ya'ara; Glick, Yair; Kipper, Sarit; Schwartz, Nika; Avrahami, Dorit; Barbiro-Michaely, Efrat; Gerber, Doron

    2013-06-21

    Viral-host interactions represent potential drug targets for novel antiviral strategies (Flisiak et al., Hepatology, 2008, 47, 817-26). Hence, it is important to establish an adequate platform for identifying and analyzing such interactions. In this review, we discuss bottlenecks in conventional protein-protein interaction methodologies and present the contribution of innovative microfluidic-based technologies towards a solution to these problems with respect to viral-host proteomics.

  6. Isolated Galaxies and Isolated Satellite Systems

    CERN Document Server

    Ann, H B; Choi, Yun-Young

    2009-01-01

    We search for isolated galaxies using a volume-limited sample of galaxies with 0.02r_{vir,nei} and \\rho <\\bar{\\rho} well segregates the CIG galaxies. We confirm the morphology conformity between the host and their satellites, which suggests importance of hydrodynamic interaction among galaxies within their virial radii in galaxy evolution.

  7. NIHAO project I: Reproducing the inefficiency of galaxy formation across cosmic time with a large sample of cosmological hydrodynamical simulations

    CERN Document Server

    Wang, Liang; Stinson, Gregory S; Macciò, Andrea V; Penzo, Camilla; Kang, Xi; Keller, Ben W; Wadsley, James

    2015-01-01

    We introduce project NIHAO (Numerical Investigation of a Hundred Astrophysical Objects), a set of 100 cosmological zoom-in hydrodynamical simulations performed using the GASOLINE code, with an improved implementation of the SPH algorithm. The haloes in our study range from dwarf to Milky Way masses, and represent an unbiased sampling of merger histories, concentrations and spin parameters. The particle masses and force softenings are chosen to resolve the mass profile to below 1% of the virial radius at all masses, ensuring that galaxy half-light radii are well resolved. Using the same treatment of star formation and stellar feedback for every object, the simulated galaxies reproduce the observed inefficiency of galaxy formation across cosmic time as expressed through the stellar mass vs halo mass relation, and the star formation rate vs stellar mass relation. We thus conclude that stellar feedback is the chief piece of physics required to limit the efficiency of star formation in galaxies less massive than t...

  8. Efficient Use of Interactive Video with Large Groups.

    Science.gov (United States)

    Jones, Brian

    1993-01-01

    Reports on ways in which interactive video-based courseware is being used with students studying for vocational qualifications at Thames Valley University (United Kingdom). Two alternative models using interactive video are described, one using multiple workstations and one using a single workstation led by a tutor. (Contains six references.) (LRW)

  9. Early Science with the Large Millimeter Telescope: discovery of the 12CO(1-0) emission line in the ring galaxy, VIIZw466

    CERN Document Server

    Wong, O Ivy; Sánchez-Argüelles, D; Narayanan, G; Wall, W F; Zwaan, M A; González, D Rosa; Zeballos, M; Bekki, K; Mayya, Y D; Montaña, A; Chung, A

    2016-01-01

    We report an early science discovery of the CO(1-0) emission line in the collisional ring galaxy, VII Zw466, using the Redshift Search Receiver instrument on the Large Millimeter Telescope Alfonso Serrano.The apparent molecular-to-atomic gas ratio either places the ISM of VII Zw466 in the HI-dominated regime or implies a large quantity of CO-dark molecular gas, given its high star formation rate. The molecular gas densities and star formation rate densities of VII Zw466 are consistent with the standard Kennicutt-Schmidt star formation law even though we find this galaxy to be H2-deficient. The choice of CO-to-H2 conversion factors cannot explain the apparent H2 deficiency in its entirety. Hence, we find that the collisional ring galaxy, VII Zw466, is either largely deficient in both H2 and HI or contains a large mass of CO-dark gas. A low molecular gas fraction could be due to the enhancement of feedback processes from previous episodes of star formation as a result of the star-forming ISM being confined to t...

  10. ALMA CO Observations of Shocks and Star Formation in the Interacting Galaxies IC 2163 and NGC 2207

    Science.gov (United States)

    Elmegreen, Debra M.; Elmegreen, Bruce; Kaufman, Michele; Brinks, Elias; Struck, Curtis; Bournaud, Frederic; Sheth, Kartik; Juneau, Stephanie

    2017-01-01

    The spiral galaxies IC 2163 and NGC 2207 are a well-studied pair undergoing a grazing collision. ALMA CO observations of masses, column densities, and velocities are combined with HI, Hα, optical, and 24 micron data to study the star formation rates and efficiencies. The close encounter of the galaxies produced in-plane tidal forces in IC 2163, resulting in a large shock with high molecular velocity gradients and both radial and azimuthal streaming (100 km/s) that formed a pile-up of molecular gas in the resulting cuspy-oval or ``eyelid'' structure at mid-radius. The encounter also produced forces nearly orthogonal to the plane of NGC 2207, resulting in a warp. By comparing with the Kennicutt-Schmidt relation for star formation, we find that some regions of NGC 2207 with unusually high turbulent speeds (40-50 km/s) and high star formation rates (>0.01 Mo/pc2/Myr) have gas that is predominantly atomic with high density cores. Half of the CO mass is in 300 clouds each more massive than 4.0x105 Mo. The mass distribution functions for the CO clouds and star complexes in the eyelid in IC 2163 both have a slope similar to what is observed in Milky Way clouds; the CO slope is steeper in NGC 2207. The CO distribution in NGC 2207 also includes a nuclear ring, a mini-bar, and a mini-starburst region that dominates the 24 micron, radio, and Hα emission in both galaxies. Dust extinction, molecular column densities, and slightly negative molecular velocities indicate the mini-starburst region has ejected a jet of molecular gas nearly perpendicular to the plane of NGC 2207 on the near side with a kinetic energy of 1052 ergs. The large scale star formation efficiency, measured as the ratio of the summed masses of the star complexes near molecular clouds to the combined star complex and cloud masses, is 7% overall; it is 23% in the mini-starburst. The maximum age of star complexes in the galactic-scale shock front at the eyelid is about the same as the time since closest

  11. Early Science with the Large Millimeter Telescope: Observations of dust continuum and CO emission lines of cluster-lensed submillimetre galaxies at z=2.0-4.7

    CERN Document Server

    Zavala, J A; Aretxaga, I; Hughes, D H; Wilson, G W; Geach, J E; Egami, E; Gurwell, M A; Wilner, D J; Smail, Ian; Blain, A W; Chapman, S C; Coppin, K E K; Dessauges-Zavadsky, M; Edge, A C; Montana, A; Nakajima, K; Rawle, T D; Sanchez-Arguelles, D; Swinbank, A M; Webb, T M A; Zeballos, M

    2015-01-01

    We present Early Science observations with the Large Millimeter Telescope, AzTEC 1.1 mm continuum images and wide bandwidth spectra (73-111 GHz) acquired with the Redshift Search Receiver (RSR), towards four bright lensed submillimetre galaxies identified through the Herschel Lensing Survey-snapshot and the SCUBA-2 Cluster Snapshot Survey. This pilot project studies the star formation history and the physical properties of the molecular gas and dust content of the highest redshift galaxies identified through the benefits of gravitational magnification. We robustly detect dust continuum emission for the full sample and CO emission lines for three of the targets. We find that one source shows spectroscopic multiplicity and is a blend of three galaxies at different redshifts (z=2.040, 3.252 and 4.680), reminiscent of previous high-resolution imaging follow-up of unlensed submillimetre galaxies, but with a completely different search method, that confirm recent theoretical predictions of physically unassociated b...

  12. Imitating intrinsic alignments: a bias to the CMB lensing-galaxy shape cross-correlation power spectrum induced by the large-scale structure bispectrum

    Science.gov (United States)

    Merkel, Philipp M.; Schäfer, Björn Malte

    2017-10-01

    Cross-correlating the lensing signals of galaxies and comic microwave background (CMB) fluctuations is expected to provide valuable cosmological information. In particular, it may help tighten constraints on parameters describing the properties of intrinsically aligned galaxies at high redshift. To access the information conveyed by the cross-correlation signal, its accurate theoretical description is required. We compute the bias to CMB lensing-galaxy shape cross-correlation measurements induced by non-linear structure growth. Using tree-level perturbation theory for the large-scale structure bispectrum, we find that the bias is negative on most angular scales, therefore mimicking the signal of intrinsic alignments. Combining Euclid-like galaxy lensing data with a CMB experiment comparable to the Planck satellite mission, the bias becomes significant only on smallest scales (ℓ ≳ 2500). For improved CMB observations, however, the corrections amount to 10-15 per cent of the CMB lensing-intrinsic alignment signal over a wide multipole range (10 ≲ ℓ ≲ 2000). Accordingly, the power spectrum bias, if uncorrected, translates into 2σ and 3σ errors in the determination of the intrinsic alignment amplitude in the case of CMB stage III and stage IV experiments, respectively.

  13. The Magellanic Clouds as a template for the study of stellar populations and galaxy interactions

    CERN Document Server

    Cioni, M -R L; Clementini, G; De Blok, W J G; Emerson, J P; Evans, C J; De Grijs, R; Gibson, B K; Girardi, L; Groenewegen, M A T; Ivanov, V D; Leisy, P; Marconi, M; Mastropietro, C; Moore, B; Naylor, T; Oliveira, J M; Ripepi, V; van Loon, J Th; Wilkinson, M I; Wood, P R

    2007-01-01

    The Magellanic System represents one of the best places to study the formation and evolution of galaxies. Photometric surveys of various depths, areas and wavelengths have had a significant impact on our understanding of the system; however, a complete picture is still lacking. VMC (the VISTA near-infrared YJKs survey of the Magellanic System) will provide new data to derive the spatially resolved star formation history and to construct a three-dimensional map of the system. These data combined with those from other ongoing and planned surveys will give us an absolutely unique view of the system opening up the doors to truly new science!

  14. Globular Clusters for Faint Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    The origin of ultra-diffuse galaxies (UDGs) has posed a long-standing mystery for astronomers. New observations of several of these faint giants with the Hubble Space Telescope are now lending support to one theory.Faint-Galaxy MysteryHubble images of Dragonfly 44 (top) and DFX1 (bottom). The right panels show the data with greater contrast and extended objects masked. [van Dokkum et al. 2017]UDGs large, extremely faint spheroidal objects were first discovered in the Virgo galaxy cluster roughly three decades ago. Modern telescope capabilities have resulted in many more discoveries of similar faint galaxies in recent years, suggesting that they are a much more common phenomenon than we originally thought.Despite the many observations, UDGs still pose a number of unanswered questions. Chief among them: what are UDGs? Why are these objects the size of normal galaxies, yet so dim? There are two primary models that explain UDGs:UDGs were originally small galaxies, hence their low luminosity. Tidal interactions then puffed them up to the large size we observe today.UDGs are effectively failed galaxies. They formed the same way as normal galaxies of their large size, but something truncated their star formation early, preventing them from gaining the brightness that we would expect for galaxies of their size.Now a team of scientists led by Pieter van Dokkum (Yale University) has made some intriguing observations with Hubble that lend weight to one of these models.Globulars observed in 16 Coma-cluster UDGs by Hubble. The top right panel shows the galaxy identifications. The top left panel shows the derived number of globular clusters in each galaxy. [van Dokkum et al. 2017]Globulars GaloreVan Dokkum and collaborators imaged two UDGs with Hubble: Dragonfly 44 and DFX1, both located in the Coma galaxy cluster. These faint galaxies are both smooth and elongated, with no obvious irregular features, spiral arms, star-forming regions, or other indications of tidal interactions

  15. A rumble in the dark: signatures of self-interacting dark matter in supermassive black hole dynamics and galaxy density profiles

    Science.gov (United States)

    Di Cintio, Arianna; Tremmel, Michael; Governato, Fabio; Pontzen, Andrew; Zavala, Jesús; Bastidas Fry, Alexander; Brooks, Alyson; Vogelsberger, Mark

    2017-08-01

    We explore for the first time the effect of self-interacting dark matter (SIDM) on the dark matter (DM) and baryonic distribution in massive galaxies formed in hydrodynamical cosmological simulations, including explicit baryonic physics treatment. A novel implementation of supermassive black hole (SMBH) formation and evolution is used, as in Tremmel et al., allowing us to explicitly follow the SMBH dynamics at the centre of galaxies. A high SIDM constant cross-section is chosen, σ = 10 cm2gr-1, to amplify differences from CDM models. Milky Way-like galaxies form a shallower DM density profile in SIDM than they do in cold dark matter (CDM), with differences already at 20 kpc scales. This demonstrates that even for the most massive spirals, the effect of SIDM dominates over the adiabatic contraction due to baryons. Strikingly, the dynamics of SMBHs differs in the SIDM and reference CDM case. SMBHs in massive spirals have sunk to the centre of their host galaxy in both the SIDM and CDM run, while in less massive galaxies about 80 per cent of the SMBH population is off-centred in the SIDM case, as opposed to the CDM case in which ∼ 90 per cent of SMBHs have reached their host's centre. SMBHs are found as far as ∼9 kpc away from the centre of their host SIDM galaxy. This difference is due to the increased dynamical friction time-scale caused by the lower DM density in SIDM galaxies compared to CDM, resulting in core stalling. This pilot work highlights the importance of simulating in a full hydrodynamical context different DM models combined to the SMBH physics to study their influence on galaxy formation.

