Sample records for extended disk galaxies

  1. Galaxy Disks

    NARCIS (Netherlands)

    van der Kruit, P. C.; Freeman, K. C.

    The disks of disk galaxies contain a substantial fraction of their baryonic matter and angular momentum, and much of the evolutionary activity in these galaxies, such as the formation of stars, spiral arms, bars and rings, and the various forms of secular evolution, takes place in their disks. The

  2. Thick Disks of Lenticular Galaxies


    Pohlen, M.; Balcells, M.; Luetticke, R.; Dettmar, R. -J.


    Thick disks are faint and extended stellar components found around several disk galaxies including our Milky Way. The Milky Way thick disk, the only one studied in detail, contains mostly old disk stars (~10 Gyr), so that thick disks are likely to trace the early stages of disk evolution. Previous detections of thick disk stellar light in external galaxies have been originally made for early-type, edge-on galaxies but detailed 2D thick/thin disk decompositions have been reported for only a sc...

  3. Exploring Our Galaxy's Thick Disk (United States)

    Kohler, Susanna


    What is the structure of the Milky Ways disk, and how did it form? A new study uses giant stars to explore these questions.A View from the InsideSchematic showing an edge-on, not-to-scale view of what we think the Milky Ways structurelookslike. The thick disk is shown in yellow and the thin disk is shown in green. [Gaba p]Spiral galaxies like ours are often observed to have disks consisting of two components: a thin disk that lies close to the galactic midplane, and a thick disk that extends above and below this. Past studies have suggested that the Milky Ways disk hosts the same structure, but our position embedded in the Milky Way makes this difficult to confirm.If we can measure the properties of a broad sample of distant tracer stars and use this to better understand the construction of the Milky Ways disk, then we can start to ask additional questions like, how did the disk components form? Formation pictures for the thick disk generally fall into two categories:Stars in the thick disk formed within the Milky Way either in situ or by migrating to their current locations.Stars in the thick disk formed in satellite galaxies around the Milky Way and then accreted when the satellites were disrupted.Scientists Chengdong Li and Gang Zhao (NAO Chinese Academy of Sciences, University of Chinese Academy of Sciences) have now used observations of giant stars which can be detected out to great distances due to their brightness to trace the properties of the Milky Ways thick disk and address the question of its origin.Best fits for the radial (top) and vertical (bottom) metallicity gradients of the thick-disk stars. [Adapted from Li Zhao 2017]Probing OriginsLi and Zhao used data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) in China to examine a sample of 35,000 giant stars. The authors sorted these stars into different disk components halo, thin disk, and thick disk based on their kinematic properties, and then explored how the orbital and

  4. Three types of galaxy disks

    NARCIS (Netherlands)

    Pohlen, M.; Erwin, P.; Trujillo, I.; Beckman, J. E.; Knapen, JH; Mahoney, TJ; Vazdekis, A


    We present our new scheme for the classification of radial stellar surface brightness profiles for disk galaxies. We summarize the current theoretical attempts to understand their origin and give an example of an application by comparing local galaxies with their counterparts at high redshift (z

  5. Secular Evolution in Disk Galaxies (United States)

    Kormendy, John


    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

  6. Bulge-Disk Evolution in Interacting Bulgeless Galaxies (United States)

    Das, M.; Ramya, S.; Sengupta, C.; Mishra, K.


    Bulgeless galaxies are an extreme class of late type spiral galaxies that have practically no bulge and are nearly pure disk in morphology. Their lack of evolution is a puzzle for theories of galaxy formation and the secular evolution of galaxy disks. However, one of the processes by which these galaxies could evolve is through interactions with other galaxies. In this study we present radio (GMRT) observations of star formation in a sample of bulgeless galaxies. We did followup Hα imaging and optical spectroscopy of two galaxies, NGC 3445 and NGC 4027. Both galaxies have extended emission associated with their tidal interactions. Their nuclei show ongoing star formation but no signs of AGN activity. The R band images suggest that their centers have oval distortions or pseudobulges that may later evolve into larger bulges. Thus interactions are an important trigger for the formation of bulges in such disk dominated systems.

  7. Star Formation Modes in Low-Mass Disk Galaxies


    Gallagher, J. S.; Matthews, L. D.


    Low-mass disk galaxies with well-organized structures are relatively common in low density regions of the nearby Universe. They display a wide range in levels of star formation activity, extending from sluggishly evolving `superthin' disk systems to nearby starbursts. Investigations of this class of galaxy therefore provides opportunities to test and define models of galactic star formation processes. In this paper we briefly explore characteristics of examples of quiescent and starbursting l...

  8. A Catalog of Edge-on Disk Galaxies: From Galaxies with a Bulge to Superthin Galaxies


    Kautsch, S. J.; Grebel, E. K.; Barazza, F. D.; Gallagher, J. S.


    The formation and evolution of disk-dominated galaxies is difficult to explain, yet these objects exist. We therefore embarked on a study aimed at a better understanding of these enigmatic objects. We used data from the SDSS DR1 in order to identify edge-on galaxies with disks in a uniform, reproducible, automated fashion. We identified 3169 edge-on disk galaxies, which we subdivided into disk galaxies with bulge, intermediate types, and simple disk galaxies without any obvious bulge componen...

  9. Extended Star-formation and Disk-like Kinematics in a z~3 Massive ``Main-Sequence'' Galaxy through [CII] Imaging and Multi-J CO Line Observations (United States)

    Leung, Tsz Kuk Daisy; Riechers, Dominik A.; Clements, David; Cooray, Asantha; Ivison, Rob; Perez-Fournon, Ismael; Wardlow, Julie


    Dusty star-forming galaxies (SFG) at high redshifts are the main contributors to the comoving star formation rate (SFR) density, which peaks between the redshift of z=1-3 (``Cosmic Noon''). Yet, new insights into their gas dynamics, and thus, structural evolution are awaiting spatially resolved observations. I will present the latest results from our kpc-scale [CII] imaging and multi-J CO line observations obtained with ALMA, CARMA, PdBI, and the VLA in one of the most massive ``main-sequence'' disk galaxy known. XMM03 (z=2.9850) is an extremely IR-luminous galaxy with a SFR of ~3000 Msun/yr, but its molecular gas excitation is surprisingly similar to the Milky Way up to J=5, which is in stark contrast with most high-z galaxies studied to date. The monotonic velocity gradient seen in the [CII] line emission suggest that it is a rotating disk galaxy. Based on the molecular gas surface density and the far-UV radiation flux determined from photo-dissociation region (PDR) modeling, the star-forming environment of XMM03 is similar to nearby SFGs. These findings together with the ~1100 km/s wide CO(1-0) line across the entire disk of ~8 kpc in radius showcase the different interstellar medium (ISM) environment that we are probing at the most massive end of galaxies in the early Universe. With a stellar mass of M*~10^12, its specific SFR is consistent with an extrapolation of the ``star-forming main-sequence'' up to M*~10^12 Msun at z~3. Our findings therefore confirm the prevalence of disk-wide star formation responsible for assembling most of the stellar masses toward the ``Cosmic Noon''.

  10. Extragalactic Thick Disks: Implications for Early Galaxy Evolution


    Dalcanton, Julianne J.; Seth, Anil; Yoachim, Peter


    I briefly review the growing evidence that thick stellar disks surround most edge-on disk galaxies. Recent studies show that these extragalactic thick disks have old ages, low metallicities, long scale lengths, and moderately flattened axial ratios, much like the thick disk of the Milky Way. However, the properties of thick disks change systematically with the mass of the galaxy. The thick disks of low mass galaxies are more prominent and somewhat more metal-poor than those surrounding massiv...

  11. Cosmic Rays in the Disk and Halo of Galaxies (United States)

    Dogiel, V. A.; Breitschwerdt, D.


    We give a review of cosmic ray propagation models. It is shown that the development of the theory of cosmic ray origin leads inevitably to the conclusion that cosmic ray propagation in the Galaxy is determined by effective particle scattering, which is described by spatial diffusion. The Galactic Disk is surrounded by an extended halo, in which cosmic rays are confined before escaping into intergalactic space. For a long time cosmic ray convective outflow from the Galaxy (galactic wind) was believed to be insignificant. However, investigations of hydrodynamic stability and an analysis of ISM dynamics (including cosmic rays) showed that a galactic wind was emanating near the disk, and accelerating towards the halo, reaching its maximum velocity far away from the disk. Therefore convective cosmic ray transport should be important in galactic halos. Recent analysis of the gamma-ray emissivity in the Galactic disk of EGRET data, which showed that cosmic rays are more or less uniformly distributed in the radial direction of the disk, as well as the interpretation of soft X-ray emission in galactic halos, give convincing evidence of the existence of a galactic wind in star forming galaxies.

  12. Galaxy Evolution with Stellar Disks, Halos, and Streams in Nearby Galaxies (United States)

    Staudaher, Shawn M.

    This thesis begins with a deep-dive into the stellar properties of the nearby spiral galaxy, M 63, a member of the EDGES (Extended Disk Galaxy Exploration Science) survey. Deep ( 28 AB mag arcsec-2) 3.6 mum imaging from the Spitzer Space Telescope reveals that the spiral structure of this galaxy is enveloped by an extended stellar halo, the result of the accretion of smaller galaxies. The mass of this stellar halo agrees well with results from the latest large scale LambdaCDM based galaxy evolution models. M 63 is also host to a tidal stream, an actively accreting satellite. The mass of the progenitor satellite is large enough that only sixteen similarly sized accretion events would account for the mass in the stellar halo. In addition, the majority of satellite accretion must have happened in the past as the average accretion rate derived from the stellar halo is significantly larger than the average accretion rate derived from the more recent tidal stream. The scope of the thesis is then extended to include the full sample of 92 nearby galaxies from EDGES. This is the largest Spitzer Space Telescope survey to probe the extended stellar properties of nearby galaxies. The surface brightness profiles of EDGES galaxies contain an unprecedented number of breaks (transitions from one galactic component to the next) given the sample size of EDGES, proving that studies of break statistics are incomplete without significantly deep imaging. The surface brightness profiles are decomposed into their individual components and the stellar mass for each component is measured. Seven galaxies contain strong evidence for the presence of stellar halos, and the masses of these halos agree with predictions from LambdaCDM based galaxy evolution models. However, the lack of stellar halos in general may be evidence that simulations continue to suffer from the so-called "missing satellite problem", where the number of satellite galaxies is overpredicted compared to observations.

  13. Exponential bulges and antitruncated disks in lenticular galaxies


    Sil'chenko, Olga K.


    The presence of exponential bulges and anti-truncated disks has been noticed in many lenticular galaxies. In fact, it could be expected because the very formation of S0 galaxies includes various processes of secular evolution. We discuss how to distinguish between a pseudobulge and an anti-truncated disk, and also what particular mechanisms may be responsible for the formation of anti-truncated disks. Some bright examples of lenticular galaxies with the multi-tiers exponential stellar structu...

  14. Ejection of Supernova-Enriched Gas From Dwarf Disk Galaxies

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    Fragile, P C; Murray, S D; Lin, D C


    We examine the efficiency with which supernova-enriched gas may be ejected from dwarf disk galaxies, using a methodology previously employed to study the self-enrichment efficiency of dwarf spheroidal systems. Unlike previous studies that focused on highly concentrated starbursts, in the current work we consider discrete supernova events spread throughout various fractions of the disk. We model disk systems having gas masses of 10{sup 8} and 10{sup 9} M{sub {circle_dot}} with supernova rates of 30, 300, and 3000 Myr{sup -1}. The supernova events are confined to the midplane of the disk, but distributed over radii of 0, 30, and 80% of the disk radius, consistent with expectations for Type II supernovae. In agreement with earlier studies, we find that the enriched material from supernovae is largely lost when the supernovae are concentrated near the nucleus, as expected for a starburst event. In contrast, we find the loss of enriched material to be much less efficient (as low as 21%) when the supernovae occur over even a relatively small fraction of the disk. The difference is due to the ability of the system to relax following supernova events that occur over more extended regions. Larger physical separations also reduce the likelihood of supernovae going off within low-density ''chimneys'' swept out by previous supernovae. We also find that, for the most distributed systems, significant metal loss is more likely to be accompanied by significant mass loss. A comparison with theoretical predications indicates that, when undergoing self-regulated star formation, galaxies in the mass range considered shall efficiently retain the products of Type II supernovae.

  15. A Fundamental Plane of Spiral Structure in Disk Galaxies

    NARCIS (Netherlands)

    Davis, Benjamin L.; Kennefick, Daniel; Kennefick, Julia; Westfall, Kyle B.; Shields, Douglas W.; Flatman, Russell; Hartley, Matthew T.; Berrier, Joel C.; Martinsson, Thomas P. K.; Swaters, Rob A.

    Spiral structure is the most distinctive feature of disk galaxies and yet debate persists about which theory of spiral structure is correct. Many versions of the density wave theory demand that the pitch angle be uniquely determined by the distribution of mass in the bulge and disk of the galaxy. We


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    Roediger, Joel C.; Courteau, Stephane [Department of Physics, Engineering Physics and Astronomy, Queen' s University, Kingston, Ontario (Canada); Sanchez-Blazquez, Patricia [Deptartamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); McDonald, Michael, E-mail:, E-mail:, E-mail:, E-mail: [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology Cambridge, MA (United States)


    We present new stellar age profiles, derived from well-resolved optical and near-infrared images of 64 Virgo cluster disk galaxies, whose analysis poses a challenge for current disk galaxy formation models. Our ability to break the age-metallicity degeneracy and the significant size of our sample represent key improvements over complementary studies of field disk galaxies. Our results can be summarized as follows: first, and contrary to observations of disk galaxies in the field, these cluster galaxies are distributed almost equally amongst the three main types of disk galaxy luminosity profiles (I/II/III), indicating that the formation and/or survival of Type II breaks is suppressed within the cluster environment. Second, we find examples of statistically significant inversions ({sup U}-shapes{sup )} in the age profiles of all three disk galaxy types, reminiscent of predictions from high-resolution simulations of classically truncated Type II disks in the field. These features characterize the age profiles for only about a third ({<=}36%) of each disk galaxy type in our sample. An even smaller fraction of cluster disks ({approx}11% of the total sample) exhibit age profiles that decrease outward (i.e., negative age gradients). Instead, flat and/or positive age gradients prevail ({>=}50%) within our Type I, II, and III subsamples. These observations thus suggest that while stellar migrations and inside-out growth can play a significant role in the evolution of all disk galaxy types, other factors contributing to the evolution of galaxies can overwhelm the predicted signatures of these processes. We interpret our observations through a scenario whereby Virgo cluster disk galaxies formed initially like their brethren in the field but which, upon falling into the cluster, were transformed into their present state through external processes linked to the environment (e.g., ram-pressure stripping and harassment). Current disk galaxy formation models, which have largely

  17. Early-type galaxies with extended HI reservoirs (United States)

    Donovan Meyer, Jennifer


    I will present observations of NGC 404 and ESO 381-47, both early-type galaxies known for hosting extended HI rings and recent star formation in their outskirts. Thanks to the Green Bank Telescope, an instrument uniquely suited to observing diffuse, low column density HI around nearby galaxies, we report new measurements of the extent of the disk around NGC 404 as well as the presence of a large, coherent HI filament which appears to be accreting onto the ring surrounding the galaxy. We compare the environments of the two systems and interpret the potential utility of such gas-bearing field early-type galaxies as tracers of galaxy accretion and growth.

  18. The Height Distribution of Core Collapse Supernovae in Disk Galaxies (United States)

    Molloy, M.; Meurs, E.; Norci, L.; Kavanagh, P.

    Core collapse (CC) supernovae are exploding massive stars and are therefore expected to occur in the disks of spiral galaxies. However, in the historical record some CC SNae can be noticed outside the disks. To investigate this further, the distribution of SNae above and below the disks of spiral galaxies is examined for the case of edge-on galaxies. The CC SNae that are observed away from their parent Population I in the galaxy planes must previously have left the disks due to dynamical encounters or SN explosions of companion stars. We develop a simple interpretative model that describes the observed height distribution of the SNae, taking into account kick velocities imparted during the explosive events. We also briefly comment on the radial distribution of SNae, utilizing face-on galaxies for this purpose.

  19. Angular Momentum Evolution Of Disk Galaxies At High Redshift (United States)

    Okamura, Taku; Kazuhiro, Shimasaku; Ryota, Kawamata


    The stellar disk size of a galaxy depends on the fraction of the dark-halo mass settled as disk stars, m★= M★/Mdh, and the fraction of the dark-halo angular momentum transferred to the disk, j★ = J★/Jdh. Since j★ is also determined by various star-formation related mechanisms such as inflows and feedbacks, measuring j★ and m★ at high redshifts is needed to understand the formation history of disk galaxies. We use the 3D-HST GOODS-S, COSMOS, and AEGIS imaging data and photo-z catalogs to examine j★ and m★ for star-forming galaxies at z 2,3,4, when disks are actively forming. We find that the j★/m★ ratio is roughly constant at ≃ 0.8 for all three redshifts over the entire halo mass range examined. This high ratio is close to those of local disk galaxies but a factor of a few higher than predicted (at z 2) by galaxy formation models. We also find that a significant fraction of our galaxies appear to be unstable against bar formation.

  20. ECO and RESOLVE: Galaxy Disk Growth in Environmental Context (United States)

    Moffett, Amanda J.; Kannappan, Sheila J.; Berlind, Andreas A.; Eckert, Kathleen D.; Stark, David V.; Hendel, David; Norris, Mark A.; Grogin, Norman A.


    We study the relationships between galaxy environments and galaxy properties related to disk (re)growth, considering two highly complete samples that are approximately baryonic mass limited into the high-mass dwarf galaxy regime, the Environmental COntext catalog (data release herein) and the B-semester region of the REsolved Spectroscopy Of a Local VolumE survey. We quantify galaxy environments using both group identification and smoothed galaxy density field methods. We use by-eye and quantitative morphological classifications plus atomic gas content measurements and estimates. We find that blue early-type (E/S0) galaxies, gas-dominated galaxies, and UV-bright disk host galaxies all become distinctly more common below group halo mass ˜ {10}11.5 {M}⊙ , implying that this low group halo mass regime may be a preferred regime for significant disk growth activity. We also find that blue early-type and blue late-type galaxies inhabit environments of similar group halo mass at fixed baryonic mass, consistent with a scenario in which blue early-types can regrow late-type disks. In fact, we find that the only significant difference in the typical group halo mass inhabited by different galaxy classes is for satellite galaxies with different colors, where at fixed baryonic mass red early- and late-types have higher typical group halo masses than blue early- and late-types. More generally, we argue that the traditional morphology-environment relation (i.e., that denser environments tend to have more early-types) can be largely attributed to the morphology-galaxy mass relation for centrals and the color-environment relation for satellites.

  1. The photometric and kinematic structure and asymmetry of disk galaxies (United States)

    Andersen, David Roger


    We establish a sample of 39 nearby, nearly face-on disk galaxies for a detailed study of their photometric and kinematic structure and asymmetries. For this sample we collected two-dimensional Halpha velocity-fields at echelle resolutions with the DensePak integral field unit on the WIYN 3.5m telescope, HI line widths taken with the Nancay radio telescope, and deep R and I-band imaging from the WIYN telescope, the 2.1m telescope at KPNO, and the Harlan J. Smith 2.7m telescope at McDonald Observatory. These data put constraints on the shape of disk galaxies and their halos and are used to study the fundamental disk galaxy scaling relationship between rotation speed and luminosity, i.e., the Tully-Fisher relation. To study the shapes of galaxy disks, we measured both photometric and kinematic asymmetries. From studies of the asymmetry, we were able to show that the now commonly used photometric rotational asymmetry index does not measure disk flocculence as previously suggested; instead it is shown to be equivalent to low order, odd Fourier amplitudes, i.e., lopsidedness. In addition to studying disk lopsidedness, a set of kinematic and photometric indices are used to present the first measurements of disk ellipticity for galaxies outside the Milky Way. These measurements are decoupled from a phase angle which plagues previous estimates of disk ellipticity. Nonetheless, our disk ellipticity measurement of 0.083 +/- 0.054 is consistent with these previous estimates. This measurement allows us to put a limit of 0.15 mag on Tully-Fisher scatter due to the intrinsic ellipticity of disk galaxies. Kinematic inclination angles, one of the primary kinematic indices used to measure disk ellipticity, were derived from model velocity-field fits to our Halpha velocity fields. These inclinations are both accurate and precise and allowed us to create the first Tully-Fisher relation for nearly face-on disk galaxies. We demonstrate that our face-on Tully-Fisher sample is well fit by

  2. A photometric study of the structure of pure disk galaxies (United States)

    Brockett, Timothy


    Pure disk galaxies are galaxies that form and evolve without a central bulge region. This morphology of galaxy is relatively unexplained and has yet to be successfully simulated using Lambda-Cold Dark Matter (ΛCDM) model parameters. The ΛCDM model is the standard framework from which astronomers and physicists understand and predict the Universe due to confirmed predictions such as the cosmic microwave background and the large scale structure of galaxy clusters. However, ΛCDM has yet to have a benchmark, observationally confirmed prediction on the galactic scale. This thesis is a study of eleven pure disk galaxies. Understanding this type of galaxy is very important in rectifying the incompatibility with the ΛCDM model. The method of analysis includes obtaining, cleaning and sky subtracting images from the Sloan Digital Sky Survey Data Release 7, deprojecting the images for a face on perspective, using g- and i-bands to construct color-index maps, using Fourier decompositions to create mode-dependent intensity ratio plots, surface density maps, mass-to-light ratio maps and surface brightness profiles, from which the radial scale length is derived. The future of this area of study is vital to understand a common feature of our Universe. Future studies can include looking for early supernova remnants or evidence of recent active galactic nuclei activity in young pure disk galaxies. Surveys and photometric analysis of edge-on pure disk galaxies may also reveal vital information to the origin and evolution of this class of galaxy.

  3. An Optimal Strategy for Accurate Bulge-to-disk Decomposition of Disk Galaxies (United States)

    Gao, Hua; Ho, Luis C.


    The development of two-dimensional (2D) bulge-to-disk decomposition techniques has shown their advantages over traditional one-dimensional (1D) techniques, especially for galaxies with non-axisymmetric features. However, the full potential of 2D techniques has yet to be fully exploited. Secondary morphological features in nearby disk galaxies, such as bars, lenses, rings, disk breaks, and spiral arms, are seldom accounted for in 2D image decompositions, even though some image-fitting codes, such as GALFIT, are capable of handling them. We present detailed, 2D multi-model and multi-component decomposition of high-quality R-band images of a representative sample of nearby disk galaxies selected from the Carnegie-Irvine Galaxy Survey, using the latest version of GALFIT. The sample consists of five barred and five unbarred galaxies, spanning Hubble types from S0 to Sc. Traditional 1D decomposition is also presented for comparison. In detailed case studies of the 10 galaxies, we successfully model the secondary morphological features. Through a comparison of best-fit parameters obtained from different input surface brightness models, we identify morphological features that significantly impact bulge measurements. We show that nuclear and inner lenses/rings and disk breaks must be properly taken into account to obtain accurate bulge parameters, whereas outer lenses/rings and spiral arms have a negligible effect. We provide an optimal strategy to measure bulge parameters of typical disk galaxies, as well as prescriptions to estimate realistic uncertainties of them, which will benefit subsequent decomposition of a larger galaxy sample.

  4. An Optimal Strategy for Accurate Bulge-to-disk Decomposition of Disk Galaxies

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    Gao Hua [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Ho, Luis C. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)


    The development of two-dimensional (2D) bulge-to-disk decomposition techniques has shown their advantages over traditional one-dimensional (1D) techniques, especially for galaxies with non-axisymmetric features. However, the full potential of 2D techniques has yet to be fully exploited. Secondary morphological features in nearby disk galaxies, such as bars, lenses, rings, disk breaks, and spiral arms, are seldom accounted for in 2D image decompositions, even though some image-fitting codes, such as GALFIT, are capable of handling them. We present detailed, 2D multi-model and multi-component decomposition of high-quality R -band images of a representative sample of nearby disk galaxies selected from the Carnegie-Irvine Galaxy Survey, using the latest version of GALFIT. The sample consists of five barred and five unbarred galaxies, spanning Hubble types from S0 to Sc. Traditional 1D decomposition is also presented for comparison. In detailed case studies of the 10 galaxies, we successfully model the secondary morphological features. Through a comparison of best-fit parameters obtained from different input surface brightness models, we identify morphological features that significantly impact bulge measurements. We show that nuclear and inner lenses/rings and disk breaks must be properly taken into account to obtain accurate bulge parameters, whereas outer lenses/rings and spiral arms have a negligible effect. We provide an optimal strategy to measure bulge parameters of typical disk galaxies, as well as prescriptions to estimate realistic uncertainties of them, which will benefit subsequent decomposition of a larger galaxy sample.

  5. Population Synthesis Models for Normal Galaxies with Dusty Disks

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    Kyung-Won Suh


    Full Text Available To investigate the SEDs of galaxies considering the dust extinction processes in the galactic disks, we present the population synthesis models for normal galaxies with dusty disks. We use PEGASE (Fioc & Rocca-Volmerange 1997 to model them with standard input parameters for stars and new dust parameters. We find that the model results are strongly dependent on the dust parameters as well as other parameters (e.g. star formation history. We compare the model results with the observations and discuss about the possible explanations. We find that the dust opacity functions derived from studies of asymptotic giant branch stars are useful for modeling a galaxy with a dusty disk.

  6. The collective origin of spiral structures in disk galaxies

    Directory of Open Access Journals (Sweden)

    Hernquist L.


    Full Text Available After almost fifty years the origin of spiral arms in disk galaxies remains one of the major unsolved problems in astrophysics. Recent attempts have indicated that substructures in the dark matter halos of galaxies could induce spiral patterns in disks by generating localized disturbances that grow by swing amplification. However, there are indications that dark matter substructures orbiting in the inner regions of galaxy halos would be destroyed by dynamical processes such as disk shocking, and hence would not be able to seed the formation of spiral structure. Instead, we use numerical simulations of unprecedented resolution explore the possibility that spiral arms might be generated by the dynamical response of the disk to overdensities corotating within the disk. These perturbations can be identified with fluctuations in the distribution of gas in the interstellar medium of galaxies, such as giant molecular clouds. We develop a new theory for spiral structure formation based on the non-linear effects of swing amplification. Our model makes numerous testable predictions, making it possible to finally confront theory with observations.

  7. A massive, dead disk galaxy in the early Universe (United States)

    Toft, Sune; Zabl, Johannes; Richard, Johan; Gallazzi, Anna; Zibetti, Stefano; Prescott, Moire; Grillo, Claudio; Man, Allison W. S.; Lee, Nicholas Y.; Gómez-Guijarro, Carlos; Stockmann, Mikkel; Magdis, Georgios; Steinhardt, Charles L.


    At redshift z = 2, when the Universe was just three billion years old, half of the most massive galaxies were extremely compact and had already exhausted their fuel for star formation. It is believed that they were formed in intense nuclear starbursts and that they ultimately grew into the most massive local elliptical galaxies seen today, through mergers with minor companions, but validating this picture requires higher-resolution observations of their centres than is currently possible. Magnification from gravitational lensing offers an opportunity to resolve the inner regions of galaxies. Here we report an analysis of the stellar populations and kinematics of a lensed z = 2.1478 compact galaxy, which—surprisingly—turns out to be a fast-spinning, rotationally supported disk galaxy. Its stars must have formed in a disk, rather than in a merger-driven nuclear starburst. The galaxy was probably fed by streams of cold gas, which were able to penetrate the hot halo gas until they were cut off by shock heating from the dark matter halo. This result confirms previous indirect indications that the first galaxies to cease star formation must have gone through major changes not just in their structure, but also in their kinematics, to evolve into present-day elliptical galaxies.

  8. A massive, dead disk galaxy in the early Universe. (United States)

    Toft, Sune; Zabl, Johannes; Richard, Johan; Gallazzi, Anna; Zibetti, Stefano; Prescott, Moire; Grillo, Claudio; Man, Allison W S; Lee, Nicholas Y; Gómez-Guijarro, Carlos; Stockmann, Mikkel; Magdis, Georgios; Steinhardt, Charles L


    At redshift z = 2, when the Universe was just three billion years old, half of the most massive galaxies were extremely compact and had already exhausted their fuel for star formation. It is believed that they were formed in intense nuclear starbursts and that they ultimately grew into the most massive local elliptical galaxies seen today, through mergers with minor companions, but validating this picture requires higher-resolution observations of their centres than is currently possible. Magnification from gravitational lensing offers an opportunity to resolve the inner regions of galaxies. Here we report an analysis of the stellar populations and kinematics of a lensed z = 2.1478 compact galaxy, which-surprisingly-turns out to be a fast-spinning, rotationally supported disk galaxy. Its stars must have formed in a disk, rather than in a merger-driven nuclear starburst. The galaxy was probably fed by streams of cold gas, which were able to penetrate the hot halo gas until they were cut off by shock heating from the dark matter halo. This result confirms previous indirect indications that the first galaxies to cease star formation must have gone through major changes not just in their structure, but also in their kinematics, to evolve into present-day elliptical galaxies.

  9. Why Buckling Stellar Bars Weaken in Disk Galaxies


    Martinez-Valpuesta, Inma; Shlosman, Isaac


    Young stellar bars in disk galaxies experience a vertical buckling instability which terminates their growth and thickens them, resulting in a characteristic peanut/boxy shape when viewed edge on. Using N-body simulations of galactic disks embedded in live halos, we have analyzed the bar structure throughout this instability and found that the outer third of the bar dissolves completely while the inner part (within the vertical inner Lindblad resonance) becomes less oval. The bar acquires the...

  10. No more active galactic nuclei in clumpy disks than in smooth galaxies at z ∼ 2 in CANDELS/3D-HST

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    Trump, Jonathan R.; Luo, Bin; Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Barro, Guillermo; Guo, Yicheng; Koo, David C.; Faber, S. M. [University of California Observatories/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Juneau, Stéphanie [Irfu/Service d' Astrophysique, CEA-Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France); Weiner, Benjamin J. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Brammer, Gabriel B.; Ferguson, Henry C.; Grogin, Norman A.; Kartaltepe, Jeyhan; Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Dekel, Avishai [Center for Astrophysics and Planetary Science, Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Hopkins, Philip F. [California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kocevski, Dale D. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); McIntosh, Daniel H. [Department of Physics and Astronomy, University of Missouri-Kansas City, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Momcheva, Ivelina [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); and others


    We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to investigate if active galactic nuclei (AGNs) are preferentially fueled by violent disk instabilities funneling gas into galaxy centers at 1.3 < z < 2.4. We select galaxies undergoing gravitational instabilities using the number of clumps and degree of patchiness as proxies. The CANDELS visual classification system is used to identify 44 clumpy disk galaxies, along with mass-matched comparison samples of smooth and intermediate morphology galaxies. We note that despite being mass-matched and having similar star formation rates, the smoother galaxies tend to be smaller disks with more prominent bulges compared to the clumpy galaxies. The lack of smooth extended disks is probably a general feature of the z ∼ 2 galaxy population, and means we cannot directly compare with the clumpy and smooth extended disks observed at lower redshift. We find that z ∼ 2 clumpy galaxies have slightly enhanced AGN fractions selected by integrated line ratios (in the mass-excitation method), but the spatially resolved line ratios indicate this is likely due to extended phenomena rather than nuclear AGNs. Meanwhile, the X-ray data show that clumpy, smooth, and intermediate galaxies have nearly indistinguishable AGN fractions derived from both individual detections and stacked non-detections. The data demonstrate that AGN fueling modes at z ∼ 1.85—whether violent disk instabilities or secular processes—are as efficient in smooth galaxies as they are in clumpy galaxies.

  11. Disk galaxy formation and evolution: models up to intermediate redshifts (United States)

    Firmani, Claudio; Avila-Reese, Vladimir


    Making use of a seminumerical method we develop a scenario of disk galaxy formation and evolution in the framework of inflationary cold dark matter (CDM) cosmologies. Within the virializing dark matter halos, disks in centrifugal equilibrium are built-up and their galactic evolution is followed through an approach which considers the gravitational interactions among the galaxy components, the turbulence and energy balance of the ISM, the star formation (SF) process due to disk gravitational instabilities, the stellar evolution and the secular formation of a bulge. We find that the main properties and correlations of disk galaxies are determined by the mass, the hierarchical mass aggregation history and the primordial angular momentum. The models follow the same trends across the Hubble sequence than the observed galaxies. The predicted TF relation is in good agreement with the observations except for the standart CDM. While the slope of this relation remains almost constant up to intermediate redshifts, its zero-point decreases in the H-band and slightly increases in the B-band. A maximum in the SF rate for most of the models is attained at z ~1.5-2.5.

  12. Observational Disk Dynamics of Late-Type Galaxies

    NARCIS (Netherlands)

    Westfall, Kyle B.

    (Abridged) The primary concern of this thesis is the measurement of the stellar velocity ellipsoid (SVE) in galaxy disks. While a few attempts exist in the literature, we know of no study providing as detailed a discussion of the empirical procedure nor of the associated errors in SVE measurements

  13. The Vertical Variation of HI Velocity Dispersion in Disk Galaxies

    NARCIS (Netherlands)

    Peters, Stephan Pieter Cornelis; Freeman, Ken; van der Kruit, Pieter C.


    One of the key assumptions in dynamical applications of the HI velocity dispersion in disk galaxies (e.g. to the flattening of the dark halo) has always been the isothermal nature of the HI distribution. There is no physical reason for this assumption: it is made because until now it has not been

  14. Steady, Near-exponential Galaxy Disks Produced by Scattering Processes (United States)

    Struck, Curtis; Elmegreen, Bruce


    Exponential surface brightness profiles are ubiquitous in galaxy disks over a wide range of Hubble types and masses. Radial migration and scattering via bars, waves, clumps and satellites have been discussed as causes, but most of these cannot account for the full range of the phenomenon. Numerical models of clump scattering show that this process can produce near-exponential or core-Sérsic profiles in a variety of circumstances, also suggesting a connection to bulge and elliptical galaxy profiles. Density profile forms do not depend on the specifics of the scattering processes, but stellar kinematics and profile evolution rates do. Analytic models, with a power-law times a Sérsic profile form, can satisfy Jeans equations in cases dominated by either halo potentials (outer disk) or self-gravity (inner disk).

  15. A High-Velocity Collision With Our Galaxy's Disk (United States)

    Kohler, Susanna


    What caused the newly discovered supershell in the outskirts of our galaxy? A new study finds evidence that a high-velocity cloud may have smashed into the Milky Ways disk millions of years ago.Mysterious Gas ShellsA single velocity-channel map of the supershell GS040.2+00.670, with red contours marking the high-velocity cloud at its center. [Adapted from Park et al. 2016]The neutral hydrogen gas that fills interstellar space is organized into structures like filaments, loops, and shells. Supershells are enormous shells of hydrogen gas that can have radii of a thousand light-years or more; weve spotted about 20 of these in our own galaxy, and more in nearby dwarfs and spiral galaxies.How do these structures form? One theory is that they result from several supernovae explosions occurring in the same area. But the energy needed to create a supershell is more than 3 x 1052 erg, which corresponds to over 30 supernovae quite a lot to have exploding in the same region.Theres an interesting alternative scenario: the supershells might instead be caused by the impacts of high-velocity clouds that fall into the galactic disk.Velocity data for the compact high-velocity cloud CHVC040. The cloud is moving fast enough to create the supershell observed. [Adapted from Park et al. 2016]The Milky Ways Speeding CloudsHigh-velocity clouds are clouds of mostly hydrogen that speed through the Milky Way with radial velocities that are very different from the material in the galactic disk. The origins of these clouds are unknown, but its proposed that they come from outside the galaxy they might be fragments of a nearby, disrupting galaxy, or they might have originated from flows of accreting gas in the space in between galaxies.Though high-velocity clouds have long been on the list of things that might cause supershells, weve yet to find conclusive evidence of this. But that might have just changed, with a recent discovery by a team of scientists led by Geumsook Park (Seoul National

  16. The catalog of edge-on disk galaxies from SDSS. I. The catalog and the structural parameters of stellar disks

    Energy Technology Data Exchange (ETDEWEB)

    Bizyaev, D. V. [Apache Point Observatory and New Mexico State University, Sunspot, NM, 88349 (United States); Kautsch, S. J. [Nova Southeastern University, Fort Lauderdale, FL 33314 (United States); Mosenkov, A. V. [Central Astronomical Observatory of RAS (Russian Federation); Reshetnikov, V. P.; Sotnikova, N. Ya.; Yablokova, N. V. [St. Petersburg State University (Russian Federation); Hillyer, R. W. [Christopher Newport University, Newport News, VA 23606 (United States)


    We present a catalog of true edge-on disk galaxies automatically selected from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS). A visual inspection of the g, r, and i images of about 15,000 galaxies allowed us to split the initial sample of edge-on galaxy candidates into 4768 (31.8% of the initial sample) genuine edge-on galaxies, 8350 (55.7%) non-edge-on galaxies, and 1865 (12.5%) edge-on galaxies not suitable for simple automatic analysis because these objects either show signs of interaction and warps, or nearby bright stars project on it. We added more candidate galaxies from RFGC, EFIGI, RC3, and Galaxy Zoo catalogs found in the SDSS footprints. Our final sample consists of 5747 genuine edge-on galaxies. We estimate the structural parameters of the stellar disks (the stellar disk thickness, radial scale length, and central surface brightness) in the galaxies by analyzing photometric profiles in each of the g, r, and i images. We also perform simplified three-dimensional modeling of the light distribution in the stellar disks of edge-on galaxies from our sample. Our large sample is intended to be used for studying scaling relations in the stellar disks and bulges and for estimating parameters of the thick disks in different types of galaxies via the image stacking. In this paper, we present the sample selection procedure and general description of the sample.

  17. Origin of Disk Lopsidedness in Spiral Galaxies

    NARCIS (Netherlands)

    Angiras, R. A.; Jog, C. J.; Dwarakanath, K. S.; Omar, A.; Verheijen, M. A. W.; Saikia, D.J.; Green, D.A.; Gupta, Y.; Venturi, T.


    In our work we have used the atomic hydrogen [H I] gas distribution in the H I 21-cm line emission to study the dark matter halo perturbations. For this analysis, the 2-D H I surface density and velocity maps (archival) of the galaxies in the Eridanus group (obtained using the GMRT) and in the Ursa

  18. Internal and environmental secular evolution of disk galaxies (United States)

    Kormendy, John


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

  19. The Westerbork HI survey of spiral and irregular galaxies - III. HI observations of early-type disk galaxies

    NARCIS (Netherlands)

    Noordermeer, E; van der Hulst, JM; Sancisi, R; Swaters, RA; van Albada, TS


    We present H. observations of 68 early-type disk galaxies from the WHISP survey. They have morphological types between S0 and Sab and absolute B-band magnitudes between - 14 and - 22. These galaxies form the massive, high surface-brightness extreme of the disk galaxy population, few of which have

  20. The Westerbork HI Survey os spiral and irregular galaxies III : HI observations of early-type disk galaxies

    NARCIS (Netherlands)

    Noordermeer, E.; Hulst, J.M. van der; Sancisi, R.; Swaters, R.A.; Abada, T.S. van


    Abstract: We present HI observations of 68 early-type disk galaxies from the WHISP survey. They have morphological types between S0 and Sab and absolute B-band magnitudes between -14 and -22. These galaxies form the massive, high surface-brightness extreme of the disk galaxy population, few of which

  1. Stellar Nuclei and Inner Polar Disks in Lenticular Galaxies (United States)

    Sil'chenko, Olga K.


    I analyze statistics of the stellar population properties for stellar nuclei and bulges of nearby lenticular galaxies in different environments by using panoramic spectral data of the integral-field spectrograph SAURON retrieved from the open archive of the Isaac Newton Group. I also estimate the fraction of nearby lenticular galaxies having inner polar gaseous disks by exploring the volume-limited sample of early-type galaxies of the ATLAS-3D survey. By inspecting the two-dimensional velocity fields of the stellar and gaseous components with the running tilted-ring technique, I have found seven new cases of inner polar disks. Together with those, the frequency of inner polar disks in nearby S0 galaxies reaches 10%, which is much higher than the frequency of large-scale polar rings. Interestingly, the properties of the nuclear stellar populations in the inner polar ring hosts are statistically the same as those in the whole S0 sample, implying similar histories of multiple gas-accretion events from various directions.


    Energy Technology Data Exchange (ETDEWEB)

    Sil’chenko, Olga K., E-mail: [Sternberg Astronomical Institute, M.V. Lomonosov Moscow State University, Moscow, 119992 (Russian Federation); Isaac Newton Institute, Chile, Moscow Branch (Chile)


    I analyze statistics of the stellar population properties for stellar nuclei and bulges of nearby lenticular galaxies in different environments by using panoramic spectral data of the integral-field spectrograph SAURON retrieved from the open archive of the Isaac Newton Group. I also estimate the fraction of nearby lenticular galaxies having inner polar gaseous disks by exploring the volume-limited sample of early-type galaxies of the ATLAS-3D survey. By inspecting the two-dimensional velocity fields of the stellar and gaseous components with the running tilted-ring technique, I have found seven new cases of inner polar disks. Together with those, the frequency of inner polar disks in nearby S0 galaxies reaches 10%, which is much higher than the frequency of large-scale polar rings. Interestingly, the properties of the nuclear stellar populations in the inner polar ring hosts are statistically the same as those in the whole S0 sample, implying similar histories of multiple gas-accretion events from various directions.


    Energy Technology Data Exchange (ETDEWEB)

    Williams, Benjamin F.; Dalcanton, Julianne J.; Stilp, Adrienne; Radburn-Smith, David [Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195 (United States); Dolphin, Andrew [Raytheon, 1151 E. Hermans Road, Tucson, AZ 85706 (United States); Skillman, Evan D., E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Department of Astronomy, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States)


    We present detailed analysis of color-magnitude diagrams of NGC 2403, obtained from a deep (m {approx}< 28) Hubble Space Telescope (HST) Wide Field Planetary Camera 2 observation of the outer disk of NGC 2403, supplemented by several shallow (m {approx}< 26) HST Advanced Camera for Surveys fields. We derive the spatially resolved star formation history of NGC 2403 out to 11 disk scale lengths. In the inner portions of the galaxy, we compare the recent star formation rates (SFRs) we derive from the resolved stars with those measured using GALEX FUV + Spitzer 24{mu} fluxes, finding excellent agreement between the methods. Our measurements also show that the radial gradient in recent SFR mirrors the disk exponential profile to 11 scale lengths with no break, extending to SFR densities a factor of {approx}100 lower than those that can be measured with GALEX and Spitzer ({approx}2 Multiplication-Sign 10{sup -6} M{sub Sun} yr{sup -1} kpc{sup -2}). Furthermore, we find that the cumulative stellar mass of the disk was formed at similar times at all radii. We compare these characteristics of NGC 2403 to those of its ''morphological twins'', NGC 300 and M 33, showing that the structure and age distributions of the NGC 2403 disk are more similar to those of the relatively isolated system NGC 300 than to those of the Local Group analog M 33. We also discuss the environments and HI morphologies of these three nearby galaxies, comparing them to integrated light studies of larger samples of more distant galaxy disks. Taken together, the physical properties and evolutionary history of NGC 2403 suggest that the galaxy has had no close encounters with other M 81 group members and may be falling into the group for the first time.

  4. Outer spiral structure in disk galaxies (United States)

    Patsis, P. A.


    In several grand design barred-spiral galaxies it is observed a second, fainter, outer set of spiral arms. Typical examples of objects of this morphology can be considered NGC 1566 and NGC 5248. I suggest that such an overall structure can be the result of two dynamical mechanisms acting in the disc. The bar and both spiral systems rotate with the same pattern speed. The inner spiral is reinforced by regular orbits trapped around the stable, elliptical, periodic orbits of the central family, while the outer system of spiral arms is supported by chaotic orbits. Chaotic orbits are also responsible for a rhomboidal area surrounding the inner barred-spiral region. In general there is a discontinuity between the two spiral structures at the corotation region.

  5. Misaligned Disks as Obscurers in Active Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence, A.; Elvis, M.; /Edinburgh U., Inst. Astron. /Harvard-Smithsonian Ctr. Astrophys.


    We review critically the evidence concerning the fraction of Active Galactic Nuclei (AGN) which appear as Type 2 AGN, carefully distinguishing strict Type 2 AGN from both more lightly reddened Type 1 AGN, and from low excitation narrow line AGN, which may represent a different mode of activity. Low excitation AGN occur predominantly at low luminosities; after removing these, true Type 2 AGN represent 58{-+}5% of all AGN, and lightly reddened Type 1 AGN a further {approx}15%. Radio, IR, and volume-limited samples all agree in showing no change of Type 2 fraction with luminosity. X-ray samples do show a change with luminosity; we discuss possible reasons for this discrepancy. We test a very simple picture which produces this Type 2 fraction with minimal assumptions. In this picture, infall from large scales occurs in random directions, but must eventually align with the inner accretion flow, producing a severely warped disk on parsec scales. If the re-alignment is dominated by tilt, with minimal twist, a wide range of covering factors is predicted in individual objects, but with an expected mean fraction of Type 2 AGN of exactly 50%. This 'tilted disc' picture predicts reasonable alignment of observed nuclear structures on average, but with distinct misalignments in individual cases. Initial case studies of the few well resolved objects show that such misalignments are indeed present.


    NARCIS (Netherlands)

    Donovan, Jennifer L.; Serra, Paolo; van Gorkom, J. H.; Trager, S. C.; Oosterloo, Tom; Hibbard, J. E.; Morganti, Raffaella; Schiminovich, David; van der Hulst, J. M.

    ESO 381-47 is an early-type galaxy with an extended Hi disk. Galaxy Evolution Explorer (GALEX) and very deep optical images reveal a distinct stellar ring far outside the optical body with a diameter of similar to 30 kpc, which has undergone recent star formation at 1.8 x 10(-4) M(circle dot) yr(-1)

  7. The z-structure of disk galaxies towards the galaxy planes

    NARCIS (Netherlands)

    Grijs, R. de; Peletier, R. F.; Kruit, P. C. van der


    We present a detailed study of a statistically complete sample of highly inclined disk galaxies in the near-infrared K' band. Since the K'-band light is relatively insensitive to contamination by galactic dust? we have been able to follow the vertical light distributions all the way down to the

  8. Extended far-infrared emission and star formation in Seyfert galaxies (United States)

    Marston, A. P.


    An investigation into the extended distribution of far-infrared (FIR) emission associated with nearby Seyfert galaxies is made using a set of MEM reconstructions of IRAS Chopped Photometric Channel (CPC) data (Marston 1993). The data is compared to a set of HII/starburst galaxy images similarly processed in order to compare distributions and FIR color properties. It is shown that the central 1 kpc or so of Seyfert galaxies show extended FIR emission. FIR colors suggest that the bulk of this emission is not directly associated with an active nucleus. They further suggest that the origins of the majority of the emission is from heated dust associated with star formation surrounding the nucleus rather than dust heated by the active nucleus. Nearby Seyfert galaxies are shown to have a higher concentration of far-infrared emission from their centers than the HII/starburst galaxies and a number appear to reside in disk galaxies with relatively low ongoing star formation in their disks. An example of this is NGC 7582 which has a smooth disk but an active nucleus/starbust center.

  9. Merger Histories of Galaxy Halos and Implications for Disk Survival

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Kyle R.; Bullock, James S.; Wechsler, Risa H.; Maller, Ariyeh H.; Zentner, Andrew R.


    The authors study the merger histories of galaxy dark matter halos using a high resolution {Lambda}CDM N-body simulation. The merger trees follow {approx} 17,000 halos with masses M{sub 0} = (10{sup 11} - 10{sup 13})h{sup -1}M{sub {circle_dot}} at z = 0 and track accretion events involving objects as small as m {approx_equal} 10{sup 10} h{sup -1}M{sub {circle_dot}}. They find that mass assembly is remarkably self-similar in m/M{sub 0}, and dominated by mergers that are {approx}10% of the final halo mass. While very large mergers, m {approx}> 0.4 M{sub 0}, are quite rare, sizeable accretion events, m {approx} 0.1 M{sub 0}, are common. Over the last {approx} 10 Gyr, an overwhelming majority ({approx} 95%) of Milky Way-sized halos with M{sub 0} = 10{sup 12} h{sup -1}M{sub {circle_dot}} have accreted at least one object with greater total mass than the Milky Way disk (m > 5 x 10{sup 10} h{sup -1}M{sub {circle_dot}}), and approximately 70% have accreted an object with more than twice that mass (m > 10{sup 11} h{sup -1}M{sub {circle_dot}}). The results raise serious concerns about the survival of thin-disk dominated galaxies within the current paradigm for galaxy formation in a {Lambda}CDM universe. in order to achieve a {approx} 70% disk-dominated fraction in Milky Way-sized {Lambda}CDM halos, mergers involving m {approx_equal} 2 x 10{sup 11} h{sup -1}M{sub {circle_dot}} objects must not destroy disks. Considering that most thick disks and bulges contain old stellar populations, the situation is even more restrictive: these mergers must not heat disks or drive gas into their centers to create young bulges.

  10. Neutral Gas Outside the Disks of Local Group Galaxies (United States)

    Lockman, Felix J.


    Of the three kinds of neutral gas found outside the stellar disks of Local Group galaxies, only the products of interaction, like the Magellanic Stream, have a clearly understandable origin. Both the high-velocity clouds and the faint H I between M31 and M33 remain a mystery. New observations of the region between M31 and M33 with the Green Bank Telescope show that the H I there resides in clouds with a size and mass similar to that of dwarf galaxies, but without stars. These clouds might be products of an interaction, or condensations in the hot circumgalactic medium of M31, but both these models have difficulties. The prevalence of clouds like this in the Local Group remains to be determined.

  11. Outskirts of Nearby Disk Galaxies: Star Formation and Stellar Populations (United States)

    Elmegreen, Bruce G.; Hunter, Deidre A.

    The properties and star formation processes in the far-outer disks of nearby spiral and dwarf irregular galaxies are reviewed. The origin and structure of the generally exponential profiles in stellar disks is considered to result from cosmological infall combined with a non-linear star formation law and a history of stellar migration and scattering from spirals, bars and random collisions with interstellar clouds. In both spirals and dwarfs, the far-outer disks tend to be older, redder and thicker than the inner disks, with the overall radial profiles suggesting inside-out star formation plus stellar scattering in spirals and outside-in star formation with a possible contribution from scattering in dwarfs. Dwarf irregulars and the far-outer parts of spirals both tend to be gas dominated, and the gas radial profile is often non-exponential although still decreasing with radius. The ratio of Hα to far-UV flux tends to decrease with lower surface brightness in these regions, suggesting either a change in the initial stellar mass function or the sampling of that function or a possible loss of Hα photons.

  12. Double-Barred Galaxies: I. A Catalog of Barred Galaxies with Stellar Secondary Bars and Inner Disks


    Erwin, Peter


    I present a catalog of 67 barred galaxies which contain distinct, elliptical stellar structures inside their bars. Fifty of these are double-barred galaxies: a small-scale, "inner" or "secondary" bar is embedded within a large-scale, "outer" or "primary" bar. I provide homogenized measurements of the sizes, ellipticities, and orientations of both inner and outer bars, along with with global parameters for the galaxies. The other 17 are classified as "inner-disk" galaxies, where a large-scale ...

  13. Extended distribution functions for our Galaxy (United States)

    Sanders, Jason L.; Binney, James


    We extend models of our Galaxy based on distribution functions that are analytic functions of the action integrals to extended distribution functions (EDFs), which have an analytic dependence on metallicity as well. We use a simple, but physically motivated, functional forms for the metallicity of the interstellar medium as a function of radius and time and for the star formation rate, and a model for the diffusion of stars through phase space to suggest the required functional form of an EDF. We introduce a simple prescription for radial migration that preserves the overall profile of the disc while allowing individual stars to migrate throughout the disc. Our models explicitly consider the thin and thick discs as two distinct components separated in age. We show how an EDF can be used to incorporate realistic selection functions in models, and to construct mock catalogues of observed samples. We show that the selection function of the Geneva-Copenhagen Survey (GCS) biases in favour of young stars, which have atypically small random velocities. With the selection function taken into account our models produce good fits of the GCS data in chemo-dynamical space and the Gilmore & Reid (1983) density data. From our EDF, we predict the structure of the Sloan Extension for Galactic Understanding and Exploration G-dwarf sample. The kinematics are successfully predicted. The predicted metallicity distribution has too few stars with [Fe/H] ≃ -0.5 dex and too many metal-rich stars. A significant problem may be the lack of any chemical-kinematic correlations in our thick disc. We argue that EDFs will prove essential tools for the analysis of both observational data and sophisticated models of Galaxy formation and evolution.

  14. Mass Distribution in Rotating Thin-Disk Galaxies According to Newtonian Dynamics

    Directory of Open Access Journals (Sweden)

    James Q. Feng


    Full Text Available An accurate computational method is presented for determining the mass distribution in a mature spiral galaxy from a given rotation curve by applying Newtonian dynamics for an axisymmetrically rotating thin disk of finite size with or without a central spherical bulge. The governing integral equation for mass distribution is transformed via a boundary-element method into a linear algebra matrix equation that can be solved numerically for rotation curves with a wide range of shapes. To illustrate the effectiveness of this computational method, mass distributions in several mature spiral galaxies are determined from their measured rotation curves. All the surface mass density profiles predicted by our model exhibit approximately a common exponential law of decay, quantitatively consistent with the observed surface brightness distributions. When a central spherical bulge is present, the mass distribution in the galaxy is altered in such a way that the periphery mass density is reduced, while more mass appears toward the galactic center. By extending the computational domain beyond the galactic edge, we can determine the rotation velocity outside the cut-off radius, which appears to continuously decrease and to gradually approach the Keplerian rotation velocity out over twice the cut-off radius. An examination of circular orbit stability suggests that galaxies with flat or rising rotation velocities are more stable than those with declining rotation velocities especially in the region near the galactic edge. Our results demonstrate the fact that Newtonian dynamics can be adequate for describing the observed rotation behavior of mature spiral galaxies.

  15. The Inner Regions of Disk Galaxies: A Constant Baryonic Fraction?

    Directory of Open Access Journals (Sweden)

    Federico Lelli


    Full Text Available For disk galaxies (spirals and irregulars, the inner circular-velocity gradient dRV0 (inner steepness of the rotation curve correlates with the central surface brightness ∑*,0 with a slope of ~0.5. This implies that the central dynamical mass density scales almost linearly with the central baryonic density. Here I show that this empirical relation is consistent with a simple model where the central baryonic fraction ƒbar,0 is fixed to 1 (no dark matter and the observed scatter is due to differences in the baryonic mass-to-light ratio Mbar / LR (ranging from 1 to 3 in the R-band and in the characteristic thickness of the central stellar component Δz (ranging from 100 to 500 pc. Models with lower baryonic fractions are possible, although they require some fine-tuning in the values of Mbar/LR and Δz. Regardless of the actual value of ƒbar,0, the fact that different types of galaxies do not show strong variations in ƒbar,0 is surprising, and may represent a challenge for models of galaxy formation in a Λ Cold Dark Matter (ΛCDM cosmology.


    Energy Technology Data Exchange (ETDEWEB)

    Leroy, Adam K.; Munoz-Mateos, Juan-Carlos [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Walter, Fabian; Sandstrom, Karin; Meidt, Sharon; Rix, Hans-Walter; Schinnerer, Eva [Max Planck Institute fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Schruba, Andreas [California Institute for Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Bigiel, Frank [Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Bolatto, Alberto [Department of Astronomy, University of Maryland, College Park, MD (United States); Brinks, Elias [Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); De Blok, W. J. G. [Astrophysics, Cosmology and Gravity Centre, Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Rosolowsky, Erik [University of British Columbia, Okanagan Campus, Kelowna, BC (Canada); Schuster, Karl-Friedrich [IRAM, 300 rue de la Piscine, F-38406 St. Martin d' Heres (France); Usero, Antonio [Observatorio Astronomico Nacional, C/ Alfonso XII, 3, E-28014 Madrid (Spain)


    We compare molecular gas traced by {sup 12}CO (2-1) maps from the HERACLES survey, with tracers of the recent star formation rate (SFR) across 30 nearby disk galaxies. We demonstrate a first-order linear correspondence between {Sigma}{sub mol} and {Sigma}{sub SFR} but also find important second-order systematic variations in the apparent molecular gas depletion time, {tau}{sub dep}{sup mol}={Sigma}{sub mol}/{Sigma}{sub SFR}. At the 1 kpc common resolution of HERACLES, CO emission correlates closely with many tracers of the recent SFR. Weighting each line of sight equally, using a fixed {alpha}{sub CO} equivalent to the Milky Way value, our data yield a molecular gas depletion time, {tau}{sub dep}{sup mol}={Sigma}{sub mol}/{Sigma}{sub SFR}{approx}2.2 Gyr with 0.3 dex 1{sigma} scatter, in very good agreement with recent literature data. We apply a forward-modeling approach to constrain the power-law index, N, that relates the SFR surface density and the molecular gas surface density, {Sigma}{sub SFR}{proportional_to}{Sigma}{sub mol}{sup N}. We find N = 1 {+-} 0.15 for our full data set with some scatter from galaxy to galaxy. This also agrees with recent work, but we caution that a power-law treatment oversimplifies the topic given that we observe correlations between {tau}{sub dep}{sup mol} and other local and global quantities. The strongest of these are a decreased {tau}{sub dep}{sup mol} in low-mass, low-metallicity galaxies and a correlation of the kpc-scale {tau}{sub dep}{sup mol} with dust-to-gas ratio, D/G. These correlations can be explained by a CO-to-H{sub 2} conversion factor ({alpha}{sub CO}) that depends on dust shielding, and thus D/G, in the theoretically expected way. This is not a unique interpretation, but external evidence of conversion factor variations makes this the most conservative explanation of the strongest observed {tau}{sub dep}{sup mol} trends. After applying a D/G-dependent {alpha}{sub CO}, some weak correlations between {tau}{sub dep

  17. Supermassive black holes do not correlate with galaxy disks or pseudobulges. (United States)

    Kormendy, John; Bender, R; Cornell, M E


    The masses of supermassive black holes are known to correlate with the properties of the bulge components of their host galaxies. In contrast, they seem not to correlate with galaxy disks. Disk-grown 'pseudobulges' are intermediate in properties between bulges and disks; it has been unclear whether they do or do not correlate with black holes in the same way that bulges do. At stake in this issue are conclusions about which parts of galaxies coevolve with black holes, possibly by being regulated by energy feedback from black holes. Here we report pseudobulge classifications for galaxies with dynamically detected black holes and combine them with recent measurements of velocity dispersions in the biggest bulgeless galaxies. These data confirm that black holes do not correlate with disks and show that they correlate little or not at all with pseudobulges. We suggest that there are two different modes of black-hole feeding. Black holes in bulges grow rapidly to high masses when mergers drive gas infall that feeds quasar-like events. In contrast, small black holes in bulgeless galaxies and in galaxies with pseudobulges grow as low-level Seyfert galaxies. Growth of the former is driven by global processes, so the biggest black holes coevolve with bulges, but growth of the latter is driven locally and stochastically, and they do not coevolve with disks and pseudobulges.


    Energy Technology Data Exchange (ETDEWEB)

    Bandara, Kaushala; Crampton, David; Peng, Chien; Simard, Luc [Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)


    We take advantage of the magnification in size and flux of a galaxy provided by gravitational lensing to analyze the properties of 62 strongly lensed galaxies from the Sloan Lens ACS (SLACS) Survey. The sample of lensed galaxies spans a redshift range of 0.20 ≤ z ≤ 1.20 with a median redshift of z = 0.61. We use the lens modeling code LENSFIT to derive the luminosities, sizes, and Sérsic indices of the lensed galaxies. The measured properties of the lensed galaxies show a primarily compact, {sup d}isk{sup -}like population with the peaks of the size and Sérsic index distributions corresponding to ∼1.50 kpc and n ∼ 1, respectively. Comparison of the SLACS galaxies to a non-lensing, broadband imaging survey shows that a lensing survey allows us to probe a galaxy population that reaches ∼2 mag fainter. Our analysis allows us to compare the (z) = 0.61 disk galaxy sample (n ≤ 2.5) to an unprecedented local galaxy sample of ∼670, 000 SDSS galaxies at z ∼ 0.1; this analysis indicates that the evolution of the luminosity-size relation since z ∼ 1 may not be fully explained by a pure-size or pure-luminosity evolution but may instead require a combination of both. Our observations are also in agreement with recent numerical simulations of disk galaxies that show evidence of a mass-dependent evolution since z ∼ 1, where high-mass disk galaxies (M{sub *} > 10{sup 9} M{sub ☉}) evolve more in size and low-mass disk galaxies (M{sub *} ≤ 10{sup 9} M{sub ☉}) evolve more in luminosity.

  19. The Link between Light and Mass in Late-type Spiral Galaxy Disks

    NARCIS (Netherlands)

    Swaters, Robert A.; Bershady, Matthew A.; Martinsson, Thomas P. K.; Westfall, Kyle B.; Andersen, David R.; Verheijen, Marc A. W.


    We present the correlation between the extrapolated central disk surface brightness (μ) and extrapolated central surface mass density (Σ) for galaxies in the DiskMass sample. This μ-Σ relation has a small scatter of 30% at the high surface brightness (HSB) end. At the low surface brightness (LSB)

  20. Ages of galaxy bulges and disks from optical and near-infrared colours

    NARCIS (Netherlands)

    Peletier, RF; Balcells, M; Bender, R; Davies, RL


    For a sample of bright nearby early-type galaxies we have obtained surface photometry in bands ranging from U to K. Since the galaxies have inclinations larger than 50 degrees it is easy to separate bulges and disks. By measuring the colours in special regions, we minimize the effects of extinction,

  1. A Comparison of Galaxy Bulge+Disk Decomposition Between Pan-STARRS and SDSS (United States)

    Lokken, Martine Elena; McPartland, Conor; Sanders, David B.


    Measurements of the size and shape of bulges in galaxies provide key constraints for models of galaxy evolution. A comprehensive catalog of bulge measurements for Sloan Digital Sky Survey (SDSS) DR7 galaxies is currently available to the public. However, the Pan-STARRS1 (PS1) 3π survey now covers the same region with ~1-2 mag deeper photometry, a ~10-30% smaller PSF, and additional coverage in y-band. To test how much improvement in galaxy parameter measurements (e.g. bulge + disk) can be achieved using the new PS1 data, we make use of ultra-deep imaging data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP). We fit bulge+disk models to images of 372 bright (mi < 18.5) galaxies detected in all three surveys. Comparison of galaxy parameters derived from SDSS and PS1 images with those measured from HSC-SSP images shows a tighter correlation between PS1 and SSP measurements for both bulge and disk parameters. Bulge parameters, such as bulge-to-total fraction and bulge radius, show the strongest improvement. However, measurements of all parameters degrade for galaxies with total r-band magnitude below the SDSS spectroscopic limit, mr = 17.7. We plan to use the PS1 3π survey data to produce an updated catalog of bulge+disk decomposition measurements for the entire SDSS DR7 spectroscopic galaxy sample.

  2. Revealing S0 Galaxies' Formation Histories Using the Stellar Kinematics of the Faint Outer Disks

    NARCIS (Netherlands)

    Cortesi, A.; Merrifield, M. R.; Noordermeer, E.; Coccato, L.; Bamford, S.; Napolitano, N. R.; Arnaboldi, M.; Gerhard, O.; Romanowsky, A. J.; Das, P.; Douglas, N. G.; Kuijken, K.; Freeman, K. C.; Capaccioli, M.; Debattista, Victor P.; Popescu, Cristina C.

    Lenticular galaxies display the prominent disks that are characteristic of late-type galaxies, but contain no gas, dust or star formation like early-type systems. So are they more closely related to spiral or ellipticals?. One important clue to their origin is recorded in the kinematics. If they are

  3. Nuclei of nearby disk galaxies .1. A Hubble Space Telescope imaging survey

    NARCIS (Netherlands)

    Phillips, AC; Illingworth, GD; MacKenty, JW; Franx, M

    We present deconvolved images of the central regions of 20 nearby disk galaxies, obtained with the original Planetary Camera of the Hubble Space Telescope. The galaxies span a range in Hubble type from SO to Sm. We have measured surface brightness profiles, and inverted these to estimate


    Energy Technology Data Exchange (ETDEWEB)

    Freeland, Emily; Tran, Kim-Vy H.; Irwin, Trevor [George P. and Cynthia W. Mitchell Institute, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Giordano, Lea [Institute for Theoretical Physics, University of Zuerich, CH-8057 Zuerich (Switzerland); Saintonge, Amelie [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Gonzalez, Anthony H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Zaritsky, Dennis; Just, Dennis, E-mail: [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)


    We detect ionized gas characteristics indicative of winds in three disk-dominated galaxies that are members of a super-group at z = 0.37 that will merge to form a Coma-mass cluster. All three galaxies are IR luminous (L{sub IR} > 4 Multiplication-Sign 10{sup 10} L{sub Sun }, SFR > 8 M{sub Sun} yr{sup -1}) and lie outside the X-ray cores of the galaxy groups. We find that the most IR-luminous galaxy has strong blueshifted and redshifted emission lines with velocities of {approx} {+-} 200 km s{sup -1} and a third, blueshifted ({approx}900 km s{sup -1}) component. This galaxy's line widths (H{beta}, [O III]{lambda}5007, [N II], H{alpha}) correspond to velocities of 100-1000 km s{sup -1}. We detect extraplanar gas in two of the three galaxies with SFR >8 M{sub Sun} yr{sup -1} whose orientations are approximately edge-on and which have integral field unit (IFU) spaxels off the stellar disk. IFU maps reveal that the extraplanar gas extends to r{sub h} {approx} 10 kpc; [N II] and H{alpha} line widths correspond to velocities of {approx}200-400 km s{sup -1} in the disk and decrease to {approx}50-150 km s{sup -1} above the disk. Multi-wavelength observations indicate that the emission is dominated by star formation. Including the most IR-luminous galaxy we find that 18% of supergroup members with SFR >8 M{sub Sun} yr{sup -1} show ionized gas characteristics indicative of outflows. This is a lower limit as showing that gas is outflowing in the remaining, moderately inclined, galaxies requires a non-trivial decoupling of contributions to the emission lines from rotational and turbulent motion. Ionized gas mass loss in these winds is {approx}0.1 M{sub Sun} yr{sup -1} for each galaxy, although the winds are likely to entrain significantly larger amounts of mass in neutral and molecular gases.