  16. Connecting Galaxy Disk and Extended Halo Gas Kinematics

    CERN Document Server

    Kacprzak, G G; Steidel, C C; Ceverino, D; Klypin, A A; Murphy, M T

    2007-01-01

    We have explored the galaxy disk/extended halo gas kinematic relationship using rotation curves (Keck/ESI) of ten intermediate redshift galaxies which were selected by MgII halo gas absorption observed in quasar spectra. Previous results of six edge-on galaxies, probed along their major axis, suggest that observed halo gas velocities are consistent with extended disk-like halo rotation at galactocentric distances of 25-72 kpc. Using our new sample, we demonstrate that the gas velocities are by and large not consistent with being directly coupled to the galaxy kinematics. Thus, mechanisms other than co-rotation dynamics (i.e., gas inflow, feedback, galaxy-galaxy interactions, etc.) must be invoked to account for the overall observed kinematics of the halo gas. In order to better understand the dynamic interaction of the galaxy/halo/cosmic web environment, we performed similar mock observations of galaxies and gaseous halos in Lambda-CDM cosmological simulations. We discuss an example case of a z=0.92 galaxy wi...

  17. Searching for dwarf spheroidal galaxies and other galactic dark matter substructures with the Fermi large area telescope

    Energy Technology Data Exchange (ETDEWEB)

    Drlica-Wagner, Alex [Stanford Univ., CA (United States). Dept. of Physics

    2013-08-01

    Over the past century, it has become clear that about a quarter of the known universe is composed of an invisible, massive component termed ''dark matter''. Some of the most popular theories of physics beyond the Standard Model suggest that dark matter may be a new fundamental particle that could self-annihilate to produce γ rays. Nearby over-densities in the dark matter halo of our Milky Way present some of the most promising targets for detecting the annihilation of dark matter. We used the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope to search for γ rays produced by dark matter annihilation in Galactic dark matter substructures. We searched for γ-ray emission coincident with Milky Way dwarf spheroidal satellite galaxies, which trace the most massive Galactic dark matter substructures. We also sought to identify nearby dark matter substructures that lack all astrophysical tracers and would be detectable only through γ-ray emission from dark matter annihilation. We found no conclusive evidence for γ-ray emission from dark matter annihilation, and we set stringent and robust constraints on the dark matter annihilation cross section. While γ-ray searches for dark matter substructure are currently the most sensitive and robust probes of dark matter annihilation, they are just beginning to intersect the theoretically preferred region of dark matter parameter space. Thus, we consider future prospects for increasing the sensitivity of γ-ray searches through improvements to the LAT instrument performance and through upcoming wide- field optical surveys.

  18. The Launching of Cold Clouds by Galaxy Outflows I: Hydrodynamic Interactions with Radiative Cooling

    CERN Document Server

    Scannapieco, Evan

    2015-01-01

    To better understand the nature of the multiphase material found in outflowing galaxies, we study the evolution of cold clouds embedded in flows of hot and fast material. Using a suite of adaptive-mesh refinement simulations that include radiative cooling, we investigate both cloud mass loss and cloud acceleration under the full range of conditions observed in galaxy outflows. The simulations are designed to track the cloud center of mass, enabling us to study the cloud evolution at long disruption times. For supersonic flows, a Mach cone forms around the cloud, which damps the Kelvin-Helmholtz instability but also establishes a streamwise pressure gradient that stretches the cloud apart. If time is expressed in units of the cloud crushing time, both the cloud lifetime and the cloud acceleration rate are independent of cloud radius, and we find simple scalings for these quantities as a function of the Mach number of the external medium. A resolution study suggests that our simulations have sufficient resoluti...

  19. 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

  20. The quasar-galaxy cross SDSS J1320+1644: A probable large-separation lensed quasar

    CERN Document Server

    Rusu, Cristian E; Iye, Masanori; Inada, Naohisa; Kayo, Issha; Shin, Min-Su; Sluse, Dominique; Strauss, Michael A

    2012-01-01

    We report the discovery of a pair of quasars at $z=1.487$, with a separation of $8\\farcs585\\pm0\\farcs002$. Subaru Telescope infrared imaging reveals the presence of an elliptical and a disk-like galaxy located almost symmetrically between the quasars, creating a cross-like configuration. Based on absorption lines in the quasar spectra and the colors of the galaxies, we estimate that both galaxies are located at redshift $z=0.899$. This, as well as the similarity of the quasar spectra, suggests that the system is a single quasar multiply imaged by a galaxy group or cluster acting as a gravitational lens, although the possibility of a binary quasar cannot be fully excluded. We show that the gravitational lensing hypothesis implies these galaxies are not isolated, but must be embedded in a dark matter halo of virial mass $\\sim 4 \\times 10^{14}\\ h_{70}^{-1}\\ {M}_\\odot$ assuming an NFW model with a concentration parameter of $c_{vir}=6$, or a singular isothermal sphere profile with a velocity dispersion of $\\sim 6...

  1. Minor Mergers or Progenitor Bias? The Stellar Ages of Small and Large Quenched Early-Type Galaxies

    CERN Document Server

    Fagioli, Martina; Renzini, Alvio; Lilly, Simon J; Onodera, Masato; Tacchella, Sandro

    2016-01-01

    We investigate the origin of the evolution of the population-averaged size of quenched galaxies (QGs) through a spectroscopic analysis of their stellar ages. The two most favoured scenarios for this evolution are either the size growth of individual galaxies through a sequence of dry minor merger events, or the addition of larger, newly quenched galaxies to the pre-existing population (i.e., a progenitor bias effect). We use the 20k zCOSMOS-bright spectroscopic survey to select bona fide quiescent galaxies at 0.2galaxies are systematically younger than those of the smalle...

  2. High Interactivity Visualization Software for Large Computational Data Sets Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Existing scientific visualization tools have specific limitations for large scale scientific data sets. Of these four limitations can be seen as paramount: (i)...

  3. High Interactivity Visualization Software for Large Computational Data Sets Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop a collection of computer tools and libraries called SciViz that enable researchers to visualize large scale data sets on HPC resources remotely...

  4. Galaxies Probing Galaxies: Cool Halo Gas from a z = 0.47 Post-Starburst Galaxy

    Science.gov (United States)

    Rubin, Kate H. R.; Prochaska, J. Xavier; Koo, David C.; Phillips, Andrew C.; Weiner, Benjamin J.

    2010-03-01

    We study the cool gas around a galaxy at z = 0.4729 using Keck/LRIS spectroscopy of a bright (B = 21.7) background galaxy at z = 0.6942 at a transverse distance of 16.5h -1 70 kpc. The background galaxy spectrum reveals strong Fe II, Mg II, Mg I, and Ca II absorption at the redshift of the foreground galaxy, with an Mg II λ2796 rest equivalent width of 3.93 ± 0.08 Å, indicative of a velocity width exceeding 400 km s-1. Because the background galaxy is large (>4h -1 70 kpc), the high covering fraction of the absorbing gas suggests that it arises in a spatially extended complex of cool clouds with large velocity dispersion. Spectroscopy of the massive (log M */M sun = 11.15 ± 0.08) host galaxy reveals that it experienced a burst of star formation about 1 Gyr ago and that it harbors a weak active galactic nucleus. We discuss the possible origins of the cool gas in its halo, including multiphase cooling of hot halo gas, cold inflow, tidal interactions, and galactic winds. We conclude that the absorbing gas was most likely ejected or tidally stripped from the interstellar medium of the host galaxy or its progenitors during the past starburst event. Adopting the latter interpretation, these results place one of only a few constraints on the radial extent of cool gas driven or stripped from a galaxy in the distant universe. Future studies with integral field unit spectroscopy of spatially extended background galaxies will provide multiple sight lines through foreground absorbers and permit analysis of the morphology and kinematics of the gas surrounding galaxies with a diverse set of properties and environments. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  5. Close neighbors of Markarian galaxies. II. Statistics and discussions

    CERN Document Server

    Nazaryan, T A; Hakobyan, A A; McLean, B J; Kunth, D

    2013-01-01

    According to the database from the first paper, we select 180 pairs with dV < 800 km/s and Dp < 60 kpc containing Markarian (MRK) galaxies. We study the dependence of galaxies integral parameters, star-formation (SF) and active galactic nuclei (AGN) properties on kinematics of pairs, their structure and large-scale environments. Following main results were obtained: projected radial separation Dp between galaxies correlates with the perturbation level P of the pairs. Both parameters do not correlate with line-of-sight velocity difference dV of galaxies. Dp and P are better measures of interaction strength than dV. The latter correlates with the density of large-scale environment and with the morphologies of galaxies. Both galaxies in a pair are of the same nature, the only difference is that MRK galaxies are usually brighter than their neighbors in average by 0.9 mag. Specific star formation rates (SSFR) of galaxies in pairs with smaller Dp or dV is in average 0.5 dex higher than that of galaxies in pai...

  6. Large space-time scale behavior of linearly interacting diffusions

    NARCIS (Netherlands)

    Swart, J.M.

    1999-01-01

    This dissertation in mathematics is devoted to systems consisting of a countably infinite collection of diffusion processes with a linear attractive interaction. Such systems have been used in population biology as a stochastic model for the distribution of genes over a population, or for the size o

  7. The jet-cloud interacting radio galaxy PKS B2152-699-I. Structures revealed in new deep radio and X-ray observations

    NARCIS (Netherlands)

    Worrall, D. M.; Birkinshaw, M.; Young, A. J.; Momtahan, K.; Fosbury, R. A. E.; Morganti, R.; Tadhunter, C. N.; Kleijn, G. Verdoes

    PKS B2152-699, which has radio power characteristic of sources that dominate radio feedback, is exceptional in showing a wide range of features associated with radio-galaxy/gas interactions. We present new deep radio (Australia Telescope Compact Array), X-ray (Chandra) and ground-based optical

  8. UNCOVERING THE DEEPLY EMBEDDED ACTIVE GALACTIC NUCLEUS ACTIVITY IN THE NUCLEAR REGIONS OF THE INTERACTING GALAXY Arp 299

    Energy Technology Data Exchange (ETDEWEB)

    Alonso-Herrero, A. [Instituto de Física de Cantabria, CSIC-UC, E-39005 Santander (Spain); Roche, P. F. [Astrophysics Department, University of Oxford, Oxford OX1 3RH (United Kingdom); Esquej, P.; Colina, L. [Centro de Astrobiología, CSIC-INTA, E-28035 Madrid (Spain); González-Martín, O.; Ramos Almeida, C.; Asensio Ramos, A.; Rodríguez Espinosa, J. M.; Alvarez, C. [Instituto de Astrofísica de Canarias, E-38205 La Laguna (Spain); Pereira-Santaella, M. [Istituto di Astrofisica e Planetologia Spaziali, INAF, I-00133 Rome (Italy); Levenson, N. A. [Gemini Observatory, La Serena (Chile); Packham, C. [University of Texas at San Antonio, San Antonio, TX 78249 (United States); Mason, R. E. [Gemini Observatory, Hilo, HI 96720 (United States); Aretxaga, I. [INAOE, 72000 Puebla (Mexico); Díaz-Santos, T. [Spitzer Science Center, Caltech, Pasadena, CA 91125 (United States); Perlman, E. [Florida Institute of Technology, Melbourne, FL 32901 (United States); Telesco, C. M., E-mail: aalonso@ifca.unican.es [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States)

    2013-12-10

    We present mid-infrared (MIR) 8-13 μm spectroscopy of the nuclear regions of the interacting galaxy Arp 299 (IC 694+NGC 3690) obtained with CanariCam (CC) on the 10.4 m Gran Telescopio Canarias (GTC). The high angular resolution (∼0.''3-0.''6) of the data allows us to probe nuclear physical scales between 60 and 120 pc, which is a factor of 10 improvement over previous MIR spectroscopic observations of this system. The GTC/CC spectroscopy displays evidence of deeply embedded active galactic nucleus (AGN) activity in both nuclei. The GTC/CC nuclear spectrum of NGC 3690/Arp 299-B1 can be explained as emission from AGN-heated dust in a clumpy torus with both a high covering factor and high extinction along the line of sight. The estimated bolometric luminosity of the AGN in NGC 3690 is 3.2 ± 0.6 × 10{sup 44} erg s{sup –1}. The nuclear GTC/CC spectrum of IC 694/Arp 299-A shows 11.3 μm polycyclic aromatic hydrocarbon emission stemming from a deeply embedded (A{sub V} ∼ 24 mag) region of less than 120 pc in size. There is also a continuum-emitting dust component. If associated with the putative AGN in IC 694, we estimate that it would be approximately five times less luminous than the AGN in NGC 3690. The presence of dual AGN activity makes Arp 299 a good example to study such phenomena in the early coalescence phase of interacting galaxies.

  9. How to quench a galaxy

    CERN Document Server

    Pontzen, Andrew; Roth, Nina; Peiris, Hiranya V; Saintonge, Amélie; Volonteri, Marta; Quinn, Tom; Governato, Fabio

    2016-01-01

    We show how the interplay between active galactic nuclei (AGN) and merger history determines whether a galaxy quenches star formation at high redshift. We first simulate, in a full cosmological context, a galaxy of total dynamical mass $10^{12}\\,M_{\\odot}$ at $z=2$. Then we systematically alter the accretion history of the galaxy by minimally changing the linear overdensity in the initial conditions. This "genetic modification" approach allows the generation of three sets of $\\Lambda$CDM initial conditions leading to maximum merger ratios of 1:10, 1:5 and 2:3 respectively. The changes leave the final halo mass, large scale structure and local environment unchanged, providing a controlled numerical experiment. Interaction between the AGN physics and mergers in the three cases lead respectively to a star-forming, temporarily-quenched and permanently-quenched galaxy. However the differences do not primarily lie in the black hole accretion rates, but in the kinetic effects of the merger: the galaxy is resilient a...

  10. The Hooked Galaxy

    Science.gov (United States)

    2006-06-01

    Life is not easy, even for galaxies. Some indeed get so close to their neighbours that they get rather distorted. But such encounters between galaxies have another effect: they spawn new generations of stars, some of which explode. ESO's VLT has obtained a unique vista of a pair of entangled galaxies, in which a star exploded. Because of the importance of exploding stars, and particularly of supernovae of Type Ia [1], for cosmological studies (e.g. relating to claims of an accelerated cosmic expansion and the existence of a new, unknown, constituent of the universe - the so called 'Dark Energy'), they are a preferred target of study for astronomers. Thus, on several occasions, they pointed ESO's Very Large Telescope (VLT) towards a region of the sky that portrays a trio of amazing galaxies. MCG-01-39-003 (bottom right) is a peculiar spiral galaxy, with a telephone number name, that presents a hook at one side, most probably due to the interaction with its neighbour, the spiral galaxy NGC 5917 (upper right). In fact, further enhancement of the image reveals that matter is pulled off MCG-01-39-003 by NGC 5917. Both these galaxies are located at similar distances, about 87 million light-years away, towards the constellation of Libra (The Balance). ESO PR Photo 22/06 ESO PR Photo 22/06 The Hooked Galaxy and its Companion NGC 5917 (also known as Arp 254 and MCG-01-39-002) is about 750 times fainter than can be seen by the unaided eye and is about 40,000 light-years across. It was discovered in 1835 by William Herschel, who strangely enough, seems to have missed its hooked companion, only 2.5 times fainter. As seen at the bottom left of this exceptional VLT image, a still fainter and nameless, but intricately beautiful, barred spiral galaxy looks from a distance the entangled pair, while many 'island universes' perform a cosmic dance in the background. But this is not the reason why astronomers look at this region. Last year, a star exploded in the vicinity of the hook

  11. Large scale star formation in galaxies. II. The spirals NGC 3377A, NGC 3507 and NGC 4394

    CERN Document Server

    Vicari, A; Capuzzo-Dolcetta, R; Wyder, T K; Arrabito, G

    2001-01-01

    The identification of young star groupings (YSG) in the three spiral galaxies NGC 3377A, NGC 3507, NGC 4394 is obtained by mean of the statistical method described in Paper I. We find 83, 90, 185 YSGs, respectively. An identification map of YSGs, as well as their size distribution, their B-luminosity function, their surface luminosity density radial behaviour, are presented and comparatively discussed. These data, in addition to those in Paper I, constitute a first sample suitable for seeking correlations among properties of galaxies and their YSG, which we briefly discuss here.

  12. Interacting with Large 3D Datasets on a Mobile Device.

    Science.gov (United States)

    Schultz, Chris; Bailey, Mike

    2016-01-01

    A detail-on-demand scheme can alleviate both memory and GPU pressure on mobile devices caused by volume rendering. This approach allows a user to explore an entire dataset at its native resolution while simultaneously constraining the texture size being rendered to a dimension that does not exceed the processing capabilities of a portable device. This scheme produces higher-quality, more focused images rendered at interactive frame rates, while preserving the native resolution of the dataset.

  13. Evidence for Shock Acceleration and Intergalactic Magnetic Fields in a Large-Scale Filament of Galaxies ZwCl 2341.1+0000

    CERN Document Server

    Bagchi, J; Miniati, F; Stalin, C S; Singh, M; Raychaudhuri, S; Humeshkar, N B; Bagchi, Joydeep; Ensslin, Torsten A.; Miniati, Francesco; Raychaudhury, Somak

    2002-01-01

    We report the discovery of large-scale diffuse radio emission from what appears to be a large-scale filamentary network of galaxies in the region of cluster ZwCl 2341.1+0000, and stretching over an area of at least $6 h^{-1}_{50}$ Mpc in diameter. Multicolour CCD observations yield photometric redshifts indicating that a significant fraction of the optical galaxies in this region is at a redshift of z=0.3. This is supported by spectroscopic measurements of 4 galaxies in the SDSS survey at a mean z=0.27. We present VLA images at 20 cm (NVSS) and 90 cm wavelengths, showing the detailed radio structure of the filaments. Comparison with the VLA high resolution FIRST radio survey shows that the diffuse emission is not due to known individual point sources. The diffuse radio-emission has a spectral index $\\alpha \\lesssim -0.5$, and is most likely synchrotron emission from relativistic charged particles in an inter-galactic magnetic field. Furthermore, this optical/radio structure is detected in X-rays by the ROSAT ...

  14. 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.

  15. The GalMer database: Galaxy Mergers in the Virtual Observatory

    CERN Document Server

    Chilingarian, Igor; Combes, Francoise; Melchior, Anne-Laure; Semelin, Benoit

    2010-01-01

    We present the GalMer database, a library of galaxy merger simulations, made available to users through tools compatible with the Virtual Observatory (VO) standards adapted specially for this theoretical database. To investigate the physics of galaxy formation through hierarchical merging, it is necessary to simulate galaxy interactions varying a large number of parameters: morphological types, mass ratios, orbital configurations, etc. On one side, these simulations have to be run in a cosmological context, able to provide a large number of galaxy pairs, with boundary conditions given by the large-scale simulations, on the other side the resolution has to be high enough at galaxy scales, to provide realistic physics. The GalMer database is a library of thousands simulations of galaxy mergers at moderate spatial resolution and it is a compromise between the diversity of initial conditions and the details of underlying physics. We provide all coordinates and data of simulated particles in FITS binary tables. Th...

  16. The Galaxies and Cosmos Explorer Tool: Charting Galaxies over Cosmic Times in The Classroom

    Science.gov (United States)

    Jogee, Shardha; Hemenway, M. K.; Miller, S.; Smith, A.; Augustine, A.; Worhatch, R.; Preston, S.; Lester, D.; Fricke, K.

    2007-12-01

    Recent large galaxy surveys conducted with NASA's Hubble Space Telescope Advanced Camera for Surveys (ACS) have provided unprecedented legacy datasets, which allow astronomers to charter the evolution of galaxies over a large fraction of the age of the Universe. The Galaxies and Cosmos Explorer Tool (GCET; http://www.as.utexas.edu/gcet/) is an online web-based tool that allows the general public and students to actively participate in this exciting adventure through quantitative analyses of HST images from the Galaxy Evolution from Morphology and SEDs (GEMS) survey, one of the widest-area galaxy surveys conducted in two filters with ACS to date. The tool allows users to surf the vast cosmos and access ACS images of over 8,000 galaxies over the last eight billion years. For galaxies of interest, users can measure the size, determine the lookback time for concordance cosmology, perform morphological classification on images at two rest-frame wavelengths, and gauge the different stellar populations present. Users can record their measurements, as well as reference information, such as coordinates and redshift, of each galaxy into Excel spreadsheets for further analysis. The celestial coordinates can be used to extract further multiwavelength data from existing archives and upcoming virtual observatories. For undergraduate classes, more advanced IDL or C-based analyses that employ the full samples, can be combined with the visualization capabilities of GCET in order to explore the nature of interesting objects, such as the most massive galaxies, starbursting systems, interacting and merging galaxies. GCET provides a powerful tool for discovery learning in undergraduate science and introductory classes, as well as high schools. We thank the GEMS collaboration, and acknowledge support from NASA grants NAG5-13063 and NASA NNG 06GB99G, NSF grant AST-0607748, and the Faculty And Student Teams for Technology (FAST Tex) award from the University of Texas Division of

  17. Forty Years of Research on Isolated Galaxies

    CERN Document Server

    Sulentic, J W

    2009-01-01

    Isolated galaxies have not been a hot topic over the past four decades. This is partly due to uncertainties about their existence. Are there galaxies isolated enough to be interesting? Do they exist in sufficient numbers to be statistically useful? Most attempts to compile isolated galaxy lists were marginally successful--too small number and not very isolated galaxies. If really isolated galaxies do exist then their value becomes obvious in a Universe where effects of interactions and environment (i.e. nurture) are important. They provide a means for better quantifying effects of nurture. The Catalog of Isolated Galaxies (CIG) compiled by Valentina Karachentseva appeared near the beginning of the review period. It becomes the focus of this review because of its obvious strengths and because the AMIGA project has increased its utility through a refinement (a vetted CIG). It contains almost 1000 galaxies with nearest neighbor crossing times of 1-3Gyr. It is large enough to serve as a zero-point or control samp...

  18. Lopsided spiral galaxies: evidence for gas accretion

    CERN Document Server

    Bournaud, F; Jog, C J; Puerari, I

    2005-01-01

    We quantify the degree of lopsidedness for a sample of 149 galaxies observed in the near-infrared from the OSUBGS sample, and try to explain the physical origin for the observed disk lopsidedness. We confirm previous studies, but now for a larger sample, that a large fraction of galaxies show significant lopsidedness in their stellar disks, measured as the Fourier amplitude of the m=1 component, normalised to the average or m=0 component, in the surface density. Late-type galaxies are found to be more lopsided, while the presence of m=2 spiral arms and bars is correlated. The m=1 amplitude is found to be uncorrelated with the tidal forces acting on a galaxy via nearby companions. Numerical simulations are carried out to study the generation of m=1 via different processes: galaxy tidal encounters, galaxy mergers, and external gas accretion and subsequent star formation. The simulations show that galaxy interactions and mergers can trigger strong lopsidedness, but do not explain several independent statistical ...

  19. Searching for evidence of jet-cloud interaction in radio galaxies. First results for 3C 381

    CERN Document Server

    Reynaldi, V

    2013-01-01

    We present results of Gemini spectroscopy and Hubble Space Telescope imaging of the 3C~381 radio galaxy. Possible ionising mechanisms for the Extended Emission-Line Region were studied through state-of-the-art diagnostic analysis employing line-ratios. Photoionisation from the central engine as well as mixed-medium photoionisation models fail in reproducing both the strengths and the behaviour of the highest-excitation lines, such as [NeV]3424, HeII, and [OIII}]5007, which are measured at very large distances from the AGN. Shock-ionisation models provide a better fit to the observation. Expanding shocks with velocities higher than 500 km/s are capable of reaching the observed intensity ratios for lines with different ionisation states and excitation degrees. This model also provide a direct explanation of the mechanical energy input needed to explain the high-velocity line-splitting observed in the velocity field.