  5. Outside-in Shrinking of the Star-forming Disk of Dwarf Irregular Galaxies (United States)

    Zhang, Hong-Xin; Hunter, Deidre A.; Elmegreen, Bruce G.; Gao, Yu; Schruba, Andreas


    We have studied multi-band surface brightness profiles of a representative sample of 34 nearby dwarf irregular galaxies. Our data include Galaxy Evolution Explorer (GALEX) FUV/NUV, UBV, and Hα and Spitzer 3.6 μm images. These galaxies constitute the majority of the LITTLE THINGS survey (Local Irregulars That Trace Luminosity Extremes—The H I Nearby Galaxy Survey). By modeling the azimuthal averages of the spectral energy distributions with a complete library of star formation histories, we derived the stellar mass surface density distributions and the star formation rate averaged over three different timescales: the recent 0.1 Gyr, 1 Gyr, and a Hubble time. We find that, for ~80% (27 galaxies) of our sample galaxies, radial profiles (at least in the outer part) at shorter wavelengths, corresponding to younger stellar populations, have shorter disk scale lengths than those at longer wavelengths, corresponding to older stellar populations. This indicates that the star-forming disk has been shrinking. In addition, the radial distributions of the stellar mass surface density are well described as piece-wise exponential profiles, and ~80% of the galaxies have steeper mass profiles in the outer disk than in the inner region. The steep radial decline of the star formation rate in the outer parts compared to that in the inner disks gives a natural explanation for the down-bending stellar mass surface density profiles. Within the inner disks, our sample galaxies on average have constant ratios of recent star formation rate to stellar mass with radius. Nevertheless, ~35% (12 galaxies, among which 7 have baryonic mass lsim108 M ⊙) of the sample exhibit negative slopes across the observed disk, which is in contrast with the so-called inside-out disk growth scenario suggested for luminous spiral galaxies. The tendency of star formation to become concentrated toward the inner disks in low-mass dwarf irregular galaxies is interpreted as a result of their susceptibility to

  6. The Star Formation Histories of Disk Galaxies: The Live, the Dead, and the Undead

    Energy Technology Data Exchange (ETDEWEB)

    Oemler, Augustus Jr; Dressler, Alan [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101-1292 (United States); Abramson, Louis E. [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Los Angeles CA 90095-1547 (United States); Gladders, Michael D. [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Poggianti, Bianca M. [INAF-Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, I-35122 Padova (Italy); Vulcani, Benedetta [School of Physics, The University of Melbourne, VIC 3010 (Australia)


    We reexamine the properties of local galaxy populations using published surveys of star formation, structure, and gas content. After recalibrating star formation measures, we are able to reliably measure specific star formation rates well below that of the so-called “main sequence” of star formation versus mass. We find an unexpectedly large population of quiescent galaxies with star formation rates intermediate between the main sequence and passive populations and with disproportionately high star formation rates. We demonstrate that a tight main sequence is a natural outcome of most histories of star formation and has little astrophysical significance but that the quiescent population requires additional astrophysics to explain its properties. Using a simple model for disk evolution based on the observed dependence of star formation on gas content in local galaxies, and assuming simple histories of cold gas inflow, we show that the evolution of galaxies away from the main sequence can be attributed to the depletion of gas due to star formation after a cutoff of gas inflow. The quiescent population is composed of galaxies in which the density of disk gas has fallen below a threshold for star formation probably set by disk stability. The evolution of galaxies beyond the quiescent state to gas exhaustion and the end of star formation requires another process, probably wind-driven mass loss. The environmental dependence of the three galaxy populations is consistent with recent numerical modeling, which indicates that cold gas inflows into galaxies are truncated at earlier epochs in denser environments.

  7. High star formation rates as the origin of turbulence in early and modern disk galaxies. (United States)

    Green, Andrew W; Glazebrook, Karl; McGregor, Peter J; Abraham, Roberto G; Poole, Gregory B; Damjanov, Ivana; McCarthy, Patrick J; Colless, Matthew; Sharp, Robert G


    Observations of star formation and kinematics in early galaxies at high spatial and spectral resolution have shown that two-thirds are massive rotating disk galaxies, with the remainder being less massive non-rotating objects. The line-of-sight-averaged velocity dispersions are typically five times higher than in today's disk galaxies. This suggests that gravitationally unstable, gas-rich disks in the early Universe are fuelled by cold, dense accreting gas flowing along cosmic filaments and penetrating hot galactic gas halos. These accreting flows, however, have not been observed, and cosmic accretion cannot power the observed level of turbulence. Here we report observations of a sample of rare, high-velocity-dispersion disk galaxies in the nearby Universe where cold accretion is unlikely to drive their high star formation rates. We find that their velocity dispersions are correlated with their star formation rates, but not their masses or gas fractions, which suggests that star formation is the energetic driver of galaxy disk turbulence at all cosmic epochs.


    Energy Technology Data Exchange (ETDEWEB)

    Comeron, Sebastien; Salo, Heikki; Laurikainen, Eija; Laine, Jarkko [Astronomy Division, Department of Physics, University of Oulu, P.O. Box 3000, FI-90014 (Finland); Elmegreen, Bruce G. [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States); Athanassoula, E.; Bosma, Albert [Laboratoire d' Astrophysique de Marseille-LAM, Universite d' Aix-Marseille and CNRS, UMR7326, 38 rue F. Joliot-Curie, F-13388 Marseille Cedex 13 (France); Knapen, Johan H. [Instituto de Astrofisica de Canarias, E-38200 La Laguna (Spain); Gadotti, Dimitri A. [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Sheth, Kartik; Munoz-Mateos, Juan Carlos; Kim, Taehyun [National Radio Astronomy Observatory, Charlottesville, VA (United States); Hinz, Joannah L. [Department of Astronomy, University of Arizona, Tucson, AZ (United States); Regan, Michael W. [Space Telescope Science Institute, Baltimore, MD (United States); Gil de Paz, Armando [Departamento de Astrofisica, Universidad Complutense de Madrid, Madrid (Spain); Menendez-Delmestre, Karin [Observatorio do Valongo, Universidade Federal de Rio de Janeiro, Ladeira Pedro Antonio, 43, Saude CEP 20080-090, Rio de Janeiro-RJ-Brazil (Brazil); Seibert, Mark; Ho, Luis C. [The Observatories of the Carnegie Institution for Science, Pasadena, CA (United States); Mizusawa, Trisha [Department of Physics and Space Sciences, Florida Institute of Technology, 150 W. University Boulevard, Melbourne, FL 32901 (United States); Holwerda, Benne [European Space Agency, ESTEC, Keplerlaan 1, 2200-AG, Noordwijk (Netherlands)


    Breaks in the radial luminosity profiles of galaxies have until now been mostly studied averaged over disks. Here, we study separately breaks in thin and thick disks in 70 edge-on galaxies using imaging from the Spitzer Survey of Stellar Structure in Galaxies. We built luminosity profiles of the thin and thick disks parallel to midplanes and we found that thin disks often truncate (77%). Thick disks truncate less often (31%), but when they do, their break radius is comparable with that in the thin disk. This suggests either two different truncation mechanisms-one of dynamical origin affecting both disks simultaneously and another one only affecting the thin disk-or a single mechanism that creates a truncation in one disk or in both depending on some galaxy property. Thin disks apparently antitruncate in around 40% of galaxies. However, in many cases, these antitruncations are an artifact caused by the superposition of a thin disk and a thick disk, with the latter having a longer scale length. We estimate the real thin disk antitruncation fraction to be less than 15%. We found that the ratio of the thick and thin stellar disk mass is roughly constant (0.2 < M{sub T} /M{sub t} < 0.7) for circular velocities v{sub c} > 120 km s{sup -1}, but becomes much larger at smaller velocities. We hypothesize that this is due to a combination of a high efficiency of supernova feedback and a slower dynamical evolution in lower-mass galaxies causing stellar thin disks to be younger and less massive than in higher-mass galaxies.

  9. Radial Profiles of Star Formation in the Far Outer Regions of Galaxy Disks


    Elmegreen, Bruce G.; Hunter, Deidre A.


    Star formation in galaxies is triggered by a combination of processes, including gravitational instabilities, spiral wave shocks, stellar compression, and turbulence compression. Some of these persist in the far outer regions where the column density is far below the threshold for instabilities, making the outer disk cutoff somewhat gradual. We show that in a galaxy with a single exponential gas profile the star formation rate can have a double exponential with a shallow one in the inner part...

  10. Wind from the black-hole accretion disk driving a molecular outflow in an active galaxy. (United States)

    Tombesi, F; Meléndez, M; Veilleux, S; Reeves, J N; González-Alfonso, E; Reynolds, C S


    Powerful winds driven by active galactic nuclei are often thought to affect the evolution of both supermassive black holes and their host galaxies, quenching star formation and explaining the close relationship between black holes and galaxies. Recent observations of large-scale molecular outflows in ultraluminous infrared galaxies support this quasar-feedback idea, because they directly trace the gas from which stars form. Theoretical models suggest that these outflows originate as energy-conserving flows driven by fast accretion-disk winds. Proposed connections between large-scale molecular outflows and accretion-disk activity in ultraluminous galaxies were incomplete because no accretion-disk wind had been detected. Conversely, studies of powerful accretion-disk winds have until now focused only on X-ray observations of local Seyfert galaxies and a few higher-redshift quasars. Here we report observations of a powerful accretion-disk wind with a mildly relativistic velocity (a quarter that of light) in the X-ray spectrum of IRAS F11119+3257, a nearby (redshift 0.189) optically classified type 1 ultraluminous infrared galaxy hosting a powerful molecular outflow. The active galactic nucleus is responsible for about 80 per cent of the emission, with a quasar-like luminosity of 1.5 × 10(46) ergs per second. The energetics of these two types of wide-angle outflows is consistent with the energy-conserving mechanism that is the basis of the quasar feedback in active galactic nuclei that lack powerful radio jets (such jets are an alternative way to drive molecular outflows).

  11. Tidal disruption events from eccentric nuclear disks in post-merger galaxies (United States)

    Madigan, Ann-Marie

    Surprisingly, in more than twenty percent of nearby elliptical galaxies, the distribution of stars orbiting the central supermassive black hole is strongly asymmetric. In these galaxies, the stars are on apsidally-aligned orbits in an eccentric nuclear disk. Long thought to be exotic, this configuration is quite common in our local universe. Despite the prevalence of eccentric disks however, their dynamics have been largely overlooked. Naively, one might expect that packing orbits so closely together would make them violently unstable to gravitational scattering, or that differential precession would wipe out their large-scale apsidal-alignment. We have recently identified a new dynamical mechanism which stabilizes eccentric nuclear disks (Madigan et al., 2016), thus explaining their observed ubiquity. The stabilizing mechanism produces oscillations of orbital eccentricities of stars in the disk, pushing many stars extremely close to the black hole. If these disks form in gas-rich mergers, as is found in cosmological simulations, there will be an enhanced rate of stellar tidal disruption events (TDEs) following the merger. In a preliminary calculation, we show the TDE rate is initially so high that the nucleus would appear as an AGN, or as a changing-look-quasar. We therefore suggest that accretion of dense stellar material may contribute significantly to the growth of supermassive black holes; if so, this could explain the presence of supermassive black holes in the extremely early universe, z>7, as well as the peaking of quasar activity around z 2, when the galaxy merger rate peaks. Our model can also explain the recently observed preference of TDEs in post-merger, post-starburst (K+A) galaxies. Here we propose to quantify these calculations. We will also undertake a statistical analysis of the literature to determine the true occurrence rate of eccentric nuclear disks. Long after the merger and the K+A phase, eccentric disks no longer directly produce TDEs

  12. On the axis ratio of the stellar velocity ellipsoid in disks of spiral galaxies

    NARCIS (Netherlands)

    van der Kruit, PC; de Grijs, R


    The spatial distribution of stars in a disk of a galaxy can be described by a radial scale length and a vertical scale height. The ratio of these two scale parameters contains information on the axis ratio of the velocity ellipsoid, i.e. the ratio of the vertical to radial stellar velocity

  13. Near-Infrared Detection of Super-Thin Disks of Massive Spiral Galaxies (United States)

    Schechtman-Rook, Andrew; Bershady, M. A.


    In the Milky Way star formation preferentially occurs close to the galactic midplane, and can be represented by a super-thin disk with an exponential-like radial and vertical profile. Unfortunately, due to dust attenuation, it is not clear if other massive spiral galaxies also possess such disks. Indirect evidence for the presence of such a component comes from the spectral energy distribution of spirals, which contains more far-infrared flux (from dust re-emission) than can be accounted for by an extrapolation of the observed light profile to the midplane. These spectral energy distributions contain no spatial information, however, so the detailed structural parameters of a star-forming disk are not recoverable. We have undertaken a program of high-resolution near-infrared imaging of edge-on spiral galaxies, which, coupled with state-of-the-art radiation transfer models, allow us to strip away the effects of the dust and reveal the intrinsic light distribution all the way down to the midplane. We find that, in addition to thin and thick disks already known from deep optical observations of these galaxies, super-thin disks similar to the Milky Way's are necessary to accurately fit the attenuation-corrected near-infrared light distributions. We acknowledge support for this work from the National Science Foundation (AST-1009491).

  14. Extended Schmidt law holds for faint dwarf irregular galaxies (United States)

    Roychowdhury, Sambit; Chengalur, Jayaram N.; Shi, Yong


    Context. The extended Schmidt law (ESL) is a variant of the Schmidt which relates the surface densities of gas and star formation, with the surface density of stellar mass added as an extra parameter. Although ESL has been shown to be valid for a wide range of galaxy properties, its validity in low-metallicity galaxies has not been comprehensively tested. This is important because metallicity affects the crucial atomic-to-molecular transition step in the process of conversion of gas to stars. Aims: We empirically investigate for the first time whether low metallicity faint dwarf irregular galaxies (dIrrs) from the local universe follow the ESL. Here we consider the "global" law where surface densities are averaged over the galactic discs. dIrrs are unique not only because they are at the lowest end of mass and star formation scales for galaxies, but also because they are metal-poor compared to the general population of galaxies. Methods: Our sample is drawn from the Faint Irregular Galaxy GMRT Survey (FIGGS) which is the largest survey of atomic hydrogen in such galaxies. The gas surface densities are determined using their atomic hydrogen content. The star formation rates are calculated using GALEX far ultraviolet fluxes after correcting for dust extinction, whereas the stellar surface densities are calculated using Spitzer 3.6 μm fluxes. The surface densities are calculated over the stellar discs defined by the 3.6 μm images. Results: We find dIrrs indeed follow the ESL. The mean deviation of the FIGGS galaxies from the relation is 0.01 dex, with a scatter around the relation of less than half that seen in the original relation. In comparison, we also show that the FIGGS galaxies are much more deviant when compared to the "canonical" Kennicutt-Schmidt relation. Conclusions: Our results help strengthen the universality of the ESL, especially for galaxies with low metallicities. We suggest that models of star formation in which feedback from previous generations

  15. Spatially-resolved SFR in nearby disk galaxies using IFS data (United States)

    Catalán-Torrecilla, C.; Gil de Paz, A.; Castillo-Morales, A.; Méndez-Abreu, J.; Pascual, S.; Ruiz-Lara, T.; de Lorenzo-Cáceres, A.; Sánchez-Menguiano, L.


    Exploring the spatial distribution of the star formation rate (SFR) in nearby galaxies is essential to understand their evolution through cosmic time. With this aim in mind, we use a representative sample that contains a variety of morphological types, the CALIFA Integral Field Spectroscopy (IFS) sample. Previous to this work, we have verified that our extinction-corrected Hα measurements successfully reproduce the values derived from other SFR tracers such as Hα obs + IR or UV obs + IR (Catalán-Torrecilla et al. 2015). Now, we go one step further applying 2-dimensional photometric decompositions (Méndez-Abreu et al. (2008), Méndez-Abreu et al. (2014)) over these datacubes. This method allows us to obtain the amount of SFR in the central part (bulge or nuclear source), the bar and the disk, separately. First, we determine the light coming from each component as the ratio between the luminosity in every component (bulge, bar or disk) and the total luminosity of the galaxy. Then, for each galaxy we multiply the IFS datacubes by these previous factors to recover the luminosity in each component. Finally, we derive the spectrum associated to each galaxy component integrating the spatial information in the weighted datacube using an elliptical aperture covering the whole galaxy. 2D photometric decomposition applied over 3D datacubes will give us a more detailed understanding of the role that disks play in more massive galaxies. Knowing if the disks in more massive SF galaxies have on average a lower or higher level of star formation activity and how these results are affected by the presence of nuclear bars are still open questions that we can now solve. We describe the behavior of these components in the SFR vs. stellar mass diagram. In particular, we highlight the role of the disks and their contribution to both the integrated SFR for the whole galaxy and the SFR in the disk at different stellar masses in the SFR vs. stellar mass diagram together with their


    Energy Technology Data Exchange (ETDEWEB)

    Mayer, Lucio; Tamburello, Valentina [Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, CH-8057 Zürich (Switzerland); Lupi, Alessandro; Madau, Piero [Institut d’Astrophysique de Paris, Sorbonne Universités, UPMC Univ Paris 6 et CNRS, UMR 7095, 98 bis bd Arago, F-75014 Paris (France); Keller, Ben; Wadsley, James [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada)


    We study the dependence of fragmentation in massive gas-rich galaxy disks at z >1 on stellar feedback schemes and hydrodynamical solvers, employing the GASOLINE2 SPH code and the lagrangian mesh-less code GIZMO in finite mass mode. Non-cosmological galaxy disk runs with the standard delayed-cooling blastwave feedback are compared with runs adopting a new superbubble feedback, which produces winds by modeling the detailed physics of supernova-driven bubbles and leads to efficient self-regulation of star formation. We find that, with blastwave feedback, massive star-forming clumps form in comparable number and with very similar masses in GASOLINE2 and GIZMO. Typical clump masses are in the range 10{sup 7}–10{sup 8} M {sub ⊙}, lower than in most previous works, while giant clumps with masses above 10{sup 9} M {sub ⊙} are exceedingly rare. By contrast, superbubble feedback does not produce massive star-forming bound clumps as galaxies never undergo a phase of violent disk instability. In this scheme, only sporadic, unbound star-forming overdensities lasting a few tens of Myr can arise, triggered by non-linear perturbations from massive satellite companions. We conclude that there is severe tension between explaining massive star-forming clumps observed at z >1 primarily as the result of disk fragmentation driven by gravitational instability and the prevailing view of feedback-regulated galaxy formation. The link between disk stability and star formation efficiency should thus be regarded as a key testing ground for galaxy formation theory.

  17. The Role of Bars in AGN Fueling in Disk Galaxies Over the Last Seven Billion Years (United States)

    Cisternas, Mauricio; Sheth, Kartik; Salvato, Mara; Knapen, Johan H.; Civano, Francesca; Santini, Paola


    We present empirical constraints on the influence of stellar bars on the fueling of active galactic nuclei (AGNs) out to z = 0.84 using a sample of X-ray-selected AGNs hosted in luminous non-interacting face-on and moderately inclined disk galaxies from the Chandra COSMOS survey. Using high-resolution Hubble Space Telescope imaging to identify bars, we find that the fraction of barred active galaxies displays a similar behavior as that of inactive spirals, declining with redshift from 71% at z∼ 0.3, to 35% at z∼ 0.8. With active galaxies being typically massive, we compare them against a mass-matched sample of inactive spirals and show that, while at face value the AGN bar fraction is slightly higher at all redshifts, we cannot rule out that the bar fractions of active and inactive galaxies are the same. The presence of a bar has no influence on the AGN strength, with barred and unbarred active galaxies showing equivalent X-ray luminosity distributions. From our results, we conclude that the occurrence and the efficiency of the fueling process is independent of the large scale structure of a galaxy. The role of bars, if any, may be restricted to providing the suitable conditions for black hole fueling to occur, i.e., bring a fresh supply of gas to the central 100 pc. At the high-redshift end, we find that roughly 60% of active disk galaxies are unbarred. We speculate this to be related with the known dynamical state of disks at higher redshifts—more gas-rich and prone to instabilities than local spirals—which could also lead to gas inflows without the need of bars.

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


    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.

  19. Impact of magnetic fields on ram pressure stripping in disk galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Ruszkowski, M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Brüggen, M. [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany); Lee, D. [The Flash Center for Computational Science, The University of Chicago, 5747 South Ellis, Chicago, IL 60637 (United States); Shin, M.-S., E-mail: [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom)


    Ram pressure stripping can remove significant amounts of gas from galaxies in clusters and massive groups and thus has a large impact on the evolution of cluster galaxies. Recent observations have shown that key properties of ram-pressure-stripped tails of galaxies, such as their width and structure, are in conflict with predictions by simulations. To increase the realism of existing simulations, we simulated for the first time a disk galaxy exposed to a uniformly magnetized wind including radiative cooling and self-gravity of the gas. We find that magnetic fields have a strong effect on the morphology of the gas in the tail of the galaxy. While in the purely hydrodynamical case the tail is very clumpy, the magnetohydrodynamical case shows very filamentary structures in the tail. The filaments can be strongly supported by magnetic pressure and, wherever this is the case, the magnetic fields vectors tend to be aligned with the filaments. The ram pressure stripping process may lead to the formation of magnetized density tails that appear as bifurcated in the plane of the sky and resemble the double tails observed in ESO 137-001 and ESO 137-002. Such tails can be formed under a variety of situations, both for the disks oriented face-on with respect to the intracluster medium (ICM) wind and for the tilted ones. While this bifurcation is the consequence of the generic tendency for the magnetic fields to produce very filamentary tail morphology, the tail properties are further shaped by the combination of the magnetic field orientation and the sliding of the field past the disk surface exposed to the wind. Despite the fact that the effect of the magnetic field on the morphology of the tail is strong, magnetic draping does not strongly change the rate of gas stripping. For a face-on galaxy, the field tends to reduce the amount of gas stripping compared to the pure hydrodynamical case, and is associated with the formation of a stable magnetic draping layer on the side of

  20. Kinematical Modeling of WARPS in the H i Disks of Galaxies (United States)

    Christodoulou, Dimitris M.; Tohline, Joel E.; Steiman-Cameron, Thomas Y.


    In order to gain an appreciation for the general structure of warped gas layers in galaxies, we have constructed kinematical, tilted-ring models of 21 galaxies for which detailed H I observations already exist in the literature. In this paper we present results for the 15 normal spiral galaxies of this sample that are not viewed edge-on. A comparison between our models and tilted-ring models of the same galaxies previously constructed by other authors shows that there is generally good agreement. We make an attempt to unify the notation of diff&rent authors who have published radio observations and/or kinematical models of individual galaxies in this sample. We also suggest how, in future work of this nature, model parameters should be presented and referenced in order to maintain a reasonable degree of consistency in the literature. When viewed in the perspective of dynamical models, a twisted warped gas layer can be understood as arising from orbiting gas which is in the process of settling to a preferred orientation in the nonspherical, gravitational potential well of the galaxy. Hence, detailed kinematical modeling of a specific galaxy disk can provide not only information regarding the orientation and structure of its warp but also information about the shape (whether oblate or prolate) of the dark halo in which the disk is embedded. By examining a large number of galaxies in a consistent manner, we have deduced some general characteristics of warped disks that have heretofore gone unnoticed. We have also identified uniqueness problems that can arise in this type of modeling procedure which can considerably cloud one's ability to completely decipher an individual disk's structure. For 14 out of 15 spiral galaxies modeled here, we have been able to determine the local kinematical structure of the warp. Gas layers do not appear to warp more than ˜40° out of the plane defined by the central disk of the galaxy, but they can twist through angles as large as ˜170

  1. VizieR Online Data Catalog: Central surface densities in SPARC disk galaxies (Lelli+, 2016) (United States)

    Lelli, F.; McGaugh, S. S.; Schombert, J. M.; Pawlowski, M. S.


    We use galaxies from the Spitzer Photometry and Accurate Rotation Curves (SPARC) database (Paper I; Lelli et al. 2016, Cat. J/AJ/152/157). SPARC spans the widest possible range for disk galaxies: morphologies from S0 to dIrr, luminosities from ~107 to ~1012L{Sun}, effective surface brightnesses from ~5 to ~5000L{Sun}/pc2, effective radii from ~0.3 to ~15kpc, rotation velocities from ~20 to ~300km/s, and gas fractions from ~0.01 to 0.95. In Paper I, we describe the analysis of [3.6] images and the rotation curve data. We also define a quality flag: Q=1 indicates galaxies with high-quality HI data or hybrid HI/Hα rotation curves (99 objects), Q=2 indicates galaxies with minor asymmetries or HI data of lower quality (64 objects), and Q=3 indicates galaxies with major asymmetries, strong non-circular motions, or off-sets between stellar and HI distributions (12 objects). We exclude objects with Q=3 since the rotation curves do not necessarily trace the equilibrium gravitational potential. We also exclude face-on (i85°) galaxies due to uncertain corrections on the rotation velocities and central surface brightnesses, respectively. Our final sample consists of 135 galaxies. (1 data file).

  2. A comprehensive study of the spatially-resolved SFR in nearby disk galaxies using CALIFA IF data (United States)

    Catalán-Torrecilla, C.; Gil de Paz, A.; Castillo-Morales, A.; Méndez-Abreu, J.; Califa Team


    A detailed analysis of the Star Formation Rate (SFR) distribution in nearby galaxies is essential to understand the mechanisms that drive the formation and evolution of galaxies. Although measurements of the integrated SFR in galaxies as a whole are also required to fulfill this goal, we focus here on the relative contribution of the SFR in the different components that shape galaxies (bulges, bars and disks). With this aim in mind, we combine for the first time in a large sample of nearby galaxies from the CALIFA survey, 2D multicomponent photometric decomposition with Integral Field Spectroscopy (IFS) data to enable measurements of the SFR in the different galaxy components. We find that not only more massive galaxies are being quenched more efficiently but also more massive disks tend to exhibit lower SFRs for a fixed value of their disk stellar masses in the SFR-M_* plane. We show that type-2 AGN host galaxies are mostly found in galaxies with the higher values of their stellar masses and that they contribute to decrease the specific SFR for bulges and disks, being this effect more important for the case of the bulges.


    Energy Technology Data Exchange (ETDEWEB)

    Davidge, T. J.; McConnachie, A. W. [Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Fardal, M. A. [Department of Astronomy, University of Massachusetts, LGRT 619-E, Amherst, MA 01003-9305 (United States); Fliri, J.; Valls-Gabaud, D. [LERMA, UMR CNRS 8112, Observatoire de Paris, 61 Avenue de l' Observatoire, 75014 Paris (France); Chapman, S. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Lewis, G. F. [Sydney Institute for Astronomy, School of Physics, A28, The University of Sydney, NSW 2006 (Australia); Rich, R. M. [Division of Astronomy and Astrophysics, University of California, Los Angeles, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States)


    We examine the star-forming history of the M31 disk during the past few hundred Myr. The luminosity functions (LFs) of main-sequence stars at distances R{sub GC} > 21 kpc (i.e., >4 disk scale lengths) are matched by models that assume a constant star formation rate (SFR). However, at smaller R{sub GC} the LFs suggest that during the past {approx}10 Myr the SFR was 2-3 times higher than during the preceding {approx}100 Myr. The rings of cool gas that harbor a significant fraction of the current star-forming activity are traced by stars with ages {approx}100 Myr, indicating that (1) these structures have ages of at least 100 Myr and (2) stars in these structures do not follow the same relation between age and random velocity as their counterparts throughout the disks of other spiral galaxies, probably due to the inherently narrow orbital angular momentum distribution of the giant molecular clouds in these structures. The distribution of evolved red stars is not azimuthally symmetric, in the sense that the projected density along the northeast segment of the major axis is roughly twice that on the opposite side of the galaxy. The northeast arm of the major axis thus appears to be a fossil star-forming area that dates to intermediate epochs. Such a structure may be the consequence of interactions with a companion galaxy.

  4. An extended cold gas absorber in a central cluster galaxy (United States)

    Smith, Russell J.; Edge, Alastair C.


    We present the serendipitous discovery of an extended cold gas structure projected close to the brightest cluster galaxy (BCG) of the z = 0.045 cluster Abell 3716, from archival integral field spectroscopy. The gas is revealed through narrow Na D line absorption, seen against the stellar light of the BCG, which can be traced for ∼25 kpc, with a width of 2-4 kpc. The gas is offset to higher velocity than the BCG (by ∼100 km s-1), showing that it is infalling rather than outflowing; the intrinsic linewidth is ∼80 km s-1 (FWHM). Very weak H α line emission is detected from the structure, and a weak dust absorption feature is suggested from optical imaging, but no stellar counterpart has been identified. We discuss some possible interpretations for the absorber: as a projected low-surface-brightness galaxy, as a stream of gas that was stripped from an infalling cluster galaxy or as a 'retired' cool-core nebula filament.

  5. A Disk Galaxy of Old Stars at z~2.5 (United States)

    Stockton, Alan; Canalizo, Gabriela; Maihara, Toshinori


    We describe observations of a galaxy in the field of the z=2.483 radio galaxy 4C 23.56, photometrically selected to have a spectral energy distribution consistent with an old stellar population at the redshift of the radio galaxy. Exploration of redshift-stellar-population-reddening constraints from the photometry indicates that the galaxy is indeed at a redshift close to that of 4C 23.56, that the age of the most recent significant star formation is roughly >~2 Gyr, and that reddening is fairly modest, with more reddening required for the younger end of stellar age range. From analysis of a deep adaptive optics image of the galaxy, we find that an r1/4-law profile, common for local spheroidal galaxies, can be excluded quite strongly. On the other hand, a pure exponential profile fits remarkably well, while the best fit is given by a Sérsic profile with index n=1.49. Reconstruction of the two-dimensional form of the galaxy from the best-fit model is consistent with a disk galaxy with neither a significant bulge component nor gross azimuthal structure. The assembly of roughly 2L* of old stars into such a configuration this early in the history of the universe is not easily explainable by any of the currently popular scenarios for galaxy formation. A galaxy with these properties would seem to require smooth but rapid infall of the large mass of gas involved, followed by a burst of extremely vigorous and efficient star formation in the resulting disk. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. 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.

  6. Disk and Bulge Morphology of WFPC2 Galaxies: The HUBBLE SPACE TELESCOPE Medium Deep Survey (United States)

    Ratnatunga, Kavan U.; Griffiths, Richard E.; Ostrander, Eric J.


    Quantitative morphological and structural parameters are estimated for galaxies detected in Hubble Space Telescope observations of WFPC2 survey fields. A modeling approach based on maximum likelihood has been developed for two-dimensional decomposition of faint undersampled galaxy images into components of disk and bulge morphology. Decomposition can be achieved for images down to F814W(I)~23.0, F606W(V)~23.8, and F450W(B)~23.3 mag in WFPC2 exposures of 1 hr. We discuss details of the fitting procedure and present the observed distributions of magnitude, color, effective half-light radius, disk and bulge axis ratios, bulge-to-(disk+bulge) flux ratio, bulge-to-disk half-light radius ratio, and surface brightness. We also discuss the various selection limits on the measured parameters. The Medium Deep Survey catalogs and images of random pure parallel fields and other similar archival primary WFPC2 fields have been made available via the Internet with a searchable browser interface to the database.

  7. Gas-Rich Mergers in LCDM: Disk Survivability and the Baryonic Assembly of Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Kyle R.; Bullock, James S.; /UC, Irvine; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC; Maller, Ariyeh H.; /New York City Coll. Tech.


    We use N-body simulations and observationally-normalized relations between dark matter halo mass, stellar mass, and cold gas mass to derive robust expectations about the baryonic content of major mergers out to redshift z {approx} 2. First, we find that the majority of major mergers (m/M > 0.3) experienced by Milky Way size dark matter halos should have been gas-rich, and that gas-rich mergers are increasingly common at high redshift. Though the frequency of major mergers into galaxy halos in our simulations greatly exceeds the observed late-type galaxy fraction, the frequency of gas-poor major mergers is consistent with the observed fraction of bulge-dominated galaxies across the halo mass range M{sub DM} {approx} 10{sup 11} - 10{sup 13} M{sub {circle_dot}}. These results lend support to the conjecture that mergers with high baryonic gas fractions play an important role in building and/or preserving disk galaxies in the universe. Secondly, we find that there is a transition mass below which a galaxy's past major mergers were primarily gas-rich and above which they were gas poor. The associated stellar mass scale corresponds closely to that marking the observed bimodal division between blue, star-forming, disk-dominated systems and red, bulge-dominated systems with old populations. Finally, we find that the overall fraction of a galaxy's cold baryons deposited directly via major mergers is substantial. Approximately 30% of the cold baryonic material in M{sub star} {approx} 10{sup 10} M{sub {circle_dot}} (M{sub DM} {approx} 10{sup 11.5} M{sub {circle_dot}}) galaxies is accreted as cold gas in major mergers. For more massive galaxies with M{sub star} {approx} 10{sup 11} M{sub {circle_dot}} (M{sub DM} {approx} 10{sup 13} M{sub {circle_dot}} the fraction of baryons amassed in mergers is even higher, {approx} 50%, but most of these accreted baryons are delivered directly in the form of stars. This baryonic mass deposition is almost unavoidable, and provides a

  8. Probing the Disk-Jet Connection of the Radio Galaxy 3C120 Observed With Suzaku

    Energy Technology Data Exchange (ETDEWEB)

    Kataoka, Jun; Reeves, James N.; Iwasawa, Kazushi; Markowitz, Alex G.; Mushotzky, Richard F.; Arimoto, Makoto; Takahashi, Tadayuki; Tsubuku, Yoshihiro; Ushio, Masayoshi; Watanabe, Shin; Gallo, Luigi C.; Madejski, Greg M.; Terashima, Yuichi; Isobe, Naoki; Tashiro, Makoto S.; Kohmura, Takayoshi; /Tokyo Inst. Tech. /NASA, Goddard /Garching, Max Planck


    Broad line radio galaxies (BLRGs) are a rare type of radio-loud AGN, in which the broad optical permitted emission lines have been detected in addition to the extended jet emission. Here we report on deep (40ksec x 4) observations of the bright BLRG 3C 120 using Suzaku. The observations were spaced a week apart, and sample a range of continuum fluxes. An excellent broadband spectrum was obtained over two decades of frequency (0.6 to 50 keV) within each 40 ksec exposure. We clearly resolved the iron K emission line complex, finding that it consists of a narrow K{sub {alpha}} core ({sigma} {approx_equal} 110 eV or an EW of 60 eV), a 6.9 keV line, and an underlying broad iron line. Our confirmation of the broad line contrasts with the XMM-Newton observation in 2003, where the broad line was not required. The most natural interpretation of the broad line is iron K line emission from a face-on accretion disk which is truncated at {approx} 10 r{sub g}. Above 10 keV, a relatively weak Compton hump was detected (reflection fraction of R {approx_equal} 0.6), superposed on the primary X-ray continuum of {Lambda} {approx_equal} 1.75. Thanks to the good photon statistics and low background of the Suzaku data, we clearly confirm the spectral evolution of 3C 120, whereby the variability amplitude decreases with increasing energy. More strikingly, we discovered that the variability is caused by a steep power-law component of {Lambda} {approx_equal} 2.7, possibly related to the non-thermal jet emission. We discuss our findings in the context of similarities and differences between radio-loud/quiet objects.


    Energy Technology Data Exchange (ETDEWEB)

    Lelli, Federico; McGaugh, Stacy S. [Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States); Schombert, James M., E-mail: [Department of Physics, University of Oregon, Eugene, OR 97403 (United States)


    We introduce SPARC ( Spitzer Photometry and Accurate Rotation Curves): a sample of 175 nearby galaxies with new surface photometry at 3.6  μ m and high-quality rotation curves from previous H i/H α studies. SPARC spans a broad range of morphologies (S0 to Irr), luminosities (∼5 dex), and surface brightnesses (∼4 dex). We derive [3.6] surface photometry and study structural relations of stellar and gas disks. We find that both the stellar mass–H i mass relation and the stellar radius–H i radius relation have significant intrinsic scatter, while the H i   mass–radius relation is extremely tight. We build detailed mass models and quantify the ratio of baryonic to observed velocity ( V {sub bar}/ V {sub obs}) for different characteristic radii and values of the stellar mass-to-light ratio (ϒ{sub ⋆}) at [3.6]. Assuming ϒ{sub ⋆} ≃ 0.5 M {sub ⊙}/ L {sub ⊙} (as suggested by stellar population models), we find that (i) the gas fraction linearly correlates with total luminosity; (ii) the transition from star-dominated to gas-dominated galaxies roughly corresponds to the transition from spiral galaxies to dwarf irregulars, in line with density wave theory; and (iii)  V {sub bar}/ V {sub obs} varies with luminosity and surface brightness: high-mass, high-surface-brightness galaxies are nearly maximal, while low-mass, low-surface-brightness galaxies are submaximal. These basic properties are lost for low values of ϒ{sub ⋆} ≃ 0.2 M {sub ⊙}/ L {sub ⊙} as suggested by the DiskMass survey. The mean maximum-disk limit in bright galaxies is ϒ{sub ⋆} ≃ 0.7 M {sub ⊙}/ L {sub ⊙} at [3.6]. The SPARC data are publicly available and represent an ideal test bed for models of galaxy formation.


    Energy Technology Data Exchange (ETDEWEB)

    Swaters, Robert A. [National Optical Astronomical Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Martinsson, Thomas P. K. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Westfall, Kyle B. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom); Andersen, David R. [NRC Herzberg Programs in Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7 (Canada); Verheijen, Marc A. W., E-mail: [University of Groningen, Kapteyn Astronomical Institute, Landleven 12, 9747-AD Groningen (Netherlands)


    We present the correlation between the extrapolated central disk surface brightness (μ) and extrapolated central surface mass density (Σ) for galaxies in the DiskMass sample. This μ-Σ relation has a small scatter of 30% at the high surface brightness (HSB) end. At the low surface brightness (LSB) end, galaxies fall above the μ-Σ relation, which we attribute to their higher dark matter content. After correcting for the dark matter as well as for the contribution of gas and the effects of radial gradients in the disk, the LSB end falls back on the linear μ-Σ relation. The resulting scatter around the corrected μ-Σ relation is 25% at the HSB end and about 50% at the LSB end. The intrinsic scatter in the μ-Σ relation is estimated to be 10%-20%. Thus, if μ {sub K,} {sub 0} is known, the stellar surface mass density is known to within 10%-20% (random error). Assuming disks have an exponential vertical distribution of mass, the average Υ{sub ∗}{sup K} is 0.24 M {sub ☉}/L {sub ☉}, with an intrinsic scatter around the mean of at most 0.05 M {sub ☉}/L {sub ☉}. This value for Υ{sub ∗}{sup K} is 20% smaller than we found in Martinsson et al., mainly due to the correction for dark matter applied here. This small scatter means that among the galaxies in our sample, variations in scale height, vertical density profile shape, and/or the ratio of vertical over radial velocity dispersion must be small.


    Energy Technology Data Exchange (ETDEWEB)

    Hanasz, M.; Kowalik, K.; Wóltański, D. [Centre for Astronomy, Nicolaus Copernicus University, Faculty of Physics, Astronomy and Informatics, Grudziadzka 5, PL-87100 Toruń (Poland); Lesch, H. [Universitäts-Sternwarte München, Scheinerstr. 1, D-81679 München (Germany); Naab, T. [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching bei München (Germany); Gawryszczak, A., E-mail: [Poznań Supercomputing and Networking Centre, ul. Noskowskiego 10, PL-61-704 Poznań (Poland)


    We present simulations of the magnetized interstellar medium (ISM) in models of massive star-forming (40 M {sub ☉} yr{sup –1}) disk galaxies with high gas surface densities (Σ{sub gas} ∼ 100 M {sub ☉} pc{sup –2}) similar to observed star-forming high-redshift disks. We assume that type II supernovae deposit 10% of their energy into the ISM as cosmic rays (CRs) and neglect the additional deposition of thermal energy or momentum. With a typical Galactic diffusion coefficient for CRs (3 × 10{sup 28} cm{sup 2} s{sup –1}), we demonstrate that this process alone can trigger the local formation of a strong low-density galactic wind maintaining vertically open field lines. Driven by the additional pressure gradient of the relativistic fluid, the wind speed can exceed 10{sup 3} km s{sup –1}, much higher than the escape velocity of the galaxy. The global mass loading, i.e., the ratio of the gas mass leaving the galactic disk in a wind to the star formation rate, becomes of order unity once the system has settled into an equilibrium. We conclude that relativistic particles accelerated in supernova remnants alone provide a natural and efficient mechanism to trigger winds similar to observed mass-loaded galactic winds in high-redshift galaxies. These winds also help in explaining the low efficiencies for the conversion of gas into stars in galaxies, as well as the early enrichment of the intergalactic medium with metals. This mechanism may be at least of similar importance to the traditionally considered momentum feedback from massive stars and thermal and kinetic feedback from supernova explosions.


    Energy Technology Data Exchange (ETDEWEB)

    Iono, Daisuke; Hatsukade, Bunyo; Kawabe, Ryohei; Matsuda, Yuichi; Nakanishi, Kouichiro [National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Yun, Min S.; Wilson, Grant [University of Massachusetts, Department of Astronomy, 710 North Pleasant Street, Amherst, MA 01003 (United States); Aretxaga, Itziar; Hughes, David [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), Luis Enrique Erro 1, Sta. Ma. Tonantzintla, Puebla (Mexico); Ikarashi, Soh [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700AV Groningen (Netherlands); Izumi, Takuma; Kohno, Kotaro; Tamura, Yoichi; Umehata, Hideki [Institute of Astronomy, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Lee, Minju; Saito, Toshiki [Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 133-0033 (Japan); Ueda, Junko [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Michiyama, Tomonari; Ando, Misaki, E-mail: [SOKENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)


    The central structure in three of the brightest unlensed z = 3–4 submillimeter galaxies is investigated through 0.″015–0.″05 (120–360 pc) 860 μ m continuum images obtained using the Atacama Large Millimeter/submillimeter Array (ALMA). The distribution in the central kiloparsec in AzTEC1 and AzTEC8 is extremely complex, and they are composed of multiple ∼200 pc clumps. AzTEC4 consists of two sources that are separated by ∼1.5 kpc, indicating a mid-stage merger. The peak star formation rate densities in the central clumps are ∼300–3000 M {sub ⊙} yr{sup −1} kpc{sup −2}, suggesting regions with extreme star formation near the Eddington limit. By comparing the flux obtained by ALMA and Submillimeter Array, we find that 68%–90% of the emission is extended (≳1 kpc) in AzTEC4 and 8. For AzTEC1, we identify at least 11 additional compact (∼200 pc) clumps in the extended 3–4 kpc region. Overall, the data presented here suggest that the luminosity surface densities observed at ≲150 pc scales are roughly similar to that observed in local ULIRGs, as in the eastern nucleus of Arp 220. Between 10% and 30% of the 860 μ m continuum is concentrated in clumpy structures in the central kiloparsec, while the remaining flux is distributed over ≳1 kpc regions, some of which could also be clumpy. These sources can be explained by a rapid inflow of gas such as a merger of gas-rich galaxies, surrounded by extended and clumpy starbursts. However, the cold mode accretion model is not ruled out.

  13. Black Hole Growth in Disk Galaxies Mediated by the Secular Evolution of Short Bars (United States)

    Du, Min; Debattista, Victor P.; Shen, Juntai; Ho, Luis C.; Erwin, Peter


    The growth of black holes (BHs) in disk galaxies lacking classical bulges, which implies an absence of significant mergers, appears to be driven by secular processes. Short bars of sub-kiloparsec radius have been hypothesized to be an important mechanism for driving gas inflows to small scale, feeding central BHs. In order to quantify the maximum BH mass allowed by this mechanism, we examine the robustness of short bars to the dynamical influence of BHs. Large-scale bars are expected to be robust, long-lived structures; extremely massive BHs, which are rare, are needed to completely destroy such bars. However, we find that short bars, which are generally embedded in large-scale outer bars, can be destroyed quickly when BHs of mass {M}{bh}˜ 0.05 % {--}0.2 % of the total stellar mass ({M}\\star ) are present. In agreement with this prediction, all galaxies observed to host short bars have BHs with a mass fraction less than 0.2 % {M}\\star . Thus, the dissolution of short inner bars is possible, perhaps even frequent, in the universe. An important implication of this result is that inner-bar-driven gas inflows may be terminated when BHs grow to ˜ 0.1 % {M}\\star . We predict that 0.2 % {M}\\star is the maximum mass of BHs allowed if they are fed predominately via inner bars. This value matches well the maximum ratio of BH-to-host-galaxy stellar mass observed in galaxies with pseudo-bulges and most nearby active galactic nucleus host galaxies. This hypothesis provides a novel explanation for the lower {M}{bh}/{M}\\star in galaxies that have avoided significant mergers compared with galaxies with classical bulges.


    Energy Technology Data Exchange (ETDEWEB)

    Bird, Jonathan C.; Kazantzidis, Stelios; Weinberg, David H. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Guedes, Javiera [Institute for Astronomy, ETH Zuerich, Wolgang-Pauli-Strasse 27, CH-8093 Zuerich (Switzerland); Callegari, Simone [Anthropology Institute and Museum, University of Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Mayer, Lucio [Institute for Theoretical Physics, University of Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Madau, Piero [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)


    We analyze the present day structure and assembly history of a high-resolution hydrodynamic simulation of the formation of a Milky-Way-(MW)-like disk galaxy, from the ''Eris'' simulation suite, dissecting it into cohorts of stars formed at different epochs of cosmic history. At z = 0, stars with t{sub form} < 2 Gyr mainly occupy the stellar spheroid, with the oldest (earliest forming) stars having more centrally concentrated profiles. The younger age cohorts populate disks of progressively longer radial scale lengths and shorter vertical scale heights. At a given radius, the vertical density profiles and velocity dispersions of stars vary smoothly as a function of age, and the superposition of old, vertically extended and young, vertically compact cohorts gives rise to a double-exponential profile like that observed in the MW. Turning to formation history, we find that the trends of spatial structure and kinematics with stellar age are largely imprinted at birth, or immediately thereafter. Stars that form during the active merger phase at z > 3 are quickly scattered into rounded, kinematically hot configurations. The oldest disk cohorts form in structures that are radially compact and relatively thick, while subsequent cohorts form in progressively larger, thinner, colder configurations from gas with increasing levels of rotational support. The disk thus forms ''inside out'' in a radial sense and ''upside down'' in a vertical sense. Secular heating and radial migration influence the final state of each age cohort, but the changes they produce are small compared to the trends established at formation. The predicted correlations of stellar age with spatial and kinematic structure are in good qualitative agreement with the correlations observed for mono-abundance stellar populations in the MW.

  15. Extragalactic archeology with the GHOSTS Survey. I. Age-resolved disk structure of nearby low-mass galaxies (United States)

    Streich, David; de Jong, Roelof S.; Bailin, Jeremy; Bell, Eric F.; Holwerda, Benne W.; Minchev, Ivan; Monachesi, Antonela; Radburn-Smith, David J.


    Aims: We study the individual evolution histories of three nearby low-mass edge-on galaxies (IC 5052, NGC 4244, and NGC 5023). Methods: Using resolved stellar populations, we constructed star count density maps for populations of different ages and analyzed the change of structural parameters with stellar age within each galaxy. Results: We do not detect a separate thick disk in any of the three galaxies, even though our observations cover a wider range in equivalent surface brightness than any integrated light study. While scale heights increase with age, each population can be well described by a single disk. Two of the galaxies contain a very weak additional component, which we identify as the faint halo. The mass of these faint halos is lower than 1% of the mass of the disk. The three galaxies show low vertical heating rates, which are much lower than the heating rate of the Milky Way. This indicates that heating agents, such as giant molecular clouds and spiral structure, are weak in low-mass galaxies. All populations in the three galaxies exhibit no or only little flaring. While this finding is consistent with previous integrated light studies, it poses strong constraints on galaxy simulations, where strong flaring is often found as a result of interactions or radial migration.

  16. The AGORA High-resolution Galaxy Simulations Comparison Project. II. Isolated Disk Test (United States)

    Kim, Ji-hoon; Agertz, Oscar; Teyssier, Romain; Butler, Michael J.; Ceverino, Daniel; Choi, Jun-Hwan; Feldmann, Robert; Keller, Ben W.; Lupi, Alessandro; Quinn, Thomas; Revaz, Yves; Wallace, Spencer; Gnedin, Nickolay Y.; Leitner, Samuel N.; Shen, Sijing; Smith, Britton D.; Thompson, Robert; Turk, Matthew J.; Abel, Tom; Arraki, Kenza S.; Benincasa, Samantha M.; Chakrabarti, Sukanya; DeGraf, Colin; Dekel, Avishai; Goldbaum, Nathan J.; Hopkins, Philip F.; Hummels, Cameron B.; Klypin, Anatoly; Li, Hui; Madau, Piero; Mandelker, Nir; Mayer, Lucio; Nagamine, Kentaro; Nickerson, Sarah; O'Shea, Brian W.; Primack, Joel R.; Roca-Fàbrega, Santi; Semenov, Vadim; Shimizu, Ikkoh; Simpson, Christine M.; Todoroki, Keita; Wadsley, James W.; Wise, John H.; AGORA Collaboration


    Using an isolated Milky Way-mass galaxy simulation, we compare results from nine state-of-the-art gravito-hydrodynamics codes widely used in the numerical community. We utilize the infrastructure we have built for the AGORA High-resolution Galaxy Simulations Comparison Project. This includes the common disk initial conditions, common physics models (e.g., radiative cooling and UV background by the standardized package Grackle) and common analysis toolkit yt, all of which are publicly available. Subgrid physics models such as Jeans pressure floor, star formation, supernova feedback energy, and metal production are carefully constrained across code platforms. With numerical accuracy that resolves the disk scale height, we find that the codes overall agree well with one another in many dimensions including: gas and stellar surface densities, rotation curves, velocity dispersions, density and temperature distribution functions, disk vertical heights, stellar clumps, star formation rates, and Kennicutt-Schmidt relations. Quantities such as velocity dispersions are very robust (agreement within a few tens of percent at all radii) while measures like newly formed stellar clump mass functions show more significant variation (difference by up to a factor of ˜3). Systematic differences exist, for example, between mesh-based and particle-based codes in the low-density region, and between more diffusive and less diffusive schemes in the high-density tail of the density distribution. Yet intrinsic code differences are generally small compared to the variations in numerical implementations of the common subgrid physics such as supernova feedback. Our experiment reassures that, if adequately designed in accordance with our proposed common parameters, results of a modern high-resolution galaxy formation simulation are more sensitive to input physics than to intrinsic differences in numerical schemes.

  17. An X-Ray Reprocessing Model of Disk Thermal Emission in Type 1 Seyfert Galaxies (United States)

    Chiang, James; White, Nicholas E. (Technical Monitor)


    Using a geometry consisting of a hot central Comptonizing plasma surrounded by a thin accretion disk, we model the optical through hard X-ray spectral energy distributions of the type 1 Seyfert. galaxies NGC 3516 and NGC 7469. As in the model proposed by Poutanen, Krolik, and Ryde for the X-ray binary Cygnus X-1 and later applied to Seyfert galaxies by Zdziarski, Lubifiski, and Smith, feedback between the radiation reprocessed by the disk and the thermal Comptonization emission from the hot central plasma plays a pivotal role in determining the X-ray spectrum, and as we show, the optical and ultraviolet spectra as well. Seemingly uncorrelated optical/UV and X-ray light curves, similar to those which have been observed from these objects can, in principle, be explained by variations in the size, shape, and temperature of the Comptonizing plasma. Furthermore, by positing a disk mass accretion rate which satisfies a condition for global energy balance between the thermal Comptonization luminosity and the power available from accretion, one can predict the spectral properties of the heretofore poorly measured hard X-ray continuum above approximately 50 keV in type 1 Seyfert galaxies. Conversely, forthcoming measurements of the hard X-ray continuum by more sensitive hard X-ray and soft gamma-ray telescopes, such as those aboard the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) in conjunction with simultaneous optical, UV, and soft X-ray monitoring, will allow the mass accretion rates to be directly constrained for these sources in the context of this model.

  18. Scaling Relations for the Efficiency of Radial Migration in Disk Galaxies (United States)

    Daniel, Kathryne J.


    Radial migration is frequently recognized as an internal, secular process that could play an important role in disk galaxy evolution. The driving mechanism for radial migration is transient spiral patterns, which rearrange the orbital angular momentum distribution of disk stars around corotation without causing kinematic heating. Should radial migration be an efficient process, it could cause a substantial fraction of disk stars to move large radial distances over the lifetime of the disk, thus having a significant impact on the disk’s kinematic, structural and chemical evolution. Observational and simulated data are consistent with radial migration being important for kinematically cold stellar populations and less so for populations with hot kinematics. I will present an analytic criterion that determines which stars are in orbits that could lead to radial migration. I will then show some scaling relations for the efficacy of radial migration that result from applying this analytic criterion to a series of models that have a variety of distribution functions and spiral patterns in systems with an assumed flat rotation curve. Most importantly, I will argue that these scaling relations can be used to place constraints on the efficiency of radial migration, where stronger spiral patterns and kinematically cold populations will lead to a higher fraction of stars in orbits that can lead to radial migration.

  19. Herschel's "Cold Debris Disks": Background Galaxies or Quiescent Rims of Planetary Systems? (United States)

    Krivov, A. V.; Eiroa, C.; Loehne, T.; Marshall, J. P.; Montesinos, B.; DelBurgo, C.; Absil, O.; Ardila, D.; Augereau, J.-C.; Bayo, A.; hide


    Infrared excesses associated with debris disk host stars detected so far peak at wavelengths around approx, 100 micron or shorter. However, 6 out of 31 excess sources studied in the Herschel Open Time Key Programme, DUNES, have been seen to show significant-and in some cases extended-excess emission at 160 micron, which is larger than the 100 micron excess. This excess emission has been attributed to circumstellar dust and has been suggested to stem from debris disks colder than those known previously. Since the excess emission of the cold disk candidates is extremely weak, challenging even the unrivaled sensitivity of Herschel, it is prudent to carefully consider whether some or even all of them may represent unrelated galactic or extragalactic emission, or even instrumental noise. We re-address these issues using several distinct methods and conclude that it is highly unlikely that none of the candidates represents a true circumstellar disk. For true disks, both the dust temperatures inferred from the spectral energy distributions and the disk radii estimated from the images suggest that the dust is nearly as cold as a blackbody. This requires the grains to be larger than approx. 100 micron, even if they are rich in ices or are composed of any other material with a low absorption in the visible. The dearth of small grains is puzzling, since collisional models of debris disks predict that grains of all sizes down to several times the radiation pressure blowout limit should be present. We explore several conceivable scenarios: transport-dominated disks, disks of low dynamical excitation, and disks of unstirred primordial macroscopic grains. Our qualitative analysis and collisional simulations rule out the first two of these scenarios, but show the feasibility of the third one. We show that such disks can indeed survive for gigayears, largely preserving the primordial size distribution. They should be composed of macroscopic solids larger than millimeters, but

  20. Dynamical Properties of Eccentric Nuclear Disks: Stability, Longevity, and Implications for Tidal Disruption Rates in Post-merger Galaxies (United States)

    Madigan, Ann-Marie; Halle, Andrew; Moody, Mackenzie; McCourt, Michael; Nixon, Chris; Wernke, Heather


    In some galaxies, the stars orbiting the supermassive black hole take the form of an eccentric nuclear disk, in which every star is on a coherent, apsidally aligned orbit. The most famous example of an eccentric nuclear disk is the double nucleus of Andromeda, and there is strong evidence for many more in the local universe. Despite their apparent ubiquity, however, a dynamical explanation for their longevity has remained a mystery: differential precession should wipe out large-scale apsidal-alignment on a short timescale. Here we identify a new dynamical mechanism which stabilizes eccentric nuclear disks, and explain for the first time the negative eccentricity gradient seen in the Andromeda nucleus. The stabilizing mechanism drives oscillations of the eccentricity vectors of individual orbits, both in direction (about the mean body of the disk) and in magnitude. Combined with the negative eccentricity gradient, the eccentricity oscillations push some stars near the inner edge of the disk extremely close to the black hole, potentially leading to tidal disruption events (TDEs). Order of magnitude calculations predict extremely high rates in recently formed eccentric nuclear disks (∼0.1–1 {{yr}}-1 {{gal}}-1). Unless the stellar disks are replenished, these rates should decrease with time as the disk depletes in mass. If eccentric nuclear disks form during gas-rich major mergers, this may explain the preferential occurrence of TDEs in recently merged and post-merger (E+A/K+A) galaxies.

  1. Circumnuclear Molecular Disks in Early-type Galaxies: Physical Properties and Precision Black Hole Mass Measurements (United States)

    Boizelle, Benjamin


    ALMA is now capable of providing the most precise determinations of the masses of supermassive black holes in early-type galaxies (ETGs). In ALMA Cycle 2 we began a program to map the molecular gas kinematics in nearby ETGs that host central dust disks as seen in Hubble Space Telescope imaging. These initial observations targeted CO(2-1) emission at ~0.3" resolution, corresponding roughly to the projected radii of influence of the central black holes. In all cases we detect significant (~108 M⊙) molecular gas reservoirs that are in dynamically cold rotation, providing the most sensitive probes of the inner gravitational potentials of luminous ETGs. Using these gas kinematics, we verify that these molecular disks are formally stable against gravitational fragmentation and collapse. In several galaxies we detect central high-velocity gas rotation that provides direct kinematic evidence for a black hole. For two of these targets, NGC 1332 and NGC 3258, we have obtained higher-resolution observations (0.044" and 0.09") in Cycles 3 and 4 that more fully map out the gas rotation within the gravitational sphere of influence. We present dynamical modeling results for these targets, demonstrating that ALMA observations can enable black hole mass measurements at a precision of 10% or better, with minimal susceptibility to the systematic uncertainties that affect other methods of black hole mass measurement in ETGs. We discuss the impact of future high-resolution ALMA observations on black hole demographics and their potential to refine the high-mass end of the black hole-host galaxy scaling relationships.

  2. Ab Initio Simulations of a Supernova-driven Galactic Dynamo in an Isolated Disk Galaxy (United States)

    Butsky, Iryna; Zrake, Jonathan; Kim, Ji-hoon; Yang, Hung-I.; Abel, Tom


    We study the magnetic field evolution of an isolated spiral galaxy, using isolated Milky Way-mass galaxy formation simulations and a novel prescription for magnetohydrodynamic (MHD) supernova feedback. Our main result is that a galactic dynamo can be seeded and driven by supernova explosions, resulting in magnetic fields whose strength and morphology are consistent with observations. In our model, supernovae supply thermal energy and a low-level magnetic field along with their ejecta. The thermal expansion drives turbulence, which serves a dual role by efficiently mixing the magnetic field into the interstellar medium and amplifying it by means of a turbulent dynamo. The computational prescription for MHD supernova feedback has been implemented within the publicly available ENZO code and is fully described in this paper. This improves upon ENZO's existing modules for hydrodynamic feedback from stars and active galaxies. We find that the field attains microgauss levels over gigayear timescales throughout the disk. The field also develops a large-scale structure, which appears to be correlated with the disk’s spiral arm density structure. We find that seeding of the galactic dynamo by supernova ejecta predicts a persistent correlation between gas metallicity and magnetic field strength. We also generate all-sky maps of the Faraday rotation measure from the simulation-predicted magnetic field, and we present a direct comparison with observations.


    Energy Technology Data Exchange (ETDEWEB)

    Laine, Seppo; Grillmair, Carl J.; Capak, Peter [Spitzer Science Center-Caltech, MS 314-6, Pasadena, CA 91125 (United States); Arendt, Richard G. [CRESST/UMBC/NASA GSFC, Code 665, Greenbelt, MD 20771 (United States); Romanowsky, Aaron J. [Department of Physics and Astronomy, San José State University, One Washington Square, San Jose, CA 95192 (United States); Martínez-Delgado, David [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany); Ashby, Matthew L. N. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Davies, James E. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Majewski, Stephen R. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Brodie, Jean P.; Arnold, Jacob A. [University of California Observatories and Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); GaBany, R. Jay, E-mail: [Black Bird Observatory, 5660 Brionne Drive, San Jose, CA 95118 (United States)


    Stellar streams have become central to studies of the interaction histories of nearby galaxies. To characterize the most prominent parts of the stellar stream around the well-known nearby ( d  = 17 Mpc) edge-on disk galaxy NGC 5907, we have obtained and analyzed new, deep gri Subaru/Suprime-Cam and 3.6 μ m Spitzer /Infrared Array Camera observations. Combining the near-infrared 3.6 μ m data with visible-light images allows us to use a long wavelength baseline to estimate the metallicity and age of the stellar population along an ∼60 kpc long segment of the stream. We have fitted the stellar spectral energy distribution with a single-burst stellar population synthesis model and we use it to distinguish between the proposed satellite accretion and minor/major merger formation models of the stellar stream around this galaxy. We conclude that a massive minor merger (stellar mass ratio of at least 1:8) can best account for the metallicity of −0.3 inferred along the brightest parts of the stream.

  4. Building the Peanut: Simulations and Observations of Peanut-shaped Structures and Ansae in Face-on Disk Galaxies (United States)

    Saha, Kanak; Graham, Alister W.; Rodríguez-Herranz, Isabel


    Peanut/x-shaped features observed in a significant fraction of disk galaxies are thought to have formed from vertically buckled bars. Despite being three-dimensional structures, they are preferentially detected in near edge-on projection. Only a few galaxies are found to have displayed such structures when their disks are relatively face-on—suggesting that either they are generally weak in face-on projection or many may be hidden by the light of their galaxy’s face-on disk. Here, we report on three (collisionless) simulated galaxies displaying peanut-shaped structures when their disks are seen both face-on and edge-on—resembling a three-dimensional peanut or dumbbell. Furthermore, these structures are accompanied by ansae and an outer ring at the end of the bar—as seen in real galaxies such as IC 5240. The same set of quantitative parameters used to measure peanut structures in real galaxies has been determined for the simulated galaxies, and a broad agreement is found. In addition, the peanut length grows in tandem with the bar, and is a maximum at half the length of the bar. Beyond the cutoff of these peanut structures, toward the end of the bar, we discover a new positive/negative feature in the B 6 radial profile associated with the isophotes of the ansae/ring. Our simulated, self-gravitating, three-dimensional peanut structures display cylindrical rotation even in the near-face-on disk projection. In addition, we report on a kinematic pinch in the velocity map along the bar minor axis, matching that seen in the surface density map.

  5. DGSAT: Dwarf Galaxy Survey with Amateur Telescopes. II. A catalogue of isolated nearby edge-on disk galaxies and the discovery of new low surface brightness systems (United States)

    Henkel, C.; Javanmardi, B.; Martínez-Delgado, D.; Kroupa, P.; Teuwen, K.


    The connection between the bulge mass or bulge luminosity in disk galaxies and the number, spatial and phase space distribution of associated dwarf galaxies is a discriminator between cosmological simulations related to galaxy formation in cold dark matter and generalised gravity models. Here, a nearby sample of isolated Milky Way-class edge-on galaxies is introduced, to facilitate observational campaigns to detect the associated families of dwarf galaxies at low surface brightness. Three galaxy pairs with at least one of the targets being edge-on are also introduced. Approximately 60% of the catalogued isolated galaxies contain bulges of different size, while the remaining objects appear to be bulgeless. Deep images of NGC 3669 (small bulge, with NGC 3625 at the edge of the image) and NGC 7814 (prominent bulge), obtained with a 0.4 m aperture, are also presented, resulting in the discovery of two new dwarf galaxy candidates, NGC 3669-DGSAT-3 and NGC 7814-DGSAT-7. Eleven additional low surface brightness galaxies are identified, previously notified with low quality measurement flags in the Sloan Digital Sky Survey (SDSS). Integrated magnitudes, surface brightnesses, effective radii, Sersic indices, axis ratios, and projected distances to their putative major hosts are displayed. At least one of the galaxies, NGC 3625-DGSAT-4, belongs with a surface brightness of μr ≈ 26 mag arcsec-2 and effective radius >1.5 kpc to the class of ultra-diffuse galaxies (UDGs). NGC 3669-DGSAT-3, the galaxy with the lowest surface brightness in our sample, may also be an UDG.

  6. The extended structure of the dwarf irregular galaxy Sagittarius

    NARCIS (Netherlands)

    Beccari, G.; Bellazzini, M.; Fraternali, F.; Battaglia, G.; Perina, S.; Sollima, A.; Oosterloo, T. A.; Testa, V.; Galleti, S.


    We present a detailed study of the stellar and H i structure of the dwarf irregular galaxy Sagittarius. We use new deep and wide field photometry to trace the surface brightness profile of the galaxy out to ≃5.0' (corresponding to ≃1600 pc) and down to μV ≃ 30.0 mag/arcsec2, thus showing that the

  7. Inner and outer star forming regions over the disks of spiral galaxies. I. Sample characterization (United States)

    Rodríguez-Baras, M.; Díaz, A. I.; Rosales-Ortega, F. F.; Sánchez, S. F.


    Context. The knowledge of abundance distributions is central to understanding the formation and evolution of galaxies. Most of the relations employed for the derivation of gas abundances have so far been derived from observations of outer disk H ii regions, despite the known differences between inner and outer regions. Aims: Using integral field spectroscopy (IFS) observations we aim to perform a systematic study and comparison of two inner and outer H ii regions samples. The spatial resolution of the IFS, the number of objects and the homogeneity and coherence of the observations allow a complete characterization of the main observational properties and differences of the regions. Methods: We analyzed a sample of 725 inner H ii regions and a sample of 671 outer H ii regions, all of them detected and extracted from the observations of a sample of 263 nearby, isolated, spiral galaxies observed by the CALIFA survey. Results: We find that inner H ii regions show smaller equivalent widths, greater extinction and luminosities, along with greater values of [N ii] λ6583/Hα and [O ii] λ3727/[O iii] λ5007 emission-line ratios, indicating higher metallicities and lower ionization parameters. Inner regions have also redder colors and higher photometric and ionizing masses, although MionMphot is slighty higher for the outer regions. Conclusions: This work shows important observational differences between inner and outer H ii regions in star forming galaxies not previously studied in detail. These differences indicate that inner regions have more evolved stellar populations and are in a later evolution state with respect to outer regions, which goes in line with the inside-out galaxy formation paradigm. Table 4 is only available at the CDS via anonymous ftp to ( or via


    Energy Technology Data Exchange (ETDEWEB)

    Nelson, Erica June; Van Dokkum, Pieter G.; Skelton, Rosalind E.; Bezanson, Rachel; Lundgren, Britt [Astronomy Department, Yale University, New Haven, CT 06511 (United States); Brammer, Gabriel [European Southern Observatory, Alonson de Cordova 3107, Casilla 19001, Vitacura, Santiago (Chile); Foerster Schreiber, Natascha [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Franx, Marijn; Fumagalli, Mattia; Patel, Shannon; Labbe, Ivo [Leiden Observatory, Leiden University, Leiden (Netherlands); Rix, Hans-Walter; Da Cunha, Elisabete; Schmidt, Kasper B. [Max Planck Institute for Astronomy (MPIA), Koenigstuhl 17, 69117 Heidelberg (Germany); Kriek, Mariska [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Quadri, Ryan [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)


    We investigate the buildup of galaxies at z {approx} 1 using maps of H{alpha} and stellar continuum emission for a sample of 57 galaxies with rest-frame H{alpha} equivalent widths >100 A in the 3D-HST grism survey. We find that the H{alpha} emission broadly follows the rest-frame R-band light but that it is typically somewhat more extended and clumpy. We quantify the spatial distribution with the half-light radius. The median H{alpha} effective radius r{sub e} (H{alpha}) is 4.2 {+-} 0.1 kpc but the sizes span a large range, from compact objects with r{sub e} (H{alpha}) {approx} 1.0 kpc to extended disks with r{sub e} (H{alpha}) {approx} 15 kpc. Comparing H{alpha} sizes to continuum sizes, we find =1.3 {+-} 0.1 for the full sample. That is, star formation, as traced by H{alpha}, typically occurs out to larger radii than the rest-frame R-band stellar continuum; galaxies are growing their radii and building up from the inside out. This effect appears to be somewhat more pronounced for the largest galaxies. Using the measured H{alpha} sizes, we derive star formation rate surface densities, {Sigma}{sub SFR}. We find that {Sigma}{sub SFR} ranges from {approx}0.05 M{sub Sun} yr{sup -1} kpc{sup -2} for the largest galaxies to {approx}5 M{sub Sun} yr{sup -1} kpc{sup -2} for the smallest galaxies, implying a large range in physical conditions in rapidly star-forming z {approx} 1 galaxies. Finally, we infer that all galaxies in the sample have very high gas mass fractions and stellar mass doubling times <500 Myr. Although other explanations are also possible, a straightforward interpretation is that we are simultaneously witnessing the rapid formation of compact bulges and large disks at z {approx} 1.