  20. HI in radio galaxies : prospects for upcoming wide-field surveys

    NARCIS (Netherlands)

    Emonts, Bjorn; Morganti, Raffaella; Struve, Christian

    2009-01-01

    We present results of an ongoing systematic study of the large-scale properties of neutral hydrogen (HI) gas in nearby radio galaxies. Our main goal is to investigate the importance of gas-rich galaxy mergers and interactions among radio-loud AGN. From an HI study of a complete sample of classical l

  1. 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

  2. Large grazers modify effects of aboveground–belowground interactions on small-scale plant community composition

    NARCIS (Netherlands)

    Veen, G.F.; Geuverink, E.; Olff, H.

    2012-01-01

    Aboveground and belowground organisms influence plant community composition by local interactions, and their scale of impact may vary from millimeters belowground to kilometers aboveground. However, it still poorly understood how large grazers that select their forage on large spatial scales

  3. Large grazers modify effects of aboveground-belowground interactions on small-scale plant community composition

    NARCIS (Netherlands)

    Veen, G. F. (Ciska); Geuverink, Elzemiek; Olff, Han; Schmid, Bernhard

    Aboveground and belowground organisms influence plant community composition by local interactions, and their scale of impact may vary from millimeters belowground to kilometers aboveground. However, it still poorly understood how large grazers that select their forage on large spatial scales

  4. Magnetic fields in ring galaxies

    CERN Document Server

    Moss, D; Silchenko, O; Sokoloff, D; Horellou, C; Beck, R

    2016-01-01

    Many galaxies contain magnetic fields supported by galactic dynamo action. However, nothing definitive is known about magnetic fields in ring galaxies. Here we investigate large-scale magnetic fields in a previously unexplored context, namely ring galaxies, and concentrate our efforts on the structures that appear most promising for galactic dynamo action, i.e. outer star-forming rings in visually unbarred galaxies. We use tested methods for modelling $\\alpha-\\Omega$ galactic dynamos, taking into account the available observational information concerning ionized interstellar matter in ring galaxies. Our main result is that dynamo drivers in ring galaxies are strong enough to excite large-scale magnetic fields in the ring galaxies studied. The variety of dynamo driven magnetic configurations in ring galaxies obtained in our modelling is much richer than that found in classical spiral galaxies. In particular, various long-lived transients are possible. An especially interesting case is that of NGC 4513 where th...

  5. Investigating H$\\alpha$, UV, and IR star-formation rate diagnostics for a large sample of z ~ 2 galaxies

    CERN Document Server

    Shivaei, Irene; Steidel, Charles C; Shapley, Alice E

    2015-01-01

    We use a sample of 262 spectroscopically confirmed star-forming galaxies at redshifts $2.08\\leq z\\leq 2.51$ to compare H$\\alpha$, UV, and IR star-formation-rate diagnostics and to investigate the dust properties of the galaxies. At these redshifts, the H$\\alpha$ line shifts to the $K_{s}$-band. By comparing $K_{s}$-band photometry to underlying stellar population model fits to other UV, optical, and near-infrared data, we infer the H$\\alpha$ flux for each galaxy. We obtain the best agreement between H$\\alpha$- and UV-based SFRs if we assume that the ionized gas and stellar continuum are reddened by the same value and that the Calzetti attenuation curve is applied to both. Aided with MIPS 24$\\mu$m data, we find that an attenuation curve steeper than the Calzetti curve is needed to reproduce the observed IR/UV ratios of galaxies younger than 100 Myr. Furthermore, using the bolometric star-formation rate inferred from the UV and mid-IR data (SFR$_{IR}$+SFR$_{UV}$), we calculated the conversion between the H$\\alp...

  6. NIHAO project - I. Reproducing the inefficiency of galaxy formation across cosmic time with a large sample of cosmological hydrodynamical simulations

    Science.gov (United States)

    Wang, Liang; Dutton, Aaron A.; Stinson, Gregory S.; Macciò, Andrea V.; Penzo, Camilla; Kang, Xi; Keller, Ben W.; Wadsley, James

    2015-11-01

    We introduce project NIHAO (Numerical Investigation of a Hundred Astrophysical Objects), a set of 100 cosmological zoom-in hydrodynamical simulations performed using the GASOLINE code, with an improved implementation of the SPH algorithm. The haloes in our study range from dwarf (M200 ˜ 5 × 109 M⊙) to Milky Way (M200 ˜ 2 × 1012 M⊙) masses, and represent an unbiased sampling of merger histories, concentrations and spin parameters. The particle masses and force softenings are chosen to resolve the mass profile to below 1 per cent of the virial radius at all masses, ensuring that galaxy half-light radii are well resolved. Using the same treatment of star formation and stellar feedback for every object, the simulated galaxies reproduce the observed inefficiency of galaxy formation across cosmic time as expressed through the stellar mass versus halo mass relation, and the star formation rate versus stellar mass relation. We thus conclude that stellar feedback is the chief piece of physics required to limit the efficiency of star formation in galaxies less massive than the Milky Way.

  7. Host galaxies and environment of active galactic nuclei : a study of the XMM large scale structure survey

    NARCIS (Netherlands)

    Tasse, Cyril

    2008-01-01

    Active galactic nuclei (AGN) result from the infall of matter onto the super-massive black holes that are situated at the centres of galaxies. This process releases an enormous amount of energy into the inter-stellar and inter-galactic medium. Hence, the study of AGN becomes essential in the context

  8. Parallel interactions at large horizontal displacement in pyridine-pyridine and benzene-pyridine dimers.

    Science.gov (United States)

    Ninković, Dragan B; Andrić, Jelena M; Zarić, Snežana D

    2013-01-14

    A study of crystal structures from the Cambridge Structural Database (CSD) and DFT calculations reveals that parallel pyridine-pyridine and benzene-pyridine interactions at large horizontal displacements (offsets) can be important, similar to parallel benzene-benzene interactions. In the crystal structures from the CSD preferred parallel pyridine-pyridine interactions were observed at a large horizontal displacement (4.0-6.0 Å) and not at an offset of 1.5 Å with the lowest calculated energy. The calculated interaction energies for pyridine-pyridine and benzene-pyridine dimers at a large offset (4.5 Å) are about 2.2 and 2.1 kcal mol(-1), respectively. Substantial attraction at large offset values is a consequence of the balance between repulsion and dispersion. That is, dispersion at large offsets is reduced, however, repulsion is also reduced at large offsets, resulting in attractive interactions.

  9. Gaseous Galaxy Halos

    CERN Document Server

    Putman, M E; Joung, M R

    2012-01-01

    Galactic halo gas traces inflowing star formation fuel and feedback from a galaxy's disk and is therefore crucial to our understanding of galaxy evolution. In this review, we summarize the multi-wavelength observational properties and origin models of Galactic and low redshift spiral galaxy halo gas. Galactic halos contain multiphase gas flows that are dominated in mass by the ionized component and extend to large radii. The densest, coldest halo gas observed in neutral hydrogen (HI) is generally closest to the disk ( 10^5.5 K) and cold mode in simulations, with the compressed material close to the disk the coldest and densest, in agreement with observations. There is evidence in halo gas observations for radiative and mechanical feedback mechanisms, including escaping photons from the disk, supernova-driven winds, and a galactic fountain. Satellite accretion also leaves behind abundant halo gas. This satellite gas interacts with the existing halo medium, and much of this gas will become part of the diffuse h...

  10. ARCHANGEL: Galaxy Photometry System

    Science.gov (United States)

    Schombert, James

    2011-07-01

    ARCHANGEL is a Unix-based package for the surface photometry of galaxies. While oriented for large angular size systems (i.e. many pixels), its tools can be applied to any imaging data of any size. The package core contains routines to perform the following critical galaxy photometry functions: sky determinationframe cleaningellipse fittingprofile fittingtotal and isophotal magnitudes The goal of the package is to provide an automated, assembly-line type of reduction system for galaxy photometry of space-based or ground-based imaging data. The procedures outlined in the documentation are flux independent, thus, these routines can be used for non-optical data as well as typical imaging datasets. ARCHANGEL has been tested on several current OS's (RedHat Linux, Ubuntu Linux, Solaris, Mac OS X). A tarball for installation is available at the download page. The main routines are Python and FORTRAN based, therefore, a current installation of Python and a FORTRAN compiler are required. The ARCHANGEL package also contains Python hooks to the PGPLOT package, an XML processor and network tools which automatically link to data archives (i.e. NED, HST, 2MASS, etc) to download images in a non-interactive manner.

  11. Mining the Galaxy Zoo Database: Machine Learning Applications

    Science.gov (United States)

    Borne, Kirk D.; Wallin, J.; Vedachalam, A.; Baehr, S.; Lintott, C.; Darg, D.; Smith, A.; Fortson, L.

    2010-01-01

    The new Zooniverse initiative is addressing the data flood in the sciences through a transformative partnership between professional scientists, volunteer citizen scientists, and machines. As part of this project, we are exploring the application of machine learning techniques to data mining problems associated with the large and growing database of volunteer science results gathered by the Galaxy Zoo citizen science project. We will describe the basic challenge, some machine learning approaches, and early results. One of the motivators for this study is the acquisition (through the Galaxy Zoo results database) of approximately 100 million classification labels for roughly one million galaxies, yielding a tremendously large and rich set of training examples for improving automated galaxy morphological classification algorithms. In our first case study, the goal is to learn which morphological and photometric features in the Sloan Digital Sky Survey (SDSS) database correlate most strongly with user-selected galaxy morphological class. As a corollary to this study, we are also aiming to identify which galaxy parameters in the SDSS database correspond to galaxies that have been the most difficult to classify (based upon large dispersion in their volunter-provided classifications). Our second case study will focus on similar data mining analyses and machine leaning algorithms applied to the Galaxy Zoo catalog of merging and interacting galaxies. The outcomes of this project will have applications in future large sky surveys, such as the LSST (Large Synoptic Survey Telescope) project, which will generate a catalog of 20 billion galaxies and will produce an additional astronomical alert database of approximately 100 thousand events each night for 10 years -- the capabilities and algorithms that we are exploring will assist in the rapid characterization and classification of such massive data streams. This research has been supported in part through NSF award #0941610.

  12. How Do Galaxies Grow?

    Science.gov (United States)

    2008-08-01

    Astronomers have caught multiple massive galaxies in the act of merging about 4 billion years ago. This discovery, made possible by combining the power of the best ground- and space-based telescopes, uniquely supports the favoured theory of how galaxies form. ESO PR Photo 24/08 ESO PR Photo 24/08 Merging Galaxies in Groups How do galaxies form? The most widely accepted answer to this fundamental question is the model of 'hierarchical formation', a step-wise process in which small galaxies merge to build larger ones. One can think of the galaxies forming in a similar way to how streams merge to form rivers, and how these rivers, in turn, merge to form an even larger river. This theoretical model predicts that massive galaxies grow through many merging events in their lifetime. But when did their cosmological growth spurts finish? When did the most massive galaxies get most of their mass? To answer these questions, astronomers study massive galaxies in clusters, the cosmological equivalent of cities filled with galaxies. "Whether the brightest galaxies in clusters grew substantially in the last few billion years is intensely debated. Our observations show that in this time, these galaxies have increased their mass by 50%," says Kim-Vy Tran from the University of Zürich, Switzerland, who led the research. The astronomers made use of a large ensemble of telescopes and instruments, including ESO's Very Large Telescope (VLT) and the Hubble Space Telescope, to study in great detail galaxies located 4 billion light-years away. These galaxies lie in an extraordinary system made of four galaxy groups that will assemble into a cluster. In particular, the team took images with VIMOS and spectra with FORS2, both instruments on the VLT. From these and other observations, the astronomers could identify a total of 198 galaxies belonging to these four groups. The brightest galaxies in each group contain between 100 and 1000 billion of stars, a property that makes them comparable

  13. Galaxy Zoo Hubble: Crowdsourced Morphologies for 169,944 Galaxies at 0

    Science.gov (United States)

    Willett, Kyle; Galloway, Melanie; Fortson, Lucy; Bamford, Steven; Masters, Karen; Lintott, Chris; Simmons, Brooke; Cheung, Edmond; Schawinski, Kevin; Scarlata, Claudia; Beck, Melanie; Galaxy Zoo volunteers

    2016-01-01

    The Galaxy Zoo project uses crowdsourced visual classifications to create large and statistically robust catalogs of detailed galaxy morphology. We present initial results for the Galaxy Zoo: Hubble dataset, which includes 169,944 images of galaxies selected from the AEGIS, COSMOS, GEMS, and GOODS surveys. The galaxies span a redshift range of 0Zoo: Hubble catalog.

  14. On the interpretation of dark matter self-interactions in Abell 3827

    DEFF Research Database (Denmark)

    Kahlhoefer, Felix; Schmidt-Hoberg, Kai; Kummer, Janis

    2015-01-01

    Self-interactions of dark matter (DM) particles can potentially lead to an observable separation between the DM halo and the stars of a galaxy moving through a region of large DM density. Such a separation has recently been observed in a galaxy falling into the core of the galaxy cluster Abell 3827...

  15. Large amplitude electromagnetic solitons in intense laser plasma interaction

    Institute of Scientific and Technical Information of China (English)

    Li Bai-Wen; Ishiguro S; Skoric M M

    2006-01-01

    This paper shows that the standing, backward- and forward-accelerated large amplitude relativistic electromagnetic solitons induced by intense laser pulse in long underdense collisionless homogeneous plasmas can be observed by particle simulations. In addition to the inhomogeneity of the plasma density, the acceleration of the solitons also depends upon not only the laser amplitude but also the plasma length. The electromagnetic frequency of the solitons is between about half and one of the unperturbed electron plasma frequency. The electrostatic field inside the soliton has a one-cycle structure in space, while the transverse electric and magnetic fields have half-cycle and one-cycle structure respectively.Analytical estimates for the existence of the solitons and their electromagnetic frequencies qualitatively coincide with our simulation results.

  16. Dynamic Soil-Pile Interaction for large diameter monopile foundations

    DEFF Research Database (Denmark)

    Zania, Varvara

    2013-01-01

    fatigue may be problematic. In the third case except from the cost increase, the wind induced fatigue is an additional issue to be dealt with. The second concept is the one prevailing in current design practice and it actually sets the natural frequency of vibration of the OWT inside the narrow margin......Monopile foundations have been used in a large extent to support offshore wind turbines (OWT), being considered as a reliable and cost effective design solution. The accurate estimation of their dynamic response characteristics is essential, since the design of support structures for OWTs has been......’ rule and are usually reported in double terms of the stiffness of the OWT and the foundation, i.e. soft –soft, soft – stiff, and stiff – stiff design approaches. In the first case the eigenfrequency of the system is reduced to excessively low values, where the cost reduction is considerable but wave...

  17. EXTREMELY METAL-POOR GALAXIES: THE ENVIRONMENT

    Energy Technology Data Exchange (ETDEWEB)

    Filho, M. E. [Universidad de Las Palmas de Gran Canaria–Universidad de La Laguna, CIE Canarias: Tri-Continental Atlantic Campus, Canary Islands (Spain); Almeida, J. Sánchez; Muñoz-Tuñón, C. [Instituto Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Nuza, S. E.; Kitaura, F.; Heß, S., E-mail: mfilho@astro.up.pt [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)

    2015-04-01

    We have analyzed bibliographical observational data and theoretical predictions, in order to probe the environment in which extremely metal-poor dwarf galaxies (XMPs) reside. We have assessed the H i component and its relation to the optical galaxy, the cosmic web type (voids, sheets, filaments and knots), the overdensity parameter and analyzed the nearest galaxy neighbors. The aim is to understand the role of interactions and cosmological accretion flows in the XMP observational properties, particularly the triggering and feeding of the star formation. We find that XMPs behave similarly to Blue Compact Dwarfs; they preferably populate low-density environments in the local universe: ∼60% occupy underdense regions, and ∼75% reside in voids and sheets. This is more extreme than the distribution of irregular galaxies, and in contrast to those regions preferred by elliptical galaxies (knots and filaments). We further find results consistent with previous observations; while the environment does determine the fraction of a certain galaxy type, it does not determine the overall observational properties. With the exception of five documented cases (four sources with companions and one recent merger), XMPs do not generally show signatures of major mergers and interactions; we find only one XMP with a companion galaxy within a distance of 100 kpc, and the H i gas in XMPs is typically well-behaved, demonstrating asymmetries mostly in the outskirts. We conclude that metal-poor accretion flows may be driving the XMP evolution. Such cosmological accretion could explain all the major XMP observational properties: isolation, lack of interaction/merger signatures, asymmetric optical morphology, large amounts of unsettled, metal-poor H i gas, metallicity inhomogeneities, and large specific star formation.

  18. Discovery of large-scale diffuse radio emission and of a new galaxy cluster in the surroundings of MACSJ0520.7-1328

    CERN Document Server

    Macario, G; Ferrari, C; Bourdin, H; Giacintucci, S; Venturi, T; Mazzotta, P; Bartalucci, I; Johnston-Hollitt, M; Cassano, R; Dallacasa, D; Pratt, G W; Kale, R; Brown, S

    2014-01-01

    We report the discovery of large-scale diffuse radio emission South-East of the galaxy cluster MACS J0520.7-1328, detected through high sensitivity Giant Metrewave Radio Telescope 323 MHz observations. This emission is dominated by an elongated diffuse radio source and surrounded by other features of lower surface brightness. Patches of these faint sources are marginally detected in a 1.4 GHz image obtained through a re-analysis of archival NVSS data. Interestingly, the elongated radio source coincides with a previously unclassified extended X-ray source. We perform a multi-wavelength analysis based on archival infrared, optical and X-ray Chandra data. We find that this source is a low-temperature (~3.6 keV) cluster of galaxies, with indications of a disturbed dynamical state, located at a redshift that is consistent with the one of the main galaxy cluster MACS J0520.7-132 (z=0.336). We suggest that the diffuse radio emission is associated with the non-thermal components in the intracluster and intergalactic ...

  19. Investigating Cross-Device Interaction between a Handheld Device and a Large Display

    DEFF Research Database (Denmark)

    Paay, Jeni; Raptis, Dimitrios; Kjeldskov, Jesper

    2017-01-01

    There is a growing interest in HCI research to explore cross-device interaction, giving rise to an interest in different approaches facilitating interaction between handheld devices and large displays. Contributing to this, we have investigated the use of four existing approaches combining touch...... and mid-air gestures, pinching, swiping, swinging and flicking. We look specifically at their relative efficiency, effectiveness and accuracy in bi-directional interaction between a smartphone and large display in a point-click context. We report findings from two user studies, which show that swiping...... that this is an important factor for designing effective cross-device interaction with large displays....

  20. A Galaxy for Science and Research

    Science.gov (United States)

    2007-11-01

    During his visit to ESO's Very Large Telescope at Paranal, the European Commissioner for Science and Research, Janez Potočnik, participated in an observing sequence and took images of a beautiful spiral galaxy. ESO PR Photo 43/07 ESO PR Photo 49/07 Twisted Spiral Galaxy NGC 134 The visit took place on 27 October and the Commissioner observed with one of the FORS instruments on Antu, the first 8.2-m Unit Telescope of the VLT. "Two hours bus ride from the nearest town, Antofagasta, in the middle of nowhere and at 2 600 m altitude, rises a state of the art astronomical observatory at which scientists from across Europe venture to exploit some of the most advanced technologies and sophisticated techniques available within astronomy. One of the facilities is the VLT, the Very Large Telescope, with which, together with the other telescopes, scientists can study objects at the far edge of the Universe," wrote Potočnik on his blog. Known until now as a simple number in a catalogue, NGC 134, the 'Island in the Universe' that was observed by the Commissioner is replete with remarkable attributes, and the VLT has clapped its eyes on them. Just like our own Galaxy, NGC 134 is a barred spiral with its spiral arms loosely wrapped around a bright, bar-shaped central region. One feature that stands out is its warped disc. While a galaxy's disc is often pictured as a flat structure of gas and stars surrounding the galaxy's centre, a warped disc is a structure that, when viewed sideways, resembles a bent record album left out too long in the burning Sun. Warps are actually not atypical. More than half of the spiral galaxies do show warps one way or another, and our own Milky Way also has a small warp. Many theories exist to explain warps. One possibility is that warps are the aftermath of interactions or collisions between galaxies. These can also produce tails of material being pulled out from the galaxy. The VLT image reveals that NGC 134 also appears to have a tail of gas

  1. New HI-detected Galaxies in the Zone of Avoidance

    CERN Document Server

    Staveley-Smith, L; Koribalski, B S; Ekers, R D; Green, A J; Haynes, R F; Henning, P A; Kesteven, M J; Kraan-Korteweg, R C; Price, R M; Sadler, E M

    1998-01-01

    We present the first results of a blind HI survey for galaxies in the southern Zone of Avoidance with a multibeam receiver on the Parkes telescope. This survey is eventually expected to catalog several thousand galaxies within Galactic latitude |b|<5 degrees, mostly unrecognised before due to Galactic extinction and confusion. We present here results of the first three detections to have been imaged with the Australia Telescope Compact Array (ATCA). The galaxies all lie near Galactic longitude 325 degrees and were selected because of their large angular sizes, up to 1.3 degrees. Linear sizes range from 53 to 108 kpc. The first galaxy is a massive 5.7x10^11 solar mass disk galaxy with a faint optical counterpart, SGC 1511.1--5249. The second is probably an interacting group of galaxies straddling the Galactic equator. No optical identification is possible. The third object appears to be an interacting pair of low column density galaxies, possibly belonging to an extended Circinus or Centaurus A galaxy group...

  2. A weak lensing mass reconstruction of the large-scale filament feeding the massive galaxy cluster MACS J0717.5+3745

    Science.gov (United States)

    Jauzac, Mathilde; Jullo, Eric; Kneib, Jean-Paul; Ebeling, Harald; Leauthaud, Alexie; Ma, Cheng-Jiun; Limousin, Marceau; Massey, Richard; Richard, Johan

    2012-11-01

    We report the first weak lensing detection of a large-scale filament funnelling matter on to the core of the massive galaxy cluster MACS J0717.5+3745. Our analysis is based on a mosaic of 18 multipassband images obtained with the Advanced Camera for Surveys aboard the Hubble Space Telescope, covering an area of ˜10 × 20 arcmin2. We use a weak lensing pipeline developed for the Cosmic Evolution Survey, modified for the analysis of galaxy clusters, to produce a weak lensing catalogue. A mass map is then computed by applying a weak gravitational lensing multiscale reconstruction technique designed to describe irregular mass distributions such as the one investigated here. We test the resulting mass map by comparing the mass distribution inferred for the cluster core with the one derived from strong lensing constraints and find excellent agreement. Our analysis detects the MACS J0717.5+3745 filament within the 3σ detection contour of the lensing mass reconstruction, and underlines the importance of filaments for theoretical and numerical models of the mass distribution in the cosmic web. We measure the filament's projected length as ˜4.5 h74-1 Mpc, and its mean density as (2.92 ± 0.66) × 108 h74 M⊙ kpc-2. Combined with the redshift distribution of galaxies obtained after an extensive spectroscopic follow-up in the area, we can rule out any projection effect resulting from the chance alignment on the sky of unrelated galaxy group-scale structures. Assuming plausible constraints concerning the structure's geometry based on its galaxy velocity field, we construct a three-dimensional (3D) model of the large-scale filament. Within this framework, we derive the 3D length of the filament to be 18 h74-1 Mpc. The filament's deprojected density in terms of the critical density of the Universe is measured as (206 ± 46) ρcrit, a value that lies at the very high end of the range predicted by numerical simulations. Finally, we study the distribution of stellar mass in the

  3. Quantum dots with disorder and interactions: a solvable large-g limit.

    Science.gov (United States)

    Murthy, Ganpathy; Shankar, R

    2003-02-14

    We analyze the problem of interacting electrons on a ballistic quantum dot with chaotic boundary conditions, where the effective interactions at low energies are characterized by Landau parameters. When the dimensionless conductance g of the dot is large, the disordered interacting problem can be solved in a saddle-point approximation which becomes exact as g --> infinity (as in a large-N theory), leading to a phase transition in each Landau interaction channel. In the weak-coupling phase constant charging and exchange interactions dominate the low-energy physics, while the strong-coupling phase displays a spontaneous distortion of the Fermi surface, smeared out by disorder.

  4. XMM-Newton Observation of a Distant X-ray Selected Cluster of Galaxies at z=1.26 with Possible Cluster Interaction

    CERN Document Server

    Hashimoto, Y; Arnaud, M; Rosati, P; Miyaji, T; Hashimoto, Yasuhiro; Hasinger, Guenther; Arnaud, Monique; Rosati, Piero; Miyaji, Takamitsu

    2002-01-01

    We report on the XMM-Newton (XMM) observation of RXJ1053.7+5735, one of the most distant (z = 1.26) X-ray selected clusters of galaxies, which also shows an unusual double-lobed X-ray morphology, indicative of possible cluster-cluster interaction. The cluster was discovered during our ROSAT deep pointings in the direction of the Lockman Hole. The XMM observations were performed with the European Photon Imaging Camera (EPIC) during the performance verification phase. Total effective exposure time was ~ 100 ksec. The best fit temperature based on a simultaneous fit of spectra from the all EPIC cameras is 4.9(+1.5/-0.9) keV. Metallicity is poorly constrained even using the joint fit of all spectra, with an upper limit on the iron abundance of 0.62 solar. Using the best fit model parameters, we derived a bolometric luminosity of L(bol) = 3.4x10^44 h_{50}^-2 erg /s. Despite the fact that it was observed at fairly large off-axis angle, the temperature errors are much smaller compared with those of typical measureme...