  9. The new Basel high-latitude field star survey of the Galaxy. II. The thick disk component: density structure, luminosity function, and metallicity distribution (United States)

    Buser, Roland; Rong, Jianxiang; Karaali, Salih


    We present an expanded and refined analysis of the Galactic thick disk as observed in seven fields of the new Basel RGU star count and color survey data. Based on the optimized structural models which were obtained in the initial analysis (Buser et al. 1998a, hereafter Paper I), we now employ the same systematic least-squares algorithm, introducing more realistic luminosity functions for each population component, applying a more adequate matrix of color transformations in simulating the data, and extending the structural parameter ranges in order to determine improved characteristics of the thick-disk model. Compared with the earlier results of Paper I, the present models provide chi (2) -fits to the data which are improved by about 25%. From these we conclude that, on the one hand, each of the thin disk, thick disk, and halo components has its own local luminosity function, characterized by a distinctly specific shape and metallicity. On the other hand, the above improvement also allows us to derive more reliable estimates of optimized parameter values and constraints for the structural thick-disk model. According to our currently best models, we find the Galactic thick disk to have local density bar n1 = 5.9 +/- 3% of the local thin-disk density, exponential scale length bar d3 = 3.0 +/- 1.5 kpc, and exponential scale height bar h4 = 0.91 +/- 0.3 kpc. We also confirm the result of Paper I that the data are consistent with a metallicity distribution of the thick disk centered on ~ -0.63 dex and having dispersion sigma_ {} ~ 0.4 dex. While these results are in remarkable agreement with the majority of independent recent determinations of the global properties of the Galactic thick disk, we cannot yet exclude the possibility that the sizeable dispersions associated with the mean parameter values are indicative of structural differences between the individual fields that may largely be due to features of the real thick disk - reflecting intrinsic deviations from the

  10. The gravitational wakefield of a molecular cloud in a disk galaxy (United States)

    Tagger, M.; Pellat, R.; Sygnet, J. F.


    A molecular cloud (considered as a point macroparticle) represents a clump of increased mass density moving in the disk of a galaxy. Its presence generates a gravitational polarization of the disk, somewhat analogous to the polarization of a dielectric medium by a test charged particle. This means that the cloud travels along with a wakefield (a region of increased mass density) which is the collective response of the stars and gas to the perturbing mass. It can represent many times the mass of the cloud, and emits spiral density waves which propagate away. In terms of statistical mechanics, this wakefield will appear as an increased two-particle correlation function which is the equivalent of the Debye sphere in a plasma - despite the absence here of negative charges. At short distances clouds will thus interact through their own gravitational field amplified by their wakefields, which might thus strongly affect their collisionality. Researchers present a calculation of this wakefield and discuss its importance in the collisional dynamics of molecular clouds.

  11. Continuum Reverberation Mapping of the Accretion Disks in Two Seyfert 1 Galaxies (United States)

    Fausnaugh, M. M.; Starkey, D. A.; Horne, Keith; Kochanek, C. S.; Peterson, B. M.; Bentz, M. C.; Denney, K. D.; Grier, C. J.; Grupe, D.; Pogge, R. W.; De Rosa, G.; Adams, S. M.; Barth, A. J.; Beatty, Thomas G.; Bhattacharjee, A.; Borman, G. A.; Boroson, T. A.; Bottorff, M. C.; Brown, Jacob E.; Brown, Jonathan S.; Brotherton, M. S.; Coker, C. T.; Crawford, S. M.; Croxall, K. V.; Eftekharzadeh, Sarah; Eracleous, Michael; Joner, M. D.; Henderson, C. B.; Holoien, T. W.-S.; Hutchison, T.; Kaspi, Shai; Kim, S.; King, Anthea L.; Li, Miao; Lochhaas, Cassandra; Ma, Zhiyuan; MacInnis, F.; Manne-Nicholas, E. R.; Mason, M.; Montuori, Carmen; Mosquera, Ana; Mudd, Dale; Musso, R.; Nazarov, S. V.; Nguyen, M. L.; Okhmat, D. N.; Onken, Christopher A.; Ou-Yang, B.; Pancoast, A.; Pei, L.; Penny, Matthew T.; Poleski, Radosław; Rafter, Stephen; Romero-Colmenero, E.; Runnoe, Jessie; Sand, David J.; Schimoia, Jaderson S.; Sergeev, S. G.; Shappee, B. J.; Simonian, Gregory V.; Somers, Garrett; Spencer, M.; Stevens, Daniel J.; Tayar, Jamie; Treu, T.; Valenti, Stefano; Van Saders, J.; Villanueva, S., Jr.; Villforth, C.; Weiss, Yaniv; Winkler, H.; Zhu, W.


    We present optical continuum lags for two Seyfert 1 galaxies, MCG+08-11-011 and NGC 2617, using monitoring data from a reverberation mapping campaign carried out in 2014. Our light curves span the ugriz filters over four months, with median cadences of 1.0 and 0.6 days for MCG+08-11-011 and NGC 2617, respectively, combined with roughly daily X-ray and near-UV data from Swift for NGC 2617. We find lags consistent with geometrically thin accretion-disk models that predict a lag-wavelength relation of τ ∝ λ 4/3. However, the observed lags are larger than predictions based on standard thin-disk theory by factors of 3.3 for MCG+08-11-011 and 2.3 for NGC 2617. These differences can be explained if the mass accretion rates are larger than inferred from the optical luminosity by a factor of 4.3 in MCG+08-11-011 and a factor of 1.3 in NGC 2617, although uncertainty in the SMBH masses determines the significance of this result. While the X-ray variability in NGC 2617 precedes the UV/optical variability, the long (2.6 day) lag is problematic for coronal reprocessing models.


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    Marinova, Irina; Jogee, Shardha; Weinzirl, Tim [Department of Astronomy, University of Texas at Austin, Austin, TX (United States); Erwin, Peter [Max-Planck-Insitut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Trentham, Neil [Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Ferguson, Henry C.; Goudfrooij, Paul [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Hammer, Derek [Department of Physics and Astronomy, Johns Hopkins, Baltimore, MD 21218 (United States); Den Brok, Mark; Peletier, Reynier F.; Kleijn, Gijs V. [Kapteyn Astronomical Institute, University of Groningen, Groningen (Netherlands); Graham, Alister W. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn (Australia); Carter, David; Mouhcine, Mustapha [Astrophysics Research Institute, Liverpool John Moores University, Birkenhead (United Kingdom); Balcells, Marc [Instituto de Astrofisica de Canarias, 38200 La Laguna, Tenerife (Spain); Guzman, Rafael; Hoyos, Carlos [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Mobasher, Bahram [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Peng, Eric W., E-mail:, E-mail: [Department of Astronomy, Peking University, Beijing 100871 (China)


    We use high-resolution ({approx}0.''1) F814W Advanced Camera for Surveys (ACS) images from the Hubble Space Telescope ACS Treasury survey of the Coma cluster at z {approx} 0.02 to study bars in massive disk galaxies (S0s), as well as low-mass dwarf galaxies in the core of the Coma cluster, the densest environment in the nearby universe. Our study helps to constrain the evolution of bars and disks in dense environments and provides a comparison point for studies in lower density environments and at higher redshifts. Our results are: (1) we characterize the fraction and properties of bars in a sample of 32 bright (M{sub V} {approx}< -18, M{sub *} > 10{sup 9.5} M{sub Sun }) S0 galaxies, which dominate the population of massive disk galaxies in the Coma core. We find that the measurement of a bar fraction among S0 galaxies must be handled with special care due to the difficulty in separating unbarred S0s from ellipticals, and the potential dilution of the bar signature by light from a relatively large, bright bulge. The results depend sensitively on the method used: the bar fraction for bright S0s in the Coma core is 50% {+-} 11%, 65% {+-} 11%, and 60% {+-} 11% based on three methods of bar detection, namely, strict ellipse fit criteria, relaxed ellipse fit criteria, and visual classification. (2) We compare the S0 bar fraction across different environments (the Coma core, A901/902, and Virgo) adopting the critical step of using matched samples and matched methods in order to ensure robust comparisons. We find that the bar fraction among bright S0 galaxies does not show a statistically significant variation (within the error bars of {+-}11%) across environments which span two orders of magnitude in galaxy number density (n {approx} 300-10,000 galaxies Mpc{sup -3}) and include rich and poor clusters, such as the core of Coma, the A901/902 cluster, and Virgo. We speculate that the bar fraction among S0s is not significantly enhanced in rich clusters compared to

  13. The red extended structure of IC 10, the nearest blue compact galaxy (United States)

    Gerbrandt, Stephanie A. N.; McConnachie, Alan W.; Irwin, Mike


    The Local Group starburst galaxy IC 10 is the closest example of a blue compact galaxy. Here, we use optical gi imaging from Canada-France-Hawaii Telescope/MegaCam and near infrared JHK imaging from United Kingdom Infrared Telescope/Wide Field Camera to conduct a comprehensive survey of the structure of IC 10. We examine the spatial distribution of its resolved young, intermediate and old stellar populations to large radius and low effective surface brightness levels. Akin to other dwarfs with multiple populations of different ages, stellar populations of decreasing average age are increasingly concentrated in this galaxy. We find that the young, starbursting population and the asymptotic giant branch population are both offset from the geometric centre of the older red giant branch (RGB) population by a few hundred parsecs, implying that the younger star formation occurred significantly away from the centre of the galaxy. The RGB population traces an extended structure that is typical of blue compact galaxies, with an effective radius of ˜5.75 arcmin (˜1.25 kpc). These measurements show that IC 10 is much more extended than has previously been realized, and this blue compact galaxy is one of the most extended dwarf galaxies in the Local Group. The outermost isophotes of this galaxy are very regular in shape and essentially circular in morphology. Based on this analysis, we do not find any evidence to suggest that IC 10 has undergone a recent, significant, interaction with an unknown companion.

  14. Stellar mass distribution of S4G disk galaxies and signatures of bar-induced secular evolution (United States)

    Díaz-García, S.; Salo, H.; Laurikainen, E.


    Context. Models of galaxy formation in a cosmological framework need to be tested against observational constraints, such as the average stellar density profiles (and their dispersion) as a function of fundamental galaxy properties (e.g. the total stellar mass). Simulation models predict that the torques produced by stellar bars efficiently redistribute the stellar and gaseous material inside the disk, pushing it outwards or inwards depending on whether it is beyond or inside the bar corotation resonance radius. Bars themselves are expected to evolve, getting longer and narrower as they trap particles from the disk and slow down their rotation speed. Aims: We use 3.6 μm photometry from the Spitzer Survey of Stellar Structure in Galaxies (S4G) to trace the stellar distribution in nearby disk galaxies (z ≈ 0) with total stellar masses 108.5 ≲ M∗/M⊙ ≲ 1011 and mid-IR Hubble types - 3 ≤ T ≤ 10. We characterize the stellar density profiles (Σ∗), the stellar contribution to the rotation curves (V3.6 μm), and the m = 2 Fourier amplitudes (A2) as a function of M∗ and T. We also describe the typical shapes and strengths of stellar bars in the S4G sample and link their properties to the total stellar mass and morphology of their host galaxy. Methods: For 1154 S4G galaxies with disk inclinations lower than 65°, we perform a Fourier decomposition and rescale their images to a common frame determined by the size in physical units, by their disk scalelength, and for 748 barred galaxies by both the length and orientation of their bars. We stack the resized density profiles and images to obtain statistically representative average stellar disks and bars in bins of M∗ and T. Based on the radial force profiles of individual galaxies we calculate the mean stellar contribution to the circular velocity. We also calculate average A2 profiles, where the radius is normalized to R25.5. Furthermore, we infer the gravitational potentials from the synthetic bars to

  15. Dust and gas in star-forming galaxies at z 3. Extending galaxy uniformity to 11.5 billion years (United States)

    Magdis, G. E.; Rigopoulou, D.; Daddi, E.; Bethermin, M.; Feruglio, C.; Sargent, M.; Dannerbauer, H.; Dickinson, M.; Elbaz, D.; Gomez Guijarro, C.; Huang, J.-S.; Toft, S.; Valentino, F.


    We present millimetre dust emission measurements of two Lyman-break galaxies at z 3 and construct for the first time fully sampled infrared spectral energy distributions (SEDs), from mid-IR to the Rayleigh-Jeans tail, of individually detected, unlensed, UV-selected, main sequence (MS) galaxies at z = 3. The SED modelling of the two sources confirms previous findings, based on stacked ensembles, of an increasing mean radiation field ⟨ U ⟩ with redshift, consistent with a rapidly decreasing gas metallicity in z> 2 galaxies. Complementing our study with CO[J = 3 → 2] emission line observations, we have measured the molecular gas mass reservoir (MH2) of the systems using three independent approaches: 1) CO line observations; 2) the dust to gas mass ratio vs. metallicity relation; and 3) a single band, dust emission flux on the Rayleigh-Jeans side of the SED. All techniques return consistent MH2 estimates within a factor of two or less, yielding gas depletion time-scales (τdep ≈ 0.35 Gyr) and gas-to-stellar mass ratios (MH2/M∗ ≈ 0.5-1) for our z 3 massive MS galaxies. The overall properties of our galaxies are consistent with trends and relations established at lower redshifts, extending the apparent uniformity of star-forming galaxies over the last 11.5 billion years. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  16. The DiskMass Survey. VI. Gas and stellar kinematics in spiral galaxies from PPak integral-field spectroscopy (United States)

    Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Bershady, Matthew A.; Schechtman-Rook, Andrew; Andersen, David R.; Swaters, Rob A.


    We present ionized-gas ([Oiii]λ5007 Å) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as many as three K-band disk scale lengths (hR). These data have been derived from PPak integral-field-unit spectroscopy from 4980-5370 Å observed at a mean resolution of λ/Δλ = 7700 (σinst = 17 km s-1). These data are a fundamental product of our survey and will be used in companion papers to, e.g., derive the detailed (baryonic+dark) mass budget of each galaxy in our sample. Our presentation provides a comprehensive description of the observing strategy and data reduction, including a robust measurement and removal of shift, scale, and rotation effects in the data due to instrumental flexure. Using an in-plane coordinate system determined by fitting circular-speed curves to our velocity fields, we derive azimuthally averaged rotation curves and line-of-sight velocity dispersion (σLOS) and luminosity profiles for both the stars and [Oiii]-emitting gas. Along with a clear presentation of the data, we demonstrate: (1) The [Oiii] and stellar rotation curves exhibit a clear signature of asymmetric drift with a rotation difference that is 11% of the maximum rotation speed of the galaxy disk, comparable to measurements in the solar neighborhood in the Milky Way. (2) The e-folding length of the stellar velocity dispersion (hσ) is 2hR on average, as expected for a disk with a constant scale height and mass-to-light ratio, with a scatter that is notably smaller for massive, high-surface-brightness disks in the most luminous galaxies. (3) At radii larger than 1.5hR, σLOS tends to decline slower than the best-fitting exponential function, which may be due to an increase in the disk mass-to-light ratio, disk flaring, or disk heating by the dark-matter halo. (4) A strong correlation exists between the central vertical stellar velocity dispersion of the disks (σz,0) and their circular rotational speed at 2.2hR (V2.2h

  17. Stellar disc truncations and extended haloes in face-on spiral galaxies (United States)

    Peters, S. P. C.; van der Kruit, P. C.; Knapen, J. H.; Trujillo, I.; Fliri, J.; Cisternas, M.; Kelvin, L. S.


    We use data from the IAC Stripe82 Legacy Project to study the surface photometry of 22 nearby, face-on to moderately inclined spiral galaxies. The reprocessed and combined Stripe 82 g',r' and I' images allow us to probe the galaxy down to 29-30 r'-magnitudes arcsec-2 and thus reach into the very faint outskirts of the galaxies. Truncations are found in three galaxies. An additional 15 galaxies are found to have an apparent extended stellar halo. Simulations show that the scattering of light from the inner galaxy by the point spread function (PSF) can produce faint structures resembling haloes, but this effect is insufficient to fully explain the observed haloes. The presence of these haloes and of truncations is mutually exclusive, and we argue that the presence of a stellar halo and/or light scattered by the PSF can hide truncations. Furthermore, we find that the onset of the stellar halo and the truncations scales tightly with galaxy size. Interestingly, the fraction of light does not correlate with dynamic mass. Nineteen galaxies are found to have breaks in their profiles, the radius of which also correlates with galaxy size.

  18. Unveiling the structure of barred galaxies at 3.6 μm with the Spitzer survey of stellar structure in galaxies (S{sup 4}G). I. Disk breaks

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    Kim, Taehyun; Lee, Myung Gyoon [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Gadotti, Dimitri A.; Muñoz-Mateos, Juan-Carlos [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Sheth, Kartik [National Radio Astronomy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Athanassoula, E.; Bosma, Albert [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Madore, Barry F.; Ho, Luis C. [The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Elmegreen, Bruce [IBM Research Division, T.J. Watson Research Center, Yorktown Heights, NY 10598 (United States); Knapen, Johan H.; Cisternas, Mauricio; Erroz-Ferrer, Santiago [Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Zaritsky, Dennis [University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721 (United States); Comerón, Sébastien; Laurikainen, Eija; Salo, Heikki [Division of Astronomy, Department of Physical Sciences, University of Oulu, Oulu, FIN-90014 (Finland); Holwerda, Benne [European Space Agency, ESTEC, Keplerlaan 1, 2200-AG, Noordwijk (Netherlands); Hinz, Joannah L. [MMTO, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Buta, Ron [Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487 (United States); and others


    We have performed two-dimensional multicomponent decomposition of 144 local barred spiral galaxies using 3.6 μm images from the Spitzer Survey of Stellar Structure in Galaxies. Our model fit includes up to four components (bulge, disk, bar, and a point source) and, most importantly, takes into account disk breaks. We find that ignoring the disk break and using a single disk scale length in the model fit for Type II (down-bending) disk galaxies can lead to differences of 40% in the disk scale length, 10% in bulge-to-total luminosity ratio (B/T), and 25% in bar-to-total luminosity ratios. We find that for galaxies with B/T ≥ 0.1, the break radius to bar radius, r {sub br}/R {sub bar}, varies between 1 and 3, but as a function of B/T the ratio remains roughly constant. This suggests that in bulge-dominated galaxies the disk break is likely related to the outer Lindblad resonance of the bar and thus moves outward as the bar grows. For galaxies with small bulges, B/T < 0.1, r {sub br}/R {sub bar} spans a wide range from 1 to 6. This suggests that the mechanism that produces the break in these galaxies may be different from that in galaxies with more massive bulges. Consistent with previous studies, we conclude that disk breaks in galaxies with small bulges may originate from bar resonances that may be also coupled with the spiral arms, or be related to star formation thresholds.

  19. Variations in the Star Formation Efficiency of the Dense Molecular Gas across the Disks of Star-forming Galaxies (United States)

    Usero, Antonio; Leroy, Adam K.; Walter, Fabian; Schruba, Andreas; García-Burillo, Santiago; Sandstrom, Karin; Bigiel, Frank; Brinks, Elias; Kramer, Carsten; Rosolowsky, Erik; Schuster, Karl-Friedrich; de Blok, W. J. G.


    We present a new survey of HCN(1-0) emission, a tracer of dense molecular gas, focused on the little-explored regime of normal star-forming galaxy disks. Combining HCN, CO, and infrared (IR) emission, we investigate the role of dense gas in star formation, finding systematic variations in both the apparent dense gas fraction (traced by the HCN-to-CO ratio) and the apparent star formation efficiency of dense gas (traced by the IR-to-HCN ratio). The latter may be unexpected, given the recent popularity of gas density threshold models to explain star formation scaling relations. Our survey used the IRAM 30 m telescope to observe HCN(1-0), CO(1-0), and several other emission lines across 29 nearby disk galaxies whose CO(2-1) emission has previously been mapped by the HERACLES survey. We detected HCN in 48 out of 62 observed positions. Because our observations achieve a typical resolution of ˜1.5 kpc and span a range of galaxies and galactocentric radii (56% lie at {r}{gal}\\gt 1 kpc), we are able to investigate the properties of the dense gas as a function of local conditions in a galaxy disk. We focus on how the ratios IR-to-CO, HCN-to-CO, and IR-to-HCN (observational cognates of the star formation efficiency, dense gas fraction, and dense gas star formation efficiency) depend on the stellar surface density, {{{Σ }}}{star}, and the molecular-to-atomic gas ratio, {{{Σ }}}{mol}/{{{Σ }}}{atom}. The HCN-to-CO ratio is low, often ˜1/30, and correlates tightly with both the molecular-to-atomic ratio and the stellar mass surface density across a range of 2.1 dex (factor of ≈125) in both parameters. Thus for the assumption of fixed CO-to-H2 and HCN-to-dense gas conversion factors, the dense gas fraction depends strongly on location in the disk, being higher in the high surface density, highly molecular parts of galaxies. At the same time, the IR-to-HCN ratio (closely related to the star formation efficiency of dense molecular gas) decreases systematically with these

  20. The Optical Structure of the Starburst Galaxy M82. I. Dynamics of the Disk and Inner-Wind (United States)

    Westmoquette, M. S.; Smith, L. J.; Gallagher, J. S., III; Trancho, G.; Bastian, N.; Konstantopoulos, I. S.


    rotation axis of the ionized emission-line gas is offset from the stellar rotation axis and the photometric major axis by ~12°, not only within the nuclear regions but over the whole inner 2 kpc of the disk. This attests to the perturbations introduced from M82's past interactions within the M81 group. Finally, finding a turn-over in the stellar and ionized gas rotation curves on both sides of the galaxy indicates that our sight line, in places, extends at least half way through disk, and conflicts with the high levels of obscuration usually associated with the nuclear regions of M82. Based on observations with the Gemini and WIYN telescopes.

  1. Disk galaxy scaling relations at intermediate redshifts. I. The Tully-Fisher and velocity-size relations (United States)

    Böhm, Asmus; Ziegler, Bodo L.


    Aims: Galaxy scaling relations such as the Tully-Fisher relation (between the maximum rotation velocity Vmax and luminosity) and the velocity-size relation (between Vmax and the disk scale length) are powerful tools to quantify the evolution of disk galaxies with cosmic time. Methods: We took spatially resolved slit spectra of 261 field disk galaxies at redshifts up to z ≈ 1 using the FORS instruments of the ESO Very Large Telescope. The targets were selected from the FORS Deep Field and William Herschel Deep Field. Our spectroscopy was complemented with HST/ACS imaging in the F814W filter. We analyzed the ionized gas kinematics by extracting rotation curves from the two-dimensional spectra. Taking into account all geometrical, observational, and instrumental effects, these rotation curves were used to derive the intrinsic Vmax. Results: Neglecting galaxies with disturbed kinematics or insufficient spatial rotation curve extent, Vmax was reliably determined for 124 galaxies covering redshifts 0.05 < z < 0.97. This is one of the largest kinematic samples of distant disk galaxies to date. We compared this data set to the local B-band Tully-Fisher relation and the local velocity-size relation. The scatter in both scaling relations is a factor of ~2 larger at z ≈ 0.5 than at z ≈ 0. The deviations of individual distant galaxies from the local Tully-Fisher relation are systematic in the sense that the galaxies are increasingly overluminous toward higher redshifts, corresponding to an overluminosity ΔMB = -(1.2 ± 0.5) mag at z = 1. This luminosity evolution at given Vmax is probably driven by younger stellar populations of distant galaxies with respect to their local counterparts, potentially combined with modest changes in dark matter mass fractions. The analysis of the velocity-size relation reveals that disk galaxies of a given Vmax have grown in size by a factor of ~1.5 over the past ~8 Gyr, most likely through accretion of cold gas and/or small satellites

  2. The nuclear properties and extended morphologies of powerful radio galaxies: the roles of host galaxy and environment (United States)

    Miraghaei, H.; Best, P. N.


    Powerful radio Galaxies exist as either compact or extended sources, with the extended sources traditionally classified by their radio morphologies as Fanaroff-Riley (FR) type I and II sources. FRI/FRII and compact radio galaxies have also been classified by their optical spectra into two different types: high excitation (HERG; quasar-mode) and low excitation (LERG; jet-mode). We present a catalogue of visual morphologies for a complete sample of >1000 1.4-GHz-selected extended radio sources from the Sloan Digital Sky Survey. We study the environment and host galaxy properties of FRI/FRII and compact sources, classified into HERG/LERG types, in order to separate and distinguish the factors that drive the radio morphological variations from those responsible for the spectral properties. Comparing FRI LERGs with FRII LERGs at fixed stellar mass and radio luminosity, we show that FRIs typically reside in richer environments and are hosted by smaller galaxies with higher mass surface density; this is consistent with extrinsic effects of jet disruption driving the Fanaroff-Riley (FR) dichotomy. Using matched samples of HERGs and LERGs, we show that HERG host galaxies are more frequently star forming, with more evidence for disc-like structure than LERGs, in accordance with currently favoured models of fundamentally different fuelling mechanisms. Comparing FRI/FRII LERGs with compact LERGs, we find the primary difference is that compact objects typically harbour less massive black holes. This suggests that lower mass black holes may be less efficient at launching stable radio jets, or do so for shorter times. Finally, we investigate rarer sub-classes: wide-angle-tailed, head-tail, FR-hybrid and double-double sources.


    Energy Technology Data Exchange (ETDEWEB)

    Andersen, David R. [NRC Herzberg Institute of Astrophysics, 5071 W Saanich Road, Victoria, BC V9E 2E7 (Canada); Bershady, Matthew A., E-mail:, E-mail: [Department of Astronomy, University of Wisconsin, 475 N Charter Street, Madison, WI 53706 (United States)


    Using the integral field unit DensePak on the WIYN 3.5 m telescope we have obtained H{alpha} velocity fields of 39 nearly face-on disks at echelle resolutions. High-quality, uniform kinematic data and a new modeling technique enabled us to derive accurate and precise kinematic inclinations with mean i{sub kin} = 23 Degree-Sign for 90% of these galaxies. Modeling the kinematic data as single, inclined disks in circular rotation improves upon the traditional tilted-ring method. We measure kinematic inclinations with a precision in sin i of 25% at 20 Degree-Sign and 6% at 30 Degree-Sign . Kinematic inclinations are consistent with photometric and inverse Tully-Fisher inclinations when the sample is culled of galaxies with kinematic asymmetries, for which we give two specific prescriptions. Kinematic inclinations can therefore be used in statistical ''face-on'' Tully-Fisher studies. A weighted combination of multiple, independent inclination measurements yield the most precise and accurate inclination. Combining inverse Tully-Fisher inclinations with kinematic inclinations yields joint probability inclinations with a precision in sin i of 10% at 15 Degree-Sign and 5% at 30 Degree-Sign . This level of precision makes accurate mass decompositions of galaxies possible even at low inclination. We find scaling relations between rotation speed and disk-scale length identical to results from more inclined samples. We also observe the trend of more steeply rising rotation curves with increased rotation speed and light concentration. This trend appears to be uncorrelated with disk surface brightness.

  4. Accretion Disk Spectra of the Ultra-Luminous X-Ray Sources in Nearby Spiral Galaxies and Galactic Superluminal Jet Sources

    Energy Technology Data Exchange (ETDEWEB)

    Mizuno, T


    Ultra-luminous Compact X-ray Sources (ULXs) in nearby spiral galaxies and Galactic superluminal jet sources share the common spectral characteristic that they have unusually high disk temperatures which cannot be explained in the framework of the standard optically thick accretion disk in the Schwarzschild metric. On the other hand, the standard accretion disk around the Kerr black hole might explain the observed high disk temperature, as the inner radius of the Kerr disk gets smaller and the disk temperature can be consequently higher. However, we point out that the observable Kerr disk spectra becomes significantly harder than Schwarzschild disk spectra only when the disk is highly inclined. This is because the emission from the innermost part of the accretion disk is Doppler-boosted for an edge-on Kerr disk, while hardly seen for a face-on disk. The Galactic superluminal jet sources are known to be highly inclined systems, thus their energy spectra may be explained with the standard Kerr disk with known black hole masses. For ULXs, on the other hand, the standard Kerr disk model seems implausible, since it is highly unlikely that their accretion disks are preferentially inclined, and, if edge-on Kerr disk model is applied, the black hole mass becomes unreasonably large (> 300 M{sub solar}). Instead, the slim disk (advection dominated optically thick disk) model is likely to explain the observed super-Eddington luminosities, hard energy spectra, and spectral variations of ULXs. We suggest that ULXs are accreting black holes with a few tens of solar mass, which is not unexpected from the standard stellar evolution scenario, and that their X-ray emission is from the slim disk shining at super-Eddington luminosities.

  5. Accretion Disk Spectra of the Ultra-luminous X-ray Sources in Nearby Spiral Galaxies and Galactic Superluminal Jet Sources (United States)

    White, Nicholas E. (Technical Monitor); Ebisawa, Ken; Zycki, Piotr; Kubota, Aya; Mizuno, Tsunefumi; Watarai, Ken-ya


    Ultra-luminous Compact X-ray Sources (ULXs) in nearby spiral galaxies and Galactic superluminal jet sources share the common spectral characteristic that they have unusually high disk temperatures which cannot be explained in the framework of the standard optically thick accretion disk in the Schwarzschild metric. On the other hand, the standard accretion disk around the Kerr black hole might explain the observed high disk temperature, as the inner radius of the Kerr disk gets smaller and the disk temperature can be consequently higher. However, we point out that the observable Kerr disk spectra becomes significantly harder than Schwarzschild disk spectra only when the disk is highly inclined. This is because the emission from the innermost part of the accretion disk is Doppler-boosted for an edge-on Kerr disk, while hardly seen for a face-on disk. The Galactic superluminal jet sources are known to be highly inclined systems, thus their energy spectra may be explained with the standard Kerr disk with known black hole masses. For ULXs, on the other hand, the standard Kerr disk model seems implausible, since it is highly unlikely that their accretion disks are preferentially inclined, and, if edge-on Kerr disk model is applied, the black hole mass becomes unreasonably large (greater than or approximately equal to 300 Solar Mass). Instead, the slim disk (advection dominated optically thick disk) model is likely to explain the observed super- Eddington luminosities, hard energy spectra, and spectral variations of ULXs. We suggest that ULXs are accreting black holes with a few tens of solar mass, which is not unexpected from the standard stellar evolution scenario, and their X-ray emission is from the slim disk shining at super-Eddington luminosities.

  6. Simulating the Growth of a Disk Galaxy and its Supermassive Black Hole in a Cosmological Simulating the Growth of a Disk Galaxy and its Supermassive Black Hole in a Cosmological Context

    Energy Technology Data Exchange (ETDEWEB)

    Levine, Robyn Deborah [Univ. of Colorado, Boulder, CO (United States)


    Supermassive black holes (SMBHs) are ubiquitous in the centers of galaxies. Their formation and subsequent evolution is inextricably linked to that of their host galaxies, and the study of galaxy formation is incomplete without the inclusion of SMBHs. The present work seeks to understand the growth and evolution of SMBHs through their interaction with the host galaxy and its environment. In the first part of the thesis (Chap. 2 and 3), we combine a simple semi-analytic model of outflows from active galactic nuclei (AGN) with a simulated dark matter density distribution to study the impact of SMBH feedback on cosmological scales. We find that constraints can be placed on the kinetic efficiency of such feedback using observations of the filling fraction of the Lyα forest. We also find that AGN feedback is energetic enough to redistribute baryons over cosmological distances, having potentially significant effects on the interpretation of cosmological data which are sensitive to the total matter density distribution (e.g. weak lensing). However, truly assessing the impact of AGN feedback in the universe necessitates large-dynamic range simulations with extensive treatment of baryonic physics to first model the fueling of SMBHs. In the second part of the thesis (Chap. 4-6) we use a hydrodynamic adaptive mesh refinement simulation to follow the growth and evolution of a typical disk galaxy hosting a SMBH, in a cosmological context. The simulation covers a dynamical range of 10 million allowing us to study the transport of matter and angular momentum from super-galactic scales all the way down to the outer edge of the accretion disk around the SMBH. Focusing our attention on the central few hundred parsecs of the galaxy, we find the presence of a cold, self-gravitating, molecular gas disk which is globally unstable. The global instabilities drive super-sonic turbulence, which maintains local stability and allows gas to fuel a SMBH without first fragmenting completely

  7. A New Family of Analytical Potential-Density Pairs for Galaxy Models Compound by Thin Disks and Spheroidal Halos (United States)

    Santos, Y. F.; Pimentel, O. M.; González, G. A.


    A new family of three-dimensional Newtonian models for galaxies is constructed. The models describe a thin disk and a matter halo, whose gravitational potentials satisfies the equation (2) presented in Gonzalez & Pimentel (2016, Phys. Rev. D, 93, 044034), and therefore, they satisfy the energy conditions for a gravitational system. The expressions for the potential of the disk and the halo are obtained by applying the "displace, cut, and reflect" method to the solution of the Laplace equation in cylindrical coordinates. Analytical expressions that describe the rotation curves and the mass distributions in the disk and in the halo are computed for the first three models of the family of solutions. It is shown that the mass densities of the disks and the haloes present a maximum at the center of the system and go to zero at infinity. Finally, for some values of the free parameters, the obtained rotation curves present a flat region for larger values of the radial coordinate. The model was obtained considering the total gravitational potential, which satisfies the equation (2) imposed by Gonzalez & Pimentel (2016). The potential generated by the spheroidal halo of matter is constructed considering a multipolar expansion, expressed in cylindrical coordinates. As this solution of the Laplace equation a substitution is done so that the Laplacian is nonzero, the z coordinate (Kuzmin, 1956, AZh, 33; Toomre, 1963, ApJ, 138, 385). So the new potential satisfies Poisson equation and represents the distribution of three-dimensional material. From the gravitational potential analytical expressions were derived for the surface density of the disk, halo density of matter and from the rotation was derived. We found that the surface densities of the disks present a maximum at the center, vanishing at infinity; and the halo density is maximum at the disk surface, also vanishing at infinity. For some values of the parameters, the derived rotation curves present a flat region for

  8. Kiloparsec-scale Simulations of Star Formation in Disk Galaxies. IV. Regulation of Galactic Star Formation Rates by Stellar Feedback

    Energy Technology Data Exchange (ETDEWEB)

    Butler, Michael J. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Tan, Jonathan C. [Departments of Astronomy and Physics, University of Florida, Gainesville, FL 32611 (United States); Teyssier, Romain; Nickerson, Sarah [Institute for Computational Science, University of Zurich, 8049 Zurich (Switzerland); Rosdahl, Joakim [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands); Van Loo, Sven [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom)


    Star formation from the interstellar medium of galactic disks is a basic process controlling the evolution of galaxies. Understanding the star formation rate (SFR) in a local patch of a disk with a given gas mass is thus an important challenge for theoretical models. Here we simulate a kiloparsec region of a disk, following the evolution of self-gravitating molecular clouds down to subparsec scales, as they form stars that then inject feedback energy by dissociating and ionizing UV photons and supernova explosions. We assess the relative importance of each feedback mechanism. We find that H{sub 2}-dissociating feedback results in the largest absolute reduction in star formation compared to the run with no feedback. Subsequently adding photoionization feedback produces a more modest reduction. Our fiducial models that combine all three feedback mechanisms yield, without fine-tuning, SFRs that are in excellent agreement with observations, with H{sub 2}-dissociating photons playing a crucial role. Models that only include supernova feedback—a common method in galaxy evolution simulations—settle to similar SFRs, but with very different temperatures and chemical states of the gas, and with very different spatial distributions of young stars.

  9. Aperture corrections for disk galaxy properties derived from the CALIFA survey. Balmer emission lines in spiral galaxies (United States)

    Iglesias-Páramo, J.; Vílchez, J. M.; Galbany, L.; Sánchez, S. F.; Rosales-Ortega, F. F.; Mast, D.; García-Benito, R.; Husemann, B.; Aguerri, J. A. L.; Alves, J.; Bekeraité, S.; Bland-Hawthorn, J.; Catalán-Torrecilla, C.; de Amorim, A. L.; de Lorenzo-Cáceres, A.; Ellis, S.; Falcón-Barroso, J.; Flores, H.; Florido, E.; Gallazzi, A.; Gomes, J. M.; González Delgado, R. M.; Haines, T.; Hernández-Fernández, J. D.; Kehrig, C.; López-Sánchez, A. R.; Lyubenova, M.; Marino, R. A.; Mollá, M.; Monreal-Ibero, A.; Mourão, A.; Papaderos, P.; Rodrigues, M.; Sánchez-Blázquez, P.; Spekkens, K.; Stanishev, V.; van de Ven, G.; Walcher, C. J.; Wisotzki, L.; Zibetti, S.; Ziegler, B.


    This work investigates the effect of the aperture size on derived galaxy properties for which we have spatially-resolved optical spectra. We focus on some indicators of star formation activity and dust attenuation for spiral galaxies that have been widely used in previous work on galaxy evolution. We investigated 104 spiral galaxies from the CALIFA survey for which 2D spectroscopy with complete spatial coverage is available. From the 3D cubes we derived growth curves of the most conspicuous Balmer emission lines (Hα, Hβ) for circular apertures of different radii centered at the galaxy's nucleus after removing the underlying stellar continuum. We find that the Hα flux (f(Hα)) growth curve follows a well-defined sequence with aperture radius that shows a low dispersion around the median value. From this analysis, we derived aperture corrections for galaxies in different magnitude and redshift intervals. Once stellar absorption is properly accounted for, the f(Hα)/f(Hβ) ratio growth curve shows a smooth decline, pointing toward the absence of differential dust attenuation as a function of radius. Aperture corrections as a function of the radius are provided in the interval [0.3, 2.5]R50. Finally, the Hα equivalent-width (EW(Hα)) growth curve increases with the size of the aperture and shows a very high dispersion for small apertures. This prevents us from using reliable aperture corrections for this quantity. In addition, this result suggests that separating star-forming and quiescent galaxies based on observed EW(Hα) through small apertures will probably result in low EW(Hα) star-forming galaxies begin classified as quiescent.

  10. Chandra survey of nearby highly inclined disk galaxies - IV. New insights into the working of stellar feedback (United States)

    Wang, Q. Daniel; Li, Jiangtao; Jiang, Xiaochuan; Fang, Taotao


    Galaxy evolution is regulated by the interplay between galactic discs and their surrounding medium. We study this interplay by examining how the galactic coronal emission efficiency of stellar feedback depends on the (surface and specific) star formation rates (SFRs) and other parameters for a sample of 52 Chandra-observed nearby highly inclined disc galaxies. We first measure the star-forming galactic disc sizes, as well as the SFRs of these galaxies, using data from the Wide-Field Infrared Survey Explorer, and then show that (1) the specific 0.5-2 keV luminosity of the coronal emission correlates with the specific SFR in a sub-linear fashion: on average, LX/LK∝(SFR/M*)Γ with Γ = 0.29 ± 0.12; (2) the efficiency of the emission LX/SFR decreases with increasing surface SFR (ISFR; Γ = -0.44 ± 0.12); and (3) the characteristic temperature of the X-ray-emitting plasma weakly correlates with ISFR (Γ = 0.08 ± 0.04). These results, somewhat surprising and anti-intuitive, suggest that (i) the linear correlation between LX and SFR, as commonly presented, is largely due to the correlation of these two parameters with galaxy mass; (ii) much of the mechanical energy from stellar feedback likely drives global outflows with little X-ray cooling and with a mass-loading efficiency decreasing fast with increasing ISFR (Γ ≲ -0.5); (iii) these outflows heat and inflate the medium around the galactic disks of massive galaxies, reducing its radiative cooling rate, whereas for relatively low-mass galaxies, the energy in the outflows is probably dissipated in regions far away from the galactic discs.

  11. The Westerbork HI survey of spiral and irregular galaxies - III. HI observations of early-type disk galaxies

    National Research Council Canada - National Science Library

    Noordermeer, E; van der Hulst, JM; Sancisi, R; Swaters, RA; van Albada, TS


    .... properties of the galaxies in our sample span a large range; the average values of M-HI/L-B and D-HI/D-25 are comparable to the ones found in later-type spirals, but the dispersions around the mean are larger...

  12. The outer disks of galaxies : "To be or not to be truncated?"

    NARCIS (Netherlands)

    Pohlen, M.; Trujillo, I.


    Abstract: We have in recent years come to view the outer parts of galaxies as having vital clues about their formation and evolution. Here, we would like to briefly present our results from a complete sample of nearby, late-type, spiral galaxies, using data from the SDSS survey, especially focused

  13. Detection of Lyman/alpha emission from a DLA galaxy

    DEFF Research Database (Denmark)

    Moller, P.; Fynbo, Johan Peter Uldall; Fall, S.M



  14. Regrowth of stellar disks in mature galaxies: The two component nature of NGC 7217 revisited with VIRUS-W† ⋄ (United States)

    Fabricius, Maximilian H.; Coccato, Lodovico; Bender, Ralf; Drory, Niv; Gössl, Claus; Landriau, Martin; Saglia, Roberto P.; Thomas, Jens; Williams, Michael J.


    We have obtained high spectral resolution (R ~ 9000), integral field observations of the three spiral galaxies NGC 3521, NGC 7217 and NGC 7331 using the new fiber-based Integral Field Unit instrument VIRUS-W at the 2.7 m telescope of the McDonald Observatory in Texas. Our data allow us to revisit previous claims of counter rotation in these objects. A detailed kinematic decomposition of NGC 7217 shows that no counter rotating stellar component is present. We find that NGC 7217 hosts a low dispersion, rotating disk that is embedded in a high velocity dispersion stellar halo or bulge that is co-rotating with the disk. Due to the very different velocity dispersions (~ 20 km s-1 vs. 150 km s-1) , we are further able to perform a Lick index analysis on both components separately which indicates that the two stellar populations are clearly separated in (Mgb,) space. The velocities and dispersions of the faster component are very similar to those of the interstellar gas as measured from the [O iii] emission. Morphological evidence of active star formation in this component further suggests that NGC 7217 may be in the process of (re)growing a disk inside a more massive and higher dispersion stellar halo.

  15. A Two-Disk Extended Jeffcott Rotor Model Distinguishing a Shaft Crack from Other Rotating Asymmetries

    Directory of Open Access Journals (Sweden)

    Xi Wu


    Full Text Available A mathematical model of a cracked rotor and an asymmetric rotor with two disks representing a turbine and a generator is utilized to study the vibrations due to imbalance and side load. Nonlinearities typically related with a “breathing” crack are included using a Mayes steering function. Numerical simulations demonstrate how the variations of rotor parameters affect the vibration response and the effect of coupling between torsional and lateral modes. Bode, spectrum, and orbit plots are used to show the differences between the vibration signatures associated with cracked shafts versus asymmetric shafts. Results show how nonlinear lateral-torsional coupling shifts the resonance peaks in the torsional vibration response for cracked shafts and asymmetric rotors. The resonance peaks shift depending on the ratio of the lateral-to-torsional natural frequencies with the peak responses occurring at noninteger values of the lateral natural frequency. When the general nonlinear models used in this study are constrained to reduce to linear torsional vibration, the peak responses occur at commonly reported integer ratios. Full spectrum analyses of the X and Y vibrations reveal distinct vibration characteristics of both cracked and asymmetric rotors including reverse vibration components. Critical speeds and vibration orders predicted using the models presented herein include and extend diagnostic indicators commonly reported.

  16. De-coding the Neutral Hydrogen (21cm) Line Profiles of Disk galaxies (United States)

    Moak, Sandy; Madore, Barry; Khatami, David


    Neutral hydrogen is the most abundant element in the interstellar medium, and it has long lent astronomers insight into galaxy structure, galactic interactions, and even dark matter prevalence. It is necessary to implement a detailed coding scheme that characterizes the 21-cm HI line profiles which exist in abundance throughout literature. We have utilized a new computer simulation program that exposes the internal architecture of a galaxy by way of mapping the one-dimensional line profile on to the three-dimensional parameters of a given galaxy. We have created a naming system to classify HI line profiles, which represents a kinematic description of the galaxy simply by considering its classification within the coding scheme.

  17. The structure of galactic disks - Studying late-type spiral galaxies using SDSS

    National Research Council Canada - National Science Library

    Pohlen, M; Trujillo, I


    Using imaging data from the SDSS survey, we present the g' and r' radial stellar light distribution of a complete sample of similar to 90 face-on to intermediate inclined, nearby, late-type (Sb-Sdm) spiral galaxies...


    Energy Technology Data Exchange (ETDEWEB)

    Martínez-García, Eric E. [Cerrada del Rey 40-A, Chimalcoyoc Tlalpan, Ciudad de México, C.P. 14630, México (Mexico); González-Lópezlira, Rosa A.; Bruzual A, Gustavo [Instituto de Radioastronomía y Astrofísica, UNAM, Campus Morelia, Michoacán, C.P. 58089, México (Mexico); Magris C, Gladis, E-mail: [Centro de Investigaciones de Astronomía, Apartado Postal 264, Mérida 5101-A (Venezuela, Bolivarian Republic of)


    Stellar masses of galaxies are frequently obtained by fitting stellar population synthesis models to galaxy photometry or spectra. The state of the art method resolves spatial structures within a galaxy to assess the total stellar mass content. In comparison to unresolved studies, resolved methods yield, on average, higher fractions of stellar mass for galaxies. In this work we improve the current method in order to mitigate a bias related to the resolved spatial distribution derived for the mass. The bias consists in an apparent filamentary mass distribution and a spatial coincidence between mass structures and dust lanes near spiral arms. The improved method is based on iterative Bayesian marginalization, through a new algorithm we have named Bayesian Successive Priors (BSP). We have applied BSP to M51 and to a pilot sample of 90 spiral galaxies from the Ohio State University Bright Spiral Galaxy Survey. By quantitatively comparing both methods, we find that the average fraction of stellar mass missed by unresolved studies is only half what previously thought. In contrast with the previous method, the output BSP mass maps bear a better resemblance to near-infrared images.

  19. Removing Biases in Resolved Stellar Mass Maps of Galaxy Disks through Successive Bayesian Marginalization (United States)

    Martínez-García, Eric E.; González-Lópezlira, Rosa A.; Magris C., Gladis; Bruzual A., Gustavo


    Stellar masses of galaxies are frequently obtained by fitting stellar population synthesis models to galaxy photometry or spectra. The state of the art method resolves spatial structures within a galaxy to assess the total stellar mass content. In comparison to unresolved studies, resolved methods yield, on average, higher fractions of stellar mass for galaxies. In this work we improve the current method in order to mitigate a bias related to the resolved spatial distribution derived for the mass. The bias consists in an apparent filamentary mass distribution and a spatial coincidence between mass structures and dust lanes near spiral arms. The improved method is based on iterative Bayesian marginalization, through a new algorithm we have named Bayesian Successive Priors (BSP). We have applied BSP to M51 and to a pilot sample of 90 spiral galaxies from the Ohio State University Bright Spiral Galaxy Survey. By quantitatively comparing both methods, we find that the average fraction of stellar mass missed by unresolved studies is only half what previously thought. In contrast with the previous method, the output BSP mass maps bear a better resemblance to near-infrared images.

  20. The evolution of the oxygen abundance radial gradient in the Milky Way Galaxy disk (United States)

    Mollá, Mercedes; Cavichia, Oscar; Costa, Roberto D. D.; Maciel, Walter J.; Gibson, Brad; Díaz, Angeles I.


    We review the state of our chemical evolution models for spiral and low mass galaxies. We analyze the consequences of using different stellar yields, infall rate laws and star formation prescriptions in the time/redshift evolution of the radial distributions of abundances, and other quantities as star formation rate or gas densities, in the Milky Way Galaxy; In particular we will study the evolution of the oxygen abundance radial gradient analyzing its relation with the ratio SFR/infall. We also compare the results with our old chemical evolution models, cosmological simulations and with the existing data, mainly with the planetary nebulae abundances.

  1. Unveiling the sources of disk heating in spiral galaxies with the CALIFA survey

    NARCIS (Netherlands)

    Pinna, F.; Falcón-Barroso, J.; Martig, M.; van de Ven, G.; Lyubenova, M.; Leaman, R.

    The stellar velocity ellipsoid (SVE) quantifies the amount of velocity dispersion in the vertical, radial and azimuthal directions. Since different disk heating mechanisms (e.g. spiral arms, giant molecular clouds, mergers, etc) affect these components differently, the SVE can constrain the sources

  2. Disk-galaxy density distribution from orbital speeds using Newton's law


    Nicholson, Kenneth F.


    Given the dimensions (including thickness) of an axisymmetric galaxy, Newton's law is used in integral form to find the density distributions required to match a wide range of orbital speed profiles. Newton's law is not modified and no dark matter halos are required. The speed distributiions can have extreme shapes if they are reasonably smooth. Several examples are given.

  3. Disk-galaxy density distribution from orbital speeds using Newton's law, version 1.1


    Nicholson, Kenneth F.


    Given the dimensions(including thickness) of an axisymmetric galaxy, Newton's law is used in integral form to find the density distributions required to match a wide range of orbital speed profiles. Newton's law is not modified and no dark-matter halos are required. The speed distributions can have extreme shapes if they are reasonably smooth. Several examples are given.

  4. Hydrostatic models for the rotation of extra-planar gas in disk galaxies

    NARCIS (Netherlands)

    Barnabe, M.; Ciotti, L.; Fraternali, F.; Sancisi, R.


    Published in: Phys. Lett., B 624 (2005) 186-194 Abstract: We show that fluid stationary models are able to reproduce the observed, negative vertical gradient of the rotation velocity of the extra-planar gas in spiral galaxies. We have constructed models based on the simple condition that the

  5. The structure of galactic disks - Studying late-type spiral galaxies using SDSS

    NARCIS (Netherlands)

    Pohlen, M.; Trujillo, I.

    Using imaging data from the SDSS survey, we present the g' and r' radial stellar light distribution of a complete sample of similar to 90 face-on to intermediate inclined, nearby, late-type (Sb-Sdm) spiral galaxies. The surface brightness profiles are reliable (1s uncertainty less than 0.2 mag) down

  6. Local anti-correlation between star-formation rate and gas-phase metallicity in disk galaxies (United States)

    Sánchez Almeida, J.; Caon, N.; Muñoz-Tuñón, C.; Filho, M.; Cerviño, M.


    Using a representative sample of 14 star-forming dwarf galaxies in the local Universe, we show the existence of a spaxel-to-spaxel anti-correlation between the index N2 ≡ log ([NII]λ6583/Hα) and the Hα flux. These two quantities are commonly employed as proxies for gas-phase metallicity and star formation rate (SFR), respectively. Thus, the observed N2 to Hα relation may reflect the existence of an anti-correlation between the metallicity of the gas forming stars and the SFR it induces. Such an anti-correlation is to be expected if variable external metal-poor gas fuels the star-formation process. Alternatively, it can result from the contamination of the star-forming gas by stellar winds and SNe, provided that intense outflows drive most of the metals out of the star-forming regions. We also explore the possibility that the observed anti-correlation is due to variations in the physical conditions of the emitting gas, other than metallicity. Using alternative methods to compute metallicity, as well as previous observations of HII regions and photoionization models, we conclude that this possibility is unlikely. The radial gradient of metallicity characterizing disk galaxies does not produce the correlation either.

  7. Consequences of Relativistic Neutron Outflow beyond the Accretion Disks of Active Galaxies (United States)

    Ekejiuba, I. E.; Okeke, P. N.


    Three channels of relativistic electron injection in the jets of extragalactic radio sources (EGRSs) are discussed. With the assumption that an active galactic nucleus (AGN) is powered by a spinning supermassive black hole of mass ~ 10(8) M_⊙ which sits at the center of the nucleus and ingests matter and energy through an accretion disk, a model for extracting relativistic neutrons from the AGN is forged. In this model, the inelastic proton--proton and proton--photon interactions within the accretion disk, of relativistic protons with background thermal protons and photons, respectively, produce copious amounts of relativistic neutrons. These neutrons travel ballistically for ~ 10(3gamma_n ) seconds and escape from the disk before they decay. The secondary particles produced from the neutron decays then interact with the ambient magnetic field and/or other particles to produce the radio emissions observed in the jets of EGRSs. IEE acknowledges the support of the World Bank and the Federal University of Technology, Yola, Nigeria as well as the hospitality of Georgia State University.

  8. The Extended Northern ROSAT Galaxy Cluster Survey (NORAS II). I. Survey Construction and First Results

    Energy Technology Data Exchange (ETDEWEB)

    Böhringer, Hans; Chon, Gayoung; Trümper, Joachim [Max-Planck-Institut für Extraterrestrische Physik, D-85748 Garching (Germany); Retzlaff, Jörg [ESO, D-85748 Garching (Germany); Meisenheimer, Klaus [Max-Planck-Institut für Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Schartel, Norbert [ESAC, Camino Bajo del Castillo, Villanueva de la Cañada, E-28692 Madrid (Spain)


    As the largest, clearly defined building blocks of our universe, galaxy clusters are interesting astrophysical laboratories and important probes for cosmology. X-ray surveys for galaxy clusters provide one of the best ways to characterize the population of galaxy clusters. We provide a description of the construction of the NORAS II galaxy cluster survey based on X-ray data from the northern part of the ROSAT All-Sky Survey. NORAS II extends the NORAS survey down to a flux limit of 1.8 × 10{sup −12} erg s{sup −1} cm{sup −2} (0.1–2.4 keV), increasing the sample size by about a factor of two. The NORAS II cluster survey now reaches the same quality and depth as its counterpart, the southern REFLEX II survey, allowing us to combine the two complementary surveys. The paper provides information on the determination of the cluster X-ray parameters, the identification process of the X-ray sources, the statistics of the survey, and the construction of the survey selection function, which we provide in numerical format. Currently NORAS II contains 860 clusters with a median redshift of z  = 0.102. We provide a number of statistical functions, including the log N –log S and the X-ray luminosity function and compare these to the results from the complementary REFLEX II survey. Using the NORAS II sample to constrain the cosmological parameters, σ {sub 8} and Ω{sub m}, yields results perfectly consistent with those of REFLEX II. Overall, the results show that the two hemisphere samples, NORAS II and REFLEX II, can be combined without problems into an all-sky sample, just excluding the zone of avoidance.

  9. Radio Galaxy Zoo: Compact and extended radio source classification with deep learning (United States)

    Lukic, V.; Brüggen, M.; Banfield, J. K.; Wong, O. I.; Rudnick, L.; Norris, R. P.; Simmons, B.


    Machine learning techniques have been increasingly useful in astronomical applications over the last few years, for example in the morphological classification of galaxies. Convolutional neural networks have proven to be highly effective in classifying objects in image data. The current work aims to establish when multiple components are present, in the astronomical context of synthesis imaging observations of radio sources. To this effect, we design a convolutional neural network to differentiate between different morphology classes using sources from the Radio Galaxy Zoo (RGZ) citizen science project. In this first step, we focus on exploring the factors that affect the performance of such neural networks, such as the amount of training data, number and nature of layers and the hyperparameters. We begin with a simple experiment in which we only differentiate between two extreme morphologies, using compact and multiple component extended sources. We found that a three convolutional layer architecture yielded very good results, achieving a classification accuracy of 97.4% on a test data set. The same architecture was then tested on a four-class problem where we let the network classify sources into compact and three classes of extended sources, achieving a test accuracy of 93.5%. The best-performing convolutional neural network setup has been verified against RGZ Data Release 1 where a final test accuracy of 94.8% was obtained, using both original and augmented images. The use of sigma clipping does not offer a significant benefit overall, except in cases with a small number of training images.

  10. Near-infrared and optical broadband surface photometry of 86 face-on disk dominated galaxies .4. Using color profiles to study stellar and dust content of galaxies

    NARCIS (Netherlands)

    deJong, RS

    The stellar and dust content of spiral galaxies as function of radius has been investigated using near-infrared and optical broadband surface photometry of 86 face-on spiral galaxies. Colors of galaxies correlate with the azimuthally averaged local surface brightness both within and among galaxies,

  11. Companions of Bright Barred Shapley Ames Galaxies


    Garcia-Barreto, J. Antonio; Carrillo, Rene; Vera-Villamizar, Nelson


    Companion galaxy environment for a subset of 78 bright and nearby barred galaxies from the Shapley Ames Catalog is presented. Among spiral barred galaxies there are Seyfert galaxies, galaxies with circumnuclear structures, galaxies not associated with any large scale galaxy cloud structure, galaxies with peculiar disk morphology (crooked arms) and galaxies with normal disk morphology; the list includes all Hubble types. The companion galaxy list includes number of companion galaxies within 20...

  12. The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: final emission line galaxy target selection (United States)

    Raichoor, A.; Comparat, J.; Delubac, T.; Kneib, J.-P.; Yèche, Ch; Dawson, K. S.; Percival, W. J.; Dey, A.; Lang, D.; Schlegel, D. J.; Gorgoni, C.; Bautista, J.; Brownstein, J. R.; Mariappan, V.; Seo, H.-J.; Tinker, J. L.; Ross, A. J.; Wang, Y.; Zhao, G.-B.; Moustakas, J.; Palanque-Delabrouille, N.; Jullo, E.; Newmann, J. A.; Prada, F.; Zhu, G. B.


    We describe the algorithm used to select the emission line galaxy (ELG) sample at z ˜ 0.85 for the extended Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey IV, using photometric data from the DECam Legacy Survey. Our selection is based on a selection box in the g - r versus r - z colour-colour space and a cut on the g-band magnitude, to favour galaxies in the desired redshift range with strong [O II] emission. It provides a target density of 200 deg-2 on the North Galactic Cap and of 240 deg-2 on the South Galactic Cap (SGC), where we use a larger selection box because of deeper imaging. We demonstrate that this selection passes the extended Baryon Oscillation Spectroscopic Survey requirements in terms of homogeneity. About 50 000 ELGs have been observed since the observations have started in 2016, September. These roughly match the expected redshift distribution, though the measured efficiency is slightly lower than expected. The efficiency can be increased by enlarging the redshift range and with incoming pipeline improvement. The cosmological forecast based on these first data predict σ _{D_V}/D_V = 0.023, in agreement with previous forecasts. Lastly, we present the stellar population properties of the ELG SGC sample. Once observations are completed, this sample will be suited to provide a cosmological analysis at z ˜ 0.85, and will pave the way for the next decade of massive spectroscopic cosmological surveys, which heavily rely on ELGs. The target catalogue over the SGC will be released along with DR14.

  13. Illuminating the Disk/Corona/Jet Connection in NLS1 Galaxies (United States)

    Brenneman, L.


    We report on the 200-ks NuSTAR observation of the narrow-line Seyfert 1 (NLS1) AGN, PMN J0948+0022, executed simultaneously with an 80-ks XMM-Newton observation in 2016. PMN J0948+0022 was chosen because it is one of seven known, powerfully-jetted radio-loud (RL) NLS1s that have been observed with Fermi. We will detail our progress toward meeting the following campaign objectives with the analysis of these datasets: (1) Confirming the presence of the soft excess and look for any evidence of reflection, either in Fe K emission or the Compton hump above 10 keV; (2) Determining the correct spectral model across the entire X-ray bandpass (e.g., Comptonization vs. blurred reflection for the soft excess); (3) Measuring the coronal parameters (temperature, optical depth, compactness) by constraining the high-energy cutoff of the power-law and the low-energy UV/optical data simultaneously; (4) Looking for any correlations between the corona, jet and accretion properties by examining radio and Fermi monitoring of the source contemporaneous with the X-ray and UV/optical data and comparing fits to pure disk/corona models vs. jet models; (5) Furthering our understanding of the jet emission mechanism(s) in RLNLS1s by adding new information to the SED modeling of this source.

  14. An alma survey of sub-millimeter galaxies in the extended Chandra deep field south: Sub-millimeter properties of color-selected galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Decarli, R.; Walter, F.; Hodge, J. A.; Rix, H.-W.; Schinnerer, E. [Max-Planck Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Smail, I.; Swinbank, A. M.; Karim, A.; Simpson, J. M. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Chapman, S. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Coppin, K. E. K. [Centre for Astrophysics, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Cox, P. [IRAM, 300 rue de la piscine, F-38406 Saint-Martin d' Hères (France); Dannerbauer, H. [Universität Wien, Institut für Astrophysik, Türenschanzstrasse 17, A-1180 Wien (Austria); Greve, T. R. [University College London, Department of Physics and Astronomy, Gower Street, London WC1E 6BT (United Kingdom); Ivison, R. [Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Knudsen, K. K.; Lindroos, L. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, Onsala SE-439 92 (Sweden); Van der Werf, P. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Weiß, A., E-mail: [Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany)


    We study the sub-millimeter properties of color-selected galaxies via a stacking analysis applied for the first time to interferometric data at sub-millimeter wavelengths. We base our study on 344 GHz ALMA continuum observations of ∼20''-wide fields centered on 86 sub-millimeter sources detected in the LABOCA Extended Chandra Deep Field South (ECDFS) Sub-millimeter Survey. We select various classes of galaxies (K-selected, star-forming sBzK galaxies, extremely red objects, and distant red galaxies) according to their optical/near-infrared fluxes. We find clear, >10σ detections in the stacked images of all these galaxy classes. We include in our stacking analysis Herschel/SPIRE data to constrain the dust spectral energy distribution of these galaxies. We find that their dust emission is well described by a modified blackbody with T {sub dust} ≈ 30 K and β = 1.6 and infrared luminosities of (5-11) × 10{sup 11} L {sub ☉} or implied star formation rates of 75-140 M {sub ☉} yr{sup –1}. We compare our results with those of previous studies based on single-dish observations at 870 μm and find that our flux densities are a factor 2-3 higher than previous estimates. The discrepancy is observed also after removing sources individually detected in ALESS maps. We report a similar discrepancy by repeating our analysis on 1.4 GHz observations of the whole ECDFS. Hence, we find tentative evidence that galaxies that are associated in projected and redshift space with sub-mm bright sources are brighter than the average population. Finally, we put our findings in the context of the cosmic star formation rate density as a function of redshift.

  15. A Radial Age Gradient in the Geometrically Thick Disk of the Milky Way (United States)

    Martig, Marie; Minchev, Ivan; Ness, Melissa; Fouesneau, Morgan; Rix, Hans-Walter


    In the Milky Way, the thick disk can be defined using individual stellar abundances, kinematics, or age, or geometrically, as stars high above the midplane. In nearby galaxies, where only a geometric definition can be used, thick disks appear to have large radial scale lengths, and their red colors suggest that they are uniformly old. The Milky Way’s geometrically thick disk is also radially extended, but it is far from chemically uniform: α-enhanced stars are confined within the inner Galaxy. In simulated galaxies, where old stars are centrally concentrated, geometrically thick disks are radially extended, too. Younger stellar populations flare in the simulated disks’ outer regions, bringing those stars high above the midplane. The resulting geometrically thick disks therefore show a radial age gradient, from old in their central regions to younger in their outskirts. Based on our age estimates for a large sample of giant stars in the APOGEE survey, we can now test this scenario for the Milky Way. We find that the geometrically defined thick disk in the Milky Way has indeed a strong radial age gradient: the median age for red clump stars goes from ∼9 Gyr in the inner disk to 5 Gyr in the outer disk. We propose that at least some nearby galaxies could also have thick disks that are not uniformly old, and that geometrically thick disks might be complex structures resulting from different formation mechanisms in their inner and outer parts.


    Energy Technology Data Exchange (ETDEWEB)

    Salas, P.; Galaz, G. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicua Mackenna 4860, 782-0436 Macul, Santiago (Chile); Salter, D.; Herrera-Camus, R.; Bolatto, A. D. [Department of Astronomy and Laboratory for Millimeter-Wave Astronomy, University of Maryland, College Park, MD 20742 (United States); Kepley, A. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States)


    We mapped 3 mm continuum and line emission from the starburst galaxy M82 using the Combined Array for Research in Millimeter-wave Astronomy. We targeted the HCN, HCO{sup +}, HNC, CS, and HC{sub 3}N lines, but here we focus on the HCN and HCO{sup +} emission. The map covers a field of 1.'2 with an ≈5'' resolution. The HCN and HCO{sup +} observations are short spacings corrected. The molecular gas in M82 had been previously found to be distributed in a molecular disk, coincident with the central starburst, and a galactic scale outflow which originates in the central starburst. With the new short spacings-corrected maps we derive some of the properties of the dense molecular gas in the base of the outflow. From the HCN and HCO{sup +} J = (1-0) line emission, and under the assumptions of the gas being optically thin and in local thermodynamic equilibrium, we place lower limits on the amount of dense molecular gas in the base of the outflow. The lower limits are 7 × 10{sup 6} M {sub ☉} and 21 × 10{sup 6} M {sub ☉}, or ≳ 2% of the total molecular mass in the outflow. The kinematics and spatial distribution of the dense gas outside the central starburst suggests that it is being expelled through chimneys. Assuming a constant outflow velocity, the derived outflow rate of dense molecular gas is ≥0.3 M {sub ☉} yr{sup –1}, which would lower the starburst lifetime by ≥5%. The energy required to expel this mass of dense gas is (1-10) × 10{sup 52} erg.