  5. Chemodynamic evolution of dwarf galaxies in tidal fields

    CERN Document Server

    Williamson, David; Romeo, Alessandro B

    2016-01-01

    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 (SPH) 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 role of tides on the mass-metallicity relation is to move dwarf galaxies to higher metallicities.

  6. Clustering of very luminous infrared galaxies and their environment

    Science.gov (United States)

    Gao, YU

    1993-01-01

    The IRAS survey reveals a class of ultraluminous infrared (IR) galaxies (ULIRG's) with IR luminosities comparable to the bolometric luminosities of quasars. The nature, origin, and evolution of ULIRG's are attracting more and more attention recently. Since galaxy morphology is certainly a function of environment, morphological observations show that ULIRG's are interacting/merging galaxies, and some ULIRG's might be the dust-enshrouded quasars (S88) or giant ellipticals, the study of ULIRG's environment and large scale clustering effects should be worthwhile. ULIRG's and very luminous IR galaxies have been selected from the 2Jy IRAS redshift survey. Meanwhile, a catalog of IRAS groups of galaxies has been constructed using a percolation-like algorithm. Therefore, whether ULIRG's and/or VLIRG's have a group environment can be checked immediately. Other aspects of the survey are discussed.

  7. The Halos and Environments of Nearby Galaxies (HERON) Survey

    CERN Document Server

    Rich, R Michael; Bullock, James; Burkert, Andreas; Collins, Michelle; de Groot, Laura; Kennefick, Julia; Koch, Andreas; Longstaff, Francis; Sales, Laura

    2016-01-01

    We have used dedicated 0.7m telescopes in California and Israel to image the halos of ~200 galaxies in the Local Volume to 29 mag/sq arcsec, the sample mainly drawn from the 2MASS Large Galaxy Atlas (LGA). We supplement the LGA sample with dwarf galaxies and more distant giant ellipticals. Low surface brightness halos exceeding 50 kpc in diameter are found only in galaxies more luminous than L* and classic interaction signatures are relatively infrequent. Halo diameter is correlated with total galaxy luminosity. Extended low surface brightness halos are present even in galaxies as faint as M_V=-18. Edge-on galaxies with boxy bulges tend to lack extended spheroidal halos, while those with large classical bulges exhibit extended round halos, supporting the notions that boxy or barlike bulges originate from disks. Most face-on spiral galaxies present features that appear to be irregular extensions of spiral arms, although rare cases show smooth boundaries with no sign of star formation. Although we serendipitous...

  8. The Role of Galaxy Interaction in Environmental Dependence of the Star Formation Activity at z~1.2

    CERN Document Server

    Ideue, Yuko; Nagao, Tohru; Shioya, Yasuhiro; Kajisawa, Masaru; Trump, Jonathan R; Vergani, Daniela; Iovino, Angela; Koekemoer, Anton M; Fevre, Olivier Le; Ilbert, Olivier; Scoville, Nick

    2011-01-01

    In order to understand environmental effects on star formation in high-redshift galaxies, we investigate the physical relationships between the star formation activity, stellar mass, and environment for z ~1.2 galaxies in the 2 deg^2 COSMOS field. We estimate star formation using the [OII] emission line and environment from the local galaxy density. Our analysis shows that for massive galaxies M_*>10^10 M_sun, the fraction of [OII] emitters in high-density environments is 1.7 times higher than in low-density environments, while the [OII] emitter fraction does not depend on environment for low-mass M_* 10^10 M_sun. In addition, massive galaxies are more likely to have companions in high-density environments. However, although the "number" of star forming galaxies increases for massive galaxies with close companions and in dense environments, the "average" star formation rate of star forming galaxies at a given mass is independent of environment and the presence/absence of a close companion. These results sugg...

  9. Galaxy Disks

    CERN Document Server

    van der Kruit, P C

    2011-01-01

    The formation and evolution of galactic disks is particularly important for understanding how galaxies form and evolve, and the cause of the variety in which they appear to us. Ongoing large surveys, made possible by new instrumentation at wavelengths from the ultraviolet (GALEX), via optical (HST and large groundbased telescopes) and infrared (Spitzer) to the radio are providing much new information about disk galaxies over a wide range of redshift. Although progress has been made, the dynamics and structure of stellar disks, including their truncations, are still not well understood. We do now have plausible estimates of disk mass-to-light ratios, and estimates of Toomre's $Q$ parameter show that they are just locally stable. Disks are mostly very flat and sometimes very thin, and have a range in surface brightness from canonical disks with a central surface brightness of about 21.5 $B$-mag arcsec$^{-2}$ down to very low surface brightnesses. It appears that galaxy disks are not maximal, except possibly in ...

  10. Galaxy formation.

    Science.gov (United States)

    Peebles, P J

    1998-01-01

    It is argued that within the standard Big Bang cosmological model the bulk of the mass of the luminous parts of the large galaxies likely had been assembled by redshift z approximately 10. Galaxy assembly this early would be difficult to fit in the widely discussed adiabatic cold dark matter model for structure formation, but it could agree with an isocurvature version in which the cold dark matter is the remnant of a massive scalar field frozen (or squeezed) from quantum fluctuations during inflation. The squeezed field fluctuations would be Gaussian with zero mean, and the distribution of the field mass therefore would be the square of a random Gaussian process. This offers a possibly interesting new direction for the numerical exploration of models for cosmic structure formation.

  11. Characterisation of an isolated galaxy sample: Astrophysical implications

    Science.gov (United States)

    Argudo Fernandez, Maria del Carmen

    2013-11-01

    In order to understand the evolution of galaxies, it is necessary to have a reference sample where the effects of the environment are minimised and quantified. Recent advances in large redshift galaxy surveys, such as the Sloan Digital Sky Survey (SDSS-DR9), allow to reach a 3-dimensional picture of the environment. In the first two parts of the thesis, we present, in the framework of the AMIGA project (Analysis of the interstellar Medium of Isolated GAlaxies), a revision of the isolation degree and a study of the 3-dimensional environment for galaxies in the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973). Using the 3-dimensional information, new catalogues of isolated galaxies, isolated pairs, and isolated triplets are assembled in the third part of the thesis. The main aims of this thesis are: * to refine the photographic-based CIG and to provide an improvement of the quantification of the isolation degree with respect to previous works, using both photometry and spectroscopy; * to identify and quantify the effects of the physical satellite distribution around galaxies in the CIG, as well as the effects of the Large Scale Structure (LSS); * to construct a catalogue of galaxies isolated in 3-dimension, and build catalogues of physically associated isolated pairs and isolated triplets. We develop an automatic method to search for neighbours around each CIG galaxy in the SDSS, within a projected area up to 3 Mpc. To recover the physically bound neighbour galaxies we focus on the satellites which are within the escape speed of each CIG galaxy. The local number density, at the 5 th nearest neighbour, and the tidal strength affecting the CIG galaxy are estimated to quantify the local and LSS isolation degrees. For the first time, the environment and the isolation degree of CIG galaxies are quantified using digital data. Besides, the availability of the spectroscopic data allows us to check the validity of the CIG isolation criterion, and shows that it is not

  12. A Ringed Dwarf LINER 1 Galaxy Hosting an Intermediate-mass Black Hole with Large-scale Rotation-like Hα Emission

    Science.gov (United States)

    Liu, Wen-Juan; Qian, Lei; Dong, Xiao-Bo; Jiang, Ning; Lira, Paulina; Cai, Zheng; Wang, Feige; Yang, Jinyi; Xiao, Ting; Kim, Minjin

    2017-03-01

    We report the discovery of a 20 kpc sized {{H}}α emission in SDSS J083803.68+540642.0, a ringed dwarf galaxy ({M}V=-17.89 mag) hosting an accreting intermediate-mass black hole at z = 0.02957. Analysis of the Hubble Space Telescope images indicates that it is an early-type galaxy with a featureless low-surface brightness disk ({μ }0=20.39 mag arcsec‑2 in the V band) and a prominent, relatively red bulge (V ‑ I = 2.03, {R}{{e}}=0.28 {kpc} or 0.″48) that accounts for ≈81% of the total light in the I band. A circumgalactic ring of a diameter 16 kpc is also detected, with a disperse shape on its south side. The optical emission lines reveal the nucleus to be a broad-line LINER. Our MMT longslit observation indicates that the kinematics of the extended {{H}}α emission is consistent with a rotational gaseous disk, with a mean blueshifted velocity of 162 {km} {{{s}}}-1 and mean redshifted velocity of 86 {km} {{{s}}}-1. According to our photoionization calculations, the large-scale {{H}}α emission is unlikely to be powered by the central nucleus or by hot evolved (post-AGB) stars interspersed in the old stellar populations, but by in situ star formation; this is vindicated by the line-ratio diagnostic of the extended emission. We propose that both the ring and large-scale {{H}}α -emitting gas are created by the tidal accretion in a collision—and then merger—with a gas-rich galaxy of a comparable mass.

  13. Interactivity-Encouraging Strategies in Large Class Multimedia-Assisted Language Learning%Interactivity-Encouraging Strategies in Large Class Multimedia-Assisted Language Learning

    Institute of Scientific and Technical Information of China (English)

    李丹; 黄金凤

    2008-01-01

    As a tentative study on multimedia-assisted English learning,this paper is gn attempt to explore the interactivity-encouraging strategies through the need analysis of large class language learning.It is of some help for the improvement of learning efficiency for hnguage learners.

  14. The nuclear and extended infrared emission of the Seyfert galaxy NGC 2992 and the interacting system Arp 245

    CERN Document Server

    García-Bernete, I; Acosta-Pulido, J A; Alonso-Herrero, A; Sánchez-Portal, M; Castillo, M; Pereira-Santaella, M; Esquej, P; González-Martín, O; Díaz-Santos, T; Roche, P; Fisher, S; Pović, M; García, A M Pérez; Valtchanov, I; Packham, C; Levenson, N A

    2015-01-01

    We present subarcsecond resolution infrared (IR) imaging and mid-IR spectroscopic observations of the Seyfert 1.9 galaxy NGC 2992, obtained with the Gemini North Telescope and the Gran Telescopio CANARIAS (GTC). The N-band image reveals faint extended emission out to ~3 kpc, and the PAH features detected in the GTC/CanariCam 7.5-13 micron spectrum indicate that the bulk of this extended emission is dust heated by star formation. We also report arcsecond resolution MIR and far-IR imaging of the interacting system Arp 245, taken with the Spitzer Space Telescope and the Herschel Space Observatory. Using these data, we obtain nuclear fluxes using different methods and find that we can only recover the nuclear fluxes obtained from the subarcsecond data at 20-25 micron, where the AGN emission dominates. We fitted the nuclear IR spectral energy distribution of NGC 2992, including the GTC/CanariCam nuclear spectrum (~50 pc), with clumpy torus models. We then used the best-fitting torus model to decompose the Spitzer/...

  15. A network inference method for large-scale unsupervised identification of novel drug-drug interactions.

    Directory of Open Access Journals (Sweden)

    Roger Guimerà

    Full Text Available Characterizing interactions between drugs is important to avoid potentially harmful combinations, to reduce off-target effects of treatments and to fight antibiotic resistant pathogens, among others. Here we present a network inference algorithm to predict uncharacterized drug-drug interactions. Our algorithm takes, as its only input, sets of previously reported interactions, and does not require any pharmacological or biochemical information about the drugs, their targets or their mechanisms of action. Because the models we use are abstract, our approach can deal with adverse interactions, synergistic/antagonistic/suppressing interactions, or any other type of drug interaction. We show that our method is able to accurately predict interactions, both in exhaustive pairwise interaction data between small sets of drugs, and in large-scale databases. We also demonstrate that our algorithm can be used efficiently to discover interactions of new drugs as part of the drug discovery process.