  17. An ALMA Survey of Submillimeter Galaxies in the Extended Chandra Deep Field South: Spectroscopic Redshifts (United States)

    Danielson, A. L. R.; Swinbank, A. M.; Smail, Ian; Simpson, J. M.; Casey, C. M.; Chapman, S. C.; da Cunha, E.; Hodge, J. A.; Walter, F.; Wardlow, J. L.; Alexander, D. M.; Brandt, W. N.; de Breuck, C.; Coppin, K. E. K.; Dannerbauer, H.; Dickinson, M.; Edge, A. C.; Gawiser, E.; Ivison, R. J.; Karim, A.; Kovacs, A.; Lutz, D.; Menten, K.; Schinnerer, E.; Weiß, A.; van der Werf, P.


    We present spectroscopic redshifts of {\\text{}}{S}870μ {{m}} ≳ 2 mJy submillimeter galaxies (SMGs), which have been identified from the ALMA follow-up observations of 870 μm detected sources in the Extended Chandra Deep Field South (the ALMA-LESS survey). We derive spectroscopic redshifts for 52 SMGs, with a median of z = 2.4 ± 0.1. However, the distribution features a high-redshift tail, with ˜23% of the SMGs at z≥slant 3. Spectral diagnostics suggest that the SMGs are young starbursts, and the velocity offsets between the nebular emission and UV ISM absorption lines suggest that many are driving winds, with velocity offsets of up to 2000 km s-1. Using the spectroscopic redshifts and the extensive UV-to-radio photometry in this field, we produce optimized spectral energy distributions (SEDs) using Magphys, and use the SEDs to infer a median stellar mass of {M}\\star = (6 ± 1)× 1010 M {}⊙ for our SMGs with spectroscopic redshift. By combining these stellar masses with the star formation rates (measured from the far-infrared SEDs), we show that SMGs (on average) lie a factor of ˜5 above the so-called “main sequence” at z˜ 2. We provide this library of 52 template fits with robust and uniquely well-sampled SEDs as a resource for future studies of SMGs, and also release the spectroscopic catalog of ˜2000 (mostly infrared-selected) galaxies targeted as part of the spectroscopic campaign.

  18. The Star-forming Histories of the Nucleus, Bulge, and Inner Disk of NGC 5102: Clues to the Evolution of a Nearby Lenticular Galaxy (United States)

    Davidge, T. J.


    Long slit spectra recorded with the Gemini Multi-Object Spectrograph on Gemini South are used to examine the star-forming history (SFH) of the lenticular galaxy NGC 5102. Structural and supplemental photometric information are obtained from archival Spitzer [3.6] images. Absorption features at blue and visible wavelengths are traced out along the minor axis to galactocentric radii ~60 arcsec (~0.9 kpc), sampling the nucleus, bulge, and disk components. Comparisons with model spectra point to luminosity-weighted metallicities that are consistent with the colors of resolved red giant branch stars in the disk. The nucleus has a luminosity-weighted age at visible wavelengths of {˜ } 1+0.2-0.1 Gyr, and the integrated light is dominated by stars that formed over a time period of only a few hundred Myr. For comparison, the luminosity-weighted ages of the bulge and disk are {˜ } 2+0.5-0.2 Gyr and 10+2-2 Gyr, respectively. The g' - [3.6] colors of the nucleus and bulge are consistent with the spectroscopically based ages. In contrast to the nucleus, models that assume star-forming activity spanning many Gyr provide a better match to the spectra of the bulge and disk than simple stellar population models. Isophotes in the bulge have a disky shape, hinting that the bulge was assembled from material with significant rotational support. The SFHs of the bulge and disk are consistent with the bulge forming from the collapse of a long-lived bar, rather than from the collapse of a transient structure that formed as the result of a tidal interaction. It is thus suggested that the progenitor of NGC 5102 was a barred disk galaxy that morphed into a lenticular galaxy through the buckling of its bar. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  19. The Tilt between Acretion Disk and Stellar Disk Shiyin Shen1,2 ...

    Indian Academy of Sciences (India)

    to a control galaxy sample. Given that the Type 2 AGN fraction is in the range of 70–90 percent for low luminosity AGNs as a priori, we find that the mean tilt between the accretion disk and stellar disk is ∼ 30 degrees. (Shen et al. 2010). Key words. Galaxies: statistics—galaxies: Seyfert—galaxies: nuclei— galaxies: spiral. 1.


    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Lopezlira, Rosa A. [On sabbatical leave from the Centro de Radioastronomia y Astrofisica, UNAM, Campus Morelia, Michoacan, C.P. 58089, Mexico. (Mexico); Pflamm-Altenburg, Jan; Kroupa, Pavel, E-mail: [Argelander Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany)


    We analyze the relationship between maximum cluster mass and surface densities of total gas ({Sigma}{sub gas}), molecular gas ({Sigma}{sub H{sub 2}}), neutral gas ({Sigma}{sub H{sub I}}), and star formation rate ({Sigma}{sub SFR}) in the grand-design galaxy M51, using published gas data and a catalog of masses, ages, and reddenings of more than 1800 star clusters in its disk, of which 223 are above the cluster mass distribution function completeness limit. By comparing the two-dimensional distribution of cluster masses and gas surface densities, we find for clusters older than 25 Myr that M{sub 3rd}{proportional_to}{Sigma}{sub H{sub I}{sup 0.4{+-}0.2}}, whereM{sub 3rd} is the median of the five most massive clusters. There is no correlation with{Sigma}{sub gas},{Sigma}{sub H2}, or{Sigma}{sub SFR}. For clusters younger than 10 Myr, M{sub 3rd}{proportional_to}{Sigma}{sub H{sub I}{sup 0.6{+-}0.1}} and M{sub 3rd}{proportional_to}{Sigma}{sub gas}{sup 0.5{+-}0.2}; there is no correlation with either {Sigma}{sub H{sub 2}} or{Sigma}{sub SFR}. The results could hardly be more different from those found for clusters younger than 25 Myr in M33. For the flocculent galaxy M33, there is no correlation between maximum cluster mass and neutral gas, but we have determined M{sub 3rd}{proportional_to}{Sigma}{sub gas}{sup 3.8{+-}0.3}, M{sub 3rd}{proportional_to}{Sigma}{sub H{sub 2}{sup 1.2{+-}0.1}}, and M{sub 3rd}{proportional_to}{Sigma}{sub SFR}{sup 0.9{+-}0.1}. For the older sample in M51, the lack of tight correlations is probably due to the combination of strong azimuthal variations in the surface densities of gas and star formation rate, and the cluster ages. These two facts mean that neither the azimuthal average of the surface densities at a given radius nor the surface densities at the present-day location of a stellar cluster represent the true surface densities at the place and time of cluster formation. In the case of the younger sample, even if the clusters have not yet

  1. ALFALFA and WSRT Imaging of Extended H I Features in the Leo Cloud of Galaxies (United States)

    Leisman, Lukas; Haynes, Martha P.; Giovanelli, Riccardo; Józsa, Gyula; Adams, Elizabeth A. K.; Hess, Kelley M.


    We present Arecibo Legacy Fast ALFA (ALFALFA) H I observations of a well-studied region of the Leo Cloud, which includes the NGC 3227 group and the NGC 3190 group. We detect optically dark H I tails and plumes with extents potentially exceeding 600 kpc, well beyond the field of view of previous observations. These H I features contain ˜40 per cent of the total H I mass in the NGC 3227 group and ˜10 per cent of the NGC 3190 group. We also present Westerbork Synthesis Radio Telescope (WSRT) maps which show the complex morphology of the extended emission in the NGC 3227 group. We comment on previously proposed models of the interactions in these groups and the implications for the scale of group processing through interactions. Motivated by the extent of the H I plumes, we place the H I observations in the context of the larger loose group, demonstrating the need for future sensitive, wide field H I surveys to understand the role of group processing in galaxy evolution.

  2. ACS Nearby Galaxy Survey (United States)

    Dalcanton, Julianne


    Existing HST observations of nearby galaxies comprise a sparse and highly non-uniform archive, making comprehensive comparative studies among galaxies essentially impossible. We propose to secure HST's lasting impact on the study of nearby galaxies by undertaking a systematic, complete, and carefully crafted imaging survey of ALL galaxies in the Local Universe outside the Local Group. The resulting images will allow unprecedented measurements of: {1} the star formation history {SFH} of a >100 Mpc^3 volume of the Universe with a time resolution of Delta[log{t}]=0.25; {2} correlations between spatially resolved SFHs and environment; {3} the structure and properties of thick disks and stellar halos; and {4} the color distributions, sizes, and specific frequencies of globular and disk clusters as a function of galaxy mass and environment. To reach these goals, we will use a combination of wide-field tiling and pointed deep imaging to obtain uniform data on all 72 galaxies within a volume-limited sample extending to 3.5 Mpc, with an extension to the M81 group. For each galaxy, the wide-field imaging will cover out to 1.5 times the optical radius and will reach photometric depths of at least 2 magnitudes below the tip of the red giant branch throughout the limits of the survey volume. One additional deep pointing per galaxy will reach SNR 10 for red clump stars, sufficient to recover the ancient SFH from the color-magnitude diagram. This proposal will produce photometric information for 100 million stars {comparable to the number in the SDSS survey} and uniform multi-color images of half a square degree of sky. The resulting archive will establish the fundamental optical database for nearby galaxies, in preparation for the shift of high-resolution imaging to the near-infrared.

  3. The extended epoch of galaxy formation: Age dating of 3600 galaxies with 2 < z < 6.5 in the VIMOS Ultra-Deep Survey (United States)

    Thomas, R.; Le Fèvre, O.; Scodeggio, M.; Cassata, P.; Garilli, B.; Le Brun, V.; Lemaux, B. C.; Maccagni, D.; Pforr, J.; Tasca, L. A. M.; Zamorani, G.; Bardelli, S.; Hathi, N. P.; Tresse, L.; Zucca, E.; Koekemoer, A. M.


    measured SFR for galaxies at these redshifts. From the smooth rise in the FzF we infer that the period of galaxy formation extends all the way from the highest possible formation redshifts that we can probe at z 15 down to redshifts z 2. This indicates that galaxy formation is a continuous process over cosmic time, with a higher number of galaxies forming at the peak in SFRD at z 2 than at earlier epochs. Based on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, under Large Programme 185.A-0791.


    Energy Technology Data Exchange (ETDEWEB)

    Krivov, A. V.; Loehne, T.; Mutschke, H.; Neuhaeuser, R. [Astrophysikalisches Institut und Universitaetssternwarte, Friedrich-Schiller-Universitaet Jena, Schillergaesschen 2-3, D-07745 Jena (Germany); Eiroa, C.; Marshall, J. P.; Mustill, A. J. [Departamento de Fisica Teorica, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Montesinos, B. [Departamento de Astrofisica, Centro de Astrobiologia (CAB, CSIC-INTA), ESAC Campus, P.O. Box 78, E-28691 Villanueva de la Canada, Madrid (Spain); Del Burgo, C. [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), Apartado Postal 51 y 216, 72000 Puebla, Pue. (Mexico); Absil, O. [Institut d' Astrophysique et de Geophysique, Universite de Liege, Allee du 6 Aout 17, B-4000 Liege (Belgium); Ardila, D. [NASA Herschel Science Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Augereau, J.-C.; Ertel, S.; Lebreton, J. [UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d' Astrophysique de Grenoble (IPAG), UMR 5274, F-38041 Grenoble (France); Bayo, A. [European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile); Bryden, G. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Danchi, W. [NASA Goddard Space Flight Center, Exoplanets and Stellar Astrophysics, Code 667, Greenbelt, MD 20771 (United States); Liseau, R. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-43992, Onsala (Sweden); Mora, A. [ESA-ESAC Gaia SOC, P.O. Box 78, E-28691 Villanueva de la Canada, Madrid (Spain); Pilbratt, G. L., E-mail: [ESA Astrophysics and Fundamental Physics Missions Division, ESTEC/SRE-SA, Keplerlaan 1, 2201 AZ Noordwijk (Netherlands); and others


    Infrared excesses associated with debris disk host stars detected so far peak at wavelengths around {approx}100 {mu}m or shorter. However, 6 out of 31 excess sources studied in the Herschel Open Time Key Programme, DUNES, have been seen to show significant-and in some cases extended-excess emission at 160 {mu}m, which is larger than the 100 {mu}m excess. This excess emission has been attributed to circumstellar dust and has been suggested to stem from debris disks colder than those known previously. Since the excess emission of the cold disk candidates is extremely weak, challenging even the unrivaled sensitivity of Herschel, it is prudent to carefully consider whether some or even all of them may represent unrelated galactic or extragalactic emission, or even instrumental noise. We re-address these issues using several distinct methods and conclude that it is highly unlikely that none of the candidates represents a true circumstellar disk. For true disks, both the dust temperatures inferred from the spectral energy distributions and the disk radii estimated from the images suggest that the dust is nearly as cold as a blackbody. This requires the grains to be larger than {approx}100 {mu}m, even if they are rich in ices or are composed of any other material with a low absorption in the visible. The dearth of small grains is puzzling, since collisional models of debris disks predict that grains of all sizes down to several times the radiation pressure blowout limit should be present. We explore several conceivable scenarios: transport-dominated disks, disks of low dynamical excitation, and disks of unstirred primordial macroscopic grains. Our qualitative analysis and collisional simulations rule out the first two of these scenarios, but show the feasibility of the third one. We show that such disks can indeed survive for gigayears, largely preserving the primordial size distribution. They should be composed of macroscopic solids larger than millimeters, but smaller

  5. GMRT Low Radio Frequency Study of the Wolf Rayet Galaxy NGC ...

    Indian Academy of Sciences (India)

    In this paper, we present the first low frequency (< 1.4 GHz) radio continuum study of a Wolf Rayet galaxy NGC 4214 using the Giant Meterwave Radio Telescope (GMRT). We detect diffuse extended emission from the galaxy disk at 325 MHz and find that the radio emission closely follows the ultraviolet emission mapped by ...

  6. GMRT Low Radio Frequency Study of the Wolf Rayet Galaxy NGC ...

    Indian Academy of Sciences (India)

    Abstract. In this paper, we present the first low frequency (< 1.4 GHz) radio continuum study of a Wolf Rayet galaxy NGC 4214 using the. Giant Meterwave Radio Telescope (GMRT). We detect diffuse extended emission from the galaxy disk at 325 MHz and find that the radio emis- sion closely follows the ultraviolet emission ...

  7. Star formation and the interstellar medium in low surface brightness galaxies - I. Oxygen abundances and abundance gradients in low surface brightness disk galaxies

    NARCIS (Netherlands)

    de Blok, WJG; van der Hulst, JM

    We present measurements of the oxygen abundances in 64 HII regions in 12 LSB galaxies. We find that oxygen abundances are low. No regions with solar abundance have been found, and most have oxygen abundances similar to 0.5 to 0.1 solar. The oxygen abundance appears to be constant as a function of

  8. The red extended structure of IC10, the nearest blue compact galaxy


    Gerbrandt, Stephanie A. N.; McConnachie, Alan W.; Irwin, Mike


    The Local Group starburst galaxy IC10 is the closest example of a blue compact galaxy. Here, we use optical gi imaging from CFHT/MegaCam and near infra-red JHK imaging from UKIRT/WFCAM to conduct a comprehensive survey of the structure of IC10. We examine the spatial distribution of its resolved young, intermediate and old stellar populations to large radius and low effective surface brightness levels. Akin to other dwarfs with multiple populations of different ages, stellar populations of de...

  9. An ALMA survey of submillimeter galaxies in the extended Chandra deep field south: The redshift distribution and evolution of submillimeter galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, J. M.; Swinbank, A. M.; Smail, Ian; Alexander, D. M.; Danielson, A. L. R.; Thomson, A. P. [Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Bertoldi, F.; Karim, A. [Argelander-Institute for Astronomy, Bonn University, Auf dem Hügel 71, D-53121 Bonn (Germany); De Breuck, C. [European Southern Observatory, Karl-Schwarzschild Straße, D-85748 Garching bei München (Germany); Chapman, S. C. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 3J5 (Canada); Coppin, K. E. K. [Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Da Cunha, E.; Hodge, J. A.; Schinnerer, E. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Dannerbauer, H. [Universität Wien, Institut für Astrophysik, Türkenschanzstraße 17, A-1180 Wien (Austria); Greve, T. R. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Ivison, R. J. [Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Knudsen, K. K. [Department of Earth and Space Science, Onsala Space Observatory, Chalmers University of Technology, SE-43992 Onsala (Sweden); Poggianti, B. M., E-mail: [INAF-Astronomical Observatory of Padova, I-35122 Padova (Italy); and others


    We present the first photometric redshift distribution for a large sample of 870 μm submillimeter galaxies (SMGs) with robust identifications based on observations with ALMA. In our analysis we consider 96 SMGs in the Extended Chandra Deep Field South, 77 of which have 4-19 band photometry. We model the SEDs for these 77 SMGs, deriving a median photometric redshift of z {sub phot} = 2.3 ± 0.1. The remaining 19 SMGs have insufficient photometry to derive photometric redshifts, but a stacking analysis of Herschel observations confirms they are not spurious. Assuming that these SMGs have an absolute H-band magnitude distribution comparable to that of a complete sample of z ∼ 1-2 SMGs, we demonstrate that they lie at slightly higher redshifts, raising the median redshift for SMGs to z {sub phot} = 2.5 ± 0.2. Critically we show that the proportion of galaxies undergoing an SMG-like phase at z ≥ 3 is at most 35% ± 5% of the total population. We derive a median stellar mass of M {sub *} = (8 ± 1) × 10{sup 10} M {sub ☉}, although there are systematic uncertainties of up to 5 × for individual sources. Assuming that the star formation activity in SMGs has a timescale of ∼100 Myr, we show that their descendants at z ∼ 0 would have a space density and M{sub H} distribution that are in good agreement with those of local ellipticals. In addition, the inferred mass-weighted ages of the local ellipticals broadly agree with the look-back times of the SMG events. Taken together, these results are consistent with a simple model that identifies SMGs as events that form most of the stars seen in the majority of luminous elliptical galaxies at the present day.

  10. Resolved 200mu M images of nearby galaxies - evidence for an extended distribution of cold dust

    NARCIS (Netherlands)

    Valentijn, E; Alton, P.B.; Threwhella, M.; Davies, J.I.; Bianchi, S.; Gear, W.; Thronson, H.; Witt, A.


    We present resolved 200mu m images for 8 nearby galaxies observed with the Infrared Space Observatory (ISO). By comparing the 200mu m observations with IRAS 60mu m and 100mu m data, we find that cold dust becomes more dominant at larger radii. We infer a grain temperature of 18-21 K for this cold

  11. The Lyman alpha reference sample VI. Lyman alpha escape from the edge-on disk galaxy Mrk 1486

    Czech Academy of Sciences Publication Activity Database

    Duval, F.; Ostlin, G.; Hayes, M.; Zackrisson, E.; Verhamme, A.; Orlitová, Ivana; Adamo, A.; Guaita, L.; Melinder, J.; Cannon, J.M.; Laursen, P.; Rivera-Thorsen, T.; Herenz, E.Ch.; Gruyters, P.; Mas-Hesse, J. M.; Kunth, D.; Sandberg, A.; Schaerer, D.; Mansson, J.-E.


    Roč. 587, March (2016), A77/1-A77/24 ISSN 0004-6361 R&D Projects: GA ČR(CZ) GP14-20666P Institutional support: RVO:67985815 Keywords : galaxies * starburst * submillimeter Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014


    Energy Technology Data Exchange (ETDEWEB)

    Matthews, Daniel J.; Newman, Jeffrey A. [Department of Physics and Astronomy, University of Pittsburgh, 3941 O' Hara Street, Pittsburgh, PA 15260 (United States); Coil, Alison L. [Department of Physics, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States); Cooper, Michael C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Gwyn, Stephen D. J., E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Canadian Astronomical Data Centre, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, British Columbia V9E 2E7 (Canada)


    This paper describes a new catalog that supplements the existing DEEP2 Galaxy Redshift Survey photometric and spectroscopic catalogs with ugriz photometry from two other surveys: the Canada-France-Hawaii Legacy Survey (CFHTLS) and the Sloan Digital Sky Survey (SDSS). Each catalog is cross-matched by position on the sky in order to assign ugriz photometry to objects in the DEEP2 catalogs. We have recalibrated the CFHTLS photometry where it overlaps DEEP2 in order to provide a more uniform data set. We have also used this improved photometry to predict DEEP2 BRI photometry in regions where only poorer measurements were available previously. In addition, we have included improved astrometry tied to SDSS rather than USNO-A2.0 for all DEEP2 objects. In total this catalog contains {approx}27, 000 objects with full ugriz photometry as well as robust spectroscopic redshift measurements, 64% of which have r > 23. By combining the secure and accurate redshifts of the DEEP2 Galaxy Redshift Survey with ugriz photometry, we have created a catalog that can be used as an excellent testbed for future photo-z studies, including tests of algorithms for surveys such as LSST and DES.

  13. Lopsided spiral galaxies

    Indian Academy of Sciences (India)

    Lopsided spiral galaxies · Outline of the talk: · Collaborators · Background : · Lopsided distribution highlighted first: Baldwin, Lynden-Bell, & Sancisi (1980) · Lopsidedness also seen in an edge-on galaxy : NGC 891 · Slide 7 · Origin of m=1 disk distribution? Early Theoretical models: · Disk response to a lopsided halo ...

  14. Local Counterparts to High-Redshift Turbulent Galaxies: What are the Stellar Kinematics? (United States)

    Bassett, Robert; Glazebrook, Karl; Fisher, David; Abraham, Roberto; Damjanov, Ivana


    We aim to measure the stellar kinematics of 4 low redshift turbulent, clumpy disks with the GMOS IFU. Recent observations of high redshift galaxies show that gaseous disks in high redshift (z 2) galaxies are turbulent. The source of this turbulence remains an open question. A possible scenario is that turbulent disks are fed by streams of cold gas, flowing along cosmic filaments, which drive the large H-alpha velocity dispersions and clumpy star formation observed (for example by the SINS survey). However, the recent discovery of low redshift disk galaxies with clumpy-high velocity dispersion disks shows that galaxies with similar properties to high-z clumpy disks can exists in absence of cold flows, therefore an alternate driver for turbulence seems likely to explain, at least these nearby galaxies. A contrasting scenario is that the turbulence is driven by feedback from extreme star formation originating from a thin stellar disk. These nearby star forming disks are very rare, yet they provide an oppurtunity to study clumpy disks with techniques which are impossible at high redshift (due to both resolution and surface brightness dimming). Here we propose one such study, to measure the stellar kinematics from Balmer absorption lines. If the stars and gas have similar velocity dispersion, this would favor externally driven turbulence by gas accretion (a rare thing in the low redshift Universe); conversely if the gas and stars have different dynamics then this would suggest that internally driven turbelence from feedback is a plausible scenario. We currently have GMOS IFU observations of two disk systems, and we propose here to extend our sample. To identify galaxies as disks we use lower resolution IFU emission line kinematics from AAO, surface photometry from UKIDSS and SDSS, and Halpha maps from Hubble Space Telescope.

  15. Small-scale Intensity Mapping: Extended Halos as a Probe of the Ionizing Escape Fraction and Faint Galaxy Populations during Reionization (United States)

    Mas-Ribas, Lluís; Hennawi, Joseph F.; Dijkstra, Mark; Davies, Frederick B.; Stern, Jonathan; Rix, Hans-Walter


    We present a new method to quantify the value of the escape fraction of ionizing photons, and the existence of ultra-faint galaxies clustered around brighter objects during the epoch of cosmic reionization, using the diffuse Lyα, continuum, and Hα emission observed around galaxies at z˜ 6. We model the surface brightness profiles of the diffuse halos, considering the fluorescent emission powered by ionizing photons escaping from the central galaxies, and the nebular emission from satellite star-forming sources, by extending the formalisms developed in Mas-Ribas & Dijkstra and Mas-Ribas et al. The comparison between our predicted profiles and Lyα observations at z = 5.7 and z = 6.6 favors a low ionizing escape fraction, {f}{esc}{ion}˜ 5 % , for galaxies in the range -19≳ {M}{UV}≳ -21.5. However, uncertainties and possible systematics in the observations do not allow for firm conclusions. We predict Hα and rest-frame visible continuum observations with the James Webb Space Telescope (JWST), and show that it will be able to detect extended (a few tens of kiloparsecs) fluorescent Hα emission powered by ionizing photons escaping from a bright, L≳ 5{L}* , galaxy. Such observations could differentiate fluorescent emission from nebular emission by satellite sources. We discuss how observations and stacking several objects may provide unique constraints on the escape fraction for faint galaxies and/or the abundance of ultra-faint radiation sources.

  16. Comparison of Multi Disk Exponential Gas Distribution vs. Single Disk (United States)

    Rao, Erica; O'Brien, James


    In fitting galactic rotation curves to data, most standard theories make use of a single exponential disk approximation of the gas distribution to account for the HI synthesis data observed at various radio telescope facilities. We take a sample of surface brightness profiles from The HI Nearby Galaxy Survey (THINGS), and apply both single disk exponentials and Multi-Disk exponentials, and use these various models to see how the modelling procedure changes the Newtonian prediction of the mass of the galaxy. Since the missing mass problem has not been fully explained in large spiral galaxies, different modelling procedures could account for some of the missing matter.

  17. The Galaxy's Eating Habits (United States)

    Putman, M. E.; Thom, C.; Gibson, B. K.; Staveley-Smith, L.


    The possibility of a gaseous halo stream which was stripped from the Sagittarius dwarf galaxy is presented. The total mass of the neutral hydrogen along the orbit of the Sgr dwarf in the direction of the Galactic Anti-Center is 4 - 10 × 106 M⊙ (at 36 kpc, the distance to the stellar debris in this region). Both the stellar and gaseous components have negative velocities in this part of the sky, but the gaseous component extends to higher negative velocities. We suggest this gaseous stream was stripped from the main body of the dwarf 0.2 - 0.3 Gyr ago during its current orbit after a passage through a diffuse edge of the Galactic disk with a density > 10-4 cm-3. The gas would then represent the dwarf's last source of star formation fuel and explains how the galaxy was forming stars 0.5-2 Gyr ago.

  18. The VLA Nascent Disk And Multiplicity Survey of Perseus Protostars (VANDAM). III. Extended Radio Emission from Protostars in Perseus (United States)

    Tychoniec, Łukasz; Tobin, John J.; Karska, Agata; Chandler, Claire; Dunham, Michael M.; Li, Zhi-Yun; Looney, Leslie W.; Segura-Cox, Dominique; Harris, Robert J.; Melis, Carl; Sadavoy, Sarah I.


    Centimeter continuum emission from protostars offers insight into the innermost part of the outflows, as shock-ionized gas produces free–free emission. We observed a complete population of Class 0 and I protostars in the Perseus molecular cloud at 4.1 and 6.4 cm with resolution and sensitivity superior to previous surveys. From a total of 71 detections, eight sources exhibit resolved emission at 4.1 cm and/or 6.4 cm. In this paper, we focus on this subsample, analyzing their spectral indices along the jet and their alignment with respect to the large-scale molecular outflow. Spectral indices for fluxes integrated toward the position of the protostar are consistent with free–free thermal emission. The value of the spectral index along a radio jet decreases with distance from the protostar. For six sources, emission is well aligned with the outflow central axis, showing that we observe the ionized base of the jet. This is not the case for two sources, where we note misalignment of the emission with respect to the large-scale outflow. This might indicate that the emission does not originate in the radio jet, but rather in an ionized outflow cavity wall or disk surface. For five of the sources, the spectral indices along the jet decrease well below the thermal free–free limit of ‑0.1 with > 2σ significance. This is indicative of synchrotron emission, meaning that high-energy electrons are being produced in the outflows close to the disk. This result can have far-reaching implications for the chemical composition of the embedded disks.


    Energy Technology Data Exchange (ETDEWEB)

    Radburn-Smith, David J.; Dalcanton, Julianne J. [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Roskar, Rok [Institut fuer Theoretische Physik, Universitaet Zuerich (Switzerland); Debattista, Victor P. [Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE (United Kingdom); Streich, David; De Jong, Roelof S.; Vlajic, Marija [Leibniz-Institut fuer Astrophysik Potsdam, D-14482 Potsdam (Germany); Holwerda, Benne W. [European Space Agency, ESTEC, 2200 AG Noordwijk (Netherlands); Purcell, Chris W. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Dolphin, Andrew E. [Raytheon, 1151 E. Hermans Road, Tucson, AZ 85756 (United States); Zucker, Daniel B. [Department of Physics and Astronomy, Macquarie University, NSW 2109 (Australia)


    We analyzed the radial surface brightness profile of the spiral galaxy NGC 7793 using HST/ACS images from the GHOSTS survey and a new HST/WFC3 image across the disk break. We used the photometry of resolved stars to select distinct populations covering a wide range of stellar ages. We found breaks in the radial profiles of all stellar populations at 280'' ({approx}5.1 kpc). Beyond this disk break, the profiles become steeper for younger populations. This same trend is seen in numerical simulations where the outer disk is formed almost entirely by radial migration. We also found that the older stars of NGC 7793 extend significantly farther than the underlying H I disk. They are thus unlikely to have formed entirely at their current radii, unless the gas disk was substantially larger in the past. These observations thus provide evidence for substantial stellar radial migration in late-type disks.

  20. Witnessing the assembly of galaxies in an extended gas-rich structure at z 3.25 (United States)

    Mackenzie, Ruari


    The direct study of star formation in Damped Lyman Alpha systems (DLAs), the reservoirs of the majority of neutral gas at high redshift, has previously been hampered by the lack of deep integral field spectroscopy for sensitive searches of faint host galaxies. Building on our successful HST shot-in-the-dark survey that has probed the in-situ star formation rate of z 2-3 DLAs, we have initiated a MUSE follow-up of 6 DLA signlines to overcome this bottleneck. In the first sightline we have studied, we have uncovered a 40 kpc Lyman alpha emitting nebula, composed of two clumps within 50 kpc of the DLA, suggestive of a merger or an extended protodisk. Within this structure, which is the largest nebula known to be associated with a z 3 DLA, we also found a compact continuum source with spectrophotometry consistent with a Lyman Break Galaxy at the same redshift. Aside from the LBG, the rest of the Lyman alpha structure has no continuum counterpart in deep UV and visible imaging. The LBG alone seems unable to power the Lyman alpha nebula and the morphology supports our conclusion that, most likely, this structure is powered by in-situ star formation below detection limit. However, from the Lyman alpha alone the origin of this incredible structure remains ambiguous. With this proposal, we aim to acquire high resolution, deep infrared imaging with HST to probe the rest-frame optical emission to search for the underlying stellar emission of this object and to infer the stellar mass of the LBG. With the powerful combination of HST and MUSE data, we will unravel the nature of this unique system.


    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chian-Chou; Smail, Ian; Swinbank, A. M.; Simpson, J. M.; Ma, Cheng-Jiun; Alexander, D. M.; Danielson, A. L. R.; Edge, A. C. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Biggs, A. D.; Ivison, R. J. [European Southern Observatory, Karl Schwarzschild Strasse 2, D-85748 Garching (Germany); Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Chapman, S. C. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 3J5 (Canada); Coppin, K. E. K. [Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Dannerbauer, H. [Institut für Astrophysik, Universität Wien, Türkenschanzstraße 17, A-1180 Wien (Austria); Greve, T. R. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Karim, A. [Argelander-Institute for Astronomy, Bonn University, Auf dem Hügel 71, D-53121 Bonn (Germany); Menten, Karl M. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Schinnerer, E.; Walter, F. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Wardlow, J. L. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); and others


    We analyze Hubble Space Telescope WFC3/H {sub 160}-band observations of a sample of 48 Atacama Large Millimeter/submillimeter Array detected submillimeter galaxies (SMGs) in the Extended Chandra Deep Field South field, to study their stellar morphologies and sizes. We detect 79% ± 17% of the SMGs in the H {sub 160}-band imaging with a median sensitivity of 27.8 mag, and most (80%) of the nondetections are SMGs with 870 μm fluxes of S {sub 870} < 3 mJy. With a surface brightness limit of μ {sub H} ∼ 26 mag arcsec{sup –2}, we find that 82% ± 9% of the H {sub 160}-band-detected SMGs at z = 1-3 appear to have disturbed morphologies, meaning they are visually classified as either irregulars or interacting systems, or both. By determining a Sérsic fit to the H {sub 160} surface brightness profiles, we derive a median Sérsic index of n = 1.2 ± 0.3 and a median half-light radius of r{sub e} = 4.4{sub −0.5}{sup +1.1} kpc for our SMGs at z = 1-3. We also find significant displacements between the positions of the H {sub 160} component and 870 μm emission in these systems, suggesting that the dusty starburst regions and less-obscured stellar distribution are not colocated. We find significant differences in the sizes and the Sérsic index between our z = 2-3 SMGs and z ∼ 2 quiescent galaxies, suggesting that a major transformation of the stellar light profile is needed in the quenching processes if SMGs are progenitors of the red-and-dead z ∼ 2 galaxies. Given the short-lived nature of SMGs, we postulate that the majority of the z = 2-3 SMGs with S {sub 870} ≳ 2 mJy are early/mid-stage major mergers.

  2. An alma survey of submillimeter galaxies in the extended Chandra deep field-south: The agn fraction and X-ray properties of submillimeter galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S. X.; Brandt, W. N.; Luo, B. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Smail, I.; Alexander, D. M.; Danielson, A. L. R.; Karim, A.; Simpson, J. M.; Swinbank, A. M. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Hodge, J. A.; Walter, F. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Lehmer, B. D. [The Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States); Wardlow, J. L. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Xue, Y. Q. [Key Laboratory for Research in Galaxies and Cosmology, Center for Astrophysics, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China); Chapman, S. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Coppin, K. E. K. [Centre for Astrophysics, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Dannerbauer, H. [Universität Wien, Institute für Astrophysik, Türkenschanzstraße 17, 1180 Wien (Austria); De Breuck, C. [European Southern Observatory, Karl-Schwarzschild Straße 2, D-85748 Garching (Germany); Menten, K. M. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Van der Werf, P., E-mail:, E-mail: [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)


    The large gas and dust reservoirs of submillimeter galaxies (SMGs) could potentially provide ample fuel to trigger an active galactic nucleus (AGN), but previous studies of the AGN fraction in SMGs have been controversial largely due to the inhomogeneity and limited angular resolution of the available submillimeter surveys. Here we set improved constraints on the AGN fraction and X-ray properties of the SMGs with Atacama Large Millimeter/submillimeter Array (ALMA) and Chandra observations in the Extended Chandra Deep Field-South (E-CDF-S). This study is the first among similar works to have unambiguously identified the X-ray counterparts of SMGs; this is accomplished using the fully submillimeter-identified, statistically reliable SMG catalog with 99 SMGs from the ALMA LABOCA E-CDF-S Submillimeter Survey. We found 10 X-ray sources associated with SMGs (median redshift z = 2.3), of which eight were identified as AGNs using several techniques that enable cross-checking. The other two X-ray detected SMGs have levels of X-ray emission that can be plausibly explained by their star formation activity. Six of the eight SMG-AGNs are moderately/highly absorbed, with N {sub H} > 10{sup 23} cm{sup –2}. An analysis of the AGN fraction, taking into account the spatial variation of X-ray sensitivity, yields an AGN fraction of 17{sub −6}{sup +16}% for AGNs with rest-frame 0.5-8 keV absorption-corrected luminosity ≥7.8 × 10{sup 42} erg s{sup –1}; we provide estimated AGN fractions as a function of X-ray flux and luminosity. ALMA's high angular resolution also enables direct X-ray stacking at the precise positions of SMGs for the first time, and we found four potential SMG-AGNs in our stacking sample.

  3. Extended Hard-X-Ray Emission in the Inner Few Parsecs of the Galaxy (United States)

    Perez, Kerstin; Hailey, Charles J.; Bauer, Franz E.; Krivonos, Roman A.; Mori, Kaya; Baganoff, Frederick K.; Barriere, Nicholas M.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; hide


    The Galactic Centre hosts a puzzling stellar population in its inner few parsecs, with a high abundance of surprisingly young, relatively massive stars bound within the deep potential well of the central supermassive black hole, Sagittarius A* (ref. 1). Previous studies suggest that the population of objects emitting soft X-rays (less than 10 kiloelectronvolts) within the surrounding hundreds of parsecs, as well as the population responsible for unresolved X-ray emission extending along the Galactic plane, is dominated by accreting white dwarf systems2, 3, 4, 5.

  4. Extended hard-X-ray emission in the inner few parsecs of the Galaxy

    DEFF Research Database (Denmark)

    Perez, Kerstin; Hailey, Charles J.; Bauer, Franz E.


    of objects emitting soft X-rays (less than 10 kiloelectronvolts) within the surrounding hundreds of parsecs, as well as the population responsible for unresolved X-ray emission extending along the Galactic plane, is dominated by accreting white dwarf systems. Observations of diffuse hard-X-ray (more than 10...... range. This emission is more sharply peaked towards the Galactic Centre than is the surface brightness of the soft-X-ray population. This could indicate a significantly more massive population of accreting white dwarfs, large populations of low-mass X-ray binaries or millisecond pulsars, or particle...

  5. The ACS Nearby Galaxy Survey Treasury: Overview (United States)

    Dalcanton, Julianne


    The ACS Nearby Galaxy Survey Treasury program (ANGST) consists of a carefully crafted imaging survey of a volume-limited sample of galaxies in the Local Universe outside the Local Group. The resulting images will allow unprecedented measurements of: (1) the SFH of a >100 Mpc3 volume of the Universe with a time resolution of Delta[log(t)]=0.25; (2) correlations between spatially resolved SFHs and environment; (3) the structure and properties of thick disks and stellar halos; and (4) the color distributions, sizes, and specific frequencies of globular and disk clusters as a function of galaxy mass and environment. To reach these goals, we are using a combination of wide-field tiling, pointed deep imaging, and archival data to carry out a uniform analysis of the ancient and recent star formation histories of 70 galaxies within a volume-limited sample extending to 3.5 Mpc, with an extension to the M81 group. For all galaxies, a radial strip of imaging will cover out to beyond the optical radius and will reach photometric depths of at least 2 magnitudes below the tip of the red giant branch throughout the limits of the survey volume. Additional deep pointings will reach SNR 10 for red clump stars, sufficient to recover the ancient star formation history (SFH) from the color-magnitude diagram for the galaxies that provide more than 99% of the star formation in the local volume. The resulting analysis will produce photometric information for several million stars.

  6. The Disk Mass Project: breaking the disk-halo degeneracy

    NARCIS (Netherlands)

    Verheijen, Marc A. W.; Bershady, Matthew A.; Swaters, Rob A.; Andersen, David R.; Westfall, Kyle B.; DE JONG, R. S.


    Little is known about the content and distribution of dark matter in spiral galaxies. To break the degeneracy in galaxy rotation curve decompositions, which allows a wide range of dark matter halo density profiles, an independent measure of the mass surface density of stellar disks is needed. Here,

  7. The Full-fledged Dwarf Irregular Galaxy Leo A (United States)

    Vansevičius, Vladas; Arimoto, Nobuo; Hasegawa, Takashi; Ikuta, Chisato; Jablonka, Pascale; Narbutis, Donatas; Ohta, Kouji; Stonkutė, Rima; Tamura, Naoyuki; Vansevičius, Valdas; Yamada, Yoshihiko


    We have studied Leo A, an isolated and extremely gas-rich dwarf irregular galaxy of very low stellar mass and metallicity. Ages of the stellar populations in Leo A range from ~10 Myr to ~10 Gyr. Here we report the discovery of an old stellar halo and a sharp stellar edge. We also find that the distribution of stars extends beyond the gaseous envelope of the galaxy. Therefore, by its structure as well as stellar and gaseous content, Leo A is found to resemble massive disk galaxies. This implies that galaxies of very low stellar mass are also able to develop complex structures, challenging contemporary understanding of galaxy evolution. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  8. The extended ROSAT-ESO Flux-Limited X-ray Galaxy Cluster Survey (REFLEX II). VII. The mass function of galaxy clusters (United States)

    Böhringer, Hans; Chon, Gayoung; Fukugita, Masataka


    The mass function of galaxy clusters is a sensitive tracer of the gravitational evolution of the cosmic large-scale structure and serves as an important census of the fraction of matter bound in large structures. We obtain the mass function by fitting the observed cluster X-ray luminosity distribution from the REFLEX galaxy cluster survey to models of cosmological structure formation. We marginalise over uncertainties in the cosmological parameters as well as those of the relevant galaxy cluster scaling relations. The mass function is determined with an uncertainty of less than 10% in the mass range 3 × 1012 to 5 × 1014M⊙. For the cumulative mass function we find a slope at the low-mass end consistent with a value of - 1, while the mass-rich end cut-off is milder than a Schechter function with an exponential term exp( - Mδ) with δ smaller than 1. Changing the Hubble parameter in the range H0 = 67 - 73 km s-1 Mpc-1 or allowing the total neutrino mass to have a value in the range 0 - 0.4 eV causes variations less than the uncertainties. We estimate the fraction of mass locked up in galaxy clusters: about 4.4% of the matter in the Universe is bound in clusters (inside r200) with a mass larger than 1014M⊙ and 14% to clusters and groups with a mass larger than 1013M⊙ at the present Universe. We also discuss the evolution of the galaxy cluster population with redshift. Our results imply that there is hardly any clusters with a mass ≥1015M⊙ above a redshift of z = 1.

  9. UV-extended E-MILES stellar population models: young components in massive early-type galaxies (United States)

    Vazdekis, A.; Koleva, M.; Ricciardelli, E.; Röck, B.; Falcón-Barroso, J.


    We present UV-extended E-MILES stellar population synthesis models covering the spectral range λλ 1680-50 000 Å at moderately high resolution. We employ the NGSL space-based stellar library to compute spectra of single-age, single-metallicity stellar populations in the wavelength range from 1680 to 3540 Å. These models represent a significant improvement in resolution and age/metallicity coverage over previous studies based on earlier space-based libraries. These model spectra were joined with those we computed in the visible using MILES, and other empirical libraries for redder wavelengths. The models span the metallicity range -1.79≤ [M/H]≤ +0.26 and ages above 30 Myr, for a suite of initial mass function types with varying slopes. We focus on the behaviour of colours, spectra and line-strength indices in the UV range as a function of relevant stellar population parameters. Whereas some indices strengthen with increasing age and metallicity, as most metallicity indicators in the visible, other indices peak around 3 Gyr for metal-rich stellar populations, such as Mg at 2800 Å. Our models provide reasonably good fits to the integrated colours and most line strengths of the stellar clusters of the Milky Way and Large Magellanic Cloud. Our full spectrum fits in the UV range for a representative set of early-type galaxies (ETGs) of varying mass yield age and metallicity estimates in very good agreement with those obtained in the optical range. The comparison of UV colours and line strengths of massive ETGs with our models reveals the presence of young stellar components, with ages in the range 0.1-0.5 Gyr and mass fractions 0.1-0.5 per cent, on the top of an old stellar population.

  10. Galactoseismology: From The Milky Way To XUV Disks (United States)

    Chakrabarti, Sukanya

    The variety of discrepancies between observations and simulations on galactic scales, from the anisotropic distribution of dwarf galaxies to the "too big to fail" problem (where massive satellites in simulations are too dense relative to observations), suggests that we may not yet fully understand galaxy formation. If these satellites exist, they would leave traces of their passage in extended HI disks. Extended HI disks of galaxies reach to several times the optical radius, presenting the largest possible cross-section for interaction with sub-halos at large distances (where theoretical models expect them to be). We will provide definitive constraints on the distribution of dark matter in spiral galaxies by building on our ongoing work in characterizing galactic satellites from analysis of disturbances in extended HI disks with respect to hydrodynamical simulations. Spiral galaxies in the Local Volume (from the Milky Way to the XUV disks discovered by GALEX) exhibit a wealth of unexplained morphology, but these morphological signatures have not yet been used to place constraints on the evolution of HI disks and the dark matter distribution. We are now poised to make significant progress in Galactoseismology, i.e. connect morphological disturbances with the mass distribution. By using the FIRE model for explicit star formation and feedback, we will also develop a better understanding for the star formation history of our Galaxy and XUV Disks. Our Milky Way models will be informed by the HST proper motions, and will match the observed planar disturbances, the warp, and vertical waves recently discovered by the RAVE and LAMOST surveys. We are also carrying high resolution simulations with the Gizmo code that incorporates the FIRE model to develop a comprehensive understanding of the star formation history and star formation rate (that matches Spitzer observations) of the Milky Way. These models will provide a much needed interpretative framework for JWST and WFIRST

  11. Galaxy masses in large surveys: Connecting luminous and dark matter with weak lensing and kinematics (United States)

    Reyes, Reinabelle


    Galaxy masses are difficult to determine because light traces stars and gas in a non-trivial way, and does not trace dark matter, which extends well beyond the luminous regions of galaxies. In this thesis, I use the most direct probes of dark matter available---weak gravitational lensing and galaxy kinematics---to trace the total mass in galaxies (and galaxy clusters) in large surveys. In particular, I use the large, homogeneous dataset from the Sloan Digital Sky Survey (SDSS), which provides spectroscopic redshifts for a large sample of galaxies at z ≲ 0.2 and imaging data to a depth of r distortions and clustering measurements to derive a robust probe of gravity on cosmological scales. Finally, I combine weak lensing with the kinematics of disk galaxies to constrain the total mass profile over several orders of magnitude. I derive a minimal-scatter relation between disk velocity and stellar mass (also known as the Tully-Fisher relation) that can be used, by construction, on a similarly-selected lens sample. Then, I combine this relation with halo mass measurements from weak lensing to place constraints on the ratio of the optical to virial velocities, as well as the ratio of halo to stellar masses, both as a function of stellar mass. These results will serve as inputs to and constraints on disk galaxy formation models, which will be explored in future work.


    Energy Technology Data Exchange (ETDEWEB)

    Olczak, C. [Astronomisches Rechen-Institut (ARI), Zentrum fuer Astronomie Universitaet Heidelberg, Moenchhofstrasse 12-14, D-69120 Heidelberg (Germany); Kaczmarek, T.; Pfalzner, S. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 7, D-53121 Bonn (Germany); Harfst, S. [Technische Universitaet Berlin, Zentrum fuer Astronomie und Astrophysik, Hardenbergstrasse 36, D-10623 Berlin (Germany); Portegies Zwart, S., E-mail: [Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden (Netherlands)


    Most stars form in a cluster environment. These stars are initially surrounded by disks from which potentially planetary systems form. Of all cluster environments, starburst clusters are probably the most hostile for planetary systems in our Galaxy. The intense stellar radiation and extreme density favor rapid destruction of circumstellar disks via photoevaporation and stellar encounters. Evolving a virialized model of the Arches cluster in the Galactic tidal field, we investigate the effect of stellar encounters on circumstellar disks in a prototypical starburst cluster. Despite its proximity to the deep gravitational potential of the Galactic center, only a moderate fraction of members escapes to form an extended pair of tidal tails. Our simulations show that encounters destroy one-third of the circumstellar disks in the cluster core within the first 2.5 Myr of evolution, preferentially affecting the least and most massive stars. A small fraction of these events causes rapid ejection and the formation of a weaker second pair of tidal tails that is overpopulated by disk-poor stars. Two predictions arise from our study. (1) If not destroyed by photoevaporation protoplanetary disks of massive late B- and early O-type stars represent the most likely hosts of planet formation in starburst clusters. (2) Multi-epoch K- and L-band photometry of the Arches cluster would provide the kinematically selected membership sample required to detect the additional pair of disk-poor tidal tails.

  13. Revisiting the Extended Schmidt Law: The Important Role of Existing Stars in Regulating Star Formation (United States)

    Shi, Yong; Yan, Lin; Armus, Lee; Gu, Qiusheng; Helou, George; Qiu, Keping; Gwyn, Stephen; Stierwalt, Sabrina; Fang, Min; Chen, Yanmei; Zhou, Luwenjia; Wu, Jingwen; Zheng, Xianzhong; Zhang, Zhi-Yu; Gao, Yu; Wang, Junzhi


    We revisit the proposed extended Schmidt law, which posits that the star formation efficiency in galaxies depends on the stellar mass surface density, by investigating spatially resolved star formation rates (SFRs), gas masses, and stellar masses of star formation regions in a vast range of galactic environments, from the outer disks of dwarf galaxies, to spiral disks and to merging galaxies, as well as individual molecular clouds in M33. We find that these regions are distributed in a tight power law as {{{Σ }}}{SFR} ∝ {({{{Σ }}}{star}0.5{{{Σ }}}{gas})}1.09, which is also valid for the integrated measurements of disk and merging galaxies at high-z. Interestingly, we show that star formation regions in the outer disks of dwarf galaxies with {{{Σ }}}{SFR} down to 10‑5 {M}ȯ yr‑1 kpc‑2, which are outliers of both the Kennicutt–Schmidt and Silk–Elmegreen laws, also follow the extended Schmidt law. Other outliers in the Kennicutt–Schmidt law, such as extremely metal-poor star formation regions, also show significantly reduced deviation from the extended Schmidt law. These results suggest an important role for existing stars in helping to regulate star formation through the effect of their gravity on the midplane pressure in a wide range of galactic environments.

  14. Galaxies: The Long Wavelength View

    National Research Council Canada - National Science Library

    Fischer, J


    ... (more than 2 orders of magnitude) in the [C II]/FIR ratios in galaxies extending from blue compact dwarfs, to normal and starburst galaxies, down to elliptical and ultraluminous galaxies (ULICs...

  15. Modeling the Evolution of Galaxy Properties across Cosmic Time with Numerical Simulations (United States)

    Torrey, Paul A.

    We present a series of numerical galaxy formation studies which apply new numerical methods to produce increasingly realistic galaxy formation models. We first investigate the metallicity evolution of a large set of idealized hydrodynamical galaxy merger simulations of colliding galaxies. We find that inflows of metal-poor interstellar gas triggered by galaxy tidal interactions can account for the systematically lower central oxygen abundances observed in local interacting galaxies. We show the central metallicity evolution during merger events is determined by a competition between the inflow of low-metallicity gas and enrichment from star formation. We find a time-averaged depression in the galactic nuclear metallicity of ~0.07 dex for gas-poor disk-disk interactions, which explains the observed close pair mass-metallicity and separation-metallicity relationships. We then pioneer the impact of a novel hydro solver in our understanding of galaxy gas disk assembly by comparing the structural properties of galaxies formed in cosmological simulations using the smoothed particle hydrodynamics (SPH) code GADGET with those using the moving-mesh code AREPO. We find that the cold gas disks formed using the moving mesh approach have systematically larger disk scale lengths and higher specific angular momenta than their GADGET counterparts across a wide range in halo masses. We articulate the numerical origins of these differences, and discuss the impact on large body of galaxy formation literature. We explore the performance of a recently implemented feedback model in AREPO which includes primordial and metal line radiative cooling with self-shielding corrections; stellar evolution with associated mass loss and chemical enrichment; feedback by stellar winds; black hole seeding, growth and merging; and AGN quasar- and radio-mode heating with a phenomenological prescription for AGN electro-magnetic feedback. We demonstrate that our feedback scheme is capable of producing

  16. Extended ionised and clumpy gas in a normal galaxy at z = 7.1 revealed by ALMA (United States)

    Carniani, S.; Maiolino, R.; Pallottini, A.; Vallini, L.; Pentericci, L.; Ferrara, A.; Castellano, M.; Vanzella, E.; Grazian, A.; Gallerani, S.; Santini, P.; Wagg, J.; Fontana, A.


    We present new ALMA observations of the [O iii]88 μm line and high angular resolution observations of the [C ii]158 μm line in a normal star forming galaxy at z = 7.1. Previous [C ii] observations of this galaxy had detected [C ii] emission consistent with the Lyα redshift but spatially slightly offset relative to the optical (UV-rest frame) emission. The new [C ii] observations reveal that the [C ii] emission is partly clumpy and partly diffuse on scales larger than about 1 kpc. [O iii] emission is also detected at high significance, offset relative to the optical counterpart in the same direction as the [C ii] clumps, but mostly not overlapping with the bulk of the [C ii] emission. The offset between different emission components (optical/UV and different far-IR tracers) is similar to that which is observed in much more powerful starbursts at high redshift. We show that the [O iii] emitting clump cannot be explained in terms of diffuse gas excited by the UV radiation emitted by the optical galaxy, but it requires excitation by in-situ (slightly dust obscured) star formation, at a rate of about 7 M⊙ yr-1. Within 20 kpc from the optical galaxy the ALMA data reveal two additional [O iii] emitting systems, which must be star forming companions. We discuss that the complex properties revealed by ALMA in the z 7.1 galaxy are consistent with expectations by recent models and cosmological simulations, in which differential dust extinction, differential excitation and different metal enrichment levels, associated with different subsystems assembling a galaxy, are responsible for the various appearance of the system when observed with distinct tracers.

  17. The Two-Point Correlation Function of Rich Clusters of Galaxies: Results from an Extended APM Cluster Redshift Survey


    G. B. Dalton; Croft, R. A. C.; Efstathiou, G.; Sutherland, W.J.; Maddox, S. J.; Davis, M.


    We present new estimates of the spatial two-point correlation function of rich clusters of galaxies selected from the APM Galaxy Survey. We have measured redshifts for a sample of $364$ clusters out to a depth of $\\sim 450\\hmpc$. The clusters have a mean space density of $\\bar{n} = 3.4\\times 10^{-5}\\hmpccc$. The two-point correlation function, $\\xi_{cc}$, for this sample is equal to unity at a pair-separation of $r_0 = 14.3\\pm1.75\\hmpc$ (2$\\sigma$ errors), consistent with our earlier results ...

  18. Kinematics in the Circumnuclear Disk (United States)

    Mills, Elisabeth; Casey-Clyde, J. Andrew; Rodriguez, Julio; Kruijssen, Diederik; Martin, Sergio; Moser, Lydia; Riquelme, Denise; Harada, Nanase; Zhao, Jun-Hui; Lu, Hauyu


    The Circumnuclear Disk (CND) extends from 1.5-5pc in radius around our Galaxy's central supermassive black hole, Sagittarius A*. New ALMA observations reveal that the CND is a more complex system than previously thought, containing multiple streams, filaments and other structures inconsistent with the uniform circular rotation that is typically assumed for this source. We will present position-position-velocity maps of this region using the HNC 3-2 and HCN 3-2 transitions, which reveal line of sight velocities that are highly discontinuous in several regions, suggesting the CND consists of several overlapping and possibly interacting clouds, rather than one continuous and circularized disk. In particular, we single out a uniquely linear stream on the eastern side of this region, which is continuous in both position and velocity, with a size of 3 x 0.1 pc and velocities ranging from -50 to 100 km/s. For this stream, we will also present the results of recently performed orbital fitting, establishing its 3 dimensional position in the central potential around Sagittarius A*.

  19. Probing interstellar turbulence in spiral galaxies using H I power spectrum analysis (United States)

    Dutta, Prasun; Begum, Ayesha; Bharadwaj, Somnath; Chengalur, Jayaram N.


    We estimate the H I intensity fluctuation power spectrum for a sample of 18 spiral galaxies chosen from THINGS. Our analysis spans a large range of length-scales from ˜300 pc to ˜16 kpc across the entire galaxy sample. We find that the power spectrum of each galaxy can be well fitted by a power law P(U)=AUα, with an index α that varies from galaxy to galaxy. For some of the galaxies the scale-invariant power-law power spectrum extends to length-scales that are comparable to the size of the galaxy's disk. The distribution of α is strongly peaked with 50% of the values in the range α=-1.9 to 1.5, and a mean and standard deviation of -1.3 and 0.5 respectively. We find no significant correlation between α and the star formation rate, dynamical mass, H I mass or velocity dispersion of the galaxies. Several earlier studies that have measured the power spectrum within our galaxy on length-scales that are considerably smaller than 500 pc have found a power-law power spectrum with α in the range ≈-2.8 to -2.5. We propose a picture where we interpret the values in the range ≈-2.8 to -2.5 as arising from three dimensional (3D) turbulence in the interstellar medium (ISM) on length-scales smaller than the galaxy's scale-height, and we interpret the values in the range ≈-1.9 to -1.5 measured in this paper as arising from two-dimensional ISM turbulence in the plane of the galaxy's disk. It however still remains a difficulty to explain the small galaxy to galaxy variations in the values of α measured here.

  20. The Tilt between Acretion Disk and Stellar Disk

    Indian Academy of Sciences (India)

    ... large sample of Type 2 AGNs selected from Sloan Digital Sky Survey (SDSS, York et al. 2000) to a control galaxy sample. Given that the Type 2 AGN fraction is in the range of 70–90 percent for low luminosity AGNs as a priori, we find that the mean tilt between the accretion disk and stellar disk is ∼ 30 degrees (Shen et al.

  1. The SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: The Clustering of Luminous Red Galaxies Using Photometric Redshifts (United States)

    Prakash, Abhishek; SDSS-IV/eBOSS


    SDSS-IV/eBOSS survey will allow a ˜1% measurement of the Baryon Acoustic Oscillation (BAO) scale and a 4.0%Redshift Space Distortion (RSD) measurement using a relatively uniform set of luminous, early-type galaxies in the redshift range 0.6 < z < 1. In this talk, I will present the 3D real space clustering of a sample of ~600,000 LRGs measured by the SDSS/eBOSS, using photometric redshifts. These galaxies have accurate photometric redshifts with an average error of z = 0.028. These LRGs range from redshift z = 0.6 to 1.0 over 10,000 deg2 of the sky, making it the largest volume ever used for galaxy clustering measurements. We measure the angular clusteringpower spectrum in different redshift slices and use well-calibrated redshift distributions to combine these into a high precision 3D real space clustering. i will present an evidence for BAO in the 2-point correlation function. The detection of BAO also allows the measurement of the comoving distance to z = 1.0. Traditionally, spectroscopic redshifts are used to estimate distances to the galaxies and, in turn, to measuregalaxy clustering. However, acquiring spectroscopic redshifts is a time consuming and expensive process even with modern multi-fiber spectrographs. Although photometric redshifts are less accurate, they are signicantly easier to obtain, and for a constant amount of time, one can image both wider areas and deeper volumes than would be possible with spectroscopy, allowing one to probe both larger scales and larger volumes. The ability to make precise clustering measurements with photometric data has been well demonstrated by Padmanabhan et al. (2007).

  2. The implications of the surprising existence of a large, massive CO disk in a distant protocluster (United States)

    Dannerbauer, H.; Lehnert, M. D.; Emonts, B.; Ziegler, B.; Altieri, B.; De Breuck, C.; Hatch, N.; Kodama, T.; Koyama, Y.; Kurk, J. D.; Matiz, T.; Miley, G.; Narayanan, D.; Norris, R. P.; Overzier, R.; Röttgering, H. J. A.; Sargent, M.; Seymour, N.; Tanaka, M.; Valtchanov, I.; Wylezalek, D.


    It is not yet known if the properties of molecular gas in distant protocluster galaxies are significantly affected by their environment as galaxies are in local clusters. Through a deep, 64 h of effective on-source integration with the Australian Telescope Compact Array (ATCA), we discovered a massive, Mmol = 2.0 ± 0.2× 1011 M⊙, extended, 40 kpc, CO(1-0)-emitting disk in the protocluster surrounding the radio galaxy, MRC 1138-262. The galaxy, at zCO = 2.1478, is a clumpy, massive disk galaxy, M∗ 5 × 1011 M⊙, which lies 250 kpc in projection from MRC 1138-262 and is a known Hα emitter, named HAE229. This source has a molecular gas fraction of 30%. The CO emission has a kinematic gradient along its major axis, centered on the highest surface brightness rest-frame optical emission, consistent with HAE229 being a rotating disk. Surprisingly, a significant fraction of the CO emission lies outside of the UV/optical emission. In spite of this, HAE229 follows the same relation between star-formation rate and molecular gas mass as normal field galaxies. HAE229 is the first CO(1-0) detection of an ordinary, star-forming galaxy in a protocluster. We compare a sample of cluster members at z > 0.4 thatare detected in low-order CO transitions, with a similar sample of sources drawn from the field. We confirm findings that the CO-luminosity and full-width at half maximum are correlated in starbursts and show that this relation is valid for normal high-z galaxies as well as for those in overdensities. We do not find a clear dichotomy in the integrated Schmidt-Kennicutt relation for protocluster and field galaxies. Our results suggest that environment does not have an impact on the "star-formation efficiency" or the molecular gas content of high-redshift galaxies. Not finding any environmental dependence in these characteristics, especially for such an extended CO disk, suggests that environmentally-specific processes such as ram pressure stripping do not operate

  3. A giant protogalactic disk linked to the cosmic web. (United States)

    Martin, D Christopher; Matuszewski, Mateusz; Morrissey, Patrick; Neill, James D; Moore, Anna; Cantalupo, Sebastiano; Prochaska, J Xavier; Chang, Daphne


    The specifics of how galaxies form from, and are fuelled by, gas from the intergalactic medium remain uncertain. Hydrodynamic simulations suggest that 'cold accretion flows'--relatively cool (temperatures of the order of 10(4) kelvin), unshocked gas streaming along filaments of the cosmic web into dark-matter halos--are important. These flows are thought to deposit gas and angular momentum into the circumgalactic medium, creating disk- or ring-like structures that eventually coalesce into galaxies that form at filamentary intersections. Recently, a large and luminous filament, consistent with such a cold accretion flow, was discovered near the quasi-stellar object QSO UM287 at redshift 2.279 using narrow-band imaging. Unfortunately, imaging is not sufficient to constrain the physical characteristics of the filament, to determine its kinematics, to explain how it is linked to nearby sources, or to account for its unusual brightness, more than a factor of ten above what is expected for a filament. Here we report a two-dimensional spectroscopic investigation of the emitting structure. We find that the brightest emission region is an extended rotating hydrogen disk with a velocity profile that is characteristic of gas in a dark-matter halo with a mass of 10(13) solar masses. This giant protogalactic disk appears to be connected to a quiescent filament that may extend beyond the virial radius of the halo. The geometry is strongly suggestive of a cold accretion flow.


    Energy Technology Data Exchange (ETDEWEB)

    Domínguez-Tenreiro, R.; Obreja, A.; Brook, C. B. [Dept. de Física Teórica, Univ. Autónoma de Madrid, E-28049 Cantoblanco Madrid (Spain); Martínez-Serrano, F. J.; Serna, A. [Dept. de Física y A.C., Universidad Miguel Hernández, E-03202 Elche (Spain); Stinson, G., E-mail: [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany)


    Models of the advanced stages of gravitational instability predict that baryons that form the stellar populations of current galaxies at z = 0 displayed a web-like structure at high z, as part of the cosmic web (CW). We explore details of these predictions using cosmological hydrodynamical simulations. When the stellar populations of the spheroid and disk components of simulated late-type galaxies are traced back separately to high zs we found CW-like structures where spheroid progenitors are more evolved than disk progenitors. The distinction between the corresponding stellar populations, as driven by their specific angular momentum content j, can be explained in terms of the CW evolution, extended to two processes occurring at lower z. First, the spheroid progenitors strongly lose j at collapse, which contrasts with the insignificant j loss of the disk progenitors. The second is related to the lack of alignment, at assembly, between the spheroid-to-be material and the already settled proto-disk, in contrast to the alignment of disk-to-be material, in some cases resulting from circumgalactic, disk-induced gravitational torques. The different final outcomes of these low-z processes have their origins in the different initial conditions driven by the CW dynamics.

  5. The extended structure of the dwarf irregular galaxies Sextans A and Sextans B. Signatures of tidal distortion in the outskirts of the Local Group (United States)

    Bellazzini, M.; Beccari, G.; Fraternali, F.; Oosterloo, T. A.; Sollima, A.; Testa, V.; Galleti, S.; Perina, S.; Faccini, M.; Cusano, F.


    We present a detailed study of the stellar and H i structure of the dwarf irregular galaxies Sextans A and Sextans B, members of the NGC 3109 association. We use newly obtained deep (r ≃ 26.5) and wide-field g and r photometry to extend the surface brightness (SB) profiles of the two galaxies down to μV ≃ 31.0 mag/arcsec2. We find that both galaxies are significantly more extended than previously traced with surface photometry, out to ~4 kpc from their centres along their major axes. Older stars are found to have more extended distribution than younger populations. We obtain the first estimate of the mean metallicity for the old stars in Sex B, from the colour distribution of the red giant branch, ⟨[Fe/H]⟩ = -1.6. The SB profiles show significant changes of slope and cannot be fitted with a single Sérsic model. Both galaxies have HI discs as massive as their respective stellar components. In both cases the H i discs display solid-body rotation with maximum amplitude of ~50 km s-1 (albeit with significant uncertainty due to the poorly constrained inclination), implying a dynamical mass ~109 M⊙, a mass-to-light ratio M / LV ~ 25, and a dark-to-baryonic mass ratio of ~10. The distribution of the stellar components is more extended than the gaseous disc in both galaxies. We find that the main, approximately round, stellar body of Sex A is surrounded by an elongated low-SB stellar halo that can be interpreted as a tidal tail, similar to that found in another member of the same association (Antlia). We discuss these, as well as other evidence of tidal disturbance, in the framework of a past passage of the NGC 3109 association close to the Milky Way, which has been hypothesised by several authors and is also supported by the recently discovered filamentary configuration of the association itself. Appendices are available in electronic form at http://www.aanda.orgTable of stellar photometry is only available at the CDS via anonymous ftp to http

  6. Herniated disk (United States)

    ... pulposus Herniated disk repair Lumbar spinal surgery - series Herniated lumbar disk References Gardocki RJ, Park AL. Lower back pain and disorders of intervertebral discs. In: Canale ST, Beaty JH, eds. Campbell's Operative ...

  7. Extending the modeling of the anisotropic galaxy power spectrum to k = 0.4 hMpc-1 (United States)

    Hand, Nick; Seljak, Uroš; Beutler, Florian; Vlah, Zvonimir


    We present a model for the redshift-space power spectrum of galaxies and demonstrate its accuracy in describing the monopole, quadrupole, and hexadecapole of the galaxy density field down to scales of k = 0.4 hMpc-1. The model describes the clustering of galaxies in the context of a halo model and the clustering of the underlying halos in redshift space using a combination of Eulerian perturbation theory and N-body simulations. The modeling of redshift-space distortions is done using the so-called distribution function approach. The final model has 13 free parameters, and each parameter is physically motivated rather than a nuisance parameter, which allows the use of well-motivated priors. We account for the Finger-of-God effect from centrals and both isolated and non-isolated satellites rather than using a single velocity dispersion to describe the combined effect. We test and validate the accuracy of the model on several sets of high-fidelity N-body simulations, as well as realistic mock catalogs designed to simulate the BOSS DR12 CMASS data set. The suite of simulations covers a range of cosmologies and galaxy bias models, providing a rigorous test of the level of theoretical systematics present in the model. The level of bias in the recovered values of f σ8 is found to be small. When including scales to k = 0.4 hMpc-1, we find 15-30% gains in the statistical precision of f σ8 relative to k = 0.2 hMpc-1 and a roughly 10-15% improvement for the perpendicular Alcock-Paczynski parameter α⊥. Using the BOSS DR12 CMASS mocks as a benchmark for comparison, we estimate an uncertainty on f σ8 that is ~10-20% larger than other similar Fourier-space RSD models in the literature that use k <= 0.2 hMpc-1, suggesting that these models likely have a too-limited parametrization.

  8. The MUSE Hubble Ultra Deep Field Survey. VIII. Extended Lyman-α haloes around high-z star-forming galaxies (United States)

    Leclercq, Floriane; Bacon, Roland; Wisotzki, Lutz; Mitchell, Peter; Garel, Thibault; Verhamme, Anne; Blaizot, Jérémy; Hashimoto, Takuya; Herenz, Edmund Christian; Conseil, Simon; Cantalupo, Sebastiano; Inami, Hanae; Contini, Thierry; Richard, Johan; Maseda, Michael; Schaye, Joop; Marino, Raffaella Anna; Akhlaghi, Mohammad; Brinchmann, Jarle; Carollo, Marcella


    We report the detection of extended Lyα haloes around 145 individual star-forming galaxies at redshifts 3 ≤ z ≤ 6 in the Hubble Ultra Deep Field observed with the Multi-Unit Spectroscopic Explorer (MUSE) at ESO-VLT. Our sample consists of continuum-faint (- 15 ≥ MUV ≥ -22) Lyα emitters (LAEs). Using a 2D, two-component (continuum-like and halo) decomposition of Lyα emission assuming circular exponential distributions, we measure scale lengths and luminosities of Lyα haloes. We find that 80% of our objects having reliable Lyα halo measurements show Lyα emission that is significantly more extended than the UV continuum detected by HST (by a factor ≈4 to >20). The median exponential scale length of the Lyα haloes in our sample is ≈4.5 kpc with a few haloes exceeding 10 kpc. By comparing the maximal detected extent of the Lyα emission with the predicted dark matter halo virial radii of simulated galaxies, we show that the detected Lyα emission of our selected sample of Lyα emitters probes a significant portion of the cold circum-galactic medium of these galaxies (>50% in average). This result therefore shows that there must be significant HI reservoirs in the circum-galactic medium and reinforces the idea that Lyα haloes are ubiquitous around high-redshift Lyα emitting galaxies. Our characterization of the Lyα haloes indicates that the majority of the Lyα flux comes from the halo (≈65%) and that their scale lengths seem to be linked to the UV properties of the galaxies (sizes and magnitudes). We do not observe a significant Lyα halo size evolution with redshift, although our sample for z> 5 is very small. We also explore the diversity of the Lyα line profiles in our sample and we find that the Lyα lines cover a large range of full width at half maximum (FWHM) from 118 to 512 km s-1. While the FWHM does not seem to be correlated to the Lyα scale length, most compact Lyα haloes and those that are not detected with high significance tend

  9. Premixed direct injection disk (United States)

    York, William David; Ziminsky, Willy Steve; Johnson, Thomas Edward; Lacy, Benjamin; Zuo, Baifang; Uhm, Jong Ho


    A fuel/air mixing disk for use in a fuel/air mixing combustor assembly is provided. The disk includes a first face, a second face, and at least one fuel plenum disposed therebetween. A plurality of fuel/air mixing tubes extend through the pre-mixing disk, each mixing tube including an outer tube wall extending axially along a tube axis and in fluid communication with the at least one fuel plenum. At least a portion of the plurality of fuel/air mixing tubes further includes at least one fuel injection hole have a fuel injection hole diameter extending through said outer tube wall, the fuel injection hole having an injection angle relative to the tube axis. The invention provides good fuel air mixing with low combustion generated NOx and low flow pressure loss translating to a high gas turbine efficiency, that is durable, and resistant to flame holding and flash back.

  10. Astrophysical disks Collective and Stochastic Phenomena

    CERN Document Server

    Fridman, Alexei M; Kovalenko, Ilya G


    The book deals with collective and stochastic processes in astrophysical discs involving theory, observations, and the results of modelling. Among others, it examines the spiral-vortex structure in galactic and accretion disks , stochastic and ordered structures in the developed turbulence. It also describes sources of turbulence in the accretion disks, internal structure of disk in the vicinity of a black hole, numerical modelling of Be envelopes in binaries, gaseous disks in spiral galaxies with shock waves formation, observation of accretion disks in a binary system and mass distribution of luminous matter in disk galaxies. The editors adaptly brought together collective and stochastic phenomena in the modern field of astrophysical discs, their formation, structure, and evolution involving the methodology to deal with, the results of observation and modelling, thereby advancing the study in this important branch of astrophysics and benefiting Professional Researchers, Lecturers, and Graduate Students.

  11. The Kinematics of Galactic Stellar Disks

    NARCIS (Netherlands)

    Merrifield, M. R.; Kuijken, K.


    Abstract: The disks of galaxies are primarily stellar systems, and fundamentally dynamical entities. Thus, to fully understand galactic disks, we must study their stellar kinematics as well as their morphologies. Observational techniques have now advanced to a point where quite detailed

  12. Scale Length of the Galactic Thin Disk

    Indian Academy of Sciences (India)

    This paper presents an analysis of the first 2MASS (The Two Micron All Sky Survey) sampler data as observed at lower Galactic latitude in our Galaxy. These new near-infrared data provide insight into the structure of the thin disk of our Galaxy, The interpretation of star counts and color distributions of stars in the ...


    NARCIS (Netherlands)


    Stellar velocity dispersion measurements of a sample of 12 galactic disks are summarized. The observed radial functionality is parameterized such that one dispersion value is assigned to each galaxy. Comparison of the galaxy dispersion with absolute magnitude and maximum rotation reveals that the

  14. Laboratory tests in the detection of extended spectrum beta-lactamase production: National Committee for Clinical Laboratory Standards (NCCLS screening test, the E-test, the double disk confirmatory test, and cefoxitin susceptibility testing

    Directory of Open Access Journals (Sweden)

    Pedro A. d'Azevedo

    Full Text Available Extended spectrum beta-lactamase (ESBL production by Klebsiella sp. and E. coli is an emerging problem. In this study, 107 clinical isolates (53 E. coli, 47 K. pneumoniae and 7 K. oxytoca screened as ESBL producers by the NCCLS disk diffusion procedure were submitted to a double disk confirmatory test (DDT and to the E-test double strip for confirmation of ESBL production by demonstration of clavulanic acid inhibition effect (CAIE. Only 72/107 (67% of the isolates were confirmed as ESBL producers by DDT, with diverse results among species. By the E-test, 58/107 (54% isolates were confirmed as ESBL producers, and 18/107 (17% were not determinable. Susceptibility to cefoxitin was found in 57/68 (83% of strains that did not show CAIE. ESBL detection remains a controversial issue and clinical laboratories are in need of a simple and effective way to recognize strains with this kind of resistance.

  15. Cold streams in early massive hot haloes as the main mode of galaxy formation. (United States)

    Dekel, A; Birnboim, Y; Engel, G; Freundlich, J; Goerdt, T; Mumcuoglu, M; Neistein, E; Pichon, C; Teyssier, R; Zinger, E


    Massive galaxies in the young Universe, ten billion years ago, formed stars at surprising intensities. Although this is commonly attributed to violent mergers, the properties of many of these galaxies are incompatible with such events, showing gas-rich, clumpy, extended rotating disks not dominated by spheroids. Cosmological simulations and clustering theory are used to explore how these galaxies acquired their gas. Here we report that they are 'stream-fed galaxies', formed from steady, narrow, cold gas streams that penetrate the shock-heated media of massive dark matter haloes. A comparison with the observed abundance of star-forming galaxies implies that most of the input gas must rapidly convert to stars. One-third of the stream mass is in gas clumps leading to mergers of mass ratio greater than 1:10, and the rest is in smoother flows. With a merger duty cycle of 0.1, three-quarters of the galaxies forming stars at a given rate are fed by smooth streams. The rarer, submillimetre galaxies that form stars even more intensely are largely merger-induced starbursts. Unlike destructive mergers, the streams are likely to keep the rotating disk configuration intact, although turbulent and broken into giant star-forming clumps that merge into a central spheroid. This stream-driven scenario for the formation of discs and spheroids is an alternative to the merger picture.

  16. The AMBRE project: The thick thin disk and thin thick disk of the Milky Way (United States)

    Hayden, M. R.; Recio-Blanco, A.; de Laverny, P.; Mikolaitis, S.; Worley, C. C.


    We analyze 494 main sequence turnoff and subgiant stars from the AMBRE:HARPS survey. These stars have accurate astrometric information from Gaia DR1, providing reliable age estimates with relative uncertainties of ±1 or 2 Gyr and allowing precise orbital determinations. The sample is split based on chemistry into a low-[Mg/Fe] sequence, which are often identified as thin disk stellar populations, and high-[Mg/Fe] sequence, which are often associated with thick disk stellar populations. We find that the high-[Mg/Fe] chemical sequence has extended star formation for several Gyr and is coeval with the oldest stars of the low-[Mg/Fe] chemical sequence: both the low- and high-[Mg/Fe] sequences were forming stars at the same time. We find that the high-[Mg/Fe] stellar populations are only vertically extended for the oldest, most-metal poor and highest [Mg/Fe] stars. When comparing vertical velocity dispersion for the low- and high-[Mg/Fe] sequences, the high-[Mg/Fe] sequence has lower vertical velocity dispersion than the low-[Mg/Fe] sequence for stars of similar age. This means that identifying either group as thin or thick disk based on chemistry is misleading. The stars belonging to the high-[Mg/Fe] sequence have perigalacticons that originate in the inner disk, while the perigalacticons of stars on the low-[Mg/Fe] sequence are generally around the solar neighborhood. From the orbital properties of the stars, the high-[Mg/Fe] and low-[Mg/Fe] sequences are most likely a reflection of the chemical enrichment history of the inner and outer disk populations, respectively; radial mixing causes both populations to be observed in situ at the solar position. Based on these results, we emphasize that it is important to be clear in defining what populations are being referenced when using the terms thin and thick disk, and that ideally the term thick disk should be reserved for purely geometric definitions to avoid confusion and be consistent with definitions in external

  17. A young star-forming galaxy at z = 3.5 with an extended Ly\\,$α$ halo seen with MUSE

    DEFF Research Database (Denmark)

    Patrício, Vera; Richard, Johan; Verhamme, Anne


    Spatially resolved studies of high redshift galaxies, an essential insight into galaxy formation processes, have been mostly limited to stacking or unusually bright objects. We present here the study of a typical (L$^{*}$, M$_\\star$ = 6 $\\times 10^9$ $M_\\odot$) young lensed galaxy at $z=3...

  18. UV-extended E-MILES stellar population models: young components in massive early-type galaxies


    Vazdekis, A.; Koleva, M.; Ricciardelli, E.; Röck, B.; Falcón-Barroso, J.


    We present UV extended E MILES stellar population synthesis models covering the spectral range ?? 1680 50 000 Å at moderately high resolution. We employ the NGSL space based stellar library to compute spectra of single age single metallicity stellar populations in the wavelength range from 1680 to 3540 Å. These models represent a significant improvement in resolution and age/metallicity coverage over previous studies based on earlier space based libraries. These model spectra were joined with...

  19. The Unexpected Past of a Dwarf Galaxy (United States)


    New Light on Cannibalism in the Local Group of Galaxies The Local Group of Galaxies consists of a few large spiral galaxies - for instance the Milky Way galaxy in which we live, and the Andromeda galaxy that is visible to the unaided eye in the northern constellation of the same name - as well as two dozen much smaller galaxies of mostly irregular shape. Whereas the larger galaxies have extended halos of very old stars, no such halos have ever been seen around the smaller ones. Now, however, Dante Minniti and Albert Zijlstra [1], working at the ESO 3.5-metre New Technology Telescope (NTT), have found a large halo of old and metal-poor stars around one of the dwarf galaxies in the Local Group. This finding is quite unexpected. It revises our understanding of star formation in these galaxies and provides important information about the past evolution of galaxies [2]. Galaxy halos The Milky Way galaxy is surrounded by a large, roughly spherical halo of old stars. The diameter is about 100,000 light years and the stars therein, known as Population II stars, are among the oldest known, with ages of 10 billion years or even more. They also differ from the younger stars nearer to the main plane of the Milky Way (in which our 4.7 billion year old Sun is located) by being very metal-poor. Many of the halo stars consist almost solely of hydrogen and helium, reflecting the composition of matter in the young Universe. This halo is important for our understanding of the processes that led to the formation of the Milky Way galaxy. It is believed that many of the halo stars and those of the same type found in globular clusters existed already before the Milky Way had fully formed. Galaxy cannibalism Many astronomers suspect that galaxies evolve and gradually grow larger and heavier by practising cannibalism on their own kind. In this picture, when two galaxies collide in space, the stars and nebulae in the smaller one will disperse and soon be taken over by the larger one, which

  20. Figuring Out Gas and Galaxies in Enzo (FOGGIE): Simulating effects of feedback on galactic outflows (United States)

    Morris, Melissa Elizabeth; Corlies, Lauren; Peeples, Molly; Tumlinson, Jason; O'Shea, Brian; Smith, Britton


    The circumgalactic medium (CGM) is the region beyond the galactic disk in which gas is accreted through pristine inflows from the intergalactic medium and expelled from the galaxy by stellar feedback in large outflows that can then be recycled back onto the disk. These gas cycles connect the galactic disk with its cosmic environment, making the CGM a vital component of galaxy evolution. However, the CGM is primarily observed in absorption, which can be difficult to interpret. In this study, we use high resolution cosmological hydrodynamic simulations of a Milky Way mass halo evolved with the code Enzo to aid the interpretation of these observations. In our simulations, we vary feedback strength and observe the effect it has on galactic outflows and the evolution of the galaxy’s CGM. We compare the star formation rate of the galaxy with the velocity flux and mass outflow rate as a function of height above the plane of the galaxy in order to measure the strength of the outflows and how far they extend outside of the galaxy.This work was supported by The Space Astronomy Summer Program at STScI and NSF grant AST-1517908.

  1. Numerical computation of gravitational field of general extended body and its application to rotation curve study of galaxies (United States)

    Fukushima, Toshio


    Reviewed are recently developed methods of the numerical integration of the gravitational field of general two- or three-dimensional bodies with arbitrary shape and mass density distribution: (i) an axisymmetric infinitely-thin disc (Fukushima 2016a, MNRAS, 456, 3702), (ii) a general infinitely-thin plate (Fukushima 2016b, MNRAS, 459, 3825), (iii) a plane-symmetric and axisymmetric ring-like object (Fukushima 2016c, AJ, 152, 35), (iv) an axisymmetric thick disc (Fukushima 2016d, MNRAS, 462, 2138), and (v) a general three-dimensional body (Fukushima 2016e, MNRAS, 463, 1500). The key techniques employed are (a) the split quadrature method using the double exponential rule (Takahashi and Mori, 1973, Numer. Math., 21, 206), (b) the precise and fast computation of complete elliptic integrals (Fukushima 2015, J. Comp. Appl. Math., 282, 71), (c) Ridder's algorithm of numerical differentiaion (Ridder 1982, Adv. Eng. Softw., 4, 75), (d) the recursive computation of the zonal toroidal harmonics, and (e) the integration variable transformation to the local spherical polar coordinates. These devices succesfully regularize the Newton kernel in the integrands so as to provide accurate integral values. For example, the general 3D potential is regularly integrated as Φ (\\vec{x}) = - G \\int_0^∞ ( \\int_{-1}^1 ( \\int_0^{2π} ρ (\\vec{x}+\\vec{q}) dψ ) dγ ) q dq, where \\vec{q} = q (√{1-γ^2} cos ψ, √{1-γ^2} sin ψ, γ), is the relative position vector referred to \\vec{x}, the position vector at which the potential is evaluated. As a result, the new methods can compute the potential and acceleration vector very accurately. In fact, the axisymmetric integration reproduces the Miyamoto-Nagai potential with 14 correct digits. The developed methods are applied to the gravitational field study of galaxies and protoplanetary discs. Among them, the investigation on the rotation curve of M33 supports a disc-like structure of the dark matter with a double-power-law surface

  2. HIghMass-high H I mass, H I-rich galaxies at z ∼ 0 sample definition, optical and Hα imaging, and star formation properties

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Shan; Matsushita, Satoki [Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, National Taiwan University, Taipei 10617, Taiwan (China); Haynes, Martha P.; Giovanelli, Riccardo; Hallenbeck, Gregory; Jones, Michael G.; Adams, Elizabeth A. K. [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Brinchmann, Jarle [Sterrewacht Leiden, Leiden University, NL-2300 RA Leiden (Netherlands); Chengalur, Jayaram N. [National Centre for Radio Astrophysics, Tata Institute for Fundamental Research, Pune 411007 (India); Hunt, Leslie K. [INAF-Osservatorio Astrofisico di Arcetri, Largo East Fermi 5, I-50125, Firenze (Italy); Masters, Karen L. [Institute of Cosmology and Gravitation, Dennis Sciama Building, Burnaby Road, Portsmouth POI 3FX (United Kingdom); Saintonge, Amelie [Department of Physics and Astronomy, University College London, Gower Place, London WC1E 6BT (United Kingdom); Spekkens, Kristine, E-mail: [Royal Military College of Canada, Department of Physics, P.O. Box 17000, Station Forces, Kingston, ON K7K 7B4 (Canada)


    We present first results of the study of a set of exceptional H I sources identified in the 40% ALFALFA extragalactic H I survey catalog α.40 as both being H I massive (M{sub HI}>10{sup 10} M{sub ⊙}) and having high gas fractions for their stellar masses: the HIghMass galaxy sample. We analyze UV- and optical-broadband and Hα images to understand the nature of their relatively underluminous disks in optical and to test whether their high gas fractions can be tracked to higher dark matter halo spin parameters or late gas accretion. Estimates of their star formation rates (SFRs) based on spectral energy distribution fitting agree within uncertainties with the Hα luminosity inferred current massive SFRs. The H II region luminosity functions, parameterized as dN/dlog L∝L {sup α}, have standard slopes at the luminous end (α ∼ –1). The global SFRs demonstrate that the HIghMass galaxies exhibit active ongoing star formation (SF) with moderate SF efficiency but, relative to normal spirals, a lower integrated SFR in the past. Because the SF activity in these systems is spread throughout their extended disks, they have overall lower SFR surface densities and lower surface brightness in the optical bands. Relative to normal disk galaxies, the majority of HIghMass galaxies have higher Hα equivalent widths and are bluer in their outer disks, implying an inside-out disk growth scenario. Downbending double exponential disks are more frequent than upbending disks among the gas-rich galaxies, suggesting that SF thresholds exist in the downbending disks, probably as a result of concentrated gas distribution.

  3. Globular Clusters for Faint Galaxies (United States)

    Kohler, Susanna


    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

  4. Evidence of Cosmic Accretion in Local Tadpole Galaxies (United States)

    Elmegreen, Debra M.; Elmegreen, Bruce; Sanchez Almeida, Jorge; Munoz-Tunon, Casiana; Rafelski, Marc; Gallagher, John S.; Mendez-Abreu, Jairo; Amorin, R.; Filho, M.; Ascasibar, Y.; Papaderos, P.; Vilchez, J.; Perez-Montero, E.


    Star formation in galaxies over cosmic time may be driven by gas accretion from the cosmic web. Spectra of local extremely metal-poor galaxies (XMPs), obtained using the Gran Telescopio Canarias, show oxygen abundances that decrease by a factor of 5 to 10 in the main star-forming regions compared with the disks in 9 of 10 observed galaxies. The results suggest that the galaxies have accreted metal-poor gas in the starburst regions. Tadpole galaxies, which have a main star-forming head and a tail, are common at high redshift but rare locally. Local tadpoles tend to be XMPs. We present multiband HST WFC3 observations of Kiso 5639, one of the tadpole XMPs in our GTC sample. There are faint extended H alpha filaments, and dense star clusters in the midst of a powerful starburst. The clusters, with log masses of 4 to 5, are reminiscent of those found in other dwarf irregular galaxies where impacting gas streams have been suggested.

  5. Why Do Disks Form Jets? (United States)

    Lynden-Bell, D.

    It is argued that jet modelers have given insufficient study to the natural magneto-static configurations of field wound up in the presence of a confining general pressure. Such fields form towers whose height grows with each twist at a velocity comparable to the circular velocity of the accretion disk that turns them. A discussion of the generation of such towers is preceded by a brief history of the idea that quasars, active galaxies, and galactic nuclei contain giant black holes with accretion disks.

  6. Spatially-resolved star formation histories of CALIFA galaxies. Implications for galaxy formation (United States)

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


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

  7. GASP. IV. A Muse View of Extreme Ram-pressure-stripping in the Plane of the Sky: The Case of Jellyfish Galaxy JO204 (United States)

    Gullieuszik, Marco; Poggianti, Bianca M.; Moretti, Alessia; Fritz, Jacopo; Jaffé, Yara L.; Hau, George; Bischko, Jan C.; Bellhouse, Callum; Bettoni, Daniela; Fasano, Giovanni; Vulcani, Benedetta; D'Onofrio, Mauro; Biviano, Andrea


    In the context of the GAs Stripping Phenomena in galaxies with Muse (GASP) survey, we present the characterization of JO204, a jellyfish galaxy in A957, a relatively low-mass cluster with M=4.4× {10}14 {M}⊙ . This galaxy shows a tail of ionized gas that extends up to 30 kpc from the main body in the opposite direction of the cluster center. No gas emission is detected in the galaxy outer disk, suggesting that gas-stripping is proceeding outside-in. The stellar component is distributed as a regular disk galaxy; the stellar kinematics shows a symmetric rotation curve with a maximum radial velocity of 200 km s-1 out to 20 kpc from the galaxy center. The radial velocity of the gas component in the central part of the disk follows the distribution of the stellar component; the gas kinematics in the tail retains the rotation of the galaxy disk, indicating that JO204 is moving at high speed in the intracluster medium. Both the emission and radial-velocity maps of the gas and stellar components indicate ram-pressure as the most likely primary mechanism for gas-stripping, as expected given that JO204 is close to the cluster center and it is likely at the first infall in the cluster. The spatially resolved star formation history of JO204 provides evidence that the onset of ram-pressure-stripping occurred in the last 500 Myr, quenching the star formation activity in the outer disk, where the gas has been already completely stripped. Our conclusions are supported by a set of hydrodynamic simulations.

  8. Compact quiescent galaxies at intermediate redshifts {sup ,}

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    Hsu, Li-Yen; Stockton, Alan; Shih, Hsin-Yi [Institute of Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)


    From several searches of the area common to the Sloan Digital Sky Survey and the United Kingdom Infrared Telescope Infrared Deep Sky Survey, we have selected 22 luminous galaxies between z ∼ 0.4 and z ∼ 0.9 that have colors and sizes similar to those of the compact quiescent galaxies at z > 2. By exploring structural parameters and stellar populations, we found that most of these galaxies actually formed most of their stars at z < 2 and are generally less compact than those found at z > 2. Several of these young objects are disk-like or possibly prolate. This lines up with several previous studies that found that massive quiescent galaxies at high redshifts often have disk-like morphologies. If these galaxies were to be confirmed to be disk-like, their formation mechanism must be able to account for both compactness and disks. On the other hand, if these galaxies were to be confirmed to be prolate, the fact that prolate galaxies do not exist in the local universe would indicate that galaxy formation mechanisms have evolved over cosmic time. We also found five galaxies forming over 80% of their stellar masses at z > 2. Three of these galaxies appear to have been modified to have spheroid-like morphologies, in agreement with the scenario of 'inside-out' buildup of massive galaxies. The remaining galaxies, SDSS J014355.21+133451.4 and SDSS J115836.93+021535.1, have truly old stellar populations and disk-like morphologies. These two objects would be good candidates for nearly unmodified compact quiescent galaxies from high redshifts that are worth future study.

  9. Exact Relativistic Magnetized Haloes around Rotating Disks

    Directory of Open Access Journals (Sweden)

    Antonio C. Gutiérrez-Piñeres


    Full Text Available The study of the dynamics of magnetic fields in galaxies is one of important problems in formation and evolution of galaxies. In this paper, we present the exact relativistic treatment of a rotating disk surrounded by a magnetized material halo. The features of the halo and disk are described by the distributional energy-momentum tensor of a general fluid in canonical form. All the relevant quantities and the metric and electromagnetic potentials are exactly determined by an arbitrary harmonic function only. For instance, the generalized Kuzmin-disk potential is used. The particular class of solutions obtained is asymptotically flat and satisfies all the energy conditions. Moreover, the motion of a charged particle on the halo is described. As far as we know, this is the first relativistic model describing analytically the magnetized halo of a rotating disk.

  10. Resolving the Disk-Halo Degeneracy using Planetary Nebulae (United States)

    Aniyan, S.; Freeman, K. C.; Arnaboldi, M.; Gerhard, O.; Coccato, L.; Fabricius, M.; Kuijken, K.; Merrifield, M.


    The decomposition of the 21 cm rotation curve of galaxies into contribution from the disk and dark halo depends on the adopted mass to light ratio (M/L) of the disk. Given the vertical velocity dispersion (σ z ) of stars in the disk and its scale height (h z ), the disk surface density and hence the M/L can be estimated. Earlier works have used this technique to conclude that galaxy disks are submaximal. Here we address an important conceptual problem: star-forming spirals have an old (kinematically hot) disk population and a young cold disk population. Both of these populations contribute to the integrated light spectra from which σ z is measured. The measured scale height h z is for the old disk population. In the Jeans equation, σ z and h z must pertain to the same population. We have developed techniques to extract the velocity dispersion of the old disk from integrated light spectra and from samples of planetary nebulae. We present the analysis of the disk kinematics of the galaxy NGC 628 using IFU data in the inner regions and planetary nebulae as tracers in the outer regions of the disk. We demonstrate that using the scale height of the old thin disk with the vertical velocity dispersion of the same population, traced by PNe, results in a maximal disk for NGC 628. Our analysis concludes that previous studies underestimate the disk surface mass density by ~ 2, sufficient to make a maximal disk for NGC 628 appear like a submaximal disk.

  11. Too Fast, Too Furious: A Galaxy's Fatal Plunge (United States)


    the galaxy looks unusually clumpy with many young star clusters and chaotic dust features. Besides the disrupted features in the galaxy's disk, HST also showed that the light in the tail is mostly attributed to recent star formation, providing a direct link to the stripping of the galaxy as it passed through the cluster core. Gas compressed along the galaxy's leading edge, like snow before a plow, ignited a firestorm of new star birth. Evidence of recent star formation also comes from the optical spectrum obtained at the 10-meter Gemini North telescope in Hawaii. The spectrum allows the researchers to estimate the time since the most recent burst of star formation. This conclusion was further bolstered when the Mosaic camera on Kitt Peak's Mayall telescope found a very long tail of extended gas coming off the galaxy. The tail was apparently generated in part by a hurricane of stellar winds boiling off the new star-birth regions and being blown backwards as the galaxy streaks through the surrounding hot gas of the cluster. Spectroscopic observations with the Gemini telescope allowed astronomers to age-date the starburst. They find that 90 percent of C153's blue light is from a population of stars that are 100 million years old. This age corresponds to the time the galaxy should have gone careening through the densest gas in the cluster core. The Gemini spectroscopic observations show the stars are in a regular pattern of orbital motion around the center, as usual for disk galaxies. However, there are multiple widespread clouds of gas moving independently of the stars. "This is an important clue that something beyond gravitational forces must be at work, since stars and gas respond the same way to purely gravitational forces," says Keel. "In other words, the galaxy's gas doesn't know what the stars are doing." NASA's Chandra X-ray Observatory discovered that the cooler clouds detected with optical telescopes and an associated radio feature are embedded in a much larger

  12. A Modern Picture of Barred Galaxy Dynamics (United States)

    Petersen, Michael; Weinberg, Martin; Katz, Neal


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


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    Pan, Zhizheng; Kong, Xu; Fan, Lulu, E-mail:, E-mail: [Center of Astrophysics, University of Science and Technology of China, Hefei 230026 (China)


    We present research on the morphologies, spectra, and environments of ≈2350 'green valley' galaxies at 0.2 < z < 1.0 in the COSMOS field. The bimodality of dust-corrected NUV–r {sup +} color is used to define 'green valley'; it removes dusty star-forming galaxies from galaxies that are truly transitioning between the blue cloud and the red sequence. Morphological parameters of green galaxies are intermediate between those of blue and red galaxy populations, both on the Gini-asymmetry and the Gini-M{sub 20} planes. Approximately 60%-70% of green disk galaxies have intermediate or big bulges, and only 5%-10% are pure disk systems, based on morphological classification using the Zurich Estimator of Structural Types. The obtained average spectra of green galaxies are intermediate between blue and red ones in terms of [O II], Hα, and Hβ emission lines. Stellar population synthesis on the average spectra shows that green galaxies are on average older than blue galaxies but younger than red galaxies. Green galaxies and blue galaxies have similar projected galaxy density (Σ{sub 10}) distributions at z > 0.7. At z < 0.7, the fractions of M{sub *} < 10{sup 10.0} M{sub ☉} green galaxies located in a dense environment are found to be significantly larger than those of blue galaxies. The morphological and spectral properties of green galaxies are consistent with the transitioning population between the blue cloud and the red sequence. The possible mechanisms for quenching star formation activities in green galaxies are discussed. The importance of active galactic nucleus feedback cannot be well constrained in our study. Finally, our findings suggest that environmental conditions, most likely starvation and harassment, significantly affect the transformation of M{sub *} < 10{sup 10.0} M{sub ☉} blue galaxies into red galaxies, especially at z < 0.5.

  14. Gas-rich dwarf galaxies in dense and sparse environments (United States)

    Hoffman, G. Lyle


    Dwarf irregular galaxies (generically labelled Im for the present purposes) pose an enigma to students of galaxy evolution. In nearby groups and the Virgo cluster, Im galaxies are at least as abundant as spiral galaxies, and their low surface brightnesses and high gas-to-stars ratios suggest that (at least in the stochastic self-propagating star formation scenario) there should be significant numbers of HI clouds with masses approaching 10(exp 8) solar mass which have undergone very little or no star formation. To date, however, no clouds with so little star formation that they would not be recognized as Im galaxies on high-quality photographic plates have been identified. There have been suggestions that such dwarfs may be tidally disrupted in regions of high galactic density, but may be prevalent in low density regions. We offer data from three parallel programs relevant to this issue. (1) A large number of Im galaxies throughout the Local Supercluster have been mapped in the HI spectral line using the Arecibo Radiotelescope, and we can establish the frequency with which HI disks much more extended than their optically visible portions are found. (2) Our extensive mapping of spiral and dwarf galaxies in the Virgo cluster allows us to set stringent limits on the density of star-free Hi clouds in that cluster. (3) We have conducted a sampling of the void in the distribution of galaxies toward the super galactic pole, optimized for finding low-mass HI clouds at redshifts out to approximately 2000 km/s.

  15. Surface photometry of bulge dominated low surface brightness galaxies

    NARCIS (Netherlands)

    Beijersbergen, M; de Blok, WJG; van der Hulst, JM


    We present results of broad band BVRI observations of a sample of galaxies with a low surface brightness (LSB) disk and a bulge. These galaxies are well described as exponential disks and exponential bulges with no preferred value for either scale length or central surface brightness. The median B

  16. Kinematic Effects of Tidal Interaction on Galaxy Rotation Curves


    Barton, Elizabeth J.; Bromley, Benjamin C.; Geller, Margaret J.


    We use self-consistent N-body models, in conjunction with models of test particles moving in galaxy potentials, to explore the initial effects of interactions on the rotation curves of spiral galaxies. Using nearly self-consistent disk/bulge/halo galaxy models (Kuijken & Dubinski 1995), we simulate the first pass of galaxies on nearly parabolic orbits; we vary orbit inclinations, galaxy halo masses and impact parameters. For each simulation, we mimic observed rotation curves of the model gala...

  17. NGC 5291: Implications for the Formation of Dwarf Galaxies (United States)

    Malphrus, Benjamin K.; Simpson, Caroline E.; Gottesman, S. T.; Hawarden, Timothy G.


    The possible formation and evolution of dwarf irregular galaxies from material derived from perturbed evolved galaxies is addressed via an H I study of a likely example, the peculiar system NGC 5291. This system, located in the western outskirts of the cluster Abell 3574, contains the lenticular galaxy NGC 5291 which is in close proximity to a disturbed companion and is flanked by an extensive complex of numerous knots extending roughly 4 min north and 4 min south of the galaxy. In an initial optical and radio study, Longmore et al. (1979, MNRAS, 188, 285) showed that these knots have the spectra of vigorous star-forming regions, and suggested that some may in fact be young dwarf irregular galaxies. High resolution 21-cm line observations taken with the VLA are presented here and reveal that the H I distribution associated with this system encompasses not only the entire N-S complex of optical knots, but also forms an incomplete ring or tail that extends approximately 3 min to the west. The H I associated with NGC 5291 itself shows a high velocity range; the Seashell is not detected. The formation mechanism for this unusual system is unclear and two models - a large, low-luminosity ram-swept disk, and a ram-swept interaction-are discussed. The H I in the system contains numerous concentrations, mostly along the N-S arc of the star-forming complexes, which generally coincide with one or more optical knots; the larger H I features contain several x 10(exp 9) solar mass of gas. Each of the knots is compared to a set of criteria designed to determine if these objects are bound against their own internal kinetic energy and are tidally stable relative to the host galaxy. An analysis of the properties of the H I concentrations surrounding the optical star-forming complexes indicates that at least the largest of these is a bound system; it also possesses a stellar component. It is suggested that this object is a genuinely young dwarf irregular galaxy that has evolved from



    This diagram shows the geometry of a warped disk of dust surrounding a suspected black hole in the active galaxy NGC 6251. The diagram is based on NASA Hubble Space Telescope images of the disk which reveal that only one side reflects light emitted from a suspected black hole, hence the disk is warped. Such a warp could be due to gravitational perturbations in the galaxy's nucleus that keep the disk from being perfectly flat, or from precession of the rotation axis of the black hole relative to the rotation axis of the galaxy. Perpendicular to the disk is a jet of high-energy particles blasted into space along the black hole's spin axis. Illustration: James Gitlin (Space Telescope Science Institute)

  19. Dust in protoplanetary disks: observations*

    Directory of Open Access Journals (Sweden)

    Waters L.B.F.M.


    Full Text Available Solid particles, usually referred to as dust, are a crucial component of interstellar matter and of planet forming disks surrounding young stars. Despite the relatively small mass fraction of ≈1% (in the solar neighborhood of our galaxy; this number may differ substantially in other galaxies that interstellar grains represent of the total mass budget of interstellar matter, dust grains play an important role in the physics and chemistry of interstellar matter. This is because of the opacity dust grains at short (optical, UV wavelengths, and the surface they provide for chemical reactions. In addition, dust grains play a pivotal role in the planet formation process: in the core accretion model of planet formation, the growth of dust grains from the microscopic size range to large, cm-sized or larger grains is the first step in planet formation. Not only the grain size distribution is affected by planet formation. Chemical and physical processes alter the structure and chemical composition of dust grains as they enter the protoplanetary disk and move closer to the forming star. Therefore, a lot can be learned about the way stars and planets are formed by observations of dust in protoplanetary disks. Ideally, one would like to measure the dust mass, the grain size distribution, grain structure (porosity, fluffiness, the chemical composition, and all of these as a function of position in the disk. Fortunately, several observational diagnostics are available to derive constrains on these quantities. In combination with rapidly increasing quality of the data (spatial and spectral resolution, a lot of progress has been made in our understanding of dust evolution in protoplanetary disks. An excellent review of dust evolution in protoplanetary disks can be found in Testi et al. (2014.

  20. Circumnuclear Structures in Megamaser Host Galaxies (United States)

    Pjanka, Patryk; Greene, Jenny E.; Seth, Anil C.; Braatz, James A.; Henkel, Christian; Lo, Fred K. Y.; Läsker, Ronald


    Using the Hubble Space Telescope, we identify circumnuclear (100-500 pc scale) structures in nine new H2O megamaser host galaxies to understand the flow of matter from kpc-scale galactic structures down to the supermassive black holes (SMBHs) at galactic centers. We double the sample analyzed in a similar way by Greene et al. and consider the properties of the combined sample of 18 sources. We find that disk-like structure is virtually ubiquitous when we can resolve hosts. We find marginal evidence that the disk-like nuclear structures show increasing misalignment from the kpc-scale host galaxy disk as the scale of the structure decreases. In turn, we find that the orientation of both the ˜100 pc scale nuclear structures and their host galaxy large-scale disks is consistent with random with respect to the orientation of their respective megamaser disks.

  1. A tidally distorted dwarf galaxy near NGC 4449. (United States)

    Rich, R M; Collins, M L M; Black, C M; Longstaff, F A; Koch, A; Benson, A; Reitzel, D B


    NGC 4449 is a nearby Magellanic irregular starburst galaxy with a B-band absolute magnitude of -18 and a prominent, massive, intermediate-age nucleus at a distance from Earth of 3.8 megaparsecs (ref. 3). It is wreathed in an extraordinary neutral hydrogen (H I) complex, which includes rings, shells and a counter-rotating core, spanning ∼90 kiloparsecs (kpc; refs 1, 4). NGC 4449 is relatively isolated, although an interaction with its nearest known companion--the galaxy DDO 125, some 40 kpc to the south--has been proposed as being responsible for the complexity of its H I structure. Here we report the presence of a dwarf galaxy companion to NGC 4449, namely NGC 4449B. This companion has a V-band absolute magnitude of -13.4 and a half-light radius of 2.7 kpc, with a full extent of around 8 kpc. It is in a transient stage of tidal disruption, similar to that of the Sagittarius dwarf near the Milky Way. NGC 4449B exhibits a striking S-shaped morphology that has been predicted for disrupting galaxies but has hitherto been seen only in a dissolving globular cluster. We also detect an additional arc or disk ripple embedded in a two-component stellar halo, including a component extending twice as far as previously known, to about 20 kpc from the galaxy's centre.

  2. Gas, Stars, and Star Formation in Alfalfa Dwarf Galaxies (United States)

    Huang, Shan; Haynes, Martha P.; Giovanelli, Riccardo; Brinchmann, Jarle; Stierwalt, Sabrina; Neff, Susan G.


    We examine the global properties of the stellar and Hi components of 229 low H i mass dwarf galaxies extracted from the ALFALFA survey, including a complete sample of 176 galaxies with H i masses dwarfs are faint and of low surface brightness; only 56% of those within the SDSS footprint have a counterpart in the SDSS spectroscopic survey. A large fraction of the dwarfs have high specific star formation rates (SSFRs), and estimates of their SFRs and M* obtained by SED fitting are systematically smaller than ones derived via standard formulae assuming a constant SFR. The increased dispersion of the SSFR distribution at M* approximately less than10(exp 8)M(sub 0) is driven by a set of dwarf galaxies that have low gas fractions and SSFRs; some of these are dE/dSphs in the Virgo Cluster. The imposition of an upper Hi mass limit yields the selection of a sample with lower gas fractions for their M* than found for the overall ALFALFA population. Many of the ALFALFA dwarfs, particularly the Virgo members, have H i depletion timescales shorter than a Hubble time. An examination of the dwarf galaxies within the full ALFALFA population in the context of global star formation (SF) laws is consistent with the general assumptions that gas-rich galaxies have lower SF efficiencies than do optically selected populations and that Hi disks are more extended than stellar ones.

  3. A Century of Galaxy Spectroscopy (United States)

    Rubin, Vera C.


    The first successful spectrum of a galaxy, M31, was obtained in 1898 and published in a two-page paper in the young Astrophysical Journal (Scheiner 1899). Thus the first century of galaxy spectroscopy and the first century of the Astrophysical Journal are almost coincident; I celebrate both in this paper. I describe the very early history of the determination of internal kinematics in spiral galaxies, often by quoting the astronomers' own published words. By mid-century, observations with improved optical and radio telescopes offered evidence that much of the matter in a galaxy is dark. As the century ends, research interests have enlarged to include study of spheroidal and disk galaxies with complex nuclear (and other) kinematics. These complicated velocity patterns are understood as the result of interactions, acquisitions, and mergers, and offer clear evidence of the important role of gravitational effects in galaxy evolution.

  4. Enhancement of features in galaxy images (United States)

    Djorgovski, S.


    Several image-enhancement techniques useful for morphological analysis of galactic or cometary images are described and compared. Such techniques can be used to search for, and investigate the properties of dust lanes, stellar disks or rings, jets, shells, tidal distortions, etc. Applications of the techniques are illustrated on CCD images of the peculiar galaxy Arp 230; this object has a rich morphology, indicative of a merger of two disk galaxies.

  5. Formation of dwarf galaxies in tidal tails (United States)

    Barnes, Joshua E.; Hernquist, Lars


    The results are reported of numerical simulations of encounters between disk galaxies, each modeled with a central bulge, an exponential disk, and a spheroidal dark-matter halo. It is found that dwarf systems form in material drawn out during the encounter; these objects can capture large amounts of moderately enriched gas but retain little dark matter from their parents' haloes. They should therefore have lower mass-to-light ratios than galaxies formed directly by the collapse of primordial matter.

  6. Stellar population properties of the most massive globular clusters and ultra-compact dwarf galaxies of the Fornax cluster (United States)

    Hilker, Michael


    Most ultra-compact dwarf galaxies (UCDs) and very massive globular clusters reside in nearby galaxy clusters or around nearby giant galaxies. Due to their distance (> 4 Mpc) and compactness (r eff simulations on the disruption process of nucleated dwarf galaxies in cluster environments showed that ~ 40% of the most massive UCDs should originate from nuclear star clusters. Some Fornax UCDs actually show evidence for this scenario, as revealed by extended low surface brightness disks around them and onsets of tidal tails. Multi-band UV to optical imaging as well as low to medium resolution spectroscopy revealed that there exist UCDs with youngish ages, (sub-)solar [α/Fe] abundances, and probably He-enriched populations.

  7. First Characterization of the Neutral ISM in Two Local Volume Dwarf Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Bralts-Kelly, Lilly; Bulatek, Alyssa M.; Chinski, Sarah; Ford, Robert N.; Gilbonio, Hannah E.; Helmel, Greta; McGlasson, Riley; Mizener, Andrew; Cannon, John M. [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); Kaisin, Serafim; Karachentsev, Igor [Special Astrophysical Observatory of RAS, Nizhnij Arkhyz, KChR, 369167 (Russian Federation); Denn, Grant, E-mail:, E-mail:, E-mail:, E-mail: [Department of Physics, Metropolitan State University of Denver, P.O. Box 173362, Denver, CO 80217 (United States)


    We present the first H i spectral-line images of the nearby, star-forming dwarf galaxies UGC 11411 and UGC 8245, acquired as part of the “Observing for University Classes” program with the Karl G. Jansky Very Large Array (VLA). These low-resolution images localize the H i gas and reveal the bulk kinematics of each system. Comparing with Hubble Space Telescope ( HST ) broadband and ground-based H α imaging, we find that the ongoing star formation in each galaxy is associated with the highest H i mass surface density regions. UGC 8245 has a much lower current star formation rate than UGC 11411, which harbors very high surface brightness H α emission in the inner disk and diffuse, lower surface brightness nebular gas that extends well beyond the stellar disk as traced by HST . We measure the dynamical masses of each galaxy and find that the halo of UGC 11411 is more than an order of magnitude more massive than the halo of UGC 8245, even though the H i and stellar masses of the sources are similar. We show that UGC 8245 shares similar physical properties with other well-studied low-mass galaxies, while UGC 11411 is more highly dark matter dominated. Both systems have negative peculiar velocities that are associated with a coherent flow of nearby galaxies at high supergalactic latitude.

  8. Moving groups in the Galactic thin disk (United States)

    Ramya, P.; Reddy, Bacham Eswar

    Apart from the large scale structures named as thick disk and thin disk, many small scale structures or overdensities are observed in the velocity fields of disk stars in the solar neighborhood. Such structures include open clusters, OB associations, stellar streams etc. Stellar streams or moving groups are kinematically coherent groups of stars which are gravitationally unbound and are seen scattered all over the sky. Although they have been known and studied for long, their origin is not well understood. The most popular scenarios explaining the origin of moving groups are cluster disruption, dynamical perturbations within the Galaxy and the tidal disruption of satellite galaxies by the Galaxy. Arcturus stream is a well known example of streams in the thick disk, while Hercules stream, Sirius stream, Hyades stream etc, are the popular ones in the thin disk of the Galaxy. Here, we present the results of our analysis of three streams -Sirius, Hercules and Hyades. Candidate members for each of the streams were chosen based on the kinematic classification provided in the literature. The kinematic motion (U, V, W) of the sample stars, and the probability with which stars belong to the Galactic thin disk are calculated. Main focus of our study is to understand the chemistry of the stream members. The detailed chemical composition is obtained through high resolution spectroscopy and the results are compared with the abundance patterns of different Galactic components. We do not find chemical homogeneity among the stream members. It appears that the member stars are of different origin. Although, the abundance patterns in these streams favour dynamical perturbations within the Galaxy, the association of Hyades stream with Hyades cluster has been discussed.

  9. Radio Continuum and H I Study of Blue Compact Dwarf Galaxies (United States)

    Ramya, S.; Kantharia, N. G.; Prabhu, T. P.


    The multifrequency radio continuum and 21 cm H I observations of five blue compact dwarf (BCD) galaxies, Mrk 104, Mrk 108, Mrk 1039, Mrk 1069, and I Zw 97, using the Giant Meterwave Radio Telescope (GMRT) are presented here. Radio continuum emission at 610 MHz and 325 MHz is detected from all the observed galaxies whereas only a few are detected at 240 MHz. In our sample, three galaxies (Mrk 104, Mrk 108, and Mrk 1039) are members of groups and two galaxies (Mrk 1069 and I Zw 97) are isolated galaxies. The radio emission from Mrk 104 and Mrk 108 is seen to encompass the entire optical galaxy whereas the radio emission from Mrk 1039, Mrk 1069, and I Zw 97 is confined to massive H II regions. This, we suggest, indicates that the star formation in the latter group of galaxies has recently been triggered and that the environment in which the galaxy is evolving plays a role. Star formation rates (SFRs) calculated from 610 MHz emission are in the range 0.01-0.1 M sun yr-1 this is similar to the SFR obtained for individual star-forming regions in BCDs. The integrated radio spectra of four galaxies are modeled over the frequency range where data is available. We find that two of the galaxies, Mrk 1069 and Mrk 1039, show a turnover at low frequencies, which is well fitted by free-free absorption whereas the other two galaxies, Mrk 104 and Mrk 108, show a power law at the lowest GMRT frequencies. The flatter spectrum, localized star formation, and radio continuum in isolated galaxies lend support to stochastic self-propagating star formation. The H I observations of four galaxies, Mrk 104, Mrk 108, Mrk 1039, and Mrk 1069, show extended disks as large as ~1.1-6 times the optical size. All the observed BCDs (except Mrk 104) show rotating disk with a half power width of ~50-124 km s-1. Solid body rotation is common in our sample. We note that the tidal dwarf origin is possible for two of the BCDs in our sample.

  10. Constraining a Thin Dark Matter Disk with Gaia


    Schutz, Katelin; Lin, Tongyan; Safdi, Benjamin R.; Wu, Chih-Liang


    If a component of the dark matter has dissipative interactions, it could collapse to form a thin dark disk in our Galaxy that is coplanar with the baryonic disk. It has been suggested that dark disks could explain a variety of observed phenomena, including periodic comet impacts. Using the first data release from the Gaia space observatory, we search for a dark disk via its effect on stellar kinematics in the Milky Way. Our new limits disfavor the presence of a thin dark matter disk, and we p...

  11. Morphology of the 12 Micron Seyfert Galaxies. I. Hubble Types, Axial Ratios, Bars, and Rings (United States)

    Hunt, L. K.; Malkan, M. A.


    We have compared the morphological characteristics of the 891 galaxies in the Extended 12 μm Galaxy Sample (E12GS) and assessed the effect of the 12 μm selection criterion on galaxy properties. The normal spirals in the E12GS have the same axial ratios, morphological types, and bar and ring fractions as other normal spirals. The H II/starburst galaxies have a higher incidence of bars and more than twice the normal rate of ``peculiar'' morphologies, both of which are attributable to relatively recent disturbances. The 12 μm Seyfert galaxies show a small (10%) deficiency of edge-on disks. This is caused by extinction but is a much less severe effect than in optically selected samples. There is a similar modest deficit of highly inclined H II/starburst galaxies in the 12 μm sample. The galaxies with active nuclei (Seyfert galaxies and LINERs) have the same incidence of bars as normal spirals but show rings significantly more often than normal galaxies or starbursts. The LINERs have elevated rates of inner rings, while the Seyfert galaxies have outer ring fractions several times those in normal galaxies. The different formation times of bars and rings suggest an interpretation of these differences. Bars form relatively quickly and indicate that material is recently being transported (by redistribution of angular momentum) to the center of the galaxy, where it is likely to trigger a short (e.g., mass transfer to reach the center and raise the black hole accretion rate, by which time the bar has dissolved or has begun to do so. Inner rings form before outer ones, with a formation time more comparable to bars. Thus, it may be that after an interaction or instability triggers an infall of gas, the galaxy in the earliest stage is likely to show enhanced star formation in its center, while later it is more likely to show LINER activity, and still later it is likely to be a Seyfert galaxy. The trends we find with morphology and nuclear activity are not biased either by

  12. VizieR Online Data Catalog: SDSS bulge, disk and total stellar mass estimates (Mendel+, 2014) (United States)

    Mendel, J. T.; Simard, L.; Palmer, M.; Ellison, S. L.; Patton, D. R.


    We present a catalog of bulge, disk, and total stellar mass estimates for ~660000 galaxies in the Legacy area of the Sloan Digital Sky Survey Data (SDSS) Release 7. These masses are based on a homogeneous catalog of g- and r-band photometry described by Simard et al. (2011, Cat. J/ApJS/196/11), which we extend here with bulge+disk and Sersic profile photometric decompositions in the SDSS u, i, and z bands. We discuss the methodology used to derive stellar masses from these data via fitting to broadband spectral energy distributions (SEDs), and show that the typical statistical uncertainty on total, bulge, and disk stellar mass is ~0.15 dex. Despite relatively small formal uncertainties, we argue that SED modeling assumptions, including the choice of synthesis model, extinction law, initial mass function, and details of stellar evolution likely contribute an additional 60% systematic uncertainty in any mass estimate based on broadband SED fitting. We discuss several approaches for identifying genuine bulge+disk systems based on both their statistical likelihood and an analysis of their one-dimensional surface-brightness profiles, and include these metrics in the catalogs. Estimates of the total, bulge and disk stellar masses for both normal and dust-free models and their uncertainties are made publicly available here. (4 data files).


    Energy Technology Data Exchange (ETDEWEB)

    Salem, Munier; Bryan, Greg L. [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Hummels, Cameron, E-mail: [Department of Astronomy and Steward Observatory, University of Arizona, 933 North Cherry Avenue, N309, Tucson, AZ 85721 (United States)


    We investigate the dynamical impact of cosmic rays (CR) in cosmological simulations of galaxy formation using adaptive-mesh refinement simulations of a 10{sup 12} M {sub ☉} halo. In agreement with previous work, a run with only our standard thermal energy feedback model results in a massive spheroid and unrealistically peaked rotation curves. However, the addition of a simple two-fluid model for CRs drastically changes the morphology of the forming disk. We include an isotropic diffusive term and a source term tied to star formation due to (unresolved) supernova-driven shocks. Over a wide range of diffusion coefficients, the CRs generate thin, extended disks with a significantly more realistic (although still not flat) rotation curve. We find that the diffusion of CRs is key to this process, as they escape dense star-forming clumps and drive outflows within the more diffuse interstellar medium.

  14. Star Formation in Tadpole Galaxies

    Directory of Open Access Journals (Sweden)

    Casiana Muñoz-Tuñon


    Full Text Available Tadpole Galaxies look like a star forming head with a tail structure to the side. They are also named cometaries. In a series of recent works we have discovered a number of issues that lead us to consider them extremely interesting targets. First, from images, they are disks with a lopsided starburst. This result is rmly  established with long slit spectroscopy in a nearby representative sample. They rotate with the head following the rotation pattern but displaced from the rotation center. Moreover, in a search for extremely metal poor (XMP galaxies, we identied tadpoles as the dominant shapes in the sample - nearly 80% of the local XMP galaxies have a tadpole morphology. In addition, the spatially resolved analysis of the metallicity shows the remarkable result that there is a metallicity drop right at the position of the head. This is contrary to what intuition would say and dicult to explain if star formation has happened from gas processed in the disk. The result could however be understood if the star formation is driven by pristine gas falling into the galaxy disk. If conrmed, we could be unveiling, for the rst time, cool  ows in action in our nearby world. The tadpole class is relatively frequent at high redshift - 10% of resolvable galaxies in the Hubble UDF but less than 1% in the local Universe. They are systems that could track cool ows and test models of galaxy formation.

  15. Giant Low Surface Brightness Galaxies: Evolution in Isolation M. Das

    Indian Academy of Sciences (India)

    Abstract. Giant Low Surface Brightness (GLSB) galaxies are amongst the most massive spiral galaxies that we know of in our Universe. Although they fall in the class of late type spiral galaxies, their properties are far more extreme. They have very faint stellar disks that are extremely rich in neutral hydrogen gas but low in ...

  16. Giant Low Surface Brightness Galaxies: Evolution in Isolation

    Indian Academy of Sciences (India)


    Jan 27, 2016 ... Giant Low Surface Brightness (GLSB) galaxies are amongst the most massive spiral galaxies that we know of in our Universe. Although they fall in the class of late type spiral galaxies, their properties are far more extreme. They have very faint stellar disks that are extremely rich in neutral hydrogen gas but ...


    Energy Technology Data Exchange (ETDEWEB)

    Savorgnan, G. A. D.; Graham, A. W., E-mail: [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia)


    Several recent studies have performed galaxy decompositions to investigate correlations between the black hole mass and various properties of the host spheroid, but they have not converged on the same conclusions. This is because their models for the same galaxy were often significantly different and not consistent with each other in terms of fitted components. Using 3.6 μm Spitzer imagery, which is a superb tracer of the stellar mass (superior to the K band), we have performed state-of-the-art multicomponent decompositions for 66 galaxies with directly measured black hole masses. Our sample is the largest to date and, unlike previous studies, contains a large number (17) of spiral galaxies with low black hole masses. We paid careful attention to the image mosaicking, sky subtraction, and masking of contaminating sources. After a scrupulous inspection of the galaxy photometry (through isophotal analysis and unsharp masking) and—for the first time—2D kinematics, we were able to account for spheroids; large-scale, intermediate-scale, and nuclear disks; bars; rings; spiral arms; halos; extended or unresolved nuclear sources; and partially depleted cores. For each individual galaxy, we compared our best-fit model with previous studies, explained the discrepancies, and identified the optimal decomposition. Moreover, we have independently performed one-dimensional (1D) and two-dimensional (2D) decompositions and concluded that, at least when modeling large, nearby galaxies, 1D techniques have more advantages than 2D techniques. Finally, we developed a prescription to estimate the uncertainties on the 1D best-fit parameters for the 66 spheroids that takes into account systematic errors, unlike popular 2D codes that only consider statistical errors.

  18. Star Formation Histories of Nearby Dwarf Galaxies


    Grebel, Eva K.


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

  19. On the occurrence of galaxy harassment (United States)

    Bialas, D.; Lisker, T.; Olczak, C.; Spurzem, R.; Kotulla, R.


    Context. Tidal interactions of galaxies in galaxy clusters have been proposed as one potential explanation of the morphology-density relation at low masses. Earlier studies have shown that galaxy harassment is a suitable mechanism for inducing a morphological transformation from low-mass late-type disk galaxies to the abundant early-type galaxies. Aims: The efficiency of tidal transformation is expected to depend strongly on the orbit of a galaxy within the cluster halo. The orbit determines both the strength of the cluster's global tidal field and the probability of encounters with other cluster members. Here we aim to explore these dependencies. Methods: We use a combination of N-body simulation and Monte-Carlo method to study the efficiency of the transformation of late-type galaxies by tidal interactions on different orbits in a galaxy cluster. Additionally, we investigate the effect of an inclination between the disk of the infalling galaxy and its orbital plane. We compare our results to observational data to assess the possible relevance of such transformations for the existing cluster galaxy population. Results: We find that galaxies that entered a cluster from the outskirts are unlikely to be significantly transformed (stellar mass loss ≤6%). Closer to the cluster centre, tidal interactions are a more efficient mechanism (stellar mass loss up to 50%) for producing harassed galaxies. The inclination of the disk can reduce the mass loss significantly, yet it amplifies the thickening of the galaxy disk. Galaxies with smaller sizes on intermediate orbits are nearly unaffected by tidal interactions. The tidal influence on an infalling galaxy and the likelihood that it leads to galaxy harassment make a very stochastical process that depends on the galaxy's specific history. Conclusions: We conclude that harassment is a suitable mechanism that could explain the transformation of at least a fraction of galaxies inside galaxy clusters. However, the transformation

  20. Inside-out formation of massive galaxies (United States)

    de la Rosa, I. G.


    A significant fraction of the present day massive galaxies have compact cores embedded inside their disks or halos. Strikingly, those compact cores are similar to the massive high-redshift quiescent compact galaxies, nicknamed red-nuggets. We present observational evidence supporting an inside-out formation scenario, where present-day massive galaxies can begin as dense spheroidal cores (red-nuggets), around which either a spheroidal halo or a disk are accreted later. This contribution is based on the paper by de la Rosa et al. (2016).


    NARCIS (Netherlands)



    Numerical simulations of the interacting galaxies in the NGC 520/UGC 957 system are presented. Two sets of models were produced to investigate the postulated three-galaxy system of two colliding disk galaxies within NGC 520 and the dwarf galaxy UGC 957. The morphology and kinematics of the models

  2. Why Do Disks Form Jets?


    Lynden-Bell, D.


    It is argued that jet modelers have given insufficient study to the natural magneto-static configurations of field wound up in the presence of a confining general pressure. Such fields form towers whose height grows with each twist at a velocity comparable to the circular velocity of the accretion disk that turns them. A discussion of the generation of such towers is preceded by a brief history of the idea that quasars, active galaxies, and galactic nuclei contain giant black holes with accre...

  3. Relations between the Sizes of Galaxies and Their Dark Matter Halos at Redshifts 0 < z < 3

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Kuang-Han [University of California Davis, 1 Shields Avenue, Davis, CA 95616 (United States); Fall, S. Michael; Ferguson, Henry C.; Grogin, Norman; Koekemoer, Anton [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Van der Wel, Arjen [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Lee, Seong-Kook [Center for the Exploration of the Origin of the Universe, Department of Physics and Astronomy, Seoul National University, Seoul (Korea, Republic of); Pérez-González, Pablo G. [Departamento de Astrofísica, Facultad de CC. Física, Universidad Complutense de Madrid, E-28040, Madrid (Spain); Wuyts, Stijn, E-mail: [Department of Physics, University of Bath, Claverton Down, Bath, BA2 7AY (United Kingdom)


    We derive relations between the effective radii R {sub eff} of galaxies and the virial radii R {sub 200} {sub c} of their dark matter halos over the redshift range 0 < z < 3. For galaxies, we use the measured sizes from deep images taken with Hubble Space Telescope for the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey; for halos, we use the inferred sizes from abundance matching to cosmological dark matter simulations via a stellar mass–halo mass (SMHM) relation. For this purpose, we derive a new SMHM relation based on the same selection criteria and other assumptions as for our sample of galaxies with size measurements. As a check on the robustness of our results, we also derive R {sub eff}–R {sub 200} {sub c} relations for three independent SMHM relations from the literature. We find that galaxy R {sub eff} is proportional on average to halo R {sub 200} {sub c}, confirming and extending to high redshifts the z = 0 results of Kravtsov. Late-type galaxies (with low Sérsic index and high specific star formation rate (sSFR)) follow a linear R {sub eff}– R {sub 200} {sub c} relation, with effective radii at 0.5 < z < 3 close to those predicted by simple models of disk formation; at z < 0.5, the sizes of late-type galaxies appear to be slightly below this prediction. Early-type galaxies (with high Sérsic index and low sSFR) follow a roughly parallel R {sub eff}– R {sub 200} {sub c} relation, ∼0.2–0.3 dex below the one for late-type galaxies. Our observational results, reinforced by recent hydrodynamical simulations, indicate that galaxies grow quasi-homologously with their dark matter halos.

  4. Galaxy Zoo: Observing secular evolution through bars

    Energy Technology Data Exchange (ETDEWEB)

    Cheung, Edmond; Faber, S. M.; Koo, David C. [Department of Astronomy and Astrophysics, 1156 High Street, University of California, Santa Cruz, CA 95064 (United States); Athanassoula, E.; Bosma, A. [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France); Masters, Karen L.; Nichol, Robert C.; Melvin, Thomas [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Lintott, Chris [Oxford Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Schawinski, Kevin [Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); Skibba, Ramin A. [Center for Astrophysics and Space Sciences, Department of Physics, 9500 Gilman Drive, University of California, San Diego, CA 92093 (United States); Willett, Kyle W., E-mail: [School of Physics and Astronomy, University of Minnesota, MN 55455 (United States)


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

  5. Star formation suppression in compact group galaxies

    DEFF Research Database (Denmark)

    Alatalo, K.; Appleton, P. N.; Lisenfeld, U.


    on poststarburst galaxies with molecular reservoirs, indicates that galaxies do not need to expel their molecular reservoirs prior to quenching SF and transitioning from blue spirals to red early-type galaxies. This may imply that SF quenching can occur without the need to starve a galaxy of cold gas first.......We present CO(1-0) maps of 12 warm H-2-selected Hickson Compact Groups (HCGs), covering 14 individually imaged warm H2 bright galaxies, with the Combined Array for Research in Millimeter Astronomy. We found a variety of molecular gas distributions within the HCGs, including regularly rotating disks......, bars, rings, tidal tails, and possibly nuclear outflows, though the molecular gas morphologies are more consistent with spirals and earlytype galaxies than mergers and interacting systems. Our CO-imaged HCG galaxies, when plotted on the Kennicutt-Schmidt relation, shows star formation (SF) suppression...

  6. The Contribution of Outer H I Disks to the Merging Binary Black Hole Population (United States)

    Chakrabarti, Sukanya; Chang, Philip; O'Shaughnessy, Richard; Brooks, Alyson M.; Shen, Sijing; Bellovary, Jillian; Gladysz, Wojciech; Belczynski, Chris


    We investigate the contribution of outer H I disks to the observable population of merging black hole binaries. Like dwarf galaxies, the outer H I disks of spirals have low star formation rates and lower metallicities than the inner disks of spirals. Since low-metallicity star formation can produce more detectable compact binaries than typical star formation, the environments in the outskirts of spiral galaxies may be conducive to producing a rich population of massive binary black holes. We consider here both detailed controlled simulations of spirals and cosmological simulations, as well as the current range of observed values for metallicity and star formation in outer disks. We find that the outer H I disks contribute at least as much as dwarf galaxies do to the observed LIGO/Virgo detection rates. Identifying the host galaxies of merging massive black holes should provide constraints on cosmological parameters and insights into the formation channels of binary mergers.

  7. Barred galaxy formation in the EAGLE cosmological simulation (United States)

    Abadi, M. G.; Algorry, D. G.


    We present results about the formation and evolution of stellar bars in Milky-Way sized galaxies using the EAGLE ΛCDM cosmological hydrodynamical simulation. In agreement with observational results, this simulation shows that ˜ 40% of our simulated disk galaxies have a stellar bar with a wide variety of bar strengths. Typical bar lengths are ˜ 6.5 kpc also comparing favourably to observed ones. Our unbarred disks are more gas-rich and star-forming than those having a strong bar. In concordance with previous work, bars develop in galaxies where the disk is gravitationally dominant over the dark matter halo.

  8. The Spiral Host Galaxy of the Double Radio Source 0313-192 (United States)

    Keel, William C.; White, Raymond E., III; Owen, Frazer N.; Ledlow, Michael J.


    We present new Hubble Space Telescope (HST), Gemini South, and Chandra observations of the radio galaxy 0313-192, which hosts a 350 kpc double source and jets, even though previous data have suggested that it is a spiral galaxy. We measure the bulge scale and the luminosity, radial, and vertical profiles of disk starlight and consider the distributions of H II regions and absorbing dust. In each case the HST data confirm its classification as an edge-on spiral galaxy, the only such system known to produce such an extended radio source of this kind. The Gemini near-IR images and Chandra spectral fit reveal a strongly obscured central active galactic nucleus (AGN), seen through the entire interstellar medium path length of the disk and showing X-ray evidence of additional absorption from warm or dense material close to the central object. We consider several possible mechanisms for producing such a rare combination of AGN and host properties, some combination of which may be at work. These include an unusually luminous bulge (suggesting a black hole of mass ~8×108 Msolar), the orientation of the jets near the pole of the gas-rich disk, and some evidence of a weak gravitational interaction that has warped the disk and could have enhanced fueling of the central engine. We detect an X-ray counterpart of the kiloparsec-scale radio jet emerging to the south; jet/counterjet limits on both radio and X-ray regimes allow them to be symmetric if seen more than 15° from the plane of the sky, still consistent with the jet axes being within ~30° of the poles of the gas-rich galaxy disk. A linear or disklike emission-line structure is seen around the nucleus, inclined by ~20° to the stellar disk but nearly perpendicular to the jets; this may represent the aftermath of a galaxy encounter, in which gas is photoionized by a direct view of the nuclear continuum. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute

  9. Thermal continua of AGN accretion disks (United States)

    Shields, G. A.; Coleman, H. H.


    We have computed the thermal continuum energy distribution of thermal radiation from the atmospheres of supermassive accretion disks around supermassive black holes. Non-LTE radiative transfer is combined with a model of the vertical structure at each radius appropriate to the low effective gravities of these disks. Locally, the Lyman edge of H can be in emission or absorption. When the emission is summed over the disk with Doppler and gravitational redshifts taken into account, the observed continuum typically shows little sign of a discontinuity near the Lyman edge. For relatively cool disks, the Lyman edge is in absorption, but it appears as a slope change extending over several hundred angstroms, rather than an abrupt discontinuity. Disks around Kerr black holes can explain the observed range of soft X-ray luminosities of AGN, but disks around Schwarzschild holes are much too faint in soft X-rays.

  10. Green valley galaxies

    Directory of Open Access Journals (Sweden)

    Salim S.


    Full Text Available The “green valley” is a wide region separating the blue and the red peaks in the ultraviolet-optical color magnitude diagram, first revealed using GALEX UV photometry. The term was coined by Christopher Martin (Caltech, in 2005. Green valley highlights the discriminating power of UV to very low relative levels of ongoing star formation, to which the optical colors, including u−r, are insensitive. It corresponds to massive galaxies below the star-forming, “main” sequence, and therefore represents a critical tool for the study of the quenching of star formation and its possible resurgence in otherwise quiescent galaxies. This article reviews the results pertaining to (predominantly disk morphology, structure, environment, dust content and gas properties of green valley galaxies in the local universe. Their relationship to AGN is also discussed. Attention is given to biases emerging from defining the “green valley” using optical colors. We review various evolutionary scenarios and we present evidence for a new one, the quasi-static view of the green valley, in which the majority (but not all of galaxies currently in the green valley were only partially quenched in the distant past and now participate in a slow cosmic decline of star formation, which also drives down the activity on the main sequence, presumably as a result of the dwindling accretion/cooling onto galaxy disks. This emerging synthetic picture is based on the findings from Fang et al. (2012, Salim et al. (2012 and Martin et al. (2007, as well as other results.

  11. Ultra-Deep Imaging: Structure of Disks and Haloes (United States)

    Knapen, Johan H.; Trujillo, Ignacio

    Deep imaging is a fundamental tool in the study of the outermost structures of galaxies. We review recent developments in ultra-deep imaging of galaxy disks and haloes, highlighting the technical advances as well as the challenges and summarizing observational results in the context of modern theory and simulations. The deepest modern galaxy imaging comes from three main sources: (1) surveys such as the Sloan Digital Sky Survey's Stripe 82 project; (2) very long exposures on small telescopes, including by amateurs; and (3) long exposures on the largest professional telescopes. The technical challenges faced are common in all these approaches and include the treatment of light scattered by atmosphere and telescope/instrument, correct flat fielding and the subtraction of non-galaxy light in the images. We review scientific results on galaxy disks and haloes obtained with deep imaging, including the detection and characterization of stellar haloes, tidal features and stellar streams, disk truncations and thick disks. The area of ultra-deep imaging is still very much unexplored territory, and future work in this area promises significant advances in our understanding of galaxy formation and evolution.

  12. Dark matter in low surface brightness galaxies

    NARCIS (Netherlands)

    de Blok, WJG; McGaugh, SS; Persic, M; Salucci, P


    Low Surface Brightness (LSB) galaxies form a large population of disc galaxies that extend the Hubble sequence towards extreme late-types. They are only slowly evolving, and still in an early evolutionary state. The Tully-Fisher relation and rotation curves of LSB galaxies both show that LSB

  13. Dark Matter in Low Surface Brightness Galaxies

    NARCIS (Netherlands)

    Blok, W. J. G. de; McGaugh, S. S.


    Abstract: Low Surface Brightness (LSB) galaxies form a large population of disc galaxies that extend the Hubble sequence towards extreme late-types. They are only slowly evolving, and still in an early evolutionary state. The Tully-Fisher relation and rotation curves of LSB galaxies both show that

  14. Protogalaxies. [with early disk and spheroid systems (United States)

    Cowie, Lennox L.


    It is argued that the observed sample of flat-spectrum galaxies seen in recent deep surveys must contain both early disk systems and early spheroid systems in order to match observed number counts if q sub 0 = 0.5. The low average density of neutral hydrogen in damped L-alpha systems at z = 2 - 3 separates the disk formation at z less than about 2 from spheroid formation at z greater than about 3. Based on color arguments, the period of spheroid formation is assigned to z = 4.

  15. ECO and RESOLVE: Morphology and Disk Growth in Environmental Context (United States)

    Moffett, Amanda J.; Kannappan, Sheila; Berlind, Andreas A.; Eckert, Kathleen D.; Stark, David; Hendel, David; Norris, Mark A.; Grogin, Norman A.; RESOLVE Team


    We present the first data release of the Environmental COntext (ECO) catalog, which was designed to surround and complement the RESOLVE survey with matched photometry, gas and stellar mass estimates, and environment metrics for ~13,000 galaxies in a >500,000 cubic Mpc volume. In the first results from ECO, we study the phenomenon of galaxy disk growth by considering by-eye and quantitative morphological classifications as well as galaxy environments quantified using group identifications and halo abundance matching (on integrated r-band luminosity) as well as smoothed galaxy density fields. Additionally, we derive HI gas masses and upper limits from ALFALFA data and HI mass estimates from the photometric gas fraction technique. We find that blue early-type (E/S0) galaxies, gas-dominated galaxies, and UV-bright disk host galaxies all become distinctly more common below group halo mass ˜10^11.5 Msun, implying that this low group halo mass regime may be a preferred regime for significant disk growth activity. We also find that blue early-type and blue late-type galaxies inhabit environments of similar group halo mass at fixed baryonic mass, consistent with a scenario in which blue early types can regrow late-type disks. More generally, we argue that the traditional morphology-environment relation (i.e., that denser environments have more early types) can be largely attributed to the morphology-galaxy mass relation for centrals and the color-environment relation for satellites. This work has been supported through NSF grant AST-0955368.

  16. Dusty Feedback from Massive Black Holes in Two Elliptical Galaxies (United States)

    Temi, P.; Brighenti, F.; Mathews, W. G.; Amblard, A.; Riguccini, L.


    Far-infrared dust emission from elliptical galaxies informs us about galaxy mergers, feedback energy outbursts from supermassive black holes and the age of galactic stars. We report on the role of AGN feedback observationally by looking for its signatures in elliptical galaxies at recent epochs in the nearby universe. We present Herschel observations of two elliptical galaxies with strong and spatially extended FIR emission from colder grains 5-10 kpc distant from the galaxy cores. Extended excess cold dust emission is interpreted as evidence of recent feedback-generated AGN energy outbursts in these galaxies, visible only in the FIR, from buoyant gaseous outflows from the galaxy cores.

  17. Could a Collision Between a Ghost Galaxy and the Milky Way be the Origin of the VPOS or DoS? (United States)

    Bohórquez, O. A.; Casas, A. R.


    At present within the area of astrophysics there are a number of unresolved problems, including the origin of the satellite galaxies of the Milky Way. Most of these galaxies are characterized as dwarf spheroidal galaxies. The large majority of them is distributed in a disk-like structure which is arranged almost perpendicular to the plane of the Galaxy, this structure is known as disk of satellites (DoS) or Vast Polar structure of Satellite galaxies (VPoS). So far there is not a model that fully reproduces the amount and spatial distribution of these galaxies. However there have been several proposed for the solutions, one of which suggests that these originated in the collision of two disk galaxies billions of years ago. Using the Gadget2 software, we have performed N-bodies numerical simulations of the collision between two disk galaxies that could give rise to disk of Milky Way satellites.


    Energy Technology Data Exchange (ETDEWEB)

    Hunter, Deidre A.; Ashburn, Allison; Wright, Teresa [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Elmegreen, Bruce G. [IBM T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598 (United States); Rubin, Vera C. [Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015 (United States); Józsa, Gyula I. G.; Struve, Christian [ASTRON (Netherlands Organisation for Scientific Research NWO), Oude Hoogeveensedijk 4, 7991-PD Dwingeloo (Netherlands)


    We examined star formation in two very luminous (M{sub V} = –22 to –23) Sc-type spiral galaxies, NGC 801 and UGC 2885, using ultra-deep Hα images. We combine these Hα images with UBV and Two-Micron All-Sky Survey JHK images and H I maps to explore the star formation characteristics of disk galaxies at high luminosity. Hα traces star formation in these galaxies to 4-6 disk scale lengths, but the lack of detection of Hα further out is likely due to the loss of Lyman continuum photons. Considering gravitational instabilities alone, we find that the gas and stars in the outer regions are marginally stable in an average sense, but considering dissipative gas and radial and azimuthal forcing, the outer regions are marginally unstable to forming spiral arms. Star formation is taking place in spiral arms, which are regions of locally higher gas densities. Furthermore, we have traced smooth exponential stellar disks over four magnitudes in V-band surface brightness and 4-6 disk scale lengths, in spite of a highly variable gravitational instability parameter. Thus, gravitational instability thresholds do not seem relevant to the stellar disk. One possibility for creating an exponential disk is that the molecular cloud densities and star formation rates have exponential profiles and this fact forces the stellar disk to build up such a profile. Another possibility is that the stellar disk is continuously adjusted to an exponential shape regardless of the star formation profile, for example, through global dynamical processes that scatter stars. However, such scattering processes are only known to operate in spiral systems, in which case they cannot explain the same dilemma of smooth exponential disks observed in dwarf irregular galaxies.

  19. Kinematic and chemical signatures of the formation processes of the galactic thick disk (United States)

    Spagna, A.; Curir, A.; Lattanzi, M. G.; Murante, G.; Re Fiorentin, P.; Smart, R. L.

    Thick disks have been observed in many disk galaxies and our Galaxy, the Milky Way, also presents a thick disk whose main spatial, kinematic, and chemical features of this population are well established. However, the origin of this ancient component is still unclear in spite the many studies carried out and several formation scenarios proposed until now. For the first time to our knowledge, we found evidence of a kinematics-metallicity correlation, of about 40-50 km s-1 per dex, amongst thick disk stars at 1 kpc halo, are presented.

  20. Evidence for azimuthal variations of the oxygen-abundance gradient tracing the spiral structure of the galaxy HCG 91c (United States)

    Vogt, F. P. A.; Pérez, E.; Dopita, M. A.; Verdes-Montenegro, L.; Borthakur, S.


    Context. The distribution of elements in galaxies forms an important diagnostic tool to characterize these systems' formation and evolution. This tool is, however, complex to use in practice, as galaxies are subject to a range of simultaneous physical processes active from pc to kpc scales. This renders observations of the full optical extent of galaxies down to sub-kpc scales essential. Aims: Using the WiFeS integral field spectrograph, we previously detected abrupt and localized variations in the gas-phase oxygen abundance of the spiral galaxy HCG 91c. Here, we follow-up on these observations to map HCG 91c's disk out to 2 Re at a resolution of 600 pc, and characterize the non-radial variations of the gas-phase oxygen abundance in the system. Methods: We obtained deep MUSE observations of the target under 0.6 arcsec seeing conditions. We perform both a spaxel-based and aperture-based analysis of the data to map the spatial variations of 12 +log (O/H) across the disk of the galaxy. Results: We confirm the presence of rapid variations of the oxygen abundance across the entire extent of the galaxy previously detected with WiFeS, for all azimuths and radii. The variations can be separated in two categories: a) localized and associated with individual H II regions; and b) extended over kpc scales, and occurring at the boundaries of the spiral structures in the galaxy. Conclusions: Our MUSE observations suggest that the enrichment of the interstellar medium in HGC 91c has proceeded preferentially along spiral structures, and less efficiently across them. Our dataset highlights the importance of distinguishing individual star-forming regions down to scales of a few 100 pc when using integral field spectrographs to spatially resolve the distribution of oxygen abundances in a given system, and accurately characterize azimuthal variations and intrinsic scatter. The movie associated to Fig. 8 is available at

  1. Galaxy Formation

    DEFF Research Database (Denmark)

    Sparre, Martin

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

  2. Active Galaxies

    DEFF Research Database (Denmark)

    Kilerci Eser, Ece

    one is related to the mass estimates of supermassive black holes (SMBHs). Mass estimates of SMBHs are important to understand the formation and evolution of SMBHs and their host galaxies. Black hole masses in Type 1 AGN are measured with the reverberation mapping (RM) technique. Reverberation mapping......Galaxy formation and evolution is one of the main research themes of modern astronomy. Active galaxies such as Active Galactic Nuclei (AGN) and Ultraluminous Infrared Galaxies (ULIRGs) are important evolutionary stages of galaxies. The ULIRG stage is mostly associated with galaxy mergers...... and interactions. During the interactions of gas-rich galaxies, the gas inflows towards the centers of the galaxies and can trigger both star formation and AGN activity. The ULIRG stage includes rapid star formation activity and fast black hole growth that is enshrouded by dust. Once the AGN emission...

  3. Evidence for accreted component in the Galactic disks (United States)

    Xing, Q. F.; Zhao, G.


    We analyze the distribution of [Mg/Fe] abundance in the Galactic disks with F- and G-type dwarf stars selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) archive. The sample stars are assigned into different stellar populations by using kinematic criteria. Our analysis reveals the chemical inhomogeneities in the Galactic thick disk. A few of metal-poor stars in the thick disk exhibit relatively low [Mg/Fe] abundance in respect to the standard thick-disk sample. The orbital eccentricities and maximum Galactocentric radii of low-α metal-poor stars are apparently greater than that of high-α thick-disk stars. The orbital parameters and chemical components of low-α stars in the thick disk suggests that they may have been formed in regions with low star formation rate that were located at large distances from the Galactic center, such as infalling dwarf spheroidal galaxies.

  4. The Promise of First Spectroscopy of Normal and Dwarf Galaxies

    National Research Council Canada - National Science Library

    Fischer, J


    ... 4418 and in the ultraluminous galaxies. Combined with ground-based, SOFIA and SIRTF studies, First will be able to study starburst evolution in galactic disks, gaseous abundance variations and gradients among Hubble types and the affects...

  5. Workshop on the Magellanic Clouds and other Dwarf Galaxies

    CERN Document Server

    Richtler, T; Richtler, Tom; Braun, Jochen M.


    The Workshop 'The Magellanic Clouds and Other Dwarf Galaxies' was held at the Physikzentrum Bad Honnef in January 1998. The proceedings comprise 79 contributions. About 1/3 of the 352 pages contain the following Reviews: The Violent Interstellar Medium in Dwarf Galaxies: Atomic Gas (Elias Brinks and Fabian Walter), Hot Gas in the Large Magellanic Cloud (You-Hua Chu), Astrophysics of Dwarf Galaxies: Structures and Stellar Populations (John S. Gallagher), Star-forming regions and ionized gas in irregular galaxies (Deidre A. Hunter), The Law of Star Formation in Disk Galaxies (Joachim Koeppen), Strange Dark Matters in Nearby Dwarf Galaxies (Mario Mateo), Holes and Shells in Galaxies: Observations versus Theoretical Concepts (Jan Palous), Detailed Recent Star Formation Histories of Dwarf Irregular Galaxies and Their Many Uses (Evan D. Skillman et al.), and Nearby Young Dwarf Galaxies (Trinh X. Thuan and Yuri I. Izotov). See the complete electronic version for further details.

  6. Jets in Active Galaxies

    Indian Academy of Sciences (India)

    tended regions of emission. These jets, which occur across the electromagnetic spectrum, are powered by supermassive black holes in the centres of the host galaxies. Jets are seen on the scale of parsecs in the nuclear regions to those which power the giant radio sources extending over several mega- parsecs. These jets ...

  7. Spatially resolved galaxy kinematics from hydrodynamic simulations (United States)

    Hung, Chao-Ling


    The recent advent of optical/near-infrared integral field spectrographs (IFS) have revealed the internal dynamics of hundreds of star-forming galaxies at 1work to use idealized galaxy merger simulations to determine the timescale over which interaction/merger signatures are visible, and the implications on our interpretation of the merger/disk nature of galaxies that display a smooth velocity gradient. Further, I will discuss our work to derive kinematic properties of simulated galaxies using the zoom-in cosmological simulations from the FIRE project. These results can inform us what might be the physical drivers of an enhanced intrinsic velocity dispersion of high-z star-forming galaxies, an important characteristic of these galaxies from recent large IFS surveys.

  8. Dissipational galaxy formation - Confrontation with observations (United States)

    Silk, J.; Norman, C.


    An exploration is presented of the hypothesis that a protogalaxy consists of an aggregate of interacting gas clouds which undergo mergers with neighboring systems, as envisaged by both the hierarchical clustering and fragmentation schemes of galaxy formation. Both gaseous dissipation and violet relaxation play fundamental roles in this galaxy formation model, in order to account for such diverse structural and dynamical properties of spheroidal galaxies as velocity anisotropy and metallicity gradients. Protogalaxy mergers during the initial stages of galaxy clustering can account for the observed spatial distribution of spiral, S0, and elliptical galaxies, and galaxy formation can occur slowly and at late epochs, since the time scale for disk formation is less than about 10 to the 10th years.

  9. Outskirts of galaxies

    CERN Document Server

    Lee, Janice; Paz, Armando


    This book consists of invited reviews written by world-renowned experts on the subject of the outskirts of galaxies, an upcoming field which has been understudied so far. These regions are faint and hard to observe, yet hide a tremendous amount of information on the origin and early evolution of galaxies. They thus allow astronomers to address some of the most topical problems, such as gaseous and satellite accretion, radial migration, and merging. The book is published in conjunction with the celebration of the end of the four-year DAGAL project, an EU-funded initial training network, and with a major international conference on the topic held in March 2016 in Toledo. It thus reflects not only the views of the experts, but also the scientific discussions and progress achieved during the project and the meeting. The reviews in the book describe the most modern observations of the outer regions of our own Galaxy, and of galaxies in the local and high-redshift Universe. They tackle disks, haloes, streams, and a...

  10. Oscillations of disks

    CERN Document Server

    Kato, Shoji


    This book presents the current state of research on disk oscillation theory, focusing on relativistic disks and tidally deformed disks. Since the launch of the Rossi X-ray Timing Explorer (RXTE) in 1996, many high-frequency quasiperiodic oscillations (HFQPOs) have been observed in X-ray binaries. Subsequently, similar quasi-periodic oscillations have been found in such relativistic objects as microquasars, ultra-luminous X-ray sources, and galactic nuclei. One of the most promising explanations of their origin is based on oscillations in relativistic disks, and a new field called discoseismology is currently developing. After reviewing observational aspects, the book presents the basic characteristics of disk oscillations, especially focusing on those in relativistic disks. Relativistic disks are essentially different from Newtonian disks in terms of several basic characteristics of their disk oscillations, including the radial distributions of epicyclic frequencies. In order to understand the basic processes...


    Energy Technology Data Exchange (ETDEWEB)

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


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

  12. GASP. II. A MUSE View of Extreme Ram-Pressure Stripping along the Line of Sight: Kinematics of the Jellyfish Galaxy JO201 (United States)

    Bellhouse, C.; Jaffé, Y. L.; Hau, G. K. T.; McGee, S. L.; Poggianti, B. M.; Moretti, A.; Gullieuszik, M.; Bettoni, D.; Fasano, G.; D'Onofrio, M.; Fritz, J.; Omizzolo, A.; Sheen, Y.-K.; Vulcani, B.


    This paper presents a spatially resolved kinematic study of the jellyfish galaxy JO201, one of the most spectacular cases of ram-pressure stripping (RPS) in the GAs Stripping Phenomena in galaxies with MUSE (GASP) survey. By studying the environment of JO201, we find that it is moving through the dense intracluster medium of Abell 85 at supersonic speeds along our line of sight, and that it is likely accompanied by a small group of galaxies. Given the density of the intracluster medium and the galaxy’s mass, projected position, and velocity within the cluster, we estimate that JO201 must so far have lost ˜50% of its gas during infall via RPS. The MUSE data indeed reveal a smooth stellar disk accompanied by large projected tails of ionized ({{H}}α ) gas, composed of kinematically cold (velocity dispersion 100 km s-1) diffuse emission, that extend out to at least ˜ 50 {kpc} from the galaxy center. The ionized {{H}}α -emitting gas in the disk rotates with the stars out to ˜6 kpc but, in the disk outskirts, it becomes increasingly redshifted with respect to the (undisturbed) stellar disk. The observed disturbances are consistent with the presence of gas trailing behind the stellar component resulting from intense face-on RPS along the line of sight. Our kinematic analysis is consistent with the estimated fraction of lost gas and reveals that stripping of the disk happens outside-in, causing shock heating and gas compression in the stripped tails.

  13. Supermassive black holes and their host galaxies. I. Bulge luminosities from dedicated near-infrared data

    Energy Technology Data Exchange (ETDEWEB)

    Läsker, Ronald; Van de Ven, Glenn [Max-Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); Ferrarese, Laura, E-mail: [NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E2E7 (Canada)


    In an effort to secure, refine, and supplement the relation between central supermassive black hole masses, M {sub •}, and the bulge luminosities of their host galaxies, L {sub bul}, we obtained deep, high spatial resolution K-band images of 35 nearby galaxies with securely measured M {sub •}, using the wide-field WIRCam imager at the Canada-France-Hawaii-Telescope. A dedicated data reduction and sky subtraction strategy was adopted to estimate the brightness and structure of the sky, a critical step when tracing the light distribution of extended objects in the near-infrared. From the final image product, bulge and total magnitudes were extracted via two-dimensional profile fitting. As a first order approximation, all galaxies were modeled using a simple Sérsic-bulge+exponential-disk decomposition. However, we found that such models did not adequately describe the structure that we observed in a large fraction of our sample galaxies which often include cores, bars, nuclei, inner disks, spiral arms, rings, and envelopes. In such cases, we adopted profile modifications and/or more complex models with additional components. The derived bulge magnitudes are very sensitive to the details and number of components used in the models, although total magnitudes remain almost unaffected. Usually, but not always, the luminosities and sizes of the bulges are overestimated when a simple bulge+disk decomposition is adopted in lieu of a more complex model. Furthermore, we found that some spheroids are not well fit when the ellipticity of the Sérsic model is held fixed. This paper presents the details of the image processing and analysis, while we discuss how model-induced biases and systematics in bulge magnitudes impact the M {sub •}-L {sub bul} relation in a companion paper.

  14. Spatial distribution of far-infrared emission in spiral galaxies. I. Relation with radio continuum emission. (United States)

    Mayya, Y. D.; Rengarajan, T. N.


    We use high resolution IRAS and 20 cm radio continuum (RC) images of a sample of 22 spiral galaxies to study the correlation between the far infra-red (FIR) and RC emissions within the galactic disks. A combination of exponential and gaussian profiles rather than a single exponential profile is found to be a better representation of the observed intensity profiles in the two bands. The gaussian component, which we show is not due to the effects of limited beam-resolution, contains more than 60% of the total flux in majority of the galaxies. The dominance of the gaussian component suggests that the nuclear star forming regions and the bulge stars are more important contributors to the emission in the two bands, rather than the outer exponential stellar disks. The RC profile is flatter compared to the FIR profile, resulting in a decrease of their ratio, Q-Sixty, away from the center. However, the Q-sixty increases in the extreme outer parts, where the dispersion in the FIR and RC correlation is also higher than in the central regions. The global Q-sixty and its dispersion match those in the inner parts of the galaxies. These results imply that the observed tight correlation in the global quantities reflects processes in the inner regions only where OB stars and the associated Type II supernovae control the FIR and RC emission. In the outer parts heating of very small dust grains by the old disk stars provides a secondary component in the FIR emission, without associated RC emission. The edge-on galaxy NGC3079 shows extended FIR and RC emissions along its minor axis, probably associated with the nuclear starburst activity. keywords - star formation - far infrared emission -- radio continuum emission

  15. Clusters of galaxies in the HST Medium Deep Survey database (United States)

    Ratnatunga, K. U.; Ostrander, E. J.; Griffiths, R. E.; Nichol, R. C.


    Quantitative morphological and structural parameters estimated for galaxies detected in the HST WFPC2 observations are now available on a set of CDROMS and is searchable via a web-interface at . A modeling approach based on maximum likelihood is used for the 2-dimensional Disk + Bulge decomposition of the faint undersampled galaxy images. We present a new objectively selected sample of galaxy overdensites found using the MDS database. These galaxy clusters represent some of the most distant systems ever detected and will facilitate more detailed studies of cluster and galaxy evolution.

  16. The baryonic Tully-Fisher relationship for S{sup 4}G galaxies and the 'condensed' baryon fraction of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Zaritsky, Dennis [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Courtois, Helene; Sorce, Jenny [Université Lyon 1, CNRS/IN2P3, Institut de Physique Nucléaire, Lyon (France); Muñoz-Mateos, Juan-Carlos; Kim, T.; Mizusawa, T.; Sheth, K. [National Radio Astronomy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Erroz-Ferrer, S. [Instituto de Astrofísica de Canarias, Vía Láctea s/n 38205 La Laguna (Spain); Comerón, S.; Laurikainen, E.; Laine, J.; Salo, H. [Astronomy Division, Department of Physical Sciences, University of Oulu, P.O. Box 3000, FI-90014, Oulu (Finland); Gadotti, D. A. [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Gil de Paz, A. [Departamento de Astrofísica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Hinz, J. L. [MMTO, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Menéndez-Delmestre, K. [Universidade Federal do Rio de Janeiro, Observatório do Valongo, Ladeira Pedro Antônio, 43, CEP 20080-090, Rio de Janeiro (Brazil); Regan, M. W. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Seibert, M. [The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Athanassoula, E.; Bosma, A., E-mail: [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France); and others


    We combine data from the Spitzer Survey for Stellar Structure in Galaxies, a recently calibrated empirical stellar mass estimator from Eskew et al., and an extensive database of H I spectral line profiles to examine the baryonic Tully-Fisher (BTF) relation. We find (1) that the BTF has lower scatter than the classic Tully-Fisher (TF) relation and is better described as a linear relationship, confirming similar previous results, (2) that the inclusion of a radial scale in the BTF decreases the scatter but only modestly, as seen previously for the TF relation, and (3) that the slope of the BTF, which we find to be 3.5 ± 0.2 (Δlog M {sub baryon}/Δlog v{sub c} ), implies that on average a nearly constant fraction (∼0.4) of all baryons expected to be in a halo are 'condensed' onto the central region of rotationally supported galaxies. The condensed baryon fraction, M {sub baryon}/M {sub total}, is, to our measurement precision, nearly independent of galaxy circular velocity (our sample spans circular velocities, v {sub c} , between 60 and 250 km s{sup –1}, but is extended to v{sub c} ∼ 10 km s{sup –1} using data from the literature). The observed galaxy-to-galaxy scatter in this fraction is generally ≤ a factor of 2 despite fairly liberal selection criteria. These results imply that cooling and heating processes, such as cold versus hot accretion, mass loss due to stellar winds, and active galactic nucleus driven feedback, to the degree that they affect the global galactic properties involved in the BTF, are independent of halo mass for galaxies with 10 < v{sub c} < 250 km s{sup –1} and typically introduce no more than a factor of two range in the resulting M {sub baryon}/M {sub total}. Recent simulations by Aumer et al. of a small sample of disk galaxies are in excellent agreement with our data, suggesting that current simulations are capable of reproducing the global properties of individual disk galaxies. More detailed comparison to models

  17. Local Galaxies as Damped LY-α Analogs

    NARCIS (Netherlands)

    Zwaan, M. A.; van der Hulst, J. M.; Briggs, F. H.; Verheijen, M. A. W.; Ryan-Weber, E. V.


    We calculate in detail the expected properties of low redshift DLAs under the assumption that they arise in the gaseous disks of galaxies like those in the z≈0 population. A sample of 355 nearby galaxies is analysed, for which high quality Hi 21-cm emission line maps are available as part of an

  18. QSO Pairs across Active Galaxies: Evidence of Blueshifts? D. Basu

    Indian Academy of Sciences (India)


    Dec 4, 2006 ... to accompany the central supermassive black holes in galaxies (Carr 1978; Carr et al. 1984) and are also ejected, some of them assuming eccentric orbits around the primaries. (Valtonen & Basu 1991). It is further known that a black hole at the centre of a galaxy possesses a gaseous accretion disk around ...

  19. Disk Storage Server

    CERN Multimedia

    This model was a disk storage server used in the Data Centre up until 2012. Each tray contains a hard disk drive (see the 5TB hard disk drive on the main disk display section - this actually fits into one of the trays). There are 16 trays in all per server. There are hundreds of these servers mounted on racks in the Data Centre, as can be seen.

  20. Two chemically similar stellar overdensities on opposite sides of the plane of the Galactic disk. (United States)

    Bergemann, Maria; Sesar, Branimir; Cohen, Judith G; Serenelli, Aldo M; Sheffield, Allyson; Li, Ting S; Casagrande, Luca; Johnston, Kathryn V; Laporte, Chervin F P; Price-Whelan, Adrian M; Schönrich, Ralph; Gould, Andrew


    Our Galaxy is thought to have an active evolutionary history, dominated over the past ten billion years or so by star formation, the accretion of cold gas and, in particular, the merging of clumps of baryonic and dark matter. The stellar halo-the faint, roughly spherical component of the Galaxy-reveals rich 'fossil' evidence of these interactions, in the form of stellar streams, substructures and chemically distinct stellar components. The effects of interactions with dwarf galaxies on the content and morphology of the Galactic disk are still being explored. Recent studies have identified kinematically distinct stellar substructures and moving groups of stars in our Galaxy, which may have extragalactic origins. There is also mounting evidence that stellar overdensities (regions with greater-than-average stellar density) at the interface between the outer disk and the halo could have been caused by the interaction of a dwarf galaxy with the disk. Here we report a spectroscopic analysis of 14 stars from two stellar overdensities, each lying about five kiloparsecs above or below the Galactic plane-locations suggestive of an association with the stellar halo. We find that the chemical compositions of these two groups of stars are almost identical, both within and between these overdensities, and closely match the abundance patterns of stars in the Galactic disk. We conclude that these stars came from the disk, and that the overdensities that they are part of were created by tidal interactions of the disk with passing or merging dwarf galaxies.

  1. CANDELS+3D-HST: Compact SFGs at z ∼ 2-3, the progenitors of the first quiescent galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Barro, G.; Faber, S. M.; Koo, D. C.; Guo, Y. [UCO/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Pérez-González, P. G. [Universidad Complutense de Madrid, F. CC. Físicas, 28040 Madrid (Spain); Pacifici, C. [Yonsei University Observatory, Yonsei University, Seoul 120-749 (Korea, Republic of); Trump, J. R. [Pennsylvania State University, University Park, PA 16802 (United States); Wuyts, S.; Hsu, L. [Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, Giessenbachstr., D-85741 Garching (Germany); Bell, E. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Dekel, A. [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Porter, L.; Primack, J. [Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA 95064 (United States); Ferguson, H. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Ashby, M. L. N.; Fazio, G. G. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Caputi, K. [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands); Ceverino, D. [Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Croton, D. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, VIC 3122 (Australia); Giavalisco, M. [Astronomy Department, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); and others


    We analyze the star-forming and structural properties of 45 massive (log(M/M{sub ☉}) >10) compact star-forming galaxies (SFGs) at 2 < z < 3 to explore whether they are progenitors of compact quiescent galaxies at z ∼ 2. The optical/NIR and far-IR Spitzer/Herschel colors indicate that most compact SFGs are heavily obscured. Nearly half (47%) host an X-ray-bright active galactic nucleus (AGN). In contrast, only about 10% of other massive galaxies at that time host AGNs. Compact SFGs have centrally concentrated light profiles and spheroidal morphologies similar to quiescent galaxies and are thus strikingly different from other SFGs, which typically are disk-like and sometimes clumpy or irregular. Most compact SFGs lie either within the star formation rate (SFR)-mass main sequence (65%) or below it (30%), on the expected evolutionary path toward quiescent galaxies. These results show conclusively that galaxies become more compact before they lose their gas and dust, quenching star formation. Using extensive HST photometry from CANDELS and grism spectroscopy from the 3D-HST survey, we model their stellar populations with either exponentially declining (τ) star formation histories (SFHs) or physically motivated SFHs drawn from semianalytic models (SAMs). SAMs predict longer formation timescales and older ages ∼2 Gyr, which are nearly twice as old as the estimates of the τ models. Both models yield good spectral energy distribution fits, indicating that the systematic uncertainty in the age due to degeneracies in the SFH is of that order of magnitude. However, SAM SFHs better match the observed slope and zero point of the SFR-mass main sequence. Contrary to expectations, some low-mass compact SFGs (log(M/M{sub ☉}) =10-10.6) have younger ages but lower specific SFRs than that of more massive galaxies, suggesting that the low-mass galaxies reach the red sequence faster. If the progenitors of compact SFGs are extended SFGs, state-of-the-art SAMs show that mergers


    Energy Technology Data Exchange (ETDEWEB)

    Graninger, Dawn; Öberg, Karin I.; Qi, Chunhua [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kastner, Joel, E-mail: [Center for Imaging Science, School of Physics and Astronomy, and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)


    The distributions and abundances of small organics in protoplanetary disks are potentially powerful probes of disk physics and chemistry. HNC is a common probe of dense interstellar regions and the target of this study. We use the Submillimeter Array (SMA) to observe HNC 3–2 toward the protoplanetary disks around the T Tauri star TW Hya and the Herbig Ae star HD 163296. HNC is detected toward both disks, constituting the first spatially resolved observations of HNC in disks. We also present SMA observations of HCN 3–2 and IRAM 30 m observations of HCN and HNC 1–0 toward HD 163296. The disk-averaged HNC/HCN emission ratio is 0.1–0.2 toward both disks. Toward TW Hya, the HNC emission is confined to a ring. The varying HNC abundance in the TW Hya disk demonstrates that HNC chemistry is strongly linked to the disk physical structure. In particular, the inner rim of the HNC ring can be explained by efficient destruction of HNC at elevated temperatures, similar to what is observed in the ISM. However, to realize the full potential of HNC as a disk tracer requires a combination of high SNR spatially resolved observations of HNC and HCN and disk-specific HNC chemical modeling.


    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Medina, L. A. [Departamento de Física, Centro de Investigación y de Estudios Avanzados del IPN, A.P. 14-740, 07000 México D.F. (Mexico); Pichardo, B.; Moreno, E. [Instituto de Astronomía, Universidad Nacional Autónoma de México, A.P. 70-264, 04510, México D.F. (Mexico); Pérez-Villegas, A., E-mail:, E-mail:, E-mail: [Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apartado Postal 3-72, 58090 Morelia, Michoacán (Mexico)


    The first mechanism invoked to explain the existence of the thick disk in the Milky Way Galaxy was the spiral arms. Up-to-date work summons several other possibilities that together seem to better explain this component of our Galaxy. All these processes must affect distinct types of galaxies differently, but the contribution of each one has not been straightforward to quantify. In this work, we present the first comprehensive study of the effect of the spiral arms on the formation of thick disks, looking at early- to late-type disk galaxies in an attempt to characterize and quantify this specific mechanism in galactic potentials. To this purpose, we perform test particle numerical simulations in a three-dimensional spiral galactic potential (for early- to late-types spiral galaxies). By varying the parameters of the spiral arms we found that the vertical heating of the stellar disk becomes very important in some cases and strongly depends on the galactic morphology, pitch angle, arm mass, and the arm pattern speed. The later the galaxy type, the larger is the effect on the disk heating. This study shows that the physical mechanism causing the vertical heating is different from simple resonant excitation. The spiral pattern induces chaotic behavior not linked necessarily to resonances but to direct scattering of disk stars, which leads to an increase of the velocity dispersion. We applied this study to the specific example of the Milky Way Galaxy, for which we have also added an experiment that includes the Galactic bar. From this study we deduce that the effect of spiral arms of a Milky-Way-like potential on the dynamical vertical heating of the disk is negligible, unlike later galactic potentials for disks.

  4. SDSS IV MaNGA: Deep observations of extra-planar, diffuse ionized gas around late-type galaxies from stacked IFU spectra (United States)

    Jones, A.; Kauffmann, G.; D'Souza, R.; Bizyaev, D.; Law, D.; Haffner, L.; Bahé, Y.; Andrews, B.; Bershady, M.; Brownstein, J.; Bundy, K.; Cherinka, B.; Diamond-Stanic, A.; Drory, N.; Riffel, R. A.; Sánchez, S. F.; Thomas, D.; Wake, D.; Yan, R.; Zhang, K.


    We have conducted a study of extra-planar diffuse ionized gas using the first year data from the MaNGA IFU survey. We have stacked spectra from 49 edge-on, late-type galaxies as a function of distance from the midplane of the galaxy. With this technique we can detect the bright emission lines Hα, Hβ, [O II]λλ3726, 3729, [O III]λ5007, [N II]λλ6549, 6584, and [S II]λλ6717, 6731 out to about 4 kpc above the midplane. With 16 galaxies we can extend this analysis out to about 9 kpc, I.e. a distance of 2Re, vertically from the midplane. In the halo, the surface brightnesses of the [O II] and Hα emission lines are comparable, unlike in the disk where Hα dominates. When we split the sample by specific star-formation rate, concentration index, and stellar mass, each subsample's emission line surface brightness profiles and ratios differ, indicating that extra-planar gas properties can vary. The emission line surface brightnesses of the gas around high specific star-formation rate galaxies are higher at all distances, and the line ratios are closer to ratios characteristic of H II regions compared with low specific star-formation rate galaxies. The less concentrated and lower stellar mass samples exhibit line ratios that are more like H II regions at larger distances than their more concentrated and higher stellar mass counterparts. The largest difference between different subsamples occurs when the galaxies are split by stellar mass. We additionally infer that gas far from the midplane in more massive galaxies has the highest temperatures and steepest radial temperature gradients based on their [N II]/Hα and [O II]/Hα ratios between the disk and the halo. SDSS IV.

  5. Magnetically Regulated Gas Accretion in High-Redshift Galactic Disks (United States)

    Birnboim, Yuval


    Disk galaxies are in hydrostatic equilibrium along their vertical axis. The pressure allowing for this configuration consists of thermal, turbulent, magnetic, and cosmic-ray components. For the Milky Way the thermal pressure contributes ~10% of the total pressure near the plane, with this fraction dropping toward higher altitudes. Out of the rest, magnetic fields contribute ~1/3 of the pressure to distances of ~3 kpc above the disk plane. In this Letter, we attempt to extrapolate these local values to high-redshift, rapidly accreting, rapidly star-forming disk galaxies and study the effect of the extra pressure sources on the accretion of gas onto the galaxies. In particular, magnetic field tension may convert a smooth cold-flow accretion to clumpy, irregular star formation regions and rates. The infalling gas accumulates on the edge of the magnetic fields, supported by magnetic tension. When the mass of the infalling gas exceeds some threshold mass, its gravitational force cannot be balanced by magnetic tension anymore, and it falls toward the disk's plane, rapidly making stars. Simplified estimations of this threshold mass are consistent with clumpy star formation observed in SINS, UDF, GOODS, and GEMS surveys. We discuss the shortcomings of pure hydrodynamic codes in simulating the accretion of cold flows into galaxies, and emphasize the need for magnetohydrodynamic simulations.

  6. Cold Dark Matter Substructure and Galactic Disks. II. Dynamical Effects of Hierarchical Satellite Accretion (United States)

    Kazantzidis, Stelios; Zentner, Andrew R.; Kravtsov, Andrey V.; Bullock, James S.; Debattista, Victor P.


    We perform a set of fully self-consistent, dissipationless N-body simulations to elucidate the dynamical response of thin galactic disks to bombardment by cold dark matter (CDM) substructure. Our method combines (1) cosmological simulations of the formation of Milky Way (MW)-sized CDM halos to derive the properties of substructure, and (2) controlled numerical experiments of consecutive subhalo impacts onto an initially thin, fully formed MW-type disk galaxy. The present study is the first to account for the evolution of satellite populations over cosmic time in such an investigation of disk structure. In contrast to what can be inferred from statistics of the z = 0 surviving substructure, we find that accretions of massive subhalos onto the central regions of host halos, where the galactic disks reside, since z ~ 1 should be common. One host halo accretion history is used to initialize the controlled simulations of satellite-disk encounters. The specific merger history involves six dark matter substructures, with initial masses in the range ~20%-60% of the disk mass and of comparable size to the disk, crossing the central regions of their host in the past ~8 Gyr. We show that these accretion events severely perturb the thin galactic disk and produce a wealth of distinctive dynamical signatures on its structure and kinematics. These include (1) considerable thickening and heating at all radii, with the disk thickness and velocity ellipsoid nearly doubling at the solar radius; (2) prominent flaring associated with an increase in disk thickness greater than a factor of 4 in the disk outskirts; (3) surface density excesses at large radii, beyond ~5 disk scale lengths, resembling those of the observed antitruncated disks; (4) long-lived, lopsidedness at levels similar to those measured in observational samples of disk galaxies; and (5) substantial tilting. The interaction with the most massive subhalo in the simulated accretion history drives the disk response while

  7. The Distribution of Mass in Spiral Galaxies.

    NARCIS (Netherlands)

    Swaters, Rob; Andersen, David; Bershady, Matthew; Verheijen, Marc


    Little is known about the content and distribution of dark matter in spiral galaxies. Mass modeling of any rotation curve can yield an alarming range of results - from entirely halo-dominated, centrally- concentrated dark distributions, to disk-dominated inner potentials with shallow, low density


    Energy Technology Data Exchange (ETDEWEB)

    Kim, Suk; Rey, Soo-Chang; Lee, Youngdae; Chung, Jiwon; Pak, Mina; Yi, Wonhyeong; Lee, Woong [Department of Astronomy and Space Science, Chungnam National University, 99 Daehak-ro, Daejeon 305-764 (Korea, Republic of); Jerjen, Helmut [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT 2611 (Australia); Lisker, Thorsten [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg (ZAH), Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Sung, Eon-Chang [Korea Astronomy and Space Science institute, 776 Daedeokdae-ro, Daejeon 305-348 (Korea, Republic of)


    We present a new catalog of galaxies in the wider region of the Virgo cluster, based on the Sloan Digital Sky Survey (SDSS) Data Release 7. The Extended Virgo Cluster Catalog (EVCC) covers an area of 725 deg{sup 2} or 60.1 Mpc{sup 2}. It is 5.2 times larger than the footprint of the classical Virgo Cluster Catalog (VCC) and reaches out to 3.5 times the virial radius of the Virgo cluster. We selected 1324 spectroscopically targeted galaxies with radial velocities less than 3000 km s{sup –1}. In addition, 265 galaxies that have been overlooked in the SDSS spectroscopic survey but have available redshifts in the NASA Extragalactic Database are also included. Our selection process secured a total of 1589 galaxies, 676 of which are not included in the VCC. The certain and possible cluster members are defined by means of redshift comparison with a cluster infall model. We employed two independent and complementary galaxy classification schemes: the traditional morphological classification based on the visual inspection of optical images and a characterization of galaxies from their spectroscopic features. SDSS u, g, r, i, and z passband photometry of all EVCC galaxies was performed using Source Extractor. We compare the EVCC galaxies with the VCC in terms of morphology, spatial distribution, and luminosity function. The EVCC defines a comprehensive galaxy sample covering a wider range in galaxy density that is significantly different from the inner region of the Virgo cluster. It will be the foundation for forthcoming galaxy evolution studies in the extended Virgo cluster region, complementing ongoing and planned Virgo cluster surveys at various wavelengths.

  9. An Exploration of Dusty Galaxies (United States)

    Kohler, Susanna


    and Durham University) to identify the multi-wavelength properties of these galaxies in a pilot study that they hope to extend to many more similar galaxies in the future.Lessons from Distant GalaxiesWhat did Simpson and collaborators learn in this study?Photometric redshift distribution of the ALMA-identified submillimeter galaxies in the authors sample (grey). [Simpson et al. 2017]For the set of galaxies for which the team could measure photometric redshifts, the median redshift was z 2.65 (though redshifts ranged up to z 5).Submillimeter galaxies are cooler and larger than local far-infrared galaxies (known as ULIRGs). The authors therefore argue that its unlikely that ULIRGs are evolved versions of submillimeter galaxies.Estimates of dust mass in these galaxies suggest that effectively all of the optical-to-near-infrared light from colocated stars is obscured by dust.Estimates of the future stellar mass of these galaxies suggest that they cannot evolve into lenticular or spiral galaxies. Instead, the authors conclude, submillimeter galaxies must be the progenitors of local elliptical galaxies.CitationJ. M. Simpson et al 2017 ApJ 839 58. doi:10.3847/1538-4357/aa65d0

  10. Detection of the effect of cosmological large-scale structure on the orientation of galaxies


    Trujillo, Ignacio; Carretero, Conrado; Patiri, Santiago G.


    Galaxies are not distributed randomly throughout space but are instead arranged in an intricate "cosmic web" of filaments and walls surrounding bubble-like voids. There is still no compelling observational evidence of a link between the structure of the cosmic web and how galaxies form within it. However, such a connection is expected on the basis of our understanding of the origin of galaxy angular momentum: disk galaxies should be highly inclined relative to the plane defined by the large-s...

  11. Exploring Disks Around Planets (United States)

    Kohler, Susanna


    Giant planets are thought to form in circumstellar disks surrounding young stars, but material may also accrete into a smaller disk around the planet. Weve never detected one of these circumplanetary disks before but thanks to new simulations, we now have a better idea of what to look for.Image from previous work simulating a Jupiter-mass planet forming inside a circumstellar disk. The planet has its own circumplanetary disk of accreted material. [Frdric Masset]Elusive DisksIn the formation of giant planets, we think the final phase consists of accretion onto the planet from a disk that surrounds it. This circumplanetary disk is important to understand, since it both regulates the late gas accretion and forms the birthplace of future satellites of the planet.Weve yet to detect a circumplanetary disk thus far, because the resolution needed to spot one has been out of reach. Now, however, were entering an era where the disk and its kinematics may be observable with high-powered telescopes (like the Atacama Large Millimeter Array).To prepare for such observations, we need models that predict the basic characteristics of these disks like the mass, temperature, and kinematic properties. Now a researcher at the ETH Zrich Institute for Astronomy in Switzerland, Judit Szulgyi, has worked toward this goal.Simulating CoolingSzulgyi performs a series of 3D global radiative hydrodynamic simulations of 1, 3, 5, and 10 Jupiter-mass (MJ) giant planets and their surrounding circumplanetary disks, embedded within the larger circumstellar disk around the central star.Density (left column), temperature (center), and normalized angular momentum (right) for a 1 MJ planet over temperatures cooling from 10,000 K (top) to 1,000 K (bottom). At high temperatures, a spherical circumplanetary envelope surrounds the planet, but as the planet cools, the envelope transitions around 64,000 K to a flattened disk. [Szulgyi 2017]This work explores the effects of different planet temperatures and

  12. Isolated unilateral disk edema

    Directory of Open Access Journals (Sweden)

    Varner P


    Full Text Available Paul VarnerJohn J Pershing VAMC, Poplar Bluff, MO, USAAbstract: Isolated unilateral disk edema is a familiar clinical presentation with myriad associations. Related, non-consensus terminology is a barrier to understanding a common pathogenesis. Mechanisms for the development of disk edema are reviewed, and a new framework for clinical differentiation of medical associations is presented.Keywords: disk edema, axoplasmic flow, clinical multiplier, optic neuritis, ischemic optic neuropathy, papilledema


    Energy Technology Data Exchange (ETDEWEB)

    Newman, Sarah F.; Genzel, Reinhard [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Foerster-Schreiber, Natascha M.; Buschkamp, Peter; Davies, Ric; Eisenhauer, Frank; Kurk, Jaron; Lutz, Dieter [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Giessenbachstr.1, D-85748 Garching (Germany); Griffin, Kristen Shapiro [Space Sciences Research Group, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States); Mancini, Chiara; Renzini, Alvio [Osservatorio Astronomico di Padova, Vicolo dellOsservatorio 5, Padova, I-35122 (Italy); Lilly, Simon J.; Carollo, C. Marcella; Peng, Yingjie [Institute of Astronomy, Department of Physics, Eidgenoessische Technische Hochschule, ETH Zuerich, CH-8093 (Switzerland); Bouche, Nicolas [Institut de Recherche en Astrophysique et Planetologie (IRAP), Universite de Toulouse, UPS-OMP, IRAP, 14, avenue Edouard Berlin, F-31400 Toulouse (France); Burkert, Andreas [Department fuer Physik, Universitaets-Sternwarte Ludwig-Maximilians-Universitaet (USM), Scheinerstr. 1, Muenchen, D-81679 (Germany); Cresci, Giovanni [Istituto Nazionale di AstrofisicaOsservatorio Astronomico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Genel, Shy [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hicks, Erin K. S. [Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195-1580 (United States); Naab, Thorsten, E-mail: [Max-Planck Institute for Astrophysics, Karl Schwarzschildstrasse 1, D-85748 Garching (Germany); and others


    Using SINFONI H{alpha}, [N II], and [S II] AO data of 27 z {approx} 2 star-forming galaxies (SFGs) from the SINS and zC-SINF surveys, we explore the dependence of outflow strength (via the broad flux fraction) on various galaxy parameters. For galaxies that have evidence for strong outflows, we find that the broad emission is spatially extended to at least the half-light radius ({approx}a few kpc). Decomposition of the [S II] doublet into broad and narrow components suggests that this outflowing gas probably has a density of {approx}10-100 cm{sup -3}, less than that of the star-forming gas (600 cm{sup -3}). There is a strong correlation of the H{alpha} broad flux fraction with the star formation surface density of the galaxy, with an apparent threshold for strong outflows occurring at 1 M{sub Sun} yr{sup -1} kpc{sup -2}. Above this threshold, we find that SFGs with log m{sub *} > 10 have similar or perhaps greater wind mass-loading factors ({eta} = M-dot{sub out}/SFR) and faster outflow velocities than lower mass SFGs, suggesting that the majority of outflowing gas at z {approx} 2 may derive from high-mass SFGs. The mass-loading factor is also correlated with the star formation rate (SFR), galaxy size, and inclination, such that smaller, more star-forming, and face-on galaxies launch more powerful outflows. We propose that the observed threshold for strong outflows and the observed mass loading of these winds can be explained by a simple model wherein break-out of winds is governed by pressure balance in the disk.

  14. Long-slit Spectroscopy of Edge-on Low Surface Brightness Galaxies (United States)

    Du, Wei; Wu, Hong; Zhu, Yinan; Zheng, WeiKang; Filippenko, Alexei V.


    We present long-slit optical spectra of 12 edge-on low surface brightness galaxies (LSBGs) positioned along their major axes. After performing reddening corrections for the emission-line fluxes measured from the extracted integrated spectra, we measured the gas-phase metallicities of our LSBG sample using both the [N II]/Hα and the R 23 diagnostics. Both sets of oxygen abundances show good agreement with each other, giving a median value of 12 + log(O/H) = 8.26 dex. In the luminosity-metallicity plot, our LSBG sample is consistent with the behavior of normal galaxies. In the mass-metallicity diagram, our LSBG sample has lower metallicities for lower stellar mass, similar to normal galaxies. The stellar masses estimated from z-band luminosities are comparable to those of prominent spirals. In a plot of the gas mass fraction versus metallicity, our LSBG sample generally agrees with other samples in the high gas mass fraction space. Additionally, we have studied stellar populations of three LSBGs, which have relatively reliable spectral continua and high signal-to-noise ratios, and qualitatively conclude that they have a potential dearth of stars with ages 1 Gyr. Regarding the chemical evolution of our sample, the LSBG data appear to allow for up to 30% metal loss, but we cannot completely rule out the closed-box model. Additionally, we find evidence that our galaxies retain up to about three times as much of their metals compared with dwarfs, consistent with metal retention being related to galaxy mass. In conclusion, our data support the view that LSBGs are probably just normal disk galaxies continuously extending to the low end of surface brightness.

  15. Centaurus A galaxy, type EO peculiar elliptical, also radio source (United States)


    Centaurus A galaxy, type EO peculiar elliptical, also radio source. CTIO 4-meter telescope, 1975. NGC 5128, a Type EO peculiar elliptical galaxy in the constellation Centaurus. This galaxy is one of the most luminous and massive galaxies known and is a strong source of both radio and X-ray radiation. Current theories suggest that the nucleus is experiencing giant explosions involving millions of stars and that the dark band across the galactic disk is material being ejected outward. Cerro Toloto 4-meter telescope photo. Photo credit: National Optical Astronomy Observatories

  16. Galaxy Formation

    CERN Document Server

    Longair, Malcolm S


    This second edition of Galaxy Formation is an up-to-date text on astrophysical cosmology, expounding the structure of the classical cosmological models from a contemporary viewpoint. This forms the background to a detailed study of the origin of structure and galaxies in the Universe. The derivations of many of the most important results are derived by simple physical arguments which illuminate the results of more advanced treatments. A very wide range of observational data is brought to bear upon these problems, including the most recent results from WMAP, the Hubble Space Telescope, galaxy surveys like the Sloan Digital Sky Survey and the 2dF Galaxy Redshift Survey, studies of Type 1a supernovae, and many other observations.


    Energy Technology Data Exchange (ETDEWEB)

    Pan, Zhizheng; Lin, Weipeng [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Science, 80 Nandan Road, Shanghai 200030 (China); Li, Jinrong; Kong, Xu [Center of Astrophysics, University of Science and Technology of China, Jinzhai Road 96, Hefei 230026 (China); Wang, Jing, E-mail:, E-mail: [CSIRO Astronomy and Space Science, Australia Telescope National Facility, PO Box 76, Epping, NSW 1710 (Australia)


    In this Letter, we analyze the radial ultraviolet-optical color distributions in a sample of low redshift green valley galaxies, with the Galaxy Evolution Explorer (GALEX)+Sloan Digital Sky Survey (SDSS) images, to investigate how the residual recent star formation is distributed in these galaxies. We find that the dust-corrected u – r colors of early-type galaxies (ETGs) are flat out to R {sub 90}, while the colors monotonously turn blue when r > 0.5 R {sub 50} for late-type galaxies (LTGs). More than half of the ETGs are blue-cored and have remarkable positive NUV – r color gradients, suggesting that their star formations are centrally concentrated. The rest have flat color distributions out to R {sub 90}. The centrally concentrated star formation activity in a large portion of ETGs is confirmed by the SDSS spectroscopy, showing that ∼50% of the ETGs have EW(Hα) >6.0 Å. Of the LTGs, 95% show uniform radial color profiles, which can be interpreted as a red bulge plus an extended blue disk. The links between the two kinds of ETGs, e.g., those objects having remarkable ''blue-cores'' and those having flat color gradients, are less known and require future investigations. It is suggested that the LTGs follow a general model by which quenching first occurs in the core regions, and then finally extend to the rest of the galaxy. Our results can be re-examined and have important implications for the IFU surveys, such as MaNGA and SAMI.

  18. The Young Outer Disk of M83 (United States)

    Davidge, T. J.


    Deep near-infrared images recorded with NICI on Gemini South are used to investigate the evolved stellar content in the outer southeast quadrant of the spiral galaxy M83. A diffuse population of asymptotic giant branch (AGB) stars is detected, indicating that there are stars outside of the previously identified young and intermediate age star clusters in the outer disk. The brightest AGB stars have M K >= -8, and the AGB luminosity function (LF) is well matched by model LFs that assume ages Ciencia e Technologia (Brazil), and the Ministerio de Ciencia, Tecnologia e Innovacion Productiva (Argentina).

  19. disk historie

    DEFF Research Database (Denmark)

    Feldt, Jakob Egholm


    Review essay om nye værker indenfor jødisk kulturhistorie. Diskussion af værker af Jay Geller, Boaz Neumann og Daniel Greene......Review essay om nye værker indenfor jødisk kulturhistorie. Diskussion af værker af Jay Geller, Boaz Neumann og Daniel Greene...

  20. Exploring Properties of HI Clouds in Dwarf Irregular Galaxies (United States)

    Berger, Clara; Hunter, Deidre Ann


    Dwarf Irregular galaxies form stars and maintain exponential stellar disks at extremely low gas densities. One proposed method of maintaining such regular outer disks is scattering stars off of HI clouds. In order to understand the processes present in dwarf irregular stellar disks, we present a survey of atomic hydrogen clouds in and around a subset of representative galaxies from the LITTLE THINGS survey. We apply a cloud identification program to the 21 cm HI line emission cubes and extract masses, radii, surface densities, and distances from the center of the galaxy in the plane of the galaxy of each cloud. Our data show a wide range of clouds characterized by low surface densities but varied in mass and size. The number of clouds found and the mass of the most massive cloud show no correlation to integrated star forming rates or luminosity in these galaxies. However, they will be used as input for models of stars scattering off of HI clouds to better understand the regular stellar disks in dwarf Irregular galaxies.We acknowledge support from the National Science Foundation grant AST-1461200 to Northern Arizona University for Research Experiences for Undergraduates summer internships.

  1. The HST Medium Deep Survey: Steward BVRIJK and FASTTRAK JHK imaging and photometry of faint field galaxies from parallel WF/PC images (United States)

    Mutz, S. B.; Windhorst, R. A.; Ostrander, E. J.; Wittman, D.; Close, L.; McCarthy, D.; Griffiths, R. E.; Neuschaefer, L. W.


    We present ground-based optical (BVRI) and infrared (JHK) photometry for 15 galaxy fields previously observed with HST as part of the Medium-Deep Survey. We use the HST images to determine bulge and disk scale-lengths at 0.1 - 0.2'' FWHM for 70 galaxies in the V and I-bands. We constrain their star-formation history from their ground-based + HST BVRIJHK colors. For galaxies too faint for MMT spectroscopy, we use their BVRIJHK photometry to constrain their redshift-range through Bruzual's (1990) spectral evolution models. Comparing these photometric redshift estimates to spectroscopic redshifts for a brighter subsample, we find acceptable agreement.We conclude this is an efficient way of finding large numbers of field galaxies with z >= 0.8. Using photometric redshift estimates, we extend the Theta -z relation for HST bulges and disks (using world models with q_o = 0.0 - 1.0, see Mutz et al. 1994, ApJL, 434, L055) to z >= 0.8 (V >= 24 mag), beyond most ground-based spectroscopy. We also observed three brighter (17.5 <= I <= 19.0) galaxies with spectroscopic redshifts of z = 0.12 - 0.28 in the K-band with the Steward 90 inch FASTTRAC tip/tilt corrector system. Under seeing conditions of 1.75'' FWHM for a single image of 1.0 second, we derived K-band imaging with FWHM = 1.076'' for a stack of 158 60-second images. We present their V, I, and K-band light profiles, and V-I and I-K color gradients. The V-I and V-K color profiles show that the object at z = 0.12 is likely an early-type galaxy with an exponentially declining star formation parameter mu = 0.4. The object at z = 0.23 is an early-type galaxy with mu = 0.7. The object at z = 0.28 is a late-type disk galaxy seen nearly edge-on. We discuss using FASTTRAC under better seeing conditions and at telescopes with a more optimal ratio of Fried-parameter to mirror-diameter. This work was supported by NASA/HST grants GO-2684-0*-93A from STScI, which is operated by AURA, Inc., under NASA contract NAS5-26555.

  2. Bar-spheroid interaction in galaxies (United States)

    Hernquist, Lars; Weinberg, Martin D.


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

  3. Cosmic evolution of stellar disk truncations: from z = 1 to the Local Universe (United States)

    Trujillo, Ignacio; Azzollini, Ruyman; Bakos, Judit; Beckman, John; Pohlen, Michael


    We present our recent results on the cosmic evolution of the outskirts of disk galaxies. In particular we focus on disk-like galaxies with stellar disk truncations. Using UDF, GOODS and SDSS data we show how the position of the break (i.e. a direct estimator of the size of the stellar disk) evolves with time since z~1. Our findings agree with an evolution on the radial position of the break by a factor of 1.3 ± 0.1 in the last 8 Gyr for galaxies with similar stellar masses. We also present radial color gradients and how they evolve with time. At all redshifts we find a radial inside-out bluing reaching a minimum at the position of the break radius, this minimum is followed by a reddening outwards. Our results constraint several galaxy disk formation models and favour a scenario where stars are formed inside the break radius and are relocated in the outskirts of galaxies through secular processes.

  4. The SAMI Galaxy Survey: disc-halo interactions in radio-selected star-forming galaxies (United States)

    Leslie, S. K.; Bryant, J. J.; Ho, I.-T.; Sadler, E. M.; Medling, A. M.; Groves, B.; Kewley, L. J.; Bland-Hawthorn, J.; Croom, S. M.; Wong, O. I.; Brough, S.; Tescari, E.; Sweet, S. M.; Sharp, R.; Green, A. W.; López-Sánchez, Á. R.; Allen, J. T.; Fogarty, L. M. R.; Goodwin, M.; Lawrence, J. S.; Konstantopoulos, I. S.; Owers, M. S.; Richards, S. N.


    In this paper, we compare the radio emission at 1.4 GHz with optical outflow signatures of edge-on galaxies. We report observations of six edge-on star-forming galaxies in the Sydney-AAO Multiobject Integral-field spectrograph Galaxy Survey with 1.4 GHz luminosities >1 × 1021 W Hz-1. Extended minor axis optical emission is detected with enhanced [N II]/H α line ratios and velocity dispersions consistent with galactic winds in three of six galaxies. These galaxies may host outflows driven by a combination of thermal and cosmic ray processes. We find that galaxies with the strongest wind signatures have extended radio morphologies. Our results form a baseline for understanding the driving mechanisms of galactic winds.

  5. The Assembly of Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Berrier, Joel C.; Stewart, Kyle R.; Bullock, James S.; Purcell, Chris W.; Barton, Elizabeth J.; Wechsler, Risa H.


    We study the formation of fifty-three galaxy cluster-size dark matter halos (M = 10{sup 14.0-14.76} M{sub {circle_dot}}) formed within a pair of cosmological {Lambda}CDM N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host {approx} 0.1L{sub *} galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters experience no 'pre-processing' in the group environment prior to their accretion into the cluster. On average, {approx} 70% of cluster galaxies fall into the cluster potential directly from the field, with no luminous companions in their host halos at the time of accretion; and less than {approx} 12% are accreted as members of groups with five or more galaxies. Moreover, we find that cluster galaxies are significantly less likely to have experienced a merger in the recent past ({approx}< 6 Gyr) than a field halo of the same mass. These results suggest that local, cluster processes like ram-pressure stripping, galaxy harassment, or strangulation play the dominant role in explaining the difference between cluster and field populations at a fixed stellar mass; and that pre-evolution or past merging in the group environment is of secondary importance for setting cluster galaxy properties for most clusters. The accretion times for z = 0 cluster members are quite extended, with {approx} 20% incorporated into the cluster halo more than 7 Gyr ago and {approx} 20% within the last 2 Gyr. By comparing the observed morphological fractions in cluster and field populations, we estimate an approximate time-scale for late-type to early-type transformation within the cluster environment to be {approx} 6 Gyr.

  6. Stellar streams in the Galactic thick disk: preliminary results (United States)

    Ramya, P.; Reddy, Bacham E.

    Here we report preliminary results of our study of chemical tagging of member stars of two Galactic stellar streams. Both the streams, kinematically belong to the thick disk component of the Galaxy. We analysed high resolution spectra of 42 member stars: 17 from Arcturus stream and 25 from ``AF06 stream''. The LTE (Local Thermodynamic Equilibrium) abundance analysis was performed differentially with respect to the sun. Abundance results suggest that both the streams are metal poor and enhanced in α-process elements (O, Mg, Si, Ca, Ti) very similar to the thick disk chemistry. Also, results suggest that the two streams probably did not originate by the dispersion of open clusters.

  7. The Interstellar Medium in Our Galaxy: a New Interpretation of the Distribution of Hot/cool Gas Boundaries in the Disk, and Models of Supernova Remnants in the Halo. (United States)

    Shelton, Robin Lynn


    O VI in the Interstellar Medium. The Copernicus O^{+5} column densities trace the 10^{5.5} K gas in the interstellar medium. We statistically re-analyze the dataset, including the possibility that local hot gas may contribute a significant O^{+5 } column density to most lines of sight. Our reanalysis includes slight improvements in the statistics and was found to be reliable when tested on simulated data sets. Our conclusions differ considerably from those of the original analysis and strongly influence the understanding of the interstellar medium, in particular the volume occupation of the hot and warm components, and mechanisms responsible for them. The Local Bubble column density compares favorably with the estimated quantity of O^{+5 } within the remnant of an ancient local explosion. Similarly, our mean O^{+5} column density per external feature agrees with models of hot interstellar bubbles from either stellar winds or ancient supernova explosions in a warm diffuse interstellar environment, suggesting that the hot gas in interstellar space may exist primarily within discrete regions of modest volume occupation rather than in a continuous and pervasive phase. Supernova Remnants in the Halo. High latitude observations of C^{+3} N^{+4}, and O ^{+5}, and the shadowing of high latitude x-ray emission by intervening hydrogen clouds indicate the presence of hot (~10 ^4 to 10^6K) gas in the halo of our galaxy. This project explores the contributions made by isolated supernova remnants. Their evolving structures were simulated with a hydrodynamic computer code. The results are intriguing. (1) At late times the remnants collapse faster than the high -stage ions can recombine. (2) The high-stage ions in the ensemble of remnants cover about ~50% of the sky. (3) The ensemble provides average column densities of >3.1 times 10 13 O^ {+5} atoms cm^{-2 }, >2.5 times 1012 N ^{+4} atoms cm^ {-2} and gg9.8 times 1012 C^{+3} atoms cm ^{-2}. The average O ^{+5} column density is

  8. Gas in Protoplanetary Disks (United States)

    Roberge, Aki


    Gas makes up the bulk of the mass in a protoplanetary disk, but it is much more difficult to observe than the smaller dust component. The l ifetime of gas in a disk has far-reaching consequences. including lim iting the time available for giant planet formation and controlling t he migration of planetary bodies of all sizes, from Jupiters to meter-sized planetesimals. Here I will discuss what is known about the gas component of protoplanetary disks, highlighting recent results from i nfrared studies with the Spitzer Space Telescope. Exciting upcoming o pportunities for gas studies will also be discussed. In particular, the first large far-IR survey of gas tracers from young disks will be p erformed using the Herschel Space Observatory, as part of the "Gas in Protoplanetary Systems" (GASPS) Open Time Key Project.

  9. Disk Defect Data (United States)

    National Aeronautics and Space Administration — How Data Was Acquired: The data presented is from a physical simulator that simulated engine disks. Sample Rates and Parameter Description: All parameters are...

  10. Understanding biases when fitting disk truncations (United States)

    Cardiel, Nicolás; Marino, Raffaella A.; Pascual, Sergio; Ceballos, M. Teresa; Gil de Paz, Armando; Sánchez, Sebastián F.


    Truncations in the stellar population at the edges of disk galaxies are thought to be a common morphological feature (e.g., Erwin et al. 2005; and more recently Marino et al. 2016). In fact, using imaging data from the SDSS, Pohlen & Trujillo (2006) showed that only ~ 10% of face-on to intermediate inclined, nearby, late-type (Sb-Sdm) spiral galaxies have a normal/standard purely exponential disk down to the noise limit. In situations like these, the simultaneous fit of two lines, joined or not at an intermediate point (the break radius), constitutes a natural step towards the modelling of radial variation in surface brightness, metallicity, or any other relevant parameter. This work shows the results of simple simulations in which the simultaneous fit to two joined lines is compared to the simultaneous fit of two independent lines (i.e., two lines that do not necessarily coincide at an intermediate point), and also to the traditional single ordinary least squares fit. These simulations reveal some biases that should be taken into account when facing these kind of fitting procedures.

  11. The Milky Way and other spiral galaxies

    Directory of Open Access Journals (Sweden)

    Wang J.L.


    Full Text Available Cosmologists have often considered the Milky Way as a typical spiral galaxy, and its properties have considerably influenced the current scheme of galaxy formation. Here we compare the general properties of the Milky Way disk and halo with those of galaxies selected from the SDSS. Assuming the recent measurements of its circular velocity results in the Milky Way being offset by ~2σ from the fundamental scaling relations. On the basis of their location in the (MK, Rd, Vflat volume, the fraction of SDSS spirals like the MilkyWay is only 1.2% in sharp contrast with M31, which appears to be quite typical. Comparison of the Milky Way with M31 and with other spirals is also discussed to investigate whether or not there is a fundamental discrepancy between their mass assembly histories. Possibly the Milky Way is one of the very few local galaxies that could be a direct descendant of very distant, z = 2-3 galaxies, thanks to its quiescent history since thick disk formation.

  12. Verbatim Floppy Disk

    CERN Multimedia


    Introduced under the name "Verbatim", Latin for "literally", these disks that sized more than 5¼ inches have become almost universal on dedicated word processing systems and personal computers. This format was replaced more slowly by the 3½-inch format, introduced for the first time in 1982. Compared to today, these large format disks stored very little data. In reality, they could only contain a few pages of text.

  13. Detecting stars, galaxies, and asteroids with Gaia (United States)

    de Bruijne, J. H. J.; Allen, M.; Azaz, S.; Krone-Martins, A.; Prod'homme, T.; Hestroffer, D.


    Context. Gaia is Europe's space astrometry mission, aiming to make a three-dimensional map of 1000 million stars in our Milky Way to unravel its kinematical, dynamical, and chemical structure and evolution. Aims: We present a study of Gaia's detection capability of objects, in particular non-saturated stars, double stars, unresolved external galaxies, and asteroids. Gaia's on-board detection software autonomously discriminates stars from spurious objects like cosmic rays and solar protons. For this, parametrised criteria of the shape of the point spread function are used, which need to be calibrated and tuned. This study aims to provide an optimum set of parameters for these filters. Methods: We developed a validated emulation of the on-board detection software, which has 20 free, so-called rejection parameters which govern the boundaries between stars on the one hand and sharp (high-frequency) or extended (low-frequency) events on the other hand. We evaluate the detection and rejection performance of the algorithm using catalogues of simulated single stars, resolved and unresolved double stars, cosmic rays, solar protons, unresolved external galaxies, and asteroids. Results: We optimised the rejection parameters, improving - with respect to the functional baseline - the detection performance of single stars and of unresolved and resolved double stars, while, at the same time, improving the rejection performance of cosmic rays and of solar protons. The optimised rejection parameters also remove the artefact of the functional-baseline parameters that the reduction of the detection probability of stars as a function of magnitude already sets in before the nominal faint-end threshold at G = 20 mag. We find, as a result of the rectangular pixel size, that the minimum separation to resolve a close, equal-brightness double star is 0.23 arcsec in the along-scan and 0.70 arcsec in the across-scan direction, independent of the brightness of the primary. To resolve double

  14. X-raying galaxies: a Chandra legacy. (United States)

    Wang, Q Daniel


    This presentation reviews Chandra's major contribution to the understanding of nearby galaxies. After a brief summary on significant advances in characterizing various types of discrete x-ray sources, the presentation focuses on the global hot gas in and around galaxies, especially normal ones like our own. The hot gas is a product of stellar and active galactic nuclear feedback--the least understood part in theories of galaxy formation and evolution. Chandra observations have led to the first characterization of the spatial, thermal, chemical, and kinetic properties of the gas in our galaxy. The gas is concentrated around the galactic bulge and disk on scales of a few kiloparsec. The column density of chemically enriched hot gas on larger scales is at least an order magnitude smaller, indicating that it may not account for the bulk of the missing baryon matter predicted for the galactic halo according to the standard cosmology. Similar results have also been obtained for other nearby galaxies. The x-ray emission from hot gas is well correlated with the star formation rate and stellar mass, indicating that the heating is primarily due to the stellar feedback. However, the observed x-ray luminosity of the gas is typically less than a few percent of the feedback energy. Thus the bulk of the feedback (including injected heavy elements) is likely lost in galaxy-wide outflows. The results are compared with simulations of the feedback to infer its dynamics and interplay with the circumgalactic medium, hence the evolution of galaxies.

  15. S0 galaxies in Formax

    DEFF Research Database (Denmark)

    Bedregal...[], A. G.; Aragón-Salamanca, A.; Merrifield, M. R.


    Galaxies: elliptical and lenticular, cD: galaxies: kinematics and dynamics Udgivelsesdato: Oct.1......Galaxies: elliptical and lenticular, cD: galaxies: kinematics and dynamics Udgivelsesdato: Oct.1...

  16. Dusty Dwarfs Galaxies Occulting A Bright Background Spiral (United States)

    Holwerda, Benne


    The role of dust in shaping the spectral energy distributions of low mass disk galaxies remains poorly understood. Recent results from the Herschel Space Observatory imply that dwarf galaxies contain large amounts of cool (T 20K) dust, coupled with very modest optical extinctions. These seemingly contradictory conclusions may be resolved if dwarfs harbor a variety of dust geometries, e.g., dust at larger galactocentric radii or in quiescent dark clumps. We propose HST observations of six truly occulting dwarf galaxies drawn from the Galaxy Zoo catalog of silhouetted galaxy pairs. Confirmed, true occulting dwarfs are rare as most low-mass disks in overlap are either close satellites or do not have a confirmed redshift. Dwarf occulters are the key to determining the spatial extent of dust, the small scale structure introduced by turbulence, and the prevailing dust attenuation law. The recent spectroscopic confirmation of bona-fide low mass occulting dwarfs offers an opportunity to map dust in these with HST. What is the role of dust in the SED of these dwarf disk galaxies? With shorter feedback scales, how does star-formation affect their morphology and dust composition, as revealed from their attenuation curve? The resolution of HST allows us to map the dust disks down to the fine scale structure of molecular clouds and multi-wavelength imaging maps the attenuation curve and hence dust composition in these disks. We therefore ask for 2 orbits on each of 6 dwarf galaxies in F275W, F475W, F606W, F814W and F125W to map dust from UV to NIR to constrain the attenuation curve.

  17. Probing the Physics of Narrow-line Regions in Active Galaxies. III. Accretion and Cocoon Shocks in the LINER NGC 1052 (United States)

    Dopita, Michael A.; Ho, I.-Ting; Dressel, Linda L.; Sutherland, Ralph; Kewley, Lisa; Davies, Rebecca; Hampton, Elise; Shastri, Prajval; Kharb, Preeti; Jose, Jessy; Bhatt, Harish; Ramya, S.; Scharwächter, Julia; Jin, Chichuan; Banfield, Julie; Zaw, Ingyin; James, Bethan; Juneau, Stéphanie; Srivastava, Shweta


    We present Wide Field Spectrograph integral field spectroscopy and Hubble Space Telescope Faint Object Spectrograph spectroscopy for the low-ionization nuclear emission line region (LINER) galaxy NGC 1052. We infer the presence of a turbulent accretion flow forming a small-scale accretion disk. We find a large-scale outflow and ionization cone along the minor axis of the galaxy. Part of this outflow region is photoionized by the active galactic nucleus and shares properties with the extended narrow-line region of Seyfert galaxies, but the inner (R≲ 1.0″) accretion disk and the region around the radio jet appear shock excited. The emission-line properties can be modeled by a “double-shock” model in which the accretion flow first passes through an accretion shock in the presence of a hard X-ray radiation, and the accretion disk is then processed through a cocoon shock driven by the overpressure of the radio jets. This model explains the observation of two distinct densities (˜104 and ˜106 cm-3) and provides a good fit to the observed emission-line spectrum. We derive estimates for the velocities of the two shock components and their mixing fractions, the black hole mass, and the accretion rate needed to sustain the LINER emission and derive an estimate for the jet power. Our emission-line model is remarkably robust against variation of input parameters and hence offers a generic explanation for the excitation of LINER galaxies, including those of spiral type such as NGC 3031 (M81).


    Energy Technology Data Exchange (ETDEWEB)

    Filho, M. E.; Almeida, J. Sánchez; Muñoz-Tuñón, C. [Instituto Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Amorín, R. [National Institute for Astrophysics, Astronomical Observatory of Rome, Via Frascati 33, I-00040 Monteporzio Catone (Rome) (Italy); Elmegreen, B. G. [IBM, T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States); Elmegreen, D. M., E-mail: [Department of Physics and Astronomy, Vassar College, Poughkeepsie, NY 12604 (United States)


    The Kennicutt–Schmidt (KS) relation between the gas mass and star formation rate (SFR) describes the star formation regulation in disk galaxies. It is a function of gas metallicity, but the low-metallicity regime of the KS diagram is poorly sampled. We have analyzed data for a representative set of extremely metal-poor galaxies (XMPs), as well as auxiliary data, and compared these to empirical and theoretical predictions. The majority of the XMPs possess high specific SFRs, similar to high-redshift star-forming galaxies. On the KS plot, the XMP H i data occupy the same region as dwarfs and extend the relation for low surface brightness galaxies. Considering the H i gas alone, a considerable fraction of the XMPs already fall off the KS law. Significant quantities of “dark” H{sub 2} mass (i.e., not traced by CO) would imply that XMPs possess low star formation efficiencies (SFE{sub gas}). Low SFE{sub gas} in XMPs may be the result of the metal-poor nature of the H i gas. Alternatively, the H i reservoir may be largely inert, the star formation being dominated by cosmological accretion. Time lags between gas accretion and star formation may also reduce the apparent SFE{sub gas}, as may galaxy winds, which can expel most of the gas into the intergalactic medium. Hence, on global scales, XMPs could be H i-dominated, high-specific-SFR (≳10{sup −10} yr{sup −1}), low-SFE{sub gas} (≲10{sup −9} yr{sup −1}) systems, in which the total H i mass is likely not a good predictor of the total H{sub 2} mass, nor of the SFR.

  19. 2TB hard disk drive

    CERN Multimedia

    This particular object was used up until 2012 in the Data Centre. It slots into one of the Disk Server trays. Hard disks were invented in the 1950s. They started as large disks up to 20 inches in diameter holding just a few megabytes (link is external). They were originally called "fixed disks" or "Winchesters" (a code name used for a popular IBM product). They later became known as "hard disks" to distinguish them from "floppy disks (link is external)." Hard disks have a hard platter that holds the magnetic medium, as opposed to the flexible plastic film found in tapes and floppies.

  20. The Galactic Centre - a laboratory for starburst galaxies (?) (United States)

    Crocker, Roland M.


    The Galactic centre - as the closest galactic nucleus - holds both intrinsic interest and possibly represents a useful analogue to starburst nuclei which we can observe with orders of magnitude finer detail than these external systems. The environmental conditions in the GC - here taken to mean the inner 200 pc in diameter of the Milky Way - are extreme with respect to those typically encountered in the Galactic disk. The energy densities of the various GC ISM components are typically ~two orders of magnitude larger than those found locally and the star-formation rate density ~three orders of magnitude larger. Unusually within the Galaxy, the Galactic centre exhibits hard-spectrum, diffuse TeV (=1012 eV) gamma-ray emission spatially coincident with the region's molecular gas. Recently the nuclei of local starburst galaxies NGC 253 and M82 have also been detected in gamma-rays of such energies. We have embarked on an extended campaign of modelling the broadband (radio continuum to TeV gamma-ray), non- thermal signals received from the inner 200 pc of the Galaxy. On the basis of this modelling we find that star-formation and associated supernova activity is the ultimate driver of the region's non-thermal activity. This activity drives a large-scale wind of hot plasma and cosmic rays out of the GC. The wind advects the locally-accelerated cosmic rays quickly, before they can lose much energy in situ or penetrate into the densest molecular gas cores where star-formation occurs. The cosmic rays can, however, heat/ionize the lower density/warm H 2 phase enveloping the cores. On very large scales (~10 kpc) the non-thermal signature of the escaping GC cosmic rays has probably been detected recently as the spectacular `Fermi bubbles' and corresponding `YWMAP haze'.

  1. Star formation in bulgeless late type spiral Galaxies (United States)

    Das, M.; Ramya, S.; Sengupta, C.; Mishra, K.

    We present radio and follow-up optical observations of a sample of bulgeless late type spiral galaxies. We searched for signs of nuclear activity and disk star formation in the sample galaxies. Interaction induced star formation can often trigger bulge formation. We found significant radio emission associated with star formation in two sample galaxies, NGC3445 and NGC4027, both of which are tidally interacting with nearby companions. For the others, the star formation was either absent or limited to only localized regions in the disk. Both galaxies also have oval bars that are possibly pseudobulges that may later evolve into bulges. We did follow up optical Hα imaging and nuclear spectroscopy of NGC3445 and NGC4027 using the Himalayan Chandra Telescope (HCT). The Hα emission is mainly associated with strong spiral arms that have been triggered by the tidal interact1ions. The nuclear spectra of both galaxies indicate ongoing nuclear star formation but do not show signs of AGN activity. We thus conclude that star formation in bulgeless galaxies is generally low but is enhanced when the galaxies interact with nearby companions; this activity may ultimately lead to the formation of bulges in these galaxies.

  2. Properties and spatial distribution of galaxy superclusters (United States)

    Liivamägi, Lauri Juhan


    Astronomy is a science that can offer plenty of unforgettable imagery, and the large-scale distribution of galaxies is no exception. Among the first features the viewer's eye is likely to be drawn to, are large concentrations of galaxies - galaxy superclusters, contrasting to the seemingly empty regions beside them. Superclusters can extend from tens to over hundred megaparsecs, they contain from hundreds to thousands of galaxies, and many galaxy groups and clusters. Unlike galaxy clusters, superclusters are clearly unrelaxed systems, not gravitationally bound as crossing times exceed the age of the universe, and show little to no radial symmetry. Superclusters, as part of the large-scale structure, are sensitive to the initial power spectrum and the following evolution. They are massive enough to leave an imprint on the cosmic microwave background radiation. Superclusters can also provide an unique environment for their constituent galaxies and galaxy clusters. In this study we used two different observational and one simulated galaxy samples to create several catalogues of structures that, we think, correspond to what are generally considered galaxy superclusters. Superclusters were delineated as continuous over-dense regions in galaxy luminosity density fields. When calculating density fields several corrections were applied to remove small-scale redshift distortions and distance-dependent selection effects. Resulting catalogues of objects display robust statistical properties, showing that flux-limited galaxy samples can be used to create nearly volume-limited catalogues of superstructures. Generally, large superclusters can be regarded as massive, often branching filamentary structures, that are mainly characterised by their length. Smaller superclusters, on the other hand, can display a variety of shapes. Spatial distribution of superclusters shows large-scale variations, with high-density concentrations often found in semi-regularly spaced groups. Future

  3. Outskirts of spiral galaxies: result of a secular evolution process?. (United States)

    Bakos, J.; Trujillo, I.; Azzollini, R.; Beckman, J. E.; Pohlen, M.

    We present our recent results on the properties of the outskirts of disk galaxies. In particular, we focus on spiral galaxies with stellar disk truncations in their radial surface brightness profiles. Using SDSS, UDF and GOODS data we show how the position of the break (i.e., a direct estimator of the size of the stellar disk) evolves with time since z˜1. Our findings agree with an evolution on the radial position of the break by a factor of 1.3±0.1 in the last 8 Gyr for galaxies with similar stellar masses. We also present radial color gradients and how they evolve with time. At all redshift we find a radial inside-out bluing reaching a minimum at the position of the break radius, this minimum is followed by a reddening outwards. Our results constrain several galaxy disk formation models and favour a scenario where stars are formed inside the break radius and are relocated in the outskirts of galaxies through secular processes.

  4. Probing the origin of thick disks using ultra-deep images (United States)

    Martínez-Lombilla, Cristina; Trujillo, Ignacio; Knapen, Johan H.


    The origin of thick disks is still a matter of debate. To explore such structures in unprecedented detail, we have developed a technique to reach a surface brightness limit of 28.5-29 mag/arcsec2 with the combined g, r, i bands images from the IAC Stripe82 Legacy Project (Fliri & Trujillo, 2016). We present the characterisation of the thick disk in the edge-on galaxy UGC 01040. We carefully analyse the background subtraction and masking process. The effects of the PSF are considered through galaxy modelling. We present the study of radial and vertical surface brightness profiles, making a comparison between our data, the convolved and deconvolved models and its galactic components. We find that PSF effects are important, but can be accounted for. Our technique will allow us to model thick disks in external galaxies and elucidate their formation and evolutionary history.

  5. Resolved imaging of the HR 8799 Debris disk with Herschel

    Energy Technology Data Exchange (ETDEWEB)

    Matthews, Brenda; Booth, Mark; Broekhoven-Fiene, Hannah; Marois, Christian [National Research Council of Canada Herzberg Astronomy and Astrophsyics, 5071 W. Saanich Road, Victoria, BC, V9E 2E7 (Canada); Kennedy, Grant; Wyatt, Mark [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Sibthorpe, Bruce [SRON Netherlands Institute for Space Research, P.O. Box 800, NL-9700 AV Groningen (Netherlands); Macintosh, Bruce [Lawrence Livermore National Labs, 7000 East Ave, Livermore, CA 94550 (United States)


    We present Herschel far-infrared and submillimeter maps of the debris disk associated with the HR 8799 planetary system. We resolve the outer disk emission at 70, 100, 160, and 250 μm and detect the disk at 350 and 500 μm. A smooth model explains the observed disk emission well. We observe no obvious clumps or asymmetries associated with the trapping of planetesimals that is a potential consequence of planetary migration in the system. We estimate that the disk eccentricity must be <0.1. As in previous work by Su et al., we find a disk with three components: a warm inner component and two outer components, a planetesimal belt extending from 100 to 310 AU, with some flexibility (±10 AU) on the inner edge, and the external halo that extends to ∼2000 AU. We measure the disk inclination to be 26° ± 3° from face-on at a position angle of 64° E of N, establishing that the disk is coplanar with the star and planets. The spectral energy distribution of the disk is well fit by blackbody grains whose semi-major axes lie within the planetesimal belt, suggesting an absence of small grains. The wavelength at which the spectrum steepens from blackbody, 47 ± 30 μm, however, is short compared with other A star debris disks, suggesting that there are atypically small grains likely populating the halo. The PACS longer wavelength data yield a lower disk color temperature than do MIPS data (24 and 70 μm), implying two distinct halo dust-grain populations.

  6. Galaxy rotation curves with log-normal density distribution


    Marr, John H.


    The log-normal distribution represents the probability of finding randomly distributed particles in a micro canonical ensemble with high entropy. To a first approximation, a modified form of this distribution with a truncated termination may represent an isolated galactic disk, and this disk density distribution model was therefore run to give the best fit to the observational rotation curves for 37 representative galaxies. The resultant curves closely matched the observational data for a wid...

  7. Bridging the Gap from Galactic to Extragalactic: Star Formation and Giant Molecular Clouds within the Nearby Spiral Galaxy NGC 300 (United States)

    Faesi, Christopher


    The questions surrounding the origins of stars are of key importance in astrophysics across a huge range in physical scales. However, until recently, investigations have been restricted to either detailed studies targeting a few nearby regions in the Milky Way, or kpc- or larger-scale studies of entire galaxies. Between these two scales lies a crucial gap in understanding. In this thesis work, I have taken steps in bridging this gap between Galactic and extragalactic star formation. I will present the results of a campaign of observations and modeling targeting the nearby spiral galaxy NGC 300. Using an extensive suite of multi-wavelength data I have characterized the star formation activity and molecular gas in a large sample of star-forming regions within this galaxy. Additionally, I have assembled an extensive (300 clouds) and high resolution (10 pc) catalog of Giant Molecular Clouds (GMCs) based on ALMA CO observations. This unprecedented look at the population of GMCs in a nearby spiral galaxy reveals an astonishing range of morphologies and properties in the Molecular Gas as well as providing a key testbed for comparison with GMCs in the Milky Way and other nearby galaxies. The GMCs in NGC 300 appear to have similar global properties and show scaling relations consistent with those seen in the Milky Way. Furthermore, the star formation rate appears to correlate with the mass of molecular gas with approximately 250 Gyr depletion time, extending the relation discovered in the Milky Way linearly to larger scales. These results suggest a level of universality in the star formation process within spiral galaxy disks like our own Milky Way.

  8. Dark Galaxies and Lost Baryons (IAU S244) (United States)

    Davies, Jonathan I.; Disney, Michael J.


    ; Numerical simulation of the dwarf companions of giant galaxies A. Nelson and P. Williams; Delayed galaxies C. Struck, M. Hancock, B. Smith, P. Appleton, V. Charmandaris and M. Giroux; Probe of dark galaxies via disturbed/lopsided isolated galaxies I. Karachentsev, V. Karachentseva, W. Huchtmeier, D. Makarov and S. Kaisin; Star formation thresholds J. Schaye; Scaling relations of dwarf galaxies without supernova-driven winds K. Tassis, A. Kravtsov and N. Gnedin; Star formation in massive low surface brightness galaxies K. O'Neil; Linking clustering properties and the evolution of low surface brightness galaxies D. Bomans and S. Rosenbaum; Too small to form a galaxy: how the UV background determines the baryon fraction M. Hoeft, G. Yepes and S. Gottlober; Star formation in damped Lyman selected galaxies L. Christensen; Dark-matter content of early-type galaxies with planetary nebulae N. Napolitano et al.; Hunting for ghosts: low surface brightnesses from pixels R. Scaramella and S. Sabatini; Baryonic properties of the darkest galaxies E. Grebel; The dwarf low surface brightness population in different environments of the local universe S. Sabatini, J. Davies, S. Roberts and R. Scaramella; Mass modelling of dwarf spheroidal galaxies J. Klimentowski et al.; Evolution of dwarf galaxies in the Centaurus A Group L. Makarova and D. Makarov; A flat faint end of the Fornax cluster galaxy luminosity function S. Mieske, M. Hilker, L. Infante and C. Mendes de Oliveira; Can massive dark halos destroy the discs of dwarf galaxies? B. Fuchs and O. Esquivel; 'Dark galaxies' and local very metal-poor gas-rich galaxies: possible interrelations S. Pustilnik; Morphology and environment of dwarf galaxies in the local universe H. Ann; Arecibo survey of HI emission from disk galaxies at redshift z 0.2 B. Catinella, M. Haynes, J. Gardner, A. Connolly and R. Giovanelli; AGES observations of

  9. Fomalhaut's Debris Disk and Planet: Constraining the Mass of Formalhaut B from Disk Morphology (United States)

    Chiang, E.; Kite, E.; Kalas, P.; Graham, J. R.; Clampin, M.


    Following the optical imaging of exoplanet candidate Fomalhaut b (Fom b), we present a numerical model of how Fomalhaut's debris disk is gravitationally shaped by a single interior planet. The model is simple, adaptable to other debris disks, and can be extended to accommodate multiple planets. If Fom b is the dominant perturber of the belt, then to produce the observed disk morphology it must have a mass M(sub pl) 101.5AU, and an orbital eccentricity e(sub pl) = 0.11 - 0.13. These conclusions are independent of Fom b's photometry. To not disrupt the disk, a greater mass for Fom b demands a smaller orbit farther removed from the disk; thus, future astrometric measurement of Fom b's orbit, combined with our model of planet-disk interaction, can be used to determine the mass more precisely. The inner edge of the debris disk at a approximately equals 133AU lies at the periphery of Fom b's chaotic zone, and the mean disk eccentricity of e approximately equals 0.11 is secularly forced by the planet, supporting predictions made prior to the discovery of Fom b. However, previous mass constraints based on disk morphology rely on several oversimplifications. We explain why our constraint is more reliable. It is based on a global model of the disk that is not restricted to the planet's chaotic zone boundary. Moreover, we screen disk parent bodies for dynamical stability over the system age of approximately 100 Myr, and model them separately from their dust grain progeny; the latter's orbits are strongly affected by radiation pressure and their lifetimes are limited to approximately 0.1 Myr by destructive grain-grain collisions. The single planet model predicts that planet and disk orbits be apsidally aligned. Fomalhaut b's nominal space velocity does not bear this out, but the astrometric uncertainties are difficult to quantify. Even if the apsidal misalignment proves real, our calculated upper mass limit of 3 M(sub J) still holds. Parent bodies are evacuated from mean


    Energy Technology Data Exchange (ETDEWEB)

    Buta, Ronald J. [Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487-0324 (United States); Sheth, Kartik; Muñoz-Mateos, Juan-Carlos; Kim, Taehyun [National Radio Astronomy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Athanassoula, E.; Bosma, A. [Aix Marseille Universite, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France); Knapen, Johan H. [Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna (Spain); Laurikainen, Eija; Salo, Heikki; Laine, Jarkko; Comerón, Sébastien [Division of Astronomy, Department of Physical Sciences, University of Oulu, Oulu, FI-90014 (Finland); Elmegreen, Debra [Vassar College, Deparment of Physics and Astronomy, Poughkeepsie, NY 12604 (United States); Ho, Luis C. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Zaritsky, Dennis; Hinz, Joannah L. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Courtois, Helene [Université Lyon 1, CNRS/IN2P3, Institut de Physique Nucléaire, Lyon (France); Regan, Michael W. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Gadotti, Dimitri A. [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Paz, Armando Gil de [Departmento de Astrofisica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Menéndez-Delmestre, Karín [University of Rio de Janeiro, Observatorio de Valongo, Ladeira Pedro Antonio, 43, CEP 20080-090, Rio de Janeiro (Brazil); and others


    The Spitzer Survey of Stellar Structure in Galaxies (S{sup 4}G) is the largest available database of deep, homogeneous middle-infrared (mid-IR) images of galaxies of all types. The survey, which includes 2352 nearby galaxies, reveals galaxy morphology only minimally affected by interstellar extinction. This paper presents an atlas and classifications of S{sup 4}G galaxies in the Comprehensive de Vaucouleurs revised Hubble-Sandage (CVRHS) system. The CVRHS system follows the precepts of classical de Vaucouleurs morphology, modified to include recognition of other features such as inner, outer, and nuclear lenses, nuclear rings, bars, and disks, spheroidal galaxies, X patterns and box/peanut structures, OLR subclass outer rings and pseudorings, bar ansae and barlenses, parallel sequence late-types, thick disks, and embedded disks in 3D early-type systems. We show that our CVRHS classifications are internally consistent, and that nearly half of the S{sup 4}G sample consists of extreme late-type systems (mostly bulgeless, pure disk galaxies) in the range Scd-Im. The most common family classification for mid-IR types S0/a to Sc is SA while that for types Scd to Sm is SB. The bars in these two type domains are very different in mid-IR structure and morphology. This paper examines the bar, ring, and type classification fractions in the sample, and also includes several montages of images highlighting the various kinds of “stellar structures” seen in mid-IR galaxy morphology.

  11. Untangling Galaxy Components - The Angular Momentum Parameter (United States)

    Tabor, Martha; Merrifield, Michael; Aragon-Salamanca, Alfonso


    We have developed a new technique to decompose Integral Field spectral data cubes into separate bulge and disk components, allowing us to study the kinematic and stellar population properties of the individual components and how they vary with position. We present here the application of this method to a sample of fast rotator early type galaxies from the MaNGA integral field survey, and demonstrate how it can be used to explore key properties of the individual components. By extracting ages, metallicities and the angular momentum parameter lambda of the bulges and disks, we show how this method can give us new insights into the underlying structure of the galaxies and discuss what this can tell us about their evolution history.

  12. Testing the dark matter hypothesis with low surface brightness galaxies and other evidence

    NARCIS (Netherlands)

    McGaugh, SS; de Blok, WJG


    The severity of the mass discrepancy in spiral galaxies is strongly correlated with the central surface brightness of their disks. Progressively lower surface brightness galaxies have ever larger mass discrepancies. No other parameter (luminosity, size, velocity, morphology) is so well correlated

  13. xGASS: Total cold gas scaling relations and molecular-to- atomic gas ratios of galaxies in the local Universe (United States)

    Catinella, Barbara; Saintonge, Amélie; Janowiecki, Steven; Cortese, Luca; Davé, Romeel; Lemonias, Jenna J.; Cooper, Andrew P.; Schiminovich, David; Hummels, Cameron B.; Fabello, Silvia; Geréb, Katinka; Kilborn, Virginia; Wang, Jing


    We present the extended GALEX Arecibo SDSS Survey (xGASS), a gas fraction-limited census of the atomic hydrogen (HI) gas content of 1179 galaxies selected only by stellar mass (M⋆=109 - 1011.5 M⊙) and redshift (0.01 < z < 0.05). This includes new Arecibo observations of 208 galaxies, for which we release catalogs and HI spectra. In addition to extending the GASS HI scaling relations by one decade in stellar mass, we quantify total (atomic+molecular) cold gas fractions and molecular-to-atomic gas mass ratios, Rmol, for the subset of 477 galaxies observed with the IRAM 30 m telescope. We find that atomic gas fractions keep increasing with decreasing stellar mass, with no sign of a plateau down to log M⋆/M⊙ = 9. Total gas reservoirs remain HI-dominated across our full stellar mass range, hence total gas fraction scaling relations closely resemble atomic ones, but with a scatter that strongly correlates with Rmol, especially at fixed specific star formation rate. On average, Rmol weakly increases with stellar mass and stellar surface density μ⋆, but individual values vary by almost two orders of magnitude at fixed M⋆ or μ⋆. We show that, for galaxies on the star-forming sequence, variations of Rmol are mostly driven by changes of the HI reservoirs, with a clear dependence on μ⋆. Establishing if galaxy mass or structure plays the most important role in regulating the cold gas content of galaxies requires an accurate separation of bulge and disk components for the study of gas scaling relations.

  14. Molecular Abundances in the Disk of AN Active Galactic Nucleus (United States)

    Harada, N.; Thompson, T. A.; Herbst, E.


    There are galactic nuclei that emit high luminosities L˜1044-46 erg S-1 including luminosity produced by X-rays from high mass accretion onto the central black holes. These nuclei are called active galactic nuclei (AGNs), and they are accompanied by molecular disks. Observations show high abundances of CN and HCN in the disks; the molecules are proposed to be probes of X-ray dominated regions (XDRs) created by the X-rays from AGNs. We have constructed a spatially-dependent chemical-abundance model of the molecular disk in NGC 1068, a typical AGN-dominated galaxy. Recently, new observations of CN and HCN have been made at much higher spatial resolution, and there are also detections of polyatomic molecules such as HC3N, c-C3H2, and C2H. We discuss how these observations and our simulations can help us to better understand the physical conditions, the disk structure, and conditions for star formation within molecular disks, which are still uncertain. We also include a comparison with other types of galaxies such as (ultra-) luminous infrared galaxies. Usero et al.Astronomy and Astrophysics. 419 (897), 2004. Initial results were presented at the International Symposium on Molecular Spectroscopy 2010, RF05 Garcia-Burillo et al. Astronomy and Astrophysics. 519 (2), 2010. Garcia-Burillo et al. Journal of Physics Conference Series, 131 (12031), 2008. Costagliola et al. ArXiv e-print arXiv:1101.2122, 2011. Nakajima et al. Astrophysical Journal Letters 728 (L38), 2008.


    NARCIS (Netherlands)


    The observed distribution and kinematics (as derived from 21-cm radio synthesis observations) of the H I gas in a sample of 24 gas-rich early-type (S0 to Sa) disk galaxies are summarized and compared to those of later type (Sb to Sm) spiral galaxies. Lenticular galaxies more frequently have inner or

  16. Creating reusable tools from scripts: the Galaxy Tool Factory. (United States)

    Lazarus, Ross; Kaspi, Antony; Ziemann, Mark


    Galaxy is a software application supporting high-throughput biology analyses and work flows, available as a free on-line service or as source code for local deployment. New tools can be written to extend Galaxy, and these can be shared using public Galaxy Tool Shed (GTS) repositories, but converting even simple scripts into tools requires effort from a skilled developer. The Tool Factory is a novel Galaxy tool that automates the generation of all code needed to execute user-supplied scripts, and wraps them into new Galaxy tools for upload to a GTS, ready for review and installation through the Galaxy administrative interface. The Galaxy administrative interface supports automated installation from the main GTS. Source code and support are available at the project website, The Tool Factory is implemented as an installable Galaxy tool.

  17. Probability of lensing magnification by cosmologically distributed galaxies (United States)

    Pei, Yichuan C.


    We present the analytical formulae for computing the magnification probability caused by cosmologically distributed galaxies. The galaxies are assumed to be singular, truncated-isothermal spheres without both evolution and clustering in redshift. We find that, for a fixed total mass, extended galaxies produce a broader shape in the magnification probability distribution and hence are less efficient as gravitational lenses than compact galaxies. The high-magnification tail caused by large galaxies is well approximated by an A exp -3 form, while the tail by small galaxies is slightly shallower. The mean magnification as a function of redshift is, however, found to be independent of the size of the lensing galaxies. In terms of the flux conservation, our formulae for the isothermal galaxy model predict a mean magnification to within a few percent with the Dyer-Roeder model of a clumpy universe.

  18. Molecular Gas and Star Formation in Void Galaxies (United States)

    Das, M.; Saito, T.; Iono, D.; Honey, M.; Ramya, S.


    We present the detection of molecular gas using CO(1-0) line emission and followup Hα imaging observations of galaxies located in nearby voids. The CO(1-0) observations were done using the 45m telescope of the Nobeyama Radio Observatory (NRO) and the optical observations were done using the Himalayan Chandra Telescope (HCT). Although void galaxies lie in the most underdense parts of our universe, a significant fraction of them are gas rich, spiral galaxies that show signatures of ongoing star formation. Not much is known about their cold gas content or star formation properties. In this study we searched for molecular gas in five void galaxies using the NRO. The galaxies were selected based on their relatively higher IRAS fluxes or Hα line luminosities. CO(1-0) emission was detected in four galaxies and the derived molecular gas masses lie between (1 - 8)×109 M⊙. The Hα imaging observations of three galaxies detected in CO emission indicates ongoing star formation and the derived star formation rates vary between from 0.2 - 1.0 M7odot; yr -1, which is similar to that observed in local galaxies. Our study shows that although void galaxies reside in underdense regions, their disks may contain molecular gas and have star formation rates similar to galaxies in denser environments.

  19. Are star formation rates of galaxies bimodal? (United States)

    Feldmann, Robert


    Star formation rate (SFR) distributions of galaxies are often assumed to be bimodal with modes corresponding to star-forming and quiescent galaxies, respectively. Both classes of galaxies are typically studied separately, and SFR distributions of star-forming galaxies are commonly modelled as lognormals. Using both observational data and results from numerical simulations, I argue that this division into star-forming and quiescent galaxies is unnecessary from a theoretical point of view and that the SFR distributions of the whole population can be well fitted by zero-inflated negative binomial distributions. This family of distributions has three parameters that determine the average SFR of the galaxies in the sample, the scatter relative to the star-forming sequence and the fraction of galaxies with zero SFRs, respectively. The proposed distributions naturally account for (i) the discrete nature of star formation, (ii) the presence of 'dead' galaxies with zero SFRs and (iii) asymmetric scatter. Excluding 'dead' galaxies, the distribution of log SFR is unimodal with a peak at the star-forming sequence and an extended tail towards low SFRs. However, uncertainties and biases in the SFR measurements can create the appearance of a bimodal distribution.

  20. Search for High Redshift Galaxy Clusters (United States)

    Haarsma, D. B.; Butler, A. R.; Donahue, M. E.; Bruch, S. S.


    Distant galaxy clusters are key to understanding many current questions in cosmology, structure formation, and galaxy evolution, yet few z>1 clusters have been identified. The ROSAT Optical X-ray Survey (Donahue et al. 2002 ApJ 569, 689) searched for galaxy clusters using both optical and x-ray detection methods. While many clusters appeared in both wavebands, 10 targets which showed extended x-ray emission (a unique signature of cluster gas) did not show significant I-band emission (expected from elliptical galaxies in the cluster). These targets may be galaxy clusters with redshift greater than 1, which would appear faint in I due to the 400 nm break in elliptical galaxy spectra. In J and K bands, such galaxies would be easier to detect, and in April 2005 we imaged the 10 fields in J and K with the FLAMINGOS camera on the NOAO 4m telescope. The infrared colors are useful in identifying clusters, because all elliptical galaxies in a cluster are expected to have similar colors (i.e. the red sequence). We report preliminary identifications of high redshift galaxy clusters in our sample.

  1. Distinguishing disks from mergers: Tracing the kinematic asymmetries in local (U)LIRGs using kinemetry-based criteria (United States)

    Bellocchi, Enrica; Arribas, Santiago; Colina, Luis


    Context. The kinematic characterization of different galaxy populations is a key observational input for distinguishing between different galaxy evolutionary scenarios because it helps to determine the number ratio of rotating disks to mergers at different cosmic epochs. Local (ultra) luminous infrared galaxies ((U)LIRGs) cover similar range of star formation rates (SFR) as normal high redshift (high-z), star-forming galaxies (SFGs). Therefore, their study offer a unique opportunity to study at high linear resolution and signal-to-noise (S/N) extreme star forming events and compare these events with those observed at high-z. Aims: Our goal is to analyze in detail the kinematics of the ionized gas as traced by the Hα emission of a large sample of 38 local (z data of a sample of 38 (U)LIRGs. These systems are morphologically classified in four groups according to their dynamical phases: isolated disk, paired disk, ongoing merger, and post-coalescence merger. The first two are referred as "disk", while the second two are referred to as "merger". The "unweighted" and "weighted" kinemetry-based methods are used to kinematically classify our galaxies in disk and merger. The total kinematic asymmetry value Ktot has been used to quantify the global kinematic asymmetry degree of the observed and simulated systems. Results: From the kinemetry-based analysis we are able classify our local (U)LIRGs in three distinct kinematic groups according to their total kinematic asymmetry values (Ktot) as derived when using the weighted (unweighted) method: (1) 25 out of 50 galaxies are kinematically classified as disk with a Ktot ≤ 0.16 (0.14); (2) 9 out of 50 galaxies are kinematically classified as merger with a Ktot ≥ 0.94 (0.66); (3) 16 out of 50 galaxies lie in the "transition region", in which disks and mergers coexist, with 0.16 (0.14) < Ktot < 0.94 (0.66). The Ktot frontier value that better classifies the highest numbers of disks and mergers, in agreement with their


    Energy Technology Data Exchange (ETDEWEB)

    Law, David R. [Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4 (Canada); Steidel, Charles C. [Department of Astronomy, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Shapley, Alice E.; Nagy, Sarah R. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Reddy, Naveen A. [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Erb, Dawn K., E-mail:, E-mail:, E-mail:, E-mail: [Department of Physics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, WI 53201 (United States)


    We analyze rest-frame optical morphologies and gas-phase kinematics as traced by rest-frame far-UV and optical spectra for a sample of 204 star-forming galaxies in the redshift range z {approx} 2-3 drawn from the Keck Baryonic Structure Survey. We find that spectroscopic properties and gas-phase kinematics are closely linked to morphology: compact galaxies with semimajor axis radii r {approx}< 2 kpc are substantially more likely than their larger counterparts to exhibit Ly{alpha} in emission. Although Ly{alpha} emission strength varies widely within galaxies of a given morphological type, all but one of 19 galaxies with Ly{alpha} equivalent width W {sub Ly{alpha}} > 20 A have compact and/or multiple-component morphologies with r {<=} 2.5 kpc. The velocity structure of absorption lines in the galactic continuum spectra also varies as a function of morphology. Galaxies of all morphological types drive similarly strong outflows (as traced by the blue wing of interstellar absorption line features), but the outflows of larger galaxies are less highly ionized and exhibit larger optical depth at the systemic redshift that may correspond to a decreasing efficiency of feedback in evacuating gas from the galaxy. This v {approx} 0 km s{sup -1} gas is responsible both for shifting the mean absorption line redshift and attenuating W {sub Ly{alpha}} (via a longer resonant scattering path) in galaxies with larger rest-optical half-light radii. In contrast to galaxies at lower redshifts, there is no evidence for a correlation between outflow velocity and inclination, suggesting that outflows from these puffy and irregular systems may be poorly collimated. Our observations are broadly consistent with theoretical models of inside-out growth of galaxies in the young universe, in which typical z {approx} 2-3 star-forming galaxies are predominantly unstable, dispersion-dominated, systems fueled by rapid gas accretion that later form extended rotationally supported disks when stabilized

  3. Probing Protoplanetary Disks: From Birth to Planets (United States)

    Guilfoil Cox, Erin


    Disks are very important in the evolution of protostars and their subsequent planets. How early disks can form has implications for early planet formation. In the youngest protostars (i.e., Class 0 sources) magnetic fields can control disk growth. When the field is parallel to the collapsing core’s rotation axis, infalling material loses angular momentum and disks form in later stages. Sub-/millimeter polarization continuum observations of Class 0 sources at ~1000 au resolution support this idea. However, in the inner (~100 au), denser regions, it is unknown if the polarization only traces aligned dust grains. Recent theoretical studies have shown that self-scattering of thermal emission in the disk may contribute significantly to the polarization. Determining the scattering contribution in these sources is important to disentangle the magnetic field. At older times (the Class II phase), the disk structure can both act as a modulator and signpost of planet formation, if there is enough of a mass reservoir. In my dissertation talk, I will present results that bear on disk evolution at both young and late ages. I will present 8 mm polarization results of two Class 0 protostars (IRAS 4A and IC348 MMS) from the VLA at ~50 au resolution. The inferred magnetic field of IRAS 4A has a circular morphology, reminiscent of material being dragged into a rotating structure. I will show results from SOFIA polarization data of the area surrounding IRAS 4A at ~4000 au. I will also present ALMA 850 micron polarization data of ten protostars in the Perseus Molecular Cloud. Most of these sources show very ordered patterns and low (~0.5%) polarization in their inner regions, while having very disordered patterns and high polarization patterns in their extended emission that may suggest different mechanisms in the inner/outer regions. Finally, I will present results from our ALMA dust continuum survey of protoplanetary disks in Rho Ophiuchus; we measured both the sizes and fluxes of

  4. Lupus Alma Disk Survey (United States)

    Ansdell, Megan


    We present the first unbiased ALMA survey of both dust and gas in a large sample of protoplanetary disks. We surveyed 100 sources in the nearby (150-200 pc), young (1-2 Myr) Lupus region to constrain M_dust to 2 M_Mars and M_gas to 1 M_Jup. Most disks have masses < MMSN and gas-to-dust ratios < ISM. Such rapid gas depletion may explain the prevalence of super-Earths in the exoplanet population.

  5. Sausage and kink oscillations in astrophysical disk configurations. (United States)

    Griv, Evgeny


    The development of hydrodynamic oscillations in various rotating astrophysical disks ranging from planetary rings to galaxies is studied analytically. The dispersion relation of wave propagation is derived. Modes of oscillation are examined from this dispersion relation that are suitable for obtaining information not just on oscillations but also on some instability properties of the disk-shaped structure. It is shown that unstable oscillations of different types, sausage compression and kink bending, may be excited effectively due to the Jeans gravitational instability and the kink transverse instability, respectively. The obtained results for the sausage oscillations may be applicable for such phenomena as the appearance of the in-plane spiral and circular structures, while the case for the kink mode is more relevant for the systematic vertical corrugations of astrophysical disks.

  6. Dwarf spheroidal galaxies: Keystones of galaxy evolution (United States)

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


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

  7. Rotation in [C II]-emitting gas in two galaxies at a redshift of 6.8 (United States)

    Smit, Renske; Bouwens, Rychard J.; Carniani, Stefano; Oesch, Pascal A.; Labbé, Ivo; Illingworth, Garth D.; van der Werf, Paul; Bradley, Larry D.; Gonzalez, Valentino; Hodge, Jacqueline A.; Holwerda, Benne W.; Maiolino, Roberto; Zheng, Wei


    The earliest galaxies are thought to have emerged during the first billion years of cosmic history, initiating the ionization of the neutral hydrogen that pervaded the Universe at this time. Studying this ‘epoch of reionization’ involves looking for the spectral signatures of ancient galaxies that are, owing to the expansion of the Universe, now very distant from Earth and therefore exhibit large redshifts. However, finding these spectral fingerprints is challenging. One spectral characteristic of ancient and distant galaxies is strong hydrogen-emission lines (known as Lyman-α lines), but the neutral intergalactic medium that was present early in the epoch of reionization scatters such Lyman-α photons. Another potential spectral identifier is the line at wavelength 157.4 micrometres of the singly ionized state of carbon (the [C II] λ = 157.74 μm line), which signifies cooling gas and is expected to have been bright in the early Universe. However, so far Lyman-α-emitting galaxies from the epoch of reionization have demonstrated much fainter [C II] luminosities than would be expected from local scaling relations, and searches for the [C II] line in sources without Lyman-α emission but with photometric redshifts greater than 6 (corresponding to the first billion years of the Universe) have been unsuccessful. Here we identify [C II] λ = 157.74 μm emission from two sources that we selected as high-redshift candidates on the basis of near-infrared photometry; we confirm that these sources are two galaxies at redshifts of z = 6.8540 ± 0.0003 and z = 6.8076 ± 0.0002. Notably, the luminosity of the [C II] line from these galaxies is higher than that found previously in star-forming galaxies with redshifts greater than 6.5. The luminous and extended [C II] lines reveal clear velocity gradients that, if interpreted as rotation, would indicate that these galaxies have similar dynamic properties to the turbulent yet rotation

  8. The Merger-Free Growth of Galaxies and Supermassive Black Holes (United States)

    Simmons, Brooke; Smethurst, Rebecca; Lintott, Chris; Martin, Garreth; Kaviraj, Sugata; Devriendt, Julien; Galaxy Zoo Team


    There is now clear evidence that the merger-driven pathway to black hole and galaxy growth is only half the story. Merger-free evolution contributes roughly equally to the overall growth of black holes in the Universe and is also responsible for a significant amount of galaxy growth over cosmic time. A recent study examining the growth of black holes in unambiguously disk-dominated galaxies shows these black holes reach quasar-like luminosities and black hole masses typical of those hosted in bulge-dominated and elliptical galaxies with major mergers in their evolutionary histories. However, while there appears to be no correlation between the size of the black hole and upper limits on the host galaxy bulges, the fitted correlation between black hole mass and total galaxy stellar mass in these merger-free systems is fully consistent with the canonical relationship based on merger-driven systems. There is further evidence via comparison between observed populations and cosmological simulations confirming that bulgeless systems are generally consistent with having merger-free histories. If bulgeless and disk-dominated galaxies are indeed signatures of systems with no violent mergers in their formation histories, the same correlation between black hole and galaxy in these systems versus that seen in elliptical galaxy samples indicates the black hole-galaxy connection must originate with a process more fundamental than the dynamical configuration of a galaxy's stars.



    Resembling a gigantic hubcap in space, a 3,700 light-year-diameter dust disk encircles a 300 million solar-mass black hole in the center of the elliptical galaxy NGC 7052. The disk, possibly a remnant of an ancient galaxy collision, will be swallowed up by the black hole in several billion years. Because the front end of the disk eclipses more stars than the back, it appears darker. Also, because dust absorbs blue light more effectively than red light, the disk is redder than the rest of the galaxy (this same phenomenon causes the Sun to appear red when it sets in a smoggy afternoon). This NASA Hubble Space Telescope image was taken with the Wide Field and Planetary Camera 2, in visible light. Details as small as 50 light-years across can be seen. Hubble's Faint Object Spectrograph (replaced by the STIS spectrograph in 1997) was used to observe hydrogen and nitrogen emission lines from gas in the disk. Hubble measurements show that the disk rotates like an enormous carousel, 341,000 miles per hour (155 kilometers per second) at 186 light-years from the center. The rotation velocity provides a direct measure of the gravitational force acting on the gas by the black hole. Though 300 million times the mass of our Sun, the black hole is still only 0.05 per cent of the total mass of the NGC 7052 galaxy. Despite its size, the disk is 100 times less massive than the black hole. Still, it contains enough raw material to make three million sun-like stars. The bright spot in the center of the disk is the combined light of stars that have crowded around the black hole due to its strong gravitational pull. This stellar concentration matches theoretical models linking stellar density to a central black hole's mass. NGC 7052 is a strong source of radio emission and has two oppositely directed `jets' emanating from the nucleus. (The jets are streams of energetic electrons moving in a strong magnetic field and unleashing radio energy). Because the jets in NGC 7052 are not


    Energy Technology Data Exchange (ETDEWEB)

    Cervantes Sodi, Bernardo, E-mail: [Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Campus Morelia, A.P. 3-72, C.P. 58089 Michoacán, México (Mexico)


    We select a sample of galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7) where galaxies are classified, through visual inspection, as hosting strong bars, weak bars, or as unbarred galaxies, and make use of H i mass and kinematic information from the Arecibo Legacy Fast ALFA survey catalog, to study the stellar, atomic gas, and dark matter content of barred disk galaxies. We find, in agreement with previous studies, that the bar fraction increases with increasing stellar mass. A similar trend is found with total baryonic mass, although the dependence is not as strong as with stellar mass, due to the contribution of gas. The bar fraction shows a decrease with increasing gas mass fraction. This anticorrelation between the likelihood of a galaxy hosting a bar with the gas richness of the galaxy results from the inhibiting effect the gas has in the formation of bars. We also find that for massive galaxies with stellar masses larger than 10{sup 10} M {sub ⊙}, at fixed stellar mass, the bar fraction decreases with increasing global halo mass (i.e., halo mass measured up to a radius of the order of the H i disk extent).

  11. The Porosity of the neutral ISM in 20 THINGS Galaxies (United States)

    Bagetakos, I.; Brinks, E.; Walter, F.; de Blok, W. J. G.; Usero, A.; Leroy, A. K.; Rich, J. W.; Kennicutt, R. C.


    We present an analysis of the properties of H i holes detected in 20 galaxies that are part of "The H i Nearby Galaxy Survey". We detected more than 1000 holes in total in the sampled galaxies. The holes are found throughout the disks of the galaxies, out to the edge of the H i disk. We find that shear limits the age of holes in spirals. Shear is less important in dwarf galaxies which explains why H i holes in dwarfs are rounder, on average than in spirals. Shear is particularly strong in the inner part of spiral galaxies, limiting the lifespan of holes there and explaining why we find that holes outside R25 are larger and older. We proceed to derive the surface and volume porosity and find that this correlates with the type of the host galaxy: later Hubble types tend to be more porous. The size distribution of the holes in our sample follows a power law with a slope of aν ~ -2.9. Assuming that the holes are the result of massive star formation, we derive values for the supernova rate (SNR) and star formation rate (SFR) which scales with the SFR derived based on other tracers. If we extrapolate the observed number of holes to include those that fall below our resolution limit, down to holes created by a single supernova, we find that our results are compatible with the hypothesis that H i holes result from star formation.

  12. Disks around young stellar objects

    Indian Academy of Sciences (India)

    ... large groundbased telescopes, mm and radiowave interferometry have been used to image disks around a large number of YSOs revealing disk structure with ever-increasing detail and variety. The disks around YSOs are believed to be the sites of planet formation and a few such associations have now been confirmed.

  13. Unveiling the Secret of a Virgo Dwarf Galaxy (United States)


    Dwarf galaxies may not be as impressive in appearance as their larger brethren, but they are at least as interesting from a scientific point of view. And sometimes they may have hidden properties that will only be found by means of careful observations, probing the signals of their stars at the faintest level. Such as the entirely unexpected, well developed spiral structure within an otherwise seemingly normal dwarf elliptical galaxy! This is the surprise result of a new study by a team of astronomers [1], headed by Helmut Jerjen from the Australian National University (Canberra) who obtained detailed observations with the ESO Very Large Telescope (VLT) of the dwarf galaxy IC 3328 in the Virgo Cluster of Galaxies, some 50 million light-years away. Dwarf galaxies Dwarf galaxies are present in all major clusters of galaxies and dominate by numbers in the universe. They may contain a few (tens of) millions of stars, as compared to galaxies of normal size with hundreds of billions of stars. About two dozen dwarf galaxies are known in the "Local Group" of galaxies of which the Milky Way galaxy in which we live is also a member. The Large and Small Magellanic Clouds are some of the best known dwarf galaxies - they are of the irregular type - while NGC 147 and NGC 205, two companions to the great Andromeda Galaxy, are of the elliptical type. Dwarf elliptical galaxies are characterized by their smooth appearance. From various studies, it is known that they are tri-axial ellipsoids of different degrees of elongation. Some are almost spherical while others are more pancake- or cigar-shaped. Like the elliptical galaxies of normal size, dwarf ellipticals are almost pure aggregates of stars. In contrast, spiral galaxies also contain clouds of gas and dust. The visible mass of spiral galaxies is in a rotating disk. Dwarf ellipticals generally keep their form because of the random motions of their stars. VLT observations of dwarf elliptical galaxies Using the FORS1 multi

  14. Selections from 2016: A Very Dark Galaxy (United States)

    Kohler, Susanna


    Editors note:In these last two weeks of 2016, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume after the AAS winter meeting.A High Stellar Velocity Dispersion and 100 Globular Clusters for the Ultra-Diffuse Galaxy Dragonfly 44Published August2016Main takeaway:Using the Keck Observatory and the Gemini North telescope in Hawaii, a team led by Pieter van Dokkum (Yale University) discovered the very dim galaxy Dragonfly 44, located in the Coma cluster. The team estimated the center of this galaxys disk to be a whopping 98% dark matter.Why its interesting:Dragonfly 44, though dim, was discovered to host around 100 globular clusters. Measuring the dynamics of these clusters allowed van Dokkum and collaborators to estimate the mass of Dragonfly 44: roughly a trillion times the mass of the Sun. This is similar to the mass of the Milky Way, and yet the Milky Way has over a hundred times more stars than this intriguing galaxy. Its very unexpected to find a galaxy this massive that has a dark-matter fraction this high.What we can learn from this:How do ultra-faint galaxies like these form? One theory is that theyre failed normal galaxies: they have the sizes, dark-matter content, and globular cluster systems of much more luminous galaxies, but they were prevented from building up a normal stellar population. So far, Dragonfly 44s properties seem consistent with this picture.CitationPieter van Dokkum et al 2016 ApJL 828 L6. doi:10.3847/2041-8205/828/1/L6

  15. Identifying Likely Disk-hosting M dwarfs with Disk Detective (United States)

    Silverberg, Steven; Wisniewski, John; Kuchner, Marc J.; Disk Detective Collaboration


    M dwarfs are critical targets for exoplanet searches. Debris disks often provide key information as to the formation and evolution of planetary systems around higher-mass stars, alongside the planet themselves. However, less than 300 M dwarf debris disks are known, despite M dwarfs making up 70% of the local neighborhood. The Disk Detective citizen science project has identified over 6000 new potential disk host stars from the AllWISE catalog over the past three years. Here, we present preliminary results of our search for new disk-hosting M dwarfs in the survey. Based on near-infrared color cuts and fitting stellar models to photometry, we have identified over 500 potential new M dwarf disk hosts, nearly doubling the known number of such systems. In this talk, we present our methodology, and outline our ongoing work to confirm systems as M dwarf disks.

  16. Spectroscopic evidence of distinct stellar populations in the counter-rotating stellar disks of NGC 3593 and NGC 4550 (United States)

    Coccato, L.; Morelli, L.; Pizzella, A.; Corsini, E. M.; Buson, L. M.; Dalla Bontà, E.


    Aims: We present the results of integral-field spectroscopic observations of the two disk galaxies NGC 3593 and NGC 4550 obtained with the Visible Multi Object Spectrograph at the Very Large Telescope. Both galaxies are known to host two counter-rotating stellar disks, with the ionized gas corotating with one of them. We measured in each galaxy the surface brightness, kinematics, mass surface density, and the stellar populations of the two stellar components, as well as the distribution, kinematics, and metallicity of the ionized-gas component to constrain the formation scenario of these peculiar galaxies. Methods: We applied a novel spectroscopic decomposition technique to both galaxies, to disentangle at each position in the field of view the relative contribution of the two counter-rotating stellar and one ionized-gas components to the observed spectrum. We measured the kinematics and the line strengths of the Lick indices of the two counter-rotating stellar components. We modeled the data of each stellar component with single stellar population models that account for the α/Fe overabundance. Results: In both galaxies we successfully separated the main from the secondary stellar component that is less massive and rotates in the same direction as the ionized-gas component. The two stellar components have exponential surface-brightness profiles. In NGC 3593 they have different scale lengths, with the secondary one dominating the innermost 500 pc. In NGC 4550 they have the same scale lengths, but slightly different scale heights. In both galaxies, the two counter-rotating stellar components have different stellar populations. The secondary stellar disk is younger, more metal poor, and more α-enhanced than the main galaxy stellar disk. Such a difference is stronger in NGC 3593 than in NGC 4550. Conclusions: Our findings rule out an internal origin of the secondary stellar component and favor a scenario where it formed from gas accreted on retrograde orbits from

  17. The SCUBA-2 Cosmology Legacy Survey: The EGS deep field - II. Morphological transformation and multi-wavelength properties of faint submillimetre galaxies (United States)

    Zavala, J. A.; Aretxaga, I.; Dunlop, J. S.; Michałowski, M. J.; Hughes, D. H.; Bourne, N.; Chapin, E.; Cowley, W.; Farrah, D.; Lacey, C.; Targett, T.; van der Werf, P.


    We present a multi-wavelength analysis of galaxies selected at 450 and 850 {μ m} from the deepest SCUBA-2 observations in the Extended Groth Strip (EGS) field, which have an average depth of σ450 = 1.9 and σ _850=0.46 mJy beam^{-1} over ˜70 arcmin2. The final sample comprises 95 sources: 56 (59 %) are detected at both wavelengths, 31 (33 %) are detected only at 850 {μ m}, and 8 (8 %) are detected only at 450 {μ m}. We identify counterparts for 75 % of the whole sample. The redshift distributions of the 450 and 850 {μ m} samples peak at different redshifts with median values of \\bar{z}=1.66± 0.18 and \\bar{z}=2.30± 0.20, respectively. However, the two populations have similar IR luminosities, SFRs, and stellar masses, with mean values of 1.5 ± 0.2 × 1012 L⊙, 150 ± 20 M⊙/yr, and 9.0 ± 0.6 × 1010 M⊙, respectively. This places most of our sources (≳ 85 %) on the high-mass end of the `main-sequence' of star-forming galaxies. Exploring the IR excess vs UV-slope (IRX-β) relation we find that the most luminous galaxies are consistent with the Meurer law, while the less luminous galaxies lie below this relation. Using the results of a two-dimensional modelling of the HST H160-band imaging, we derive a median Sérsic index of n=1.4^{+0.3}_{-0.1} and a median half-light radius of r1/2 = 4.8 ± 0.4 kpc. Based on a visual-like classification in the same band, we find that the dominant component for most of the galaxies at all redshifts is a disk-like structure, although there is a transition from irregular disks to disks with a spheroidal component at z ˜ 1.4, which morphologically supports the scenario of SMGs as progenitors of massive elliptical galaxies.

  18. Disentangling Accretion Disk and Dust Emissions in the Infrared Spectrum of Type 1 AGN

    Directory of Open Access Journals (Sweden)

    Antonio Hernán-Caballero


    Full Text Available We use a semi-empirical model to reproduce the 0.1–10 μm spectral energy distribution (SED of a sample of 85 luminous quasars. In the model, the continuum emission from the accretion disk as well as the nebular lines are represented by a single empirical template (disk, where differences in the optical spectral index are reproduced by varying the amount of extinction. The near- and mid-infrared emission of the AGN-heated dust is modeled as the combination of two black-bodies (dust. The model fitting shows that the disk and dust components are remarkably uniform among individual quasars, with differences in the observed SED largely accounted for by varying levels of obscuration in the disk as well as differences in the relative luminosity of the disk and dust components. By combining the disk-subtracted SEDs of the 85 quasars, we generate a template for the 1–10 μm emission of the AGN-heated dust. Additionally, we use a sample of local Seyfert 1 galaxies with full spectroscopic coverage in the 0.37–39 μm range to demonstrate a method for stitching together spectral segments obtained with different PSF and extraction apertures. We show that the disk and dust templates obtained from luminous quasars also reproduce the optical-to-mid-infrared spectra of local Seyfert 1s when the contribution from the host galaxy is properly subtracted.


    Energy Technology Data Exchange (ETDEWEB)

    Bednarek, W., E-mail: [Department of Astrophysics, The University of Lodz, 90-236 Lodz, ul. Pomorska 149/153 (Poland)


    We investigate the consequences of acceleration of nuclei in jets of active galaxies not far from the surface of an accretion disk. The nuclei can be accelerated in the re-connection regions in the jet and/or at the jet boundary, between the relativistic jet and its cocoon. It is shown that the relativistic nuclei can efficiently fragment onto specific nucleons in collisions with the disk radiation. Neutrons, directed toward the accretion disk, take a significant part of energy from the relativistic nuclei. These neutrons develop a cascade in the dense accretion disk. We calculate the neutrino spectra produced in such a hadronic cascade within the accretion disk. We propose that the neutrinos produced in such a scenario, from the whole population of super-massive black holes in active galaxies, can explain the extragalactic neutrino background recently measured by the IceCube neutrino detector, provided that a 5% fraction of galaxies have an active galactic nucleus and a few percent of neutrons reach the accretion disk. We predict that the neutrino signals in the present neutrino detectors, produced in terms of such a model, will not be detectable even from the nearby radio galaxies similar to M87.

  20. Galaxy Zoo: Comparing the visual morphology of synthetic galaxies from the Illustris simulation with those in the real Universe. (United States)

    Dickinson, Hugh; Lintott, Chris; Scarlata, Claudia; Fortson, Lucy; Bamford, Steven; Cardamone, Carolin; Keel, William C.; Kruk, Sandor; Masters, Karen; Simmons, Brooke D.; Vogelsberger, Mark; Torrey, Paul; Snyder, Gregory; Galaxy Zoo Science Team


    We present a comparision between the Illustris simulations and classifications from Galaxy Zoo, aiming to test the ability of modern large-scale cosmological simulations to accurately reproduce the local galaxy population. This comparison is enabled by the increasingly high spatial and temporal resolution obtained by such surveys.Using classifications that were accumulated via the Galaxy Zoo citizen science interface, we compare the visual morphologies for simulated images of Illustris galaxies with a compatible sample of images drawn from the Sloan Digital Sky Survey (SDSS) Legacy Survey.For simulated galaxies with stellar masses less than 1011 M⊙, significant differences are identified, which are most likely due to the limited resolution of the simulation, but could be revealing real differences in the dynamical evolution of populations of galaxies in the real and model universes. Above 1011 M⊙, Illustris galaxy morphologies correspond better with those of their SDSS counterparts, although even in this mass range the simulation appears to underproduce obviously disk-like galaxies. Morphologies of Illustris galaxies less massive than 1011 M⊙ should be treated with care.

  1. Probing outflows in z = 1 ∼ 2 galaxies through Fe II/Fe II* multiplets

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yuping; Giavalisco, Mauro [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Guo, Yicheng [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Kurk, Jaron, E-mail: [Max-Planck-Institut für Extraterrestrial Physik, Gießenbachstrasse, D-85748 Garching bei München (Germany)


    We report on a study of the 2300-2600 Å Fe II/Fe II* multiplets in the rest-UV spectra of star-forming galaxies at 1.0 < z < 2.6 as probes of galactic-scale outflows. We extracted a mass-limited sample of 97 galaxies at z ∼ 1.0-2.6 from ultra-deep spectra obtained during the GMASS spectroscopic survey in the GOODS South field with the Very Large Telescope and FORS2. We obtain robust measures of the rest equivalent width of the Fe II absorption lines down to a limit of W{sub r} > 1.5 Å and of the Fe II* emission lines to W{sub r} > 0.5 Å. Whenever we can measure the systemic redshift of the galaxies from the [O II] emission line, we find that both the Fe II and Mg II absorption lines are blueshifted, indicating that both species trace gaseous outflows. We also find, however, that the Fe II gas has generally lower outflow velocity relative to that of Mg II. We investigate the variation of Fe II line profiles as a function of the radiative transfer properties of the lines, and find that transitions with higher oscillator strengths are more blueshifted in terms of both line centroids and line wings. We discuss the possibility that Fe II lines are suppressed by stellar absorptions. The lower velocities of the Fe II lines relative to the Mg II doublet, as well as the absence of spatially extended Fe II* emission in two-dimensional stacked spectra, suggest that most clouds responsible for Fe II absorption lie close (3 ∼ 4 kpc) to the disks of galaxies. We show that the Fe II/Fe II* multiplets offer unique probes of the kinematic structure of galactic outflows.

  2. Structure and kinematics of edge-on galaxy disks

    NARCIS (Netherlands)

    Kregel, Michiel


    TIJDENS het aanschouwen van de pracht van de sterrenhemel bekruipt menigeen een gevoel van verwondering en nietigheid, waarna al gauw vragen rijzen omtrent haar oorsprong, samenstelling en toekomst. In de voorgaande eeuw zijn, dankzij de versnelde samenloop van wetenschappelijke ontdekkingen en

  3. The dynamics of face-on galaxies in MOND (United States)

    Angus, Garry W.


    We present an overview of the dynamical analysis using the DiskMass Survey’s measurements of vertical velocity dispersions of nearly face-on galaxy disks in both MOND and the standard model of cosmology. We found that the only, even partly realistic, solution is to have galaxy disks that are twice as thin as current surveys suggest. In the standard theory, with cold dark matter, after improving upon the original analysis we found the typical mass-to-light ratios to be less than 0.1 for almost half the sample. This is unrealistically low compared to the 0.6 found by stellar evolution models. Both these issues would disappear if the stellar vertical velocity dispersions were incorrectly measured and are actually 30% larger.

  4. Resolving the Stellar Outskirts of M81: Evidence for a Faint, Extended Structural Component (United States)

    Barker, M. K.; Ferguson, A. M. N.; Irwin, M.; Arimoto, N.; Jablonka, P.


    We present a wide field census of resolved stellar populations in the northern half of M81, conducted with Suprime-Cam on the 8 m Subaru telescope and covering an area ~0.3 deg2. The resulting color-magnitude diagram reaches over one magnitude below the red giant branch (RGB) tip, allowing a detailed comparison between the young and old stellar spatial distributions. The surface density of stars with ages lsim100 Myr is correlated with that of neutral hydrogen in a manner similar to the disk-averaged Kennicutt-Schmidt relation. We trace this correlation down to gas densities of ~2 × 1020 cm-2, lower than typically probed with Hα flux. Both diffuse light and resolved RGB star counts show compelling evidence for a faint, extended structural component beyond the bright optical disk, with a much flatter surface brightness profile. The star counts allow us to probe this component to significantly fainter levels than is possible with the diffuse light alone. From the colors of its RGB stars, we estimate that this component has a peak global metallicity [M/H] ~ -1.1 ± 0.3 at deprojected radii 32-44 kpc assuming an age of 10 Gyr and distance of 3.6 Mpc. The spatial distribution of its RGB stars follows a power-law surface density profile, I(r) vprop r -γ, with γ ~ 2. If this component were separate from the bulge and from the bright optical disk, then it would contain ~10%-15% of M81's total V-band luminosity. We discuss the possibility that this is M81's halo or thick disk, and in particular highlight its similarities and differences with these components in the Milky Way. Other possibilities for its nature, such as a perturbed disk or the faint extension of the bulge, cannot be completely ruled out, though our data disfavor the latter. These observations add to the growing body of evidence for faint, complex extended structures beyond the bright disks of spiral galaxies. Based on data collected at the Subaru telescope, which is operated by the National Astronomical

  5. Cervical Total Disk Arthroplasty. (United States)

    Roberts, Timothy T; Filler, Ryan J; Savage, Jason W; Benzel, Edward C


    In the United States, cervical total disk arthroplasty (TDA) is US Federal Drug Administration (FDA) approved for use in both 1 and 2-level constructions for cervical disk disease resulting in myelopathy and/or radiculopathy. TDA designs vary in form, function, material composition, and even performance in?vivo. However, the therapeutic goals are the same: to remove the painful degenerative/damaged elements of the intervertebral discoligamenous joint complex, to preserve or restore the natural range of spinal motion, and to mitigate stresses on adjacent spinal segments, thereby theoretically limiting adjacent segment disease (ASDis). Cervical vertebrae exhibit complex, coupled motions that can be difficult to artificially replicate. Commonly available TDA designs include ball-and-socket rotation-only prostheses, ball-and-trough rotation and anterior-posterior translational prostheses, as well as unconstrained elastomeric disks that can rotate and translate freely in all directions. Each design has its respective advantages and disadvantages. At this time, available clinical evidence does not favor 1 design philosophy over another. The superiority of cervical TDA over the gold-standard anterior cervical discectomy and fusion is a subject of great controversy. Although most studies agree that cervical TDA is at least as effective as anterior cervical discectomy and fusion at reducing or eliminating preoperative pain and neurological symptoms, the clinical benefits of motion preservation- that is, reduced incidence of ASDis-are far less clear. Several short-to-mid-term studies suggest that disk arthroplasty reduces the radiographic incidence of adjacent segment degeneration; however, the degree to which this is clinically significant is disputed. At this time, TDA has not been clearly demonstrated to reduce symptomatic?ASDis.

  6. Brown dwarf disks with ALMA

    Energy Technology Data Exchange (ETDEWEB)

    Ricci, L.; Isella, A. [Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Testi, L.; De Gregorio-Monsalvo, I. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Natta, A. [INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze (Italy); Scholz, A., E-mail: [School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)


    We present Atacama Large Millimeter/submillimeter Array continuum and spectral line data at 0.89 mm and 3.2 mm for three disks surrounding young brown dwarfs and very low mass stars in the Taurus star forming region. Dust thermal emission is detected and spatially resolved for all the three disks, while CO(J = 3-2) emission is seen in two disks. We analyze the continuum visibilities and constrain the disks' physical structure in dust. The results of our analysis show that the disks are relatively large; the smallest one has an outer radius of about 70 AU. The inferred disk radii, radial profiles of the dust surface density, and disk to central object mass ratios lie within the ranges found for disks around more massive young stars. We derive from our observations the wavelength dependence of the millimeter dust opacity. In all the three disks, data are consistent with the presence of grains with at least millimeter sizes, as also found for disks around young stars, and confirm that the early stages of the solid growth toward planetesimals occur also around very low-mass objects. We discuss the implications of our findings on models of solids evolution in protoplanetary disks, the main mechanisms proposed for the formation of brown dwarfs and very low-mass stars, as well as the potential of finding rocky and giant planets around very low-mass objects.

  7. Vibration of imperfect rotating disk

    Directory of Open Access Journals (Sweden)

    Půst L.


    Full Text Available This study is concerned with the theoretical and numerical calculations of the flexural vibrations of a bladed disk. The main focus of this study is to elaborate the basic background for diagnostic and identification methods for ascertaining the main properties of the real structure or an experimental model of turbine disks. The reduction of undesirable vibrations of blades is proposed by using damping heads, which on the experimental model of turbine disk are applied only on a limited number of blades. This partial setting of damping heads introduces imperfection in mass, stiffness and damping distribution on the periphery and leads to more complicated dynamic properties than those of a perfect disk. Calculation of FEM model and analytic—numerical solution of disk behaviour in the limited (two modes frequency range shows the splitting of resonance with an increasing speed of disk rotation. The spectrum of resonance is twice denser than that of a perfect disk.

  8. Galaxy Zoo: Morphological Classification of Galaxy Images from the Illustris  Simulation (United States)

    Dickinson, Hugh; Fortson, Lucy; Lintott, Chris; Scarlata, Claudia; Willett, Kyle; Bamford, Steven; Beck, Melanie; Cardamone, Carolin; Galloway, Melanie; Simmons, Brooke; Keel, William; Kruk, Sandor; Masters, Karen; Vogelsberger, Mark; Torrey, Paul; Snyder, Gregory F.


    Modern large-scale cosmological simulations model the universe with increasing sophistication and at higher spatial and temporal resolutions. These ongoing enhancements permit increasingly detailed comparisons between the simulation outputs and real observational data. Recent projects such as Illustris are capable of producing simulated images that are designed to be comparable to those obtained from local surveys. This paper tests the degree to which Illustris achieves this goal across a diverse population of galaxies using visual morphologies derived from Galaxy Zoo citizen scientists. Morphological classifications provided by these volunteers for simulated galaxies are compared with similar data for a compatible sample of images drawn from the Sloan Digital Sky Survey (SDSS) Legacy Survey. This paper investigates how simple morphological characterization by human volunteers asked to distinguish smooth from featured systems differs between simulated and real galaxy images. Significant differences are identified, which are most likely due to the limited resolution of the simulation, but which could be revealing real differences in the dynamical evolution of populations of galaxies in the real and model universes. Specifically, for stellar masses {M}\\star ≲ {10}11 {M}ȯ , a substantially larger proportion of Illustris galaxies that exhibit disk-like morphology or visible substructure, relative to their SDSS counterparts. Toward higher masses, the visual morphologies for simulated and observed galaxies converge and exhibit similar distributions. The stellar mass threshold indicated by this divergent behavior confirms recent works using parametric measures of morphology from Illustris simulated images. When {M}\\star ≳ {10}11 {M}ȯ , the Illustris data set contains substantially fewer galaxies that classifiers regard as unambiguously featured. In combination, these results suggest that comparison between the detailed properties of observed and simulated galaxies


    Energy Technology Data Exchange (ETDEWEB)

    Guzmán, V. V.; Öberg, K. I.; Loomis, R.; Qi, C., E-mail: [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)


    HCN is a commonly observed molecule in Solar System bodies and in interstellar environments. Its abundance with respect to CN is a proposed tracer of UV exposure. HCN is also frequently used to probe the thermal history of objects, by measuring its degree of nitrogen fractionation. To address the utility of HCN as a probe of disks, we present Atacama Large (sub-) Millimeter Array observations of CN, HCN, H{sup 13}CN, and HC{sup 15}N toward the protoplanetary disk around Herbig Ae star MWC 480, and of CN and HCN toward the disk around T Tauri star DM Tau. Emission from all molecules is clearly detected and spatially resolved, including the first detection of HC{sup 15}N in a disk. Toward MWC 480, CN emission extends radially more than 1″ exterior to the observed cut-off of HCN emission. Quantitative modeling further reveals very different radial abundance profiles for CN and HCN, with best-fit outer cut-off radii of >300 AU and 110 ± 10 AU, respectively. This result is in agreement with model predictions of efficient HCN photodissociation into CN in the outer-part of the disk where the vertical gas and dust column densities are low. No such difference in CN and HCN emission profiles are observed toward DM Tau, suggestive of different photochemical structures in Herbig Ae and T Tauri disks. We use the HCN isotopologue data toward the MWC 480 disk to provide the first measurement of the {sup 14}N/{sup 15}N ratio in a disk. We find a low disk averaged {sup 14}N/{sup 15}N ratio of 200 ± 100, comparable to what is observed in cloud cores and comets, demonstrating interstellar inheritance and/or efficient nitrogen fractionation in this disk.

  10. Rapid Formation of Supermassive Black Hole Binaries in Galaxy Mergers with Gas

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, L.; /Zurich U. /Zurich, ETH; Kazantzidis, S.; /KIPAC, Menlo Park; Madau, P.; /UC, Santa Cruz /Garching, Max Planck Inst.; Colpi, M.; /Milan Bicocca U.; Quinn, T.; /Washington U., Seattle; Wadsley, J.; /McMaster U.


    Supermassive black holes (SMBHs) are a ubiquitous component of the nuclei of galaxies. It is normally assumed that, following the merger of two massive galaxies, a SMBH binary will form, shrink due to stellar or gas dynamical processes and ultimately coalesce by emitting a burst of gravitational waves. However, so far it has not been possible to show how two SMBHs bind during a galaxy merger with gas due to the difficulty of modeling a wide range of spatial scales. Here we report hydrodynamical simulations that track the formation of a SMBH binary down to scales of a few light years following the collision between two spiral galaxies. A massive, turbulent nuclear gaseous disk arises as a result of the galaxy merger. The black holes form an eccentric binary in the disk in less than a million years as a result of the gravitational drag from the gas rather than from the stars.

  11. DGSAT: Dwarf Galaxy Survey with Amateur Telescopes. I. Discovery of low surface brightness systems around nearby spiral galaxies (United States)

    Javanmardi, B.; Martinez-Delgado, D.; Kroupa, P.; Henkel, C.; Crawford, K.; Teuwen, K.; Gabany, R. J.; Hanson, M.; Chonis, T. S.; Neyer, F.


    Context. We introduce the Dwarf Galaxy Survey with Amateur Telescopes (DGSAT) project and report the discovery of eleven low surface brightness (LSB) galaxies in the fields of the nearby galaxies NGC 2683, NGC 3628, NGC 4594 (M 104), NGC 4631, NGC 5457 (M 101), and NGC 7814. Aims: The DGSAT project aims to use the potential of small-sized telescopes to probe LSB features around large galaxies and to increase the sample size of the dwarf satellite galaxies in the Local Volume. Methods: Using long exposure images, fields of the target spiral galaxies are explored for extended LSB objects. After identifying dwarf galaxy candidates, their observed properties are extracted by fitting models to their light profiles. Results: We find three, one, three, one, one, and two new LSB galaxies in the fields of NGC 2683, 3628, 4594, 4631, 5457, and 7814, respectively. In addition to the newly found galaxies, we analyse the structural properties of nine already known galaxies. All of these 20 dwarf galaxy candidates have effective surface brightnesses in the range 25.3 ≲ μe ≲ 28.8 mag arcsec-2 and are fit with Sersic profiles with indices n ≲ 1. Assuming that they are in the vicinity of the above mentioned massive galaxies, their r-band absolute magnitudes, their effective radii, and their luminosities are in the ranges -15.6 ≲ Mr ≲ -7.8, 160 pc ≲ Re ≲ 4.1 kpc, and 0.1 × 106 ≲ (L/L⊙)r ≲ 127 × 106, respectively. To determine whether these LSB galaxies are indeed satellites of the above mentioned massive galaxies, their distances need to be determined via further observations. Conclusions: Using small telescopes, we are readily able to detect LSB galaxies with similar properties to the known dwarf galaxies of the Local Group.

  12. Modelling colour-dependent galaxy clustering in cosmological simulations (United States)

    Masaki, Shogo; Lin, Yen-Ting; Yoshida, Naoki


    We extend the subhalo abundance matching method to assign galaxy colour to subhaloes. We separate a luminosity-binned subhalo sample into two groups by a secondary subhalo property which is presumed to be correlated with galaxy colour. The two subsamples then represent red and blue galaxy populations. We explore two models for the secondary property, namely subhalo assembly time and local dark matter density around each subhalo. The model predictions for the galaxy two-point correlation functions are compared with the recent results from the Sloan Digital Sky Survey. We show that the observed colour dependence of galaxy clustering can be reproduced well by our method applied to cosmological N-body simulations without baryonic processes. We then compare the model predictions for the colour-dependent galaxy-mass cross-correlation functions with the results from gravitational lensing observations. The comparison allows us to distinguish the models, and also to discuss what subhalo property should be used to assign colour to subhaloes accurately. We show that the extended abundance matching method using the local dark matter density as a colour proxy provides an accurate description of the galaxy populations in the local universe. We also study impacts of scatter on the local dark matter density-colour relations. Introducing scatter improves agreements of our model predictions with the observed red and blue galaxy clustering and is needed to explain observed correlation functions in finer colour bins. Finally, we study red galaxy fraction profiles in galaxy group- and cluster-sized haloes and find that the red fraction profiles have a relatively strong dependence on our model parameters. We argue that the red fraction profiles can be an important observational clue, in addition to galaxy clustering and galaxy-galaxy lensing, to explore the galaxy-(sub)halo connections.

  13. DVD - digital versatile disks

    Energy Technology Data Exchange (ETDEWEB)

    Gaunt, R.


    An international standard has emerged for the first true multimedia format. Digital Versatile Disk (by its official name), you may know it as Digital Video Disks. DVD has applications in movies, music, games, information CD-ROMS, and many other areas where massive amounts of digital information is needed. Did I say massive amounts of data? Would you believe over 17 gigabytes on a single piece of plastic the size of an audio-CD? That`s the promise, at least, by the group of nine electronics manufacturers who have agreed to the format specification, and who hope to make this goal a reality by 1998. In this major agreement, which didn`t come easily, the manufacturers will combine Sony and Phillip`s one side double-layer NMCD format with Toshiba and Matsushita`s double sided Super-Density disk. By Spring of this year, they plan to market the first 4.7 gigabyte units. The question is: Will DVD take off? Some believe that read-only disks recorded with movies will be about as popular as video laser disks. They say that until the eraseable/writable DVD arrives, the consumer will most likely not buy it. Also, DVD has a good market for replacement of CD- Roms. Back in the early 80`s, the international committee deciding the format of the audio compact disk decided its length would be 73 minutes. This, they declared, would allow Beethoven`s 9th Symphony to be contained entirely on a single CD. Similarly, today it was agreed that playback length of a single sided, single layer DVD would be 133 minutes, long enough to hold 94% of all feature-length movies. Further, audio can be in Dolby`s AC-3 stereo or 5.1 tracks of surround sound, better than CD-quality audio (16-bits at 48kHz). In addition, there are three to five language tracks, copy protection and parental ``locks`` for R rated movies. DVD will be backwards compatible with current CD-ROM and audio CD formats. Added versatility comes by way of multiple aspect rations: 4:3 pan-scan, 4:3 letterbox, and 16:9 widescreen. MPEG

  14. Galactic-scale Feedback Observed in the 3C 298 Quasar Host Galaxy (United States)

    Vayner, Andrey; Wright, Shelley A.; Murray, Norman; Armus, Lee; Larkin, James E.; Mieda, Etsuko


    We present high angular resolution multiwavelength data of the 3C 298 radio-loud quasar host galaxy (z = 1.439) taken using the W.M. Keck Observatory OSIRIS integral field spectrograph (IFS) with adaptive optics, the Atacama Large Millimeter/submillimeter Array (ALMA), the Hubble Space Telescope (HST) WFC3, and the Very Large Array (VLA). Extended emission is detected in the rest-frame optical nebular emission lines Hβ, [O III], Hα, [N II], and [S II], as well as in the molecular lines CO (J = 3‑2) and (J = 5‑4). Along the path of the relativistic jets of 3C 298, we detect conical outflows in ionized gas emission with velocities of up to 1700 {km} {{{s}}}-1 and an outflow rate of 450–1500 {M}ȯ {{yr}}-1 extended over 12 kpc. Near the spatial center of the conical outflow, CO (J = 3‑2) emission shows a molecular gas disk with a rotational velocity of ±150 {km} {{{s}}}-1 and total molecular mass ({M}{{{H}}2}) of 6.6+/- 0.36× {10}9 {M}ȯ . On the blueshifted side of the molecular disk, we observe broad extended emission that is due to a molecular outflow with a rate of 2300 {M}ȯ {{yr}}-1 and depletion timescale of 3 Myr. We detect no narrow Hα emission in the outflow regions, suggesting a limit on star formation of 0.3 {M}ȯ {{yr}}-1 {{kpc}}-2. Quasar-driven winds are evacuating the molecular gas reservoir, thereby directly impacting star formation in the host galaxy. The observed mass of the supermassive black hole is {10}9.37{--9.56} {M}ȯ , and we determine a dynamical bulge mass of {M}{bulge}=1{--}1.7× {10}10\\tfrac{R}{1.6 {kpc}} {M}ȯ . The bulge mass of 3C 298 lies 2–2.5 orders of magnitude below the expected value from the local galactic bulge—supermassive black hole mass ({M}{bulge}{--}{M}{BH}) relationship. A second galactic disk observed in nebular emission is offset from the quasar by 9 kpc, suggesting that the system is an intermediate-stage merger. These results show that galactic-scale negative feedback is occurring early in the merger

  15. What Drives the Kinematic Evolution of Galaxies? (United States)

    Hung, Chao-Ling


    One important result from recent large integral field spectrograph (IFS) surveys is that the intrinsic velocity dispersion of galaxies increases at high redshift. While massive, rotation-dominated disks are already in place at z 2, they are dynamically hotter compared to spiral galaxies in the local Universe. Although several plausible mechanisms have been proposed (e.g., star formation feedback, elevated gas supply, or galaxy interaction), it remains unclear what is the fundamental driver of the velocity dispersion enhancement at high-z. We investigate the origin of this kinematic evolution using a suite of cosmological simulations from the FIRE (Feedback In Realistic Environments) project. Although the velocity dispersion of simulated galaxies is systematically lower compared to the observed values, the simulations successfully reproduce the observed trends between velocity dispersion, SFR, and redshift. In the FIRE simulations, the variation in velocity dispersion is highly dynamic across cosmic time, and it can vary significantly within a timescale of 100 Myr. These variations closely mirror the evolution of star formation and gas inflow histories. By cross-correlating any two parameters of velocity dispersion, gas inflow rates, and SFR, we show that the increase of gas inflowing into the galaxy lead to the subsequent star formation activities, and the enhancement of velocity dispersion follows closely in time with the increasing gas inflow rates and SFR.


    Energy Technology Data Exchange (ETDEWEB)

    Swardt, Bonita de [South African Astronomical Observatory, Observatory, 7935 Cape Town (South Africa); Sheth, Kartik; Kim, Taehyun; Muñoz-Mateos, Juan-Carlos [National Radio Astronomy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Stephen Pardy; Elena D’ Onghia; Eric Wilcots [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Hinz, Joannah [MMTO, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Regan, Michael W. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Athanassoula, E.; Bosma, Albert [Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Buta, Ronald J. [Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487 (United States); Cisternas, Mauricio; Erroz-Ferrer, Santiago [Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Comerón, Sébastien [Division of Astronomy, Department of Physical Sciences, University of Oulu, Oulu, FI-90014 (Finland); Gadotti, Dimitri A. [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Paz, Armando Gil de [Departamento de Astrofísica, Universidad Complutense de Madrid, Madrid E-28040 (Spain); Jarrett, Thomas H. [Astronomy Department, University of Cape Town, Rondebosch 7701 (South Africa); Elmegreen, Bruce G. [IBM Research Division, T.J. Watson Research Center, Yorktown Hts., NY 10598 (United States); Ho, Luis C. [The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); and others


    We use mid-infrared 3.6 and 4.5 μm imaging of NGC 3906 from the Spitzer Survey of Stellar Structure in Galaxies (S{sup 4}G) to understand the nature of an unusual offset between its stellar bar and the photometric center of an otherwise regular, circular outer stellar disk. We measure an offset of ∼910 pc between the center of the stellar bar and photometric center of the stellar disk; the bar center coincides with the kinematic center of the disk determined from previous HI observations. Although the undisturbed shape of the disk suggests that NGC 3906 has not undergone a significant merger event in its recent history, the most plausible explanation for the observed offset is an interaction. Given the relatively isolated nature of NGC 3906 this interaction could be with dark matter substructure in the galaxy's halo or from a recent interaction with a fast moving neighbor that remains to be identified. Simulations aimed at reproducing the observed offset between the stellar bar/kinematic center of the system and the photometric center of the disk are necessary to confirm this hypothesis and constrain the interaction history of the galaxy.

  17. A vast, thin plane of corotating dwarf galaxies orbiting the Andromeda galaxy. (United States)

    Ibata, Rodrigo A; Lewis, Geraint F; Conn, Anthony R; Irwin, Michael J; McConnachie, Alan W; Chapman, Scott C; Collins, Michelle L; Fardal, Mark; Ferguson, Annette M N; Ibata, Neil G; Mackey, A Dougal; Martin, Nicolas F; Navarro, Julio; Rich, R Michael; Valls-Gabaud, David; Widrow, Lawrence M


    Dwarf satellite galaxies are thought to be the remnants of the population of primordial structures that coalesced to form giant galaxies like the Milky Way. It has previously been suspected that dwarf galaxies may not be isotropically distributed around our Galaxy, because several are correlated with streams of H I emission, and may form coplanar groups. These suspicions are supported by recent analyses. It has been claimed that the apparently planar distribution of satellites is not predicted within standard cosmology, and cannot simply represent a memory of past coherent accretion. However, other studies dispute this conclusion. Here we report the existence of a planar subgroup of satellites in the Andromeda galaxy (M 31), comprising about half of the population. The structure is at least 400 kiloparsecs in diameter, but also extremely thin, with a perpendicular scatter of less than 14.1 kiloparsecs. Radial velocity measurements reveal that the satellites in this structure have the same sense of rotation about their host. This shows conclusively that substantial numbers of dwarf satellite galaxies share the same dynamical orbital properties and direction of angular momentum. Intriguingly, the plane we identify is approximately aligned with the pole of the Milky Way's disk and with the vector between the Milky Way and Andromeda.

  18. The Nature of Optically-Luminous Stellar Clusters in a Large Sample of Luminous Infrared Galaxies (United States)

    Vavilkin, Tatjana


    Luminous Star Clusters (SCs) are fundamental building blocks of galaxies, and they provide basic information regarding the mechanisms of star formation and the process of galaxy formation and evolution. In my PhD thesis project I investigated properties of young SCs in a sample of 87 nearby Luminous Infrared Galaxies (LIRGs: LIR>10^11 L_sun) imaged with the Hubble Space Telescope's Advanced Camera for Surveys at 0.4μm (F435W) and 0.9μm (F814W). Many LIRGs are observed to be ongoing mergers of gas-rich disk galaxies. They contain extreme starbursts and hence are expected to host particularly rich and luminous populations of SCs. This project represents the largest sample of galaxies with uniformly characterized properties of their SC population. The size of the sample allows an identification of trends in SC properties with merger stage and star formation rate. A large fraction (∼17%) of the cluster population is younger than 10 Myr. There is uncertainty in the determination of the ages of the bulk of the SCs due to an age-extinction degeneracy--the majority of the detected cluster population may have ages of up to a few hundred Myr. The median SC luminosity function index of the LIRG sample is alpha=-1.8, which is in a good agreement with previously published studies in various galaxy types. This sample contains some of the most luminous clusters observed so far, with Mmax (F435W) exceeding -17 mag. LIRGs follow the "brightest cluster--star formation rate" correlation observed for lower luminosity star-forming galaxies quite closely, although a large degree of scatter possibly due to extinction and over-estimation of Star Formation Rates (SFRs) in galaxies containing an Active Galactic Nucleus (AGN) is present. Thus, the size-of-sample effect and the observed high SFRs are responsible for high luminosity of SCs found in LIRGs. The specific luminosity TL(F435W)--SFR(far-IR + far-UV) relation observed for nearby non-interacting spiral galaxies is not applicable

  19. Hot Molecular Gas in the Circumnuclear Disk (United States)

    Mills, Elisabeth A. C.; Togi, Aditya; Kaufman, Michael


    We present an analysis of archival Infrared Space Observatory observations of H2 for three 14\\prime\\prime × 20\\prime\\prime pointings in the central 3 pc of the Galaxy: toward the southwest region and northeast region of the Galactic center circumnuclear disk (CND), and toward the supermassive black hole Sgr A*. We detect pure rotational lines from 0-0 S(0) to S(13), as well as a number of rovibrationally excited transitions. Using the pure rotational lines, we perform both fits to a discrete temperature distribution (measuring up to three temperature components with T = 500-600 K, T = 1250-1350 K, and T > 2600 K) and fits to a continuous temperature distribution, assuming a power-law distribution of temperatures. We measure power-law indices of n = 3.22 for the northeast region and n = 2.83 for the southwest region. These indices are lower than those measured for other galaxies or other Galactic center clouds, indicating a larger fraction of gas at high temperatures. We also test whether extrapolating this temperature distribution can yield a reasonable estimate of the total molecular mass, as has been recently done for H2 observations in other galaxies. Extrapolating to a cutoff temperature of 50 K in the southwest (northeast) region, we would measure 32% (140%) of the total molecular gas mass inferred from the dust emission, and 26% (125%) of the total molecular gas mass inferred from the CO emission. Ultimately, the inconsistency of the masses inferred in this way suggests that a simple application of this method cannot yield a reliable estimate of the mass of the CND.

  20. [Financial expenses incurred by herniated disk in health professionals]. (United States)

    Zonana-Nacach, Abraham; Moreno-Cazares, Marco Cesar; Gómez-Naranjo, Rafael


    Long-term sick leave by illeness is cause of financial expences and worker's loss of productivity. To evaluate the financial expense incurred by spinal disk herniation in health professionals. 3000 health professionals of the Instituto Mexicano del Seguro Social work in Tecate, Tijuana and Rosarito, cities of Baja California, Mexico. During 2009-2011, 1070 health professionals had long sick leave certificates and 48 had a cervical or lumbar disk herniation. We evaluated the total days of absenteeism in comparison with the absenteeism days suggested by the Medical Disability Advisor. Of the 48 spinal herniated disks, 54% were cervical and 65% had surgical management. The mean (± SD) days of absence was 125 ± 84 and 24 (50%) of the spinal herniated disks exceeded the Medical Disability Advisor disability duration parameters, in 6 (26%), 12 (52%), and 5 (22%) patients due to no diagnostic concordance, diagnosis delay and residual pain, respectively. The total cost of the spinal herniated disks that extended outside of the Medical Disability Advisor disability duration parameters was 683,026 pesos versus 367,081 pesos of the spinal herniated disks that did not exceed the Medical Disability Advisor disability duration parameters. After 12 months of follow-up, 9 (18.8%) continue with sick leave and 2 (4%) had permanent disability. In patients with a spinal herniated disk, the costs of subsidies were two-fold more due principally to a not diagnostic agreement.

  1. Self-gravity in Magnetized Neutrino-dominated Accretion Disks

    Energy Technology Data Exchange (ETDEWEB)

    Shahamat, Narjes; Abbassi, Shahram, E-mail: [Department of Physics, School of Science, Ferdowsi University of Mashhad, Mashhad, P.O. Box 91775-1436 (Iran, Islamic Republic of)


    In the present work we study self-gravity effects on the vertical structure of a magnetized neutrino-dominated accretion disk as a central engine for gamma-ray bursts (GRBs). Some of the disk physical timescales that are supposed to play a pivotal role in the late-time evolutions of the disk, such as viscous, cooling, and diffusion timescales, have been studied. We are interested in investigating the possibility of the occurrence of X-ray flares, observed in late-time GRBs’ extended emission through the “magnetic barrier” and “fragmentation” processes in our model. The results lead us to interpret self-gravity as an amplifier for Blandford–Payne luminosity (BP power) and the generated magnetic field, but a suppressor for neutrino luminosity and magnetic barrier processes via highlighting the fragmentation mechanism in the outer disk, especially for the higher mass accretion rates.

  2. On the morphological dichotomies observed in the powerful radio galaxies (United States)

    Miraghaei, H.; Best, P. N.


    We study environment and host galaxy properties of powerful radio galaxies with different radio morphologies from compact sources to very extended double lobed radio galaxies and with different optical spectra classified as high excitation (HERG; quasar-mode) and low excitation (LERG; jet-mode) radio galaxies. We use a complete sample of morphologically classified radio sources from [1] and perform three different analyses: i) we compare compact radio sources with the extended sources from the same class of excitation. ii) we compare HERGs with the LERGs using a combined sample of compact and extended sources. iii) we investigate the origin of different morphologies observed in the very extended powerful radio galaxies, historically classified as Fanaroff-Riley (FR) radio galaxies of type I and type II by comparing a sample of FRIs with the FRIIs from the same excitation class. We discuss the results and what causes the differences in each comparison. The role of host galaxy and the central super massive black hole, and the galaxy interactions are all investigated.

  3. Emission line imaging of 3CR quasars and radio galaxies

    NARCIS (Netherlands)

    Hes, R; Barthel, PD; Fosbury, RAE

    Optical emission line images and spectra of sixteen 3CR powerful radio galaxies and quasars are presented. Extended line emission is detected in both radio galaxies and quasars. We show that line luminosities, derived from the spatially integrated [OII]lambda 3727 narrow emission line, are on

  4. The influence of halo evolution on galaxy structure (United States)

    White, Simon


    If Einstein-Newton gravity holds on galactic and larger scales, then current observations demonstrate that the stars and interstellar gas of a typical bright galaxy account for only a few percent of its total nonlinear mass. Dark matter makes up the rest and cannot be faint stars or any other baryonic form because it was already present and decoupled from the radiation plasma at z = 1000, long before any nonlinear object formed. The weak gravito-sonic waves so precisely measured by CMB observations are detected again at z = 4 as order unity fluctuations in intergalactic matter. These subsequently collapse to form today's galaxy/halo systems, whose mean mass profiles can be accurately determined through gravitational lensing. High-resolution simulations link the observed dark matter structures seen at all these epochs, demonstrating that they are consistent and providing detailed predictions for all aspects of halo structure and growth. Requiring consistency with the abundance and clustering of real galaxies strongly constrains the galaxy-halo relation, both today and at high redshift. This results in detailed predictions for galaxy assembly histories and for the gravitational arena in which galaxies live. Dark halos are not expected to be passive or symmetric but to have a rich and continually evolving structure which will drive evolution in the central galaxy over its full life, exciting warps, spiral patterns and tidal arms, thickening disks, producing rings, bars and bulges. Their growth is closely related to the provision of new gas for galaxy building.

  5. Galaxy And Mass Assembly (GAMA): Gas Fueling of Spiral Galaxies in the Local Universe. I. The Effect of the Group Environment on Star Formation in Spiral Galaxies (United States)

    Grootes, M. W.; Tuffs, R. J.; Popescu, C. C.; Norberg, P.; Robotham, A. S. G.; Liske, J.; Andrae, E.; Baldry, I. K.; Gunawardhana, M.; Kelvin, L. S.; Madore, B. F.; Seibert, M.; Taylor, E. N.; Alpaslan, M.; Brown, M. J. I.; Cluver, M. E.; Driver, S. P.; Bland-Hawthorn, J.; Holwerda, B. W.; Hopkins, A. M.; Lopez-Sanchez, A. R.; Loveday, J.; Rushton, M.


    We quantify the effect of the galaxy group environment (for group masses of 1012.5-1014.0 M ⊙) on the current star formation rate (SFR) of a pure, morphologically selected sample of disk-dominated (I.e., late-type spiral) galaxies with redshift ≤0.13. The sample embraces a full representation of quiescent and star-forming disks with stellar mass M * ≥ 109.5 M ⊙. We focus on the effects on SFR of interactions between grouped galaxies and the putative intrahalo medium (IHM) of their host group dark matter halos, isolating these effects from those induced through galaxy-galaxy interactions, and utilizing a radiation transfer analysis to remove the inclination dependence of derived SFRs. The dependence of SFR on M * is controlled for by measuring offsets Δlog(ψ *) of grouped galaxies about a single power-law relation in specific SFR, {\\psi }* \\propto {M}* -0.45+/- 0.01, exhibited by non-grouped “field” galaxies in the sample. While a small minority of the group satellites are strongly quenched, the group centrals and a large majority of satellites exhibit levels of ψ * statistically indistinguishable from their field counterparts, for all M *, albeit with a higher scatter of 0.44 dex about the field reference relation (versus 0.27 dex for the field). Modeling the distributions in Δlog(ψ *), we find that (I) after infall into groups, disk-dominated galaxies continue to be characterized by a similar rapid cycling of gas into and out of their interstellar medium shown prior to infall, with inflows and outflows of ˜1.5-5 x SFR and ˜1-4 x SFR, respectively; and (II) the independence of the continuity of these gas flow cycles on M * appears inconsistent with the required fueling being sourced from gas in the circumgalactic medium on scales of ˜100 kpc. Instead, our data favor ongoing fueling of satellites from the IHM of the host group halo on ˜Mpc scales, I.e., from gas not initially associated with the galaxies upon infall. Consequently, the color

  6. Integral-field spectroscopy of a Lyman-break galaxy at z = 3.2: evidence for merging (United States)

    Nesvadba, N. P. H.; Lehnert, M. D.; Davies, R. I.; Verma, A.; Eisenhauer, F.


    We present spatially-resolved, rest-frame optical spectroscopy of a z˜ 3 Lyman-break galaxy (LBG), Q0347-383 C5, obtained with SINFONI on the VLT. This galaxy, among the ˜ 10% brightest LBGs, is only the second z˜ 3 LBG observed with an integral-field spectrograph. It was first described by Pettini et al. (2001, ApJ, 554, 981), who obtained WFPC2 F702W imaging and longslit spectroscopy in the K-band. We find that the emission line morphology is dominated by two unresolved blobs at a projected distance of ˜ 5 kpc with a velocity offset of ˜ 33 km s-1. Velocity dispersions suggest that each blob has a mass of ˜ 1010 M⊙. Unlike Pettini et al. (2001), our spectra are deep enough to detect Hβ, and we derive star-formation rates of ˜ 20{-}40 M⊙ yr-1, and use the Hβ/[OIII] ratio to crudely estimate an oxygen abundance 12+[O/H]=7.9{-}8.6, which is in the range typically observed for LBGs. We compare the properties of Q0347-383 C5 with what is found for other LBGs, including the gravitationally lensed “arc+core” galaxy (Nesvadba et al. 2006, ApJ, 650, 661), and discuss possible scenarios for the nature of the source, namely disk rotation, a starburst-driven wind, disk fragmentation, and merging of two LBGs. We favor the merging interpretation for bright, extended LBGs like Q0347-383 C5, in broad agreement with predicted merger rates from hierarchical models.

  7. Spectrophotometric Properties of E+A Galaxies in SDSS-IV MaNGA (United States)

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


    Quenched post-starburst galaxies, or E+A galaxies, represent a unique and informative phase in the evolution of galaxies. We used a qualitative rubric-based methodology, informed by the literature, to manually select galaxies from the SDSS-IV IFU survey Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) using the single-fiber spectra from the Sloan Digital Sky Survey Data Release 8. Of the 2,812 galaxies observed so far in MaNGA, we found 39 galaxies meeting our criteria for E+A classification. Spectral energy distributions of these 39 galaxies from the far-UV to the mid-infrared demonstrate a heterogeneity in our sample emerging in the infrared, indicating many distinct paths to visually similar optical spectra. We used SDSS-IV MaNGA Pipe3D data products to analyze stellar population ages, and found that 34 galaxies exhibited stellar populations that were older at 1 effective radius than at the center of the galaxy. Given that our sample was manually chosen based on E+A markers in the single-fiber spectra aimed at the center of each galaxy, our E+A galaxies may have only experienced their significant starbursts in the central region, with a disk of quenched or quenching material further outward. This work was supported by grants AST-1460860 from the National Science Foundation and SDSS FAST/SSP-483 from the Alfred P. Sloan Foundation to the CUNY College of Staten Island.

  8. Detection of Molecular Gas in Void Galaxies : Implications for Star Formation in Isolated Environments (United States)

    Das, M.; Saito, T.; Iono, D.; Honey, M.; Ramya, S.


    We present the detection of molecular gas from galaxies located in nearby voids using the CO(1-0) line emission as a tracer. The observations were performed using the 45 m single dish radio telescope of the Nobeyama Radio Observatory. Void galaxies lie in the most underdense parts of our universe and a significant fraction of them are gas rich, late-type spiral galaxies. Although isolated, they have ongoing star formation but appear to be slowly evolving compared to galaxies in denser environments. Not much is known about their star formation properties or cold gas content. In this study, we searched for molecular gas in five void galaxies. The galaxies were selected based on their relatively high IRAS fluxes or Hα line luminosities, both of which signify ongoing star formation. All five galaxies appear to be isolated and two lie within the Bootes void. We detected CO(1-0) emission from four of the five galaxies in our sample and their molecular gas masses lie between 108 and 109 M⊙. We conducted follow-up Hα imaging observations of three detected galaxies using the Himalayan Chandra Telescope and determined their star formation rates (SFRs) from their Hα fluxes. The SFR varies from 0.2 to 1 M⊙ yr-1 which is similar to that observed in local galaxies. Our study indicates that although void galaxies reside in underdense regions, their disks contain molecular gas and have SFRs similar to galaxies in denser environments. We discuss the implications of our results.

  9. Audit: Automated Disk Investigation Toolkit

    Directory of Open Access Journals (Sweden)

    Umit Karabiyik


    Full Text Available Software tools designed for disk analysis play a critical role today in forensics investigations. However, these digital forensics tools are often difficult to use, usually task specific, and generally require professionally trained users with IT backgrounds. The relevant tools are also often open source requiring additional technical knowledge and proper configuration. This makes it difficult for investigators without some computer science background to easily conduct the needed disk analysis. In this paper, we present AUDIT, a novel automated disk investigation toolkit that supports investigations conducted by non-expert (in IT and disk technology and expert investigators. Our proof of concept design and implementation of AUDIT intelligently integrates open source tools and guides non-IT professionals while requiring minimal technical knowledge about the disk structures and file systems of the target disk image.

  10. Angular Momentum of Dwarf Galaxies (United States)

    Butler, Kirsty M.; Obreschkow, Danail; Oh, Se-Heon


    We present measurements of baryonic mass {M}{{b}} and specific angular momentum (sAM) {j}{{b}} in 14 rotating dwarf Irregular (dIrr) galaxies from the LITTLE THINGS sample. These measurements, based on 21 cm kinematic data from the Very Large Array and stellar mass maps from the Spitzer Space Telescope, extend previous AM measurements by more than two orders of magnitude in {M}{{b}}. The dwarf galaxies show systematically higher {j}{{b}} values than expected from the {j}{{b}}\\propto {M}{{b}}2/3 scaling of spiral galaxies, representative of a scale-free galaxy formation scenario. This offset can be explained by decreasing baryon mass fractions {f}{{M}}={M}{{b}}/{M}{dyn} (where {M}{dyn} is the dynamical mass) with decreasing {M}{{b}} (for {M}{{b}}< {10}11 {M}⊙ ). We find that the sAM of neutral atomic hydrogen (H I) alone is about 2.5 times higher than that of the stars. The M-j relation of H I is significantly steeper than that of the stars, as a direct consequence of the systematic variation of the H I fraction with {M}{{b}}.

  11. 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)


    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.

  12. IBM 3390 Hard Disk Platter

    CERN Multimedia


    The 3390 disks rotated faster than those in the previous model 3380. Faster disk rotation reduced rotational delay (ie. the time required for the correct area of the disk surface to move to the point where data could be read or written). In the 3390's initial models, the average rotational delay was reduced to 7.1 milliseconds from 8.3 milliseconds for the 3380 family.

  13. Spiral galaxy HI models, rotation curves and kinematic classifications (United States)

    Wiegert, Theresa B. V.

    Although galaxy interactions cause dramatic changes, galaxies also continue to form stars and evolve when they are isolated. The dark matter (DM) halo may influence this evolution since it generates the rotational behaviour of galactic disks which could affect local conditions in the gas. Therefore we study neutral hydrogen kinematics of non-interacting, nearby spiral galaxies, characterising their rotation curves (RC) which probe the DM halo; delineating kinematic classes of galaxies; and investigating relations between these classes and galaxy properties such as disk size and star formation rate (SFR). To generate the RCs, we use GalAPAGOS (by J. Fiege). My role was to test and help drive the development of this software, which employs a powerful genetic algorithm, constraining 23 parameters while using the full 3D data cube as input. The RC is here simply described by a tanh-based function which adequately traces the global RC behaviour. Extensive testing on artificial galaxies show that the kinematic properties of galaxies with inclination >40 degrees, including edge-on galaxies, are found reliably. Using a hierarchical clustering algorithm on parametrised RCs from 79 galaxies culled from literature generates a preliminary scheme consisting of five classes. These are based on three parameters: maximum rotational velocity, turnover radius and outer slope of the RC. To assess the relationship between DM content and the kinematic classes, we generate mass models for 10 galaxies from the THINGS and WHISP surveys, and J. Irwin's sample. In most cases mass models using GalAPAGOS RCs were similar to those using traditional "tilted-ring'' method RCs. The kinematic classes are mainly distinguished by their rotational velocity. We confirm correlations between increasing velocity and B-magnitude, optical disk size, and find earlier type galaxies among the strong rotators. SFR also increases with maximum rotational velocity. Given our limited subsample, we cannot discern a

  14. Morphology of Seyfert Galaxies


    Chen, Yen-Chen; Hwang, Chorng-Yuan


    We probed the relation between properties of Seyfert nuclei and morphology of their host galaxies. We selected Seyfert galaxies from the Sloan Digital Sky Survey with redshifts less 0.2 identified by the V\\'{e}ron Catalog (13th). We used the "{\\it{FracDev}}" parameter from SDSS galaxy fitting models to represent the bulge fractions of the Seyfert host galaxies. We found that the host galaxies of Seyfert 1 and Seyfert 2 are dominated by large bulge fractions, and Seyfert 2 galaxies are more li...

  15. Traces de l'interaction entre galaxies (United States)

    Duc, Pierre-Alain


    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.

  16. GASP. I. Gas Stripping Phenomena in Galaxies with MUSE (United States)

    Poggianti, Bianca M.; Moretti, Alessia; Gullieuszik, Marco; Fritz, Jacopo; Jaffé, Yara; Bettoni, Daniela; Fasano, Giovanni; Bellhouse, Callum; Hau, George; Vulcani, Benedetta; Biviano, Andrea; Omizzolo, Alessandro; Paccagnella, Angela; D'Onofrio, Mauro; Cava, Antonio; Sheen, Y.-K.; Couch, Warrick; Owers, Matt


    GAs Stripping Phenomena in galaxies with MUSE (GASP) is a new integral-field spectroscopic survey with MUSE at the VLT aimed at studying gas removal processes in galaxies. We present an overview of the survey and show a first example of a galaxy undergoing strong gas stripping. GASP is obtaining deep MUSE data for 114 galaxies at z = 0.04-0.07 with stellar masses in the range {10}9.2{--}{10}11.5 {M}⊙ in different environments (galaxy clusters and groups over more than four orders of magnitude in halo mass). GASP targets galaxies with optical signatures of unilateral debris or tails reminiscent of gas-stripping processes (“jellyfish galaxies”), as well as a control sample of disk galaxies with no morphological anomalies. GASP is the only existing integral field unit (IFU) survey covering both the main galaxy body and the outskirts and surroundings, where the IFU data can reveal the presence and origin of the outer gas. To demonstrate GASP’s ability to probe the physics of gas and stars, we show the complete analysis of a textbook case of a jellyfish galaxy, JO206. This is a massive galaxy (9× {10}10 {M}⊙ ) in a low-mass cluster (σ ˜ 500 {km} {{{s}}}-1) at a small projected clustercentric radius and a high relative velocity, with ≥90 kpc long tentacles of ionized gas stripped away by ram pressure. We present the spatially resolved kinematics and physical properties of the gas and stars and depict the evolutionary history of this galaxy.

  17. Simulations of ram-pressure stripping in galaxy-cluster interactions (United States)

    Steinhauser, Dominik; Schindler, Sabine; Springel, Volker


    Context. 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. Aims: 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. In particular, we compare our findings for the mass loss and evolution of the star formation rate in our simulations with prescriptions commonly employed in SAMs. We also analyse the gaseous wake of the galaxy, focusing on gas mixing and metal enrichment of the intracluster medium (ICM). Methods: 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. Cooling, star formation, and stellar feedback are included according to a simple sub-resolution model. Stellar light maps and the evolution of galaxy colours are computed with the stellar synthesis code FSPS to draw conclusions about quenching timescales of our model galaxies. Results: We find that the stripping models employed in current SAMs often differ substantially from our direct simulations. In most cases, the actual stripping radius of the simulated disk galaxies is larger than assumed in the SAMs, corresponding to an over prediction of the mass loss in SAMs. As long as the disk is not completely stripped in peaks of RPS during pericentre passage, some gas that remains bound to the galaxies is redistributed to the outer parts of disks as soon as the ram pressure becomes weaker again, an

  18. Disk storage at CERN

    CERN Document Server

    Mascetti, L; Chan, B; Espinal, X; Fiorot, A; Labrador, H Gonz; Iven, J; Lamanna, M; Presti, G Lo; Mościcki, JT; Peters, AJ; Ponce, S; Rousseau, H; van der Ster, D


    CERN IT DSS operates the main storage resources for data taking and physics analysis mainly via three system: AFS, CASTOR and EOS. The total usable space available on disk for users is about 100 PB (with relative ratios 1:20:120). EOS actively uses the two CERN Tier0 centres (Meyrin and Wigner) with 50:50 ratio. IT DSS also provide sizeable on-demand resources for IT services most notably OpenStack and NFS-based clients: this is provided by a Ceph infrastructure (3 PB) and few proprietary servers (NetApp). We will describe our operational experience and recent changes to these systems with special emphasis to the present usages for LHC data taking, the convergence to commodity hardware (nodes with 200-TB each with optional SSD) shared across all services. We also describe our experience in coupling commodity and home-grown solution (e.g. CERNBox integration in EOS, Ceph disk pools for AFS, CASTOR and NFS) and finally the future evolution of these systems for WLCG and beyond.

  19. FISICA observations of the starburst galaxy, NGC 1569 (United States)

    Clark, D. M.; Eikenberry, S. S.; Raines, S. N.; Gruel, N.; Elston, R.; Guzman, R.; Julian, J.; Boreman, G.; Glenn, P. E.; Hull-Allen, C. G.; Hoffman, J.; Rodgers, M.; Thompson, K.; Flint, S.; Comstock, L.; Myrick, B.


    Using the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) we obtained observations of the dwarf starburst galaxy NGC 1569. We present our JH band spectra, particularly noting the existence of extended emission in Paschen β and He I.

  20. Interposing Flash between Disk and DRAM to Save Energy for Streaming Workloads

    NARCIS (Netherlands)

    Khatib, M.G.; van der Zwaag, B.J.; Hartel, Pieter H.; Smit, Gerardus Johannes Maria


    In computer systems, the storage hierarchy, composed of a disk drive and a DRAM, is responsible for a large portion of the total energy consumed. This work studies the energy merit of interposing flash memory as a streaming buffer between the disk drive and the DRAM. Doing so, we extend the spin-off

  1. WFPC2 Studies of the Disk and Jet of HH 30 (United States)

    Watson, A.; Stapelfeldt, K.


    Hubble Space Telescope imaging of HH 30 has revealed this object to be a prototype young stellar object (YSO) accretion disk system. An optically thick circumstellar absorption disk, 450 AU in diameter, is seen extending perpendicular to highly collimated bipolar jets.

  2. Secular evolution of Milky Way-type galaxies (United States)

    Combes, F.


    The internal evolution of disk galaxies like the Milky Way is driven by non-axisymmetries (bars) and the implied angular momentum transfer of the matter; baryons are essentially driven inwards to build a more concentrated disk. This mass concentration may lead to the decoupling of a secondary bar, since the orbit precessing frequency is then much enhanced. Vertical resonances with the bar will form a box/peanut bulge on a Gyr time-scale. Gas flows due to gravity torques can lead to a young nuclear disk forming stars, revealed by a σ-drop in velocity dispersion. These gas flows moderated by feedback produce intermittent accretion onto the super-massive black hole, and cycles of AGN activity. The fountain effect due to nuclear star formation may lead to inclined, and even polar nuclear disks.

  3. A Portrait of One Hundred Thousand and One Galaxies (United States)


    NGC 300 and the surrounding sky field, obtained in 1999 and 2000 with the Wide-Field Imager (WFI) on the MPG/ESO 2.2-m telescope at the La Silla Observatory. See the text for details about the many different uses of this photo. Smaller areas in this large field are shown in Photos 18b-h/02 , cf. below. The High-Res version of this image has been compressed by a factor 4 (2 x 2 pixel rebinning) to reduce it to a reasonably transportable size. Technical information about this and the other photos is available at the end of this communication. Located some 7 million light-years away, the spiral galaxy NGC 300 [1] is a beautiful representative of its class, a Milky-Way-like member of the prominent Sculptor group of galaxies in the southern constellation of that name. NGC 300 is a big object in the sky - being so close, it extends over an angle of almost 25 arcmin, only slightly less than the size of the full moon. It is also relative bright, even a small pair of binoculars will unveil this magnificent spiral galaxy as a hazy glowing patch on a dark sky background. The comparatively small distance of NGC 300 and its face-on orientation provide astronomers with a wonderful opportunity to study in great detail its structure as well as its various stellar populations and interstellar medium. It was exactly for this purpose that some images of NGC 300 were obtained with the Wide-Field Imager (WFI) on the MPG/ESO 2.2-m telescope at the La Silla Observatory. This advanced 67-million pixel digital camera has already produced many impressive pictures, some of which are displayed in the WFI Photo Gallery [2]. With its large field of view, 34 x 34 arcmin 2 , the WFI is optimally suited to show the full extent of the spiral galaxy NGC 300 and its immediate surroundings in the sky, cf. PR Photo 18a/02 . NGC 300 and "Virtual Astronomy" In addition to being a beautiful sight in its own right, the present WFI-image of NGC 300 is also a most instructive showcase of how astronomers with

  4. Galaxy Zoo: morphological classifications for 120 000 galaxies in HST legacy imaging (United States)

    Willett, Kyle W.; Galloway, Melanie A.; Bamford, Steven P.; Lintott, Chris J.; Masters, Karen L.; Scarlata, Claudia; Simmons, B. D.; Beck, Melanie; Cardamone, Carolin N.; Cheung, Edmond; Edmondson, Edward M.; Fortson, Lucy F.; Griffith, Roger L.; Häußler, Boris; Han, Anna; Hart, Ross; Melvin, Thomas; Parrish, Michael; Schawinski, Kevin; Smethurst, R. J.; Smith, Arfon M.


    We present the data release paper for the Galaxy Zoo: Hubble (GZH) project. This is the third phase in a large effort to measure reliable, detailed morphologies of galaxies by using crowdsourced visual classifications of colour-composite images. Images in GZH were selected from various publicly released Hubble Space Telescope legacy programmes conducted with the Advanced Camera for Surveys, with filters that probe the rest-frame optical emission from galaxies out to z ˜ 1. The bulk of the sample is selected to have mI814W = 0.9 ± 0.6, with a tail extending out to z ≃ 4. The GZH morphological data include measurements of both bulge- and disc-dominated galaxies, details on spiral disc structure that relate to the Hubble type, bar identification, and numerous measurements of clump identification and geometry. This paper also describes a new method for calibrating morphologies for galaxies of different luminosities and at different redshifts by using artificially redshifted galaxy images as a baseline. The GZH catalogue contains both raw and calibrated morphological vote fractions for 119 849 galaxies, providing the largest data set to date suitable for large-scale studies of galaxy evolution out to z ˜ 1.

  5. A Zoo of Galaxies (United States)

    Masters, Karen L.


    We live in a universe filled with galaxies with an amazing variety of sizes and shapes. One of the biggest challenges for astronomers working in this field is to understand how all these types relate to each other in the background of an expanding universe. Modern astronomical surveys (like the Sloan Digital Sky Survey) have revolutionised this field of astronomy, by providing vast numbers of galaxies to study. The sheer size of the these databases made traditional visual classification of the types galaxies impossible and in 2007 inspired the Galaxy Zoo project (; starting the largest ever scientific collaboration by asking members of the public to help classify galaxies by type and shape. Galaxy Zoo has since shown itself, in a series of now more than 30 scientific papers, to be a fantastic database for the study of galaxy evolution. In this Invited Discourse I spoke a little about the historical background of our understanding of what galaxies are, of galaxy classification, about our modern view of galaxies in the era of large surveys. I finish with showcasing some of the contributions galaxy classifications from the Galaxy Zoo project are making to our understanding of galaxy evolution.

  6. Star Formation Quenching in Quasar Host Galaxies

    Directory of Open Access Journals (Sweden)

    Stefano Carniani


    Full Text Available Galaxy evolution is likely to be shaped by negative feedback from active galactic nuclei (AGN. In the whole range of redshifts and luminosities studied so far, galaxies hosting an AGN frequently show fast and extended outflows consisting in both ionized and molecular gas. Such outflows could potentially quench the start formation within the host galaxy, but a clear evidence of negative feedback in action is still missing. Hereby I will analyse integral-field spectroscopic data for six quasars at z ~ 2.4 obtained with SINFONI in the H- and K-band. All the quasars show [Oiii]λ5007 line detection of fast, extended outflows. Also, the high signal-to-noise SINFONI observations allow the identification of faint narrow Hα emission (FWHM < 500 km/s, which is spatially extended and associated with star formation in the host galaxy. On paper fast outflows are spatially anti-correlated with star-formation powered emission, i.e., star formation is suppressed in the area affected by the outflow. Nonetheless as narrow, spatially-extended Hα emission, indicating star formation rates of at least 50–100 M⊙ yr−1, has been detected, either AGN feedback is not affecting the whole host galaxy, or star formation is completely quenched only by several feedback episodes. On the other hand, a positive feedback scenario, supported by narrow emission in Hα extending along the edges of the outflow cone, suggests that galaxy-wide outflows could also have a twofold role in the evolution of the host galaxy. Finally, I will present CO(3-2 ALMA data for three out of the six QSOs observed with SINFONI. Flux maps obtained for the CO(3-2 transition suggest that molecular gas within the host galaxy is swept away by fast winds. A negative-feedback scenario is supported by the inferred molecular gas mass in all three objects, which is significantly below what observed in non-active main-sequence galaxies at high-z.

  7. The Galex Large Galaxy Atlas (glga) (United States)

    Seibert, Mark

    GALEX surveys contain the most comprehensive collection of UV imaged extended galaxies likely to exist for decades. Unfortunately, with the exception of the 1,000 galaxies contained in the Nearby Galaxy Atlas (NGA), this impressive resource is under-utilized because 1) the pipeline-generated source catalogs split extended objects into many pieces (""shredding"") and 2) co-adding of data using multiple survey types is not regularly performed. We propose to solve both of these problems by constructing the GALEX Large Galaxy Atlas (GLGA) using all observations of galaxies with diameters of at least 1 arcmin, make it available to the public via the NASA/IPAC Extragalactic Database (NED), and provide our software for the co-adding and mosaicing of GALEX data to the astronomical community. The GLGA will build upon and extend the NGA in three significant ways; it will 1) contain 21,000 galaxies, 2) co-add data from multiple survey types, and 3) preserve multi-epoch observations to facilitate time domain studies. Extending the NGA to 21,000 galaxies will be a major contribution to the legacy of GALEX. Although the GLGA will be a tremendous resource available to anyone, our team was inspired to its construction for several projects. We will use the GLGA to measure proper UV-optical-NIR colors for a large sample of extended galaxies for the first time. This is a critical step for locating examples of nearby ``green-valley"" or transition galaxies which may be the best objects for understanding blue-red sequence evolution. We are compiling a matching catalog of HI single dish fluxes and images with the goal of using it to study the detailed relationship between gas content and star formation rate, implications for star formation ``laws'' and the triggering and quenching of star formation. Finally, we are compiling IRAS HiRes data for objects with diameters >2 arcmin with the objective of constraining UV extinction derived from the UV spectral-slope/infrared-excess correlation."

  8. How to Detect Inclined Water Maser Disks (and Possibly Measure Black Hole Masses)

    Energy Technology Data Exchange (ETDEWEB)

    Darling, Jeremy, E-mail: [Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, University of Colorado, 389 UCB, Boulder, CO 80309-0389 (United States)


    We describe a method for identifying inclined water maser disks orbiting massive black holes and for potentially using them to measure black hole masses. Owing to the geometry of maser amplification pathways, the minority of water maser disks are observable: only those viewed nearly edge-on have been identified, suggesting that an order of magnitude additional maser disks exist. We suggest that inward-propagating masers are gravitationally deflected by the central black hole, thereby scattering water maser emission out of the disk plane and enabling detection. The signature of an inclined water maser disk would be narrow masers near the systemic velocity that appear to emit from the black hole position, as identified by the radio continuum core. To explore this possibility, we present high-resolution (0.″07–0.″17) Very Large Array line and continuum observations of 13 galaxies with narrow water maser emission and show that three are good inclined-disk candidates (five remain ambiguous). For the best case, CGCG 120−039, we show that the maser and continuum emission are coincident to within 3.5 ± 1.4 pc (6.7 ± 2.7 mas). Subsequent very long baseline interferometric maps can confirm candidate inclined disks and have the potential to show maser rings or arcs that provide a direct measurement of black hole mass, although the mass precision will rely on knowledge of the size of the maser disk.

  9. The Effects of Accretion Disk Thickness on the Black Hole Reflection Spectrum (United States)

    Taylor, Corbin; Reynolds, Christopher S.


    Despite being the gravitational engines that power galactic-scale winds and mega parsec-scale jets in active galaxies, black holes are remarkably simple objects, typically being fully described by their angular momenta (spin) and masses. The modelling of AGN X-ray reflection spectra has proven fruitful in estimating the spin of AGN, as well as giving insight into their accretion histories and into the properties of plasmas in the strong gravity regime. However, current models make simplifying assumptions about the geometry of the reflecting material in the accretion disk and the irradiating X-ray corona, approximating the disk as an optically thick, infinitely thin disk of material in the orbital plane. We present results from the new relativistic raytracing suite, Fenrir, that explore the effects that disk thickness may have on the reflection spectrum and the accompanying reverberation signatures. Approximating the accretion disk as an optically thick, geometrically thin, radiation pressure dominated disk (Shakura & Sunyaev 1973), one finds that the disk geometry is non-negligible in many cases, with significant changes in the broad Fe K line profile. Finally, we explore the systematic errors inherent in other contemporary models that approximate that disk as having negligible vertical extent.

  10. Extended Emotions


    Krueger, Joel; Szanto, Thomas


    Until recently, philosophers and psychologists conceived of emotions as brain- and body-bound affairs. But researchers have started to challenge this internalist and individualist orthodoxy. A rapidly growing body of work suggests that some emotions incorporate external resources and thus extend beyond the neurophysiological confines of organisms; some even argue that emotions can be socially extended and shared by multiple agents. Call this the extended emotions thesis (ExE). In this article...

  11. On The Missing Dwarf Problem In Clusters And Around The Nearby Galaxy M33 (United States)

    Keenan, Olivia Charlotte


    This thesis explores possible solutions to the dwarf galaxy problem. This is a discrepancy between the number of dwarf galaxies we observe, and the number predicted from cosmological computer simulations. Simulations predict around ten times more dwarf galaxy satellites than are currently observed. I have investigated two possible solutions: dark galaxies and the low surface brightness universe. Dark galaxies are dark matter halos which contain gas, but few or no stars, hence are optically dark. As part of the Arecibo Galaxy Environment Survey I surveyed the neutral hydrogen gas around the nearby galaxy M33. I found 32 gas clouds, 11 of which are new detections. Amongst these there was one particularly interesting cloud. AGESM33-32 is ring shaped and larger than M33 itself, if at the same distance. It has a velocity width which is similar to the velocity dispersion of gas in a disk galaxy, as well as having a clear velocity gradient across it which may be due to rotation. The fact that it also currently has no observed associated stars means it is a dark galaxy candidate. Optically, dwarf galaxies may be out there, but too faint for us to detect. This means that with newer, deeper, images we may be able to unveil a large, low surface brightness, population of dwarf galaxies. However, the question remains as to how these can be distinguished from background galaxies. I have used Next Generation Virgo Survey (NGVS) data to carry out photometry on 852 Virgo galaxies in four bands. I also measured the photometric properties of galaxies on a background (non-cluster) NGVS frame. I discovered that a combination of colour, magnitude and surface brightness information could be used to identify cluster dwarf galaxies from background field galaxies. The most effective method is to use the surface brightness-magnitude relation.

  12. Herman's Condition and Siegel Disks of Bi-Critical Polynomials (United States)

    Chéritat, Arnaud; Roesch, Pascale


    We extend a theorem of Herman from the case of unicritical polynomials to the case of polynomials with two finite critical values. This theorem states that Siegel disks of such polynomials, under a diophantine condition (called Herman's condition) on the rotation number, must have a critical point on their boundaries.

  13. Metallic Winds in Dwarf Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Robles-Valdez, F.; Rodríguez-González, A.; Hernández-Martínez, L.; Esquivel, A., E-mail: [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, A.P. 70-543, 04510, Mexico City (Mexico)


    We present results from models of galactic winds driven by energy injected from nuclear (at the galactic center) and non-nuclear starbursts. The total energy of the starburst is provided by very massive young stellar clusters, which can push the galactic interstellar medium and produce an important outflow. Such outflow can be a well or partially mixed wind, or a highly metallic wind. We have performed adiabatic 3D N -Body/Smooth Particle Hydrodynamics simulations of galactic winds using the gadget-2 code. The numerical models cover a wide range of parameters, varying the galaxy concentration index, gas fraction of the galactic disk, and radial distance of the starburst. We show that an off-center starburst in dwarf galaxies is the most effective mechanism to produce a significant loss of metals (material from the starburst itself). At the same time, a non-nuclear starburst produces a high efficiency of metal loss, in spite of having a moderate to low mass loss rate.


    Energy Technology Data Exchange (ETDEWEB)

    Matsunaga, Noriyuki; Fukue, Kei [Department of Astronomy, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Yamamoto, Ryo; Kobayashi, Naoto; Hamano, Satoshi [Institute of Astronomy, School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Inno, Laura [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München (Germany); Genovali, Katia; Bono, Giuseppe [Dipartimento di Fisica, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Rome (Italy); Baba, Junichi [Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan); Fujii, Michiko S.; Aoki, Wako; Tsujimoto, Takuji [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Kondo, Sohei; Ikeda, Yuji [Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555 (Japan); Nishiyama, Shogo [Miyagi University of Education, 149 Aramaki-aza-Aoba, Aoba-ku, Sendai, Miyagi 980-0845 (Japan); Nagata, Tetsuya, E-mail: [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan)


    Classical Cepheids are useful tracers of the Galactic young stellar population because their distances and ages can be determined from their period-luminosity and period-age relations. In addition, the radial velocities and chemical abundance of the Cepheids can be derived from spectroscopic observations, providing further insights into the structure and evolution of the Galaxy. Here, we report the radial velocities of classical Cepheids near the Galactic center, three of which were reported in 2011 and a fourth being reported for the first time. The velocities of these Cepheids suggest that the stars orbit within the nuclear stellar disk, a group of stars and interstellar matter occupying a region of ∼200 pc around the center, although the three-dimensional velocities cannot be determined until the proper motions are known. According to our simulation, these four Cepheids formed within the nuclear stellar disk like younger stars and stellar clusters therein.

  15. Galaxy Formation through Filamentary Accretion at z = 6.1 (United States)

    Jones, G. C.; Willott, C. J.; Carilli, C. L.; Ferrara, A.; Wang, R.; Wagg, J.


    We present Atacama Large Millimeter/submillimeter Array observations of the dust continuum and [C II] 158 μm line emission from the z = 6.0695 Lyman-Break Galaxy (LBG) WMH5. These observations at 0.″3 spatial resolution show a compact (˜3 kpc) main galaxy in dust and [C II] emission, with a “tail” of emission extending to the east by about 5 kpc (in projection). The [C II] tail is comprised predominantly of two distinct sub-components in velocity, separated from the core by ˜100 and 250 km s-1, with narrow intrinsic widths of about 80 km s-1, which we call “sub-galaxies.” The sub-galaxies themselves are extended east-west by about 3 kpc in individual channel images. The [C II] tail joins smoothly into the main galaxy velocity field. The [C II] line to continuum ratios are comparable for the main and sub-galaxy positions, within a factor two. In addition, these ratios are comparable to z˜ 5.5 LBGs. We conjecture that the WMH5 system represents the early formation of a galaxy through the accretion of smaller satellite galaxies, embedded in a smoother gas distribution, along a possibly filamentary structure. The results are consistent with current cosmological simulations of early galaxy formation and support the idea of very early enrichment with dust and heavy elements of the accreting material.

  16. Structure and Spectroscopy of Black Hole Accretion Disks

    Energy Technology Data Exchange (ETDEWEB)

    Liedahl, D; Mauche, C


    The warped spacetime near black holes is one of the most exotic observable environments in the Universe. X-ray spectra from active galaxies obtained with the current generation of X-ray observatories reveal line emission that is modified by both special relativistic and general relativistic effects. The interpretation is that we are witnessing X-ray irradiated matter orbiting in an accretion disk around a supermassive black hole, as it prepares to cross the event horizon. This interpretation, however, is based upon highly schematized models of accretion disk structure. This report describes a project to design a detailed computer model of accretion disk atmospheres, with the goal of elucidating the high radiation density environments associated with mass flows in the curved spacetime near gravitationally collapsed objects. We have evolved the capability to generate realistic theoretical X-ray line spectra of accretion disks, thereby providing the means for a workable exploration of the behavior of matter in the strong-field limit of gravitation.

  17. Hubble's Menagerie of Galaxies

    Indian Academy of Sciences (India)


    typ es form an evolutionary sequence: does one type of galaxy evolve into another? 1. T he D iscovery of G alaxies. A stronom ers began to ponder these issues only after they discovered w hat w as m eant by a galaxy. It w as in the 1920s that astronom ers realised that w e live in a separate galaxy, and that other galaxies w ...

  18. Disks around young stellar objects

    Indian Academy of Sciences (India)

    (1734), Immanuel Kant (1755) and by Pierre-Simon Laplace (1796) in the 18th century. 4. The circumstantial evidence for circumstellar disks. Till around early 1980s, the evidence for the existence of circumstellar disks around YSOs had been indirect, based on the interpretation of optical-infrared spectral energy distribu-.

  19. Millimeter observations of the disk around GW Orionis (United States)

    Fang, M.; Sicilia-Aguilar, A.; Wilner, D.; Wang, Y.; Roccatagliata, V.; Fedele, D.; Wang, J. Z.


    The GW Ori system is a pre-main sequence triple system (GW Ori A/B/C) with companions (GW Ori B/C) at 1 AU and 8 AU, respectively, from the primary (GW Ori A). The primary of the system has a mass of 3.9 M⊙, but shows a spectral type of G8. Thus, GW Ori A could be a precursor of a B star, but it is still at an earlier evolutionary stage than Herbig Be stars. GW Ori provides an ideal target for experiments and observations (being a "blown-up" solar system with a very massive sun and at least two upscaled planets). We present the first spatially resolved millimeter