  16. Comment on 'The role of 3-D interactive visualization in blind surveys of HI in galaxies'

    CERN Document Server

    Taylor, Rhys

    2015-01-01

    Punzo et al. (2015) recently reported on the state of the art for visualisation of H I data cubes. I here briefly describe another program, FRELLED, specifically designed for dealing with H I data. Unlike many 3D viewers, FRELLED can handle astronomical world coordinates, easily and interactively mask and label specific volumes within the data, overlay optical data from the SDSS, generate contour plots and renzograms, make basic spectral profile measurements via an interface with MIRIAD, and can switch between viewing the data in 3D and 2D. The code is open source and can potentially be extended to include any astronomical function possible with Python, displaying the result in an interactive 3D environment.

  17. Triple Scoop from Galaxy Hunter

    Science.gov (United States)

    2006-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Figure 1Figure 2Figure 3 Silver Dollar Galaxy: NGC 253 (figure 1) Located 10 million light-years away in the southern constellation Sculptor, the Silver Dollar galaxy, or NGC 253, is one of the brightest spiral galaxies in the night sky. In this edge-on view from NASA's Galaxy Evolution Explorer, the wisps of blue represent relatively dustless areas of the galaxy that are actively forming stars. Areas of the galaxy with a soft golden glow indicate regions where the far-ultraviolet is heavily obscured by dust particles. Gravitational Dance: NGC 1512 and NGC 1510 (figure 2) In this image, the wide ultraviolet eyes of NASA's Galaxy Evolution Explorer show spiral galaxy NGC 1512 sitting slightly northwest of elliptical galaxy NGC 1510. The two galaxies are currently separated by a mere 68,000 light-years, leading many astronomers to suspect that a close encounter is currently in progress. The overlapping of two tightly wound spiral arm segments makes up the light blue inner ring of NGC 1512. Meanwhile, the galaxy's outer spiral arm is being distorted by strong gravitational interactions with NGC 1510. Galaxy Trio: NGC 5566, NGC 5560, and NGC 5569 (figure 3) NASA's Galaxy Evolution Explorer shows a triplet of galaxies in the Virgo cluster: NGC 5560 (top galaxy), NGC 5566 (middle galaxy), and NGC 5569 (bottom galaxy). The inner ring in NGC 5566 is formed by two nearly overlapping bright arms, which themselves spring from the ends of a central bar. The bar is not visible in ultraviolet because it consists of older stars or low mass stars that do not emit energy at ultraviolet wavelengths. The outer disk of NGC 5566 appears warped, and the disk of NGC 5560 is clearly disturbed. Unlike its galactic neighbors, the disk of NGC 5569 does not appear to have been distorted by any passing galaxies.

  18. The visible environment of galaxies with counterrotation

    CERN Document Server

    Bettoni, D; Prada, F

    2001-01-01

    In this paper we present a statistical study of the environments of 49 galaxies in which there is gas- or stellar- counterrotation. The number of possible companions in the field (to apparent magnitude 22), their size and concentration were considered. All the statistical parameters were analysed by means of Kolgomorov-Smirnov tests, using a control sample of 43 galaxies without counterrotation. From our data, no significant differences between the counter-rotating and control samples appear. This is different to Seyfert or radio-loud galaxies which lie in environments with a higher density of companions. On the contrary, if a weak tendency exists, for galaxies with gas counterrotation only, it is discovered in regions of space where the large scale density of galaxies is smaller. Our results tend to disprove the hypothesis that counterrotation and polar rings derive from a recent interaction with a small satellite or a galaxy of similar size. To a first approximation, they seem to follow the idea that all ga...

  19. Outliers from the Mass--Metallicity Relation II: A Sample of Massive Metal-Poor Galaxies from SDSS

    CERN Document Server

    Peeples, Molly S; Stanek, K Z

    2008-01-01

    We present a sample of 42 high-mass low-metallicity outliers from the mass--metallicity relation of star-forming galaxies. These galaxies have stellar masses that span log(M_*/M_sun) ~9.4 to 11.1 and are offset from the mass--metallicity relation by -0.3 to -0.85 dex in 12+log(O/H). In general, they are extremely blue, have high star formation rates for their masses, and are morphologically disturbed. Tidal interactions are expected to induce large-scale gas inflow to the galaxies' central regions, and we find that these galaxies' gas-phase oxygen abundances are consistent with large quantities of low-metallicity gas from large galactocentric radii diluting the central metal-rich gas. We conclude with implications for deducing gas-phase metallicities of individual galaxies based solely on their luminosities, specifically in the case of long gamma-ray burst host galaxies.

  20. A Study in Blue: The Baryon Content of Isolated Low Mass Galaxies

    CERN Document Server

    Bradford, Jeremy D; Blanton, Michael R

    2015-01-01

    We study the baryon content of low mass galaxies selected from the Sloan Digital Sky Survey (SDSS DR8), focusing on galaxies in isolated environments where the complicating physics of galaxy-galaxy interactions are minimized. We measure neutral hydrogen (HI) gas masses and line-widths for 148 isolated galaxies with stellar mass between $10^7$ and $10^{9.5} M_{\\odot}$. We compare isolated low mass galaxies to more massive galaxies and galaxies in denser environments by remeasuring HI emission lines from the Arecibo Legacy Fast ALFA (ALFALFA) survey 40% data release. All isolated low mass galaxies either have large atomic gas fractions or large atomic gas fractions cannot be ruled out via their upper limits. We measure a median atomic gas fraction of $f_{\\rm gas} = 0.82 \\pm 0.13$ for our isolated low mass sample with no systems below 0.30. At all stellar masses, the correlations between galaxy radius, baryonic mass and velocity width are not significantly affected by environment. Finally, we estimate a median b...

  1. The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater

    CERN Document Server

    Torrealba, G; Belokurov, V; Irwin, M

    2016-01-01

    We announce the discovery of the Crater 2 dwarf galaxy, identified in imaging data of the VST ATLAS survey. Given its half-light radius of ~1100 pc, Crater 2 is the fourth largest dwarf in the Milky Way, surpassed only by the LMC, SMC and the Sgr dwarf. With a total luminosity of $M_V\\approx-8$, this satellite galaxy is also one of the lowest surface brightness dwarfs. Falling under the nominal detection boundary of 30 mag arcsec$^{-2}$, it compares in nebulosity to the recently discovered Tuc 2 and Tuc IV and UMa II. Crater 2 is located ~120 kpc from the Sun and appears to be aligned in 3-D with the enigmatic globular cluster Crater, the pair of ultra-faint dwarfs Leo IV and Leo V and the classical dwarf Leo II. We argue that such arrangement is probably not accidental and, in fact, can be viewed as the evidence for the accretion of the Crater-Leo group.

  2. SCALE INTERACTION IN A MIXING LAYER. THE ROLE OF THE LARGE-SCALE GRADIENTS

    KAUST Repository

    Fiscaletti, Daniele

    2015-08-23

    The interaction between scales is investigated in a turbulent mixing layer. The large-scale amplitude modulation of the small scales already observed in other works depends on the crosswise location. Large-scale positive fluctuations correlate with a stronger activity of the small scales on the low speed-side of the mixing layer, and a reduced activity on the high speed-side. However, from physical considerations we would expect the scales to interact in a qualitatively similar way within the flow and across different turbulent flows. Therefore, instead of the large-scale fluctuations, the large-scale gradients modulation of the small scales has been additionally investigated.

  3. How environment drives galaxy evolution: lessons learnt from satellite galaxies

    CERN Document Server

    Pasquali, A

    2015-01-01

    It is by now well established that galaxy evolution is driven by intrinsic and environmental processes, both contributing to shape the observed properties of galaxies. A number of early studies, both observational and theoretical, have shown that the star formation activity of galaxies depends on their environmental local density and also on galaxy hierarchy, i.e. centrals vs. satellites. In fact, contrary to their central (most massive) galaxy of a group/cluster, satellite galaxies are stripped of their gas and stars, and have their star formation quenched by their environment. Large galaxy surveys like SDSS now permit us to investigate in detail environment-driven transformation processes by comparing centrals and satellites. In this paper I summarize what we have so far learnt about environmental effects by analysing the observed properties of local central and satellite galaxies in SDSS, as a function of their stellar mass and the dark matter mass of their host group/cluster.

  4. The MUSE view of QSO PG1307+085: An elliptical galaxy on the $M_{BH}-\\sigma_*$ relation interacting with its group environment

    CERN Document Server

    Husemann, B; Scharwächter, J; Woo, J -H; Choudhury, O S

    2015-01-01

    We report deep optical integral-field spectroscopy with the MUSE of the luminous radio-quiet QSO PG1307+085 (z=0.154) obtained during the commissioning of the instrument. Given the high sensitivity and spatial resolution delivered by MUSE, we are able to resolve the compact ($r_e$~1.3") elliptical host galaxy. After careful spectroscopic deblending of the QSO and host galaxy emission, we infer a stellar velocity dispersion of $155\\pm19$km/s. This places PG1307+085 local $M_{BH}-\\sigma_*$ relation within the intrinsic scatter but offset towards a higher black hole mass with respect to the mean relation. The observations with MUSE also reveal a large extended ENLR around PG1307+085 reaching out to 30kpc. In addition, we detect a faint bridge of ionized gas towards the most massive galaxy of the galaxy group being just 20" (50kpc) away. Previous long-slit spectroscopic observations missed most of these extended features due to a miss-aligned slit. The ionized gas kinematics does not show any evidence for gas out...

  5. Analysis and application of large-scale protein-protein interaction data sets

    Institute of Scientific and Technical Information of China (English)

    SUN Jingchun; XU Jinlin; LI Yixue; SHI Tieliu

    2005-01-01

    Protein-protein interactions play key roles in cells. Lots of experimental approaches and in silico methods have been developed to identify and predict large-scale protein-protein interactions. However, compared with the traditionally experimental results, the high-throughput protein-protein interaction data often contain the false positives in high probability. In order to fully utilize the large-scale data, it is necessary to develop bioinformatic methods for systematically evaluating those data in order to further improve the data reliability and mine biological information. This review summarizes the methodologies of analysis and application of high-throughput protein-protein interaction data, including the evaluation methods, the relationship between protein-protein interaction data and other protein biological information, and their applications in biological study. In addition, this paper also suggests some interesting topics on mining high-throughput protein-protein interaction data.

  6. Role of subgrid-scale modeling in large eddy simulation of wind turbine wake interactions

    DEFF Research Database (Denmark)

    Sarlak, Hamid; Meneveau, C.; Sørensen, Jens Nørkær

    2015-01-01

    A series of simulations are carried out to evaluate specific features of the Large Eddy Simulation (LES) technique in wind turbine wake interactions. We aim to model wake interactions of two aligned model rotors. The effects of the rotor resolution, actuator line force filter size, and Reynolds...

  7. Large herbivores change the direction of interactions within plant communities along a salt marsh stress gradient

    NARCIS (Netherlands)

    Howison, Ruth A.; Olff, Han; Steever, Rutger; Smit, Christian

    2015-01-01

    Question: How multiple abiotic stress factors combined with herbivory affect interactions within plant communities is poorly understood. We ask how large herbivore grazing affects the direction of plant-plant interactions along an environmental gradient in a salt marsh. Location: Grazed (cattle) and

  8. Measuring Student Interactions Using Networks: Insights into the Learning Community of a Large Active Learning Course

    Science.gov (United States)

    Buchenroth-Martin, Cynthia; DiMartino, Trevor; Martin, Andrew P.

    2017-01-01

    Collaborative learning in small groups is commonly implemented as a part of student-centered curricula. In large-enrollment courses, details of the interactions among students as a consequence of working in collaborative groups are often unknown but are important because how students interact influences the effectiveness of peer learning. We…

  9. The Automatic Galaxy Collision Software

    CERN Document Server

    Smith, Beverly J; Pfeiffer, Phillip; Perkins, Sam; Barkanic, Jason; Fritts, Steve; Southerland, Derek; Manchikalapudi, Dinikar; Baker, Matt; Luckey, John; Franklin, Coral; Moffett, Amanda; Struck, Curtis

    2009-01-01

    The key to understanding the physical processes that occur during galaxy interactions is dynamical modeling, and especially the detailed matching of numerical models to specific systems. To make modeling interacting galaxies more efficient, we have constructed the `Automatic Galaxy Collision' (AGC) code, which requires less human intervention in finding good matches to data. We present some preliminary results from this code for the well-studied system Arp 284 (NGC 7714/5), and address questions of uniqueness of solutions.

  10. Progress of Large-Scale Air-Sea Interaction Studies in China

    Institute of Scientific and Technical Information of China (English)

    蒲书箴; 赵进平; 于卫东; 赵永平; 杨波

    2004-01-01

    This paper summarizes the progress of large-scale air-sea interaction studies that has been achieved in China in the four-year period from July 1998 to July 2002, including seven aspects in the area of the air-sea interaction, namely air-sea interaction related to the tropical Pacific Ocean, monsoon-related air-sea interaction, air-sea interaction in the north Pacific Ocean, air-sea interaction in the Indian Ocean, air-sea interactions in the global oceans, field experiments, and oceanic cruise surveys. However more attention has been paid to the first and the second aspects because a large number of papers in the reference literature for preparing and organizing this paper are concentrated in the tropical Pacific Ocean, such as the ENSO process with its climatic effects and dynamics, and the monsoon-related air-sea interaction. The literature also involves various phenomena with their different time and spatial scales such as intraseasonal, annual, interannual, and interdecadal variabilities in the atmosphere/ocean interaction system, reflecting the contemporary themes in the four-year period at the beginning of an era from the post-TOGA to CLIVAR studies. Apparently, it is a difficult task to summarize the great progress in this area, as it is extracted from a large quantity of literature, although the authors tried very hard.

  11. Fluid-structure interaction simulation of floating structures interacting with complex, large-scale ocean waves and atmospheric turbulence

    CERN Document Server

    Calderer, Antoni; Shen, Lian; Sotiropoulos, Fotis

    2016-01-01

    We develop a numerical method for simulating coupled interactions of complex floating structures with large-scale ocean waves and atmospheric turbulence. We employ an efficient large-scale model to develop offshore wind and wave environmental conditions, which are then incorporated into a high resolution two-phase flow solver with fluid-structure interaction (FSI). The large-scale wind-wave interaction model is based on the two-fluid dynamically-coupled approach of Yang and Shen (2011), which employs a high-order spectral method for simulating the water motion and a viscous solver with undulatory boundaries for the air motion. The two-phase flow FSI solver, developed by Calderer, Kang, and Sotiropoulos (2014), is based on the level set method and is capable of simulating the coupled dynamic interaction of arbitrarily complex bodies with airflow and waves. The large-scale wave field solver is coupled with the near-field FSI solver by feeding into the latter waves via the pressure-forcing method of Guo and Shen...

  12. The Activity of the Neighbours of AGN and Starburst Galaxies

    CERN Document Server

    Koulouridis, E; Chavushyan, V; Dultzin, D; Krongold, Y; Georgantopoulos, I; Leon-Tavares, J

    2011-01-01

    We present a follow-up study on a series of papers concerning the role of close interactions as a possible triggering mechanism of the activity of AGN and starburst galaxies. We have already studied the close (< 100 kpc/h) and the large scale (< 1 Mpc/h) environment of Sy1, Sy2 and Bright IRAS galaxies (BIRG) and their respective control samples. The results led us to the conclusion that a close encounter appears capable of activating a sequence where a normal galaxy becomes first a starburst, then a Sy2 and finally a Sy1. However since both galaxies of an interacting pair should be affected, we present here optical spectroscopy and X-ray imaging of the neighbouring galaxies around our original Seyfert and BIRG galaxy samples. Based on optical spectroscopy we find that more than 70% of all neighbouring galaxies exhibit thermal or/and nuclear activity (namely enhanced star formation, starbursting and/or AGN), while an additional X-ray analysis showed that this percentage can reach up to 100%. Furthermore...

  13. Strategies for Building Positive Student-Instructor Interactions in Large Classes

    Science.gov (United States)

    Solis, Oscar J.; Turner, Windi D.

    2016-01-01

    Although large classes in and of themselves are pragmatic for universities, they can be challenging for both students and instructors. The purpose of this study was to investigate pedagogical strategies that instructors teaching large classes can utilize to create positive student-instructor interactions to counter these challenges. Both…

  14. Interactive computer graphics and its role in control system design of large space structures

    Science.gov (United States)

    Reddy, A. S. S. R.

    1985-01-01

    This paper attempts to show the relevance of interactive computer graphics in the design of control systems to maintain attitude and shape of large space structures to accomplish the required mission objectives. The typical phases of control system design, starting from the physical model such as modeling the dynamics, modal analysis, and control system design methodology are reviewed and the need of the interactive computer graphics is demonstrated. Typical constituent parts of large space structures such as free-free beams and free-free plates are used to demonstrate the complexity of the control system design and the effectiveness of the interactive computer graphics.

  15. Star-forming galaxies versus low- and high-excitation radio AGN in the VLA-COSMOS 3GHz Large Project

    CERN Document Server

    Baran, N; Novak, M; Delhaize, J; Delvecchio, I; Capak, P; Civano, F; Herrera-Ruiz, N; Ilbert, O; Laigle, C; Marchesi, S; McCracken, H J; Middelberg, E; Salvato, M; Schinnerer, E

    2016-01-01

    We study the composition of the faint radio population selected from the VLA-COSMOS 3GHz Large Project, a radio continuum survey performed at 10 cm wavelength. The survey covers the full 2 square degree COSMOS field with mean $rms\\sim2.3$ $\\mu$Jy/beam, cataloging 10,899 source components above $5\\times rms$. By combining these radio data with UltraVISTA, optical, near-infrared, and Spitzer/IRAC mid-infrared data, as well as X-ray data from the Chandra Legacy, and Chandra COSMOS surveys, we gain insight into the emission mechanisms within our radio sources out to redshifts of $z\\sim5$. From these emission characteristics we classify our souces as star forming galaxies or AGN. Using their multi-wavelength properties we further separate the AGN into sub-samples dominated by radiatively efficient and inefficient AGN, often referred to as high- and low-excitation emission line AGN. We compare our method with other results based on fitting of the sources' spectral energy distributions using both galaxy and AGN spec...

  16. Karl G. Jansky Very Large Array observations of cold dust and molecular gas in starbursting quasar host galaxies at z~4.5

    CERN Document Server

    Wagg, J; Aravena, M; Cox, P; Lentati, L; Maiolino, R; McMahon, R G; Riechers, D; Walter, F; Andreani, P; Hills, R; Wolfe, A

    2014-01-01

    We present Karl G. Jansky Very Large Array (VLA) observations of 44 GHz continuum and CO J=2-1 line emission in BR1202-0725 at z=4.7 (a starburst galaxy and quasar pair) and BRI1335-0417 at z=4.4 (also hosting a quasar). With the full 8 GHz bandwidth capabilities of the upgraded VLA, we study the (rest-frame) 250 GHz thermal dust continuum emission for the first time along with the cold molecular gas traced by the Low-J CO line emission. The measured CO J=2-1 line luminosities of BR1202-0725 are L'(CO) = (8.7+/-0.8)x10^10 K km/s pc^2 and L'(CO) = (6.0+/-0.5)x10^10 K km/s pc^2 for the submm galaxy (SMG) and quasar, which are equal to previous measurements of the CO J=5-4 line luminosities implying thermalized line emission and we estimate a combined cold molecular gas mass of ~9x10^10 Msun. In BRI1335-0417 we measure L'(CO) = (7.3+/-0.6)x10^10 K km/s pc^2. We detect continuum emission in the SMG BR1202-0725 North (S(44GHz) = 51+/-6 microJy), while the quasar is detected with S(44GHz) = 24+/-6 microJy and in BR...

  17. HerMES: A search for high-redshift dusty galaxies in the HerMES Large Mode Survey - Catalogue, number counts and early results

    CERN Document Server

    Asboth, V; Sayers, J; Bethermin, M; Chapman, S C; Clements, D L; Cooray, A; Dannerbauer, H; Farrah, D; Glenn, J; Golwala, S R; Halpern, M; Ibar, E; Ivison, R J; Maloney, P R; Marques-Chaves, R; Martinez-Navajas, P I; Oliver, S J; Perez-Fournon, I; Riechers, D A; Rowan-Robinson, M; Scott, Douglas; Siegel, S R; Vieira, J D; Viero, M; Wang, L; Wardlow, J; Wheeler, J

    2016-01-01

    Selecting sources with rising flux densities towards longer wavelengths from Herschel/SPIRE maps is an efficient way to produce a catalogue rich in high-redshift (z > 4) dusty star-forming galaxies. The effectiveness of this approach has already been confirmed by spectroscopic follow-up observations, but the previously available catalogues made this way are limited by small survey areas. Here we apply a map-based search method to 274 deg$^2$ of the HerMES Large Mode Survey (HeLMS) and create a catalogue of 477 objects with SPIRE flux densities $S_{500} > S_{350} >S_{250}$ and a 5 \\sigma cut-off $S_{500}$ > 52 mJy. From this catalogue we determine that the total number of these "red" sources is at least an order of magnitude higher than predicted by galaxy evolution models. These results are in agreement with previous findings in smaller HerMES fields; however, due to our significantly larger sample size we are also able to investigate the shape of the red source counts for the first time. We examine the 500 $...

  18. Lyman-alpha Forest Tomography from Background Galaxies: The First Megaparsec-Resolution Large-Scale Structure Map at z>2

    CERN Document Server

    Lee, Khee-Gan; Stark, Casey; Prochaska, J Xavier; White, Martin; Schlegel, David J; Eilers, Anna-Christina; Arinyo-i-Prats, Andreu; Suzuki, Nao; Croft, Rupert A C; Caputi, Karina I; Cassata, Paolo; Ilbert, Olivier; Garilli, Bianca; Koekemoer, Anton M; Brun, Vincent Le; Fèvre, Olivier Le; Maccagni, Dario; Nugent, Peter; Taniguchi, Yoshiaki; Tasca, Lidia A M; Tresse, Laurence; Zamorani, Gianni; Zucca, Elena

    2014-01-01

    We present the first observations of foreground Lyman-$\\alpha$ forest absorption from high-redshift galaxies, targeting 24 star-forming galaxies (SFGs) with $z\\sim 2.3-2.8$ within a $5' \\times 15'$ region of the COSMOS field. The transverse sightline separation is $\\sim 2\\,h^{-1}\\mathrm{Mpc}$ comoving, allowing us to create a tomographic reconstruction of the 3D Ly$\\alpha$ forest absorption field over the redshift range $2.20\\leq z\\leq 2.45$. The resulting map covers $6\\,h^{-1}\\mathrm{Mpc} \\times 14\\,h^{-1}\\mathrm{Mpc}$ in the transverse plane and $230\\,h^{-1}\\mathrm{Mpc}$ along the line-of-sight with a spatial resolution of $\\approx 3.5\\,h^{-1}\\mathrm{Mpc}$, and is the first high-fidelity map of large-scale structure on $\\sim\\mathrm{Mpc}$ scales at $z>2$. Our map reveals significant structures with $\\gtrsim 10\\,h^{-1}\\mathrm{Mpc}$ extent, including several spanning the entire transverse breadth, providing qualitative evidence for the filamentary structures predicted to exist in the high-redshift cosmic web. ...

  19. A diversity of progenitors and histories for isolated spiral galaxies

    CERN Document Server

    Martig, Marie; Croton, Darren J; Dekel, Avishai; Teyssier, Romain

    2012-01-01

    We analyze a suite of 33 cosmological simulations following the evolution of Milky Way-mass galaxies in low-density environments. Our sample at z = 0 comprises galaxies with a broad range of Hubble types, from nearly bulgeless disks to bulge-dominated galaxies. The bulges are typically pseudo-bulges, with a Sersic index lower than 2, and 70% of the galaxies have bars. Despite the fact that a large fraction of the bulge is typically in place by z = 1, we find no significant correlation between the morphology at z = 1 and at z = 0. The progenitors of disk galaxies span a whole range of morphologies at z = 1, including smooth disks, unstable disks, interacting galaxies and bulge-dominated systems. By z = 0.5, the progenitor morphology is correlated with the z = 0 morphology, with spiral arms and bars largely in place at z = 0.5. From this sample we analyze the formation histories of galaxies with a bulge-to-total ratio below 0.3 (typically Sb and later types). They do form in our simulations, but with a lower ab...

  20. Interactive Generalization on Large-Scale Topographical Map Supported by a Database Platform

    Institute of Scientific and Technical Information of China (English)

    CAI Zhongliang; WU Hehai; DU Qingyun; LIAO Chujiang

    2003-01-01

    This paper makes astudy on the interactive digital gener-alization, where map generalizationcan be divided into intellective reason-ing procedure and operational proce-dure, which are done by human andcomputer, respectively. And an inter-active map generalization environmentfor large scale topographic map is thendesigned and realized. This researchfocuses on: ① the significance of re-searching an interactive map generali-zation environment, ② the features oflarge scale topographic map and inter-active map generalization, ③ the con-struction of map generalization-orien-ted database platform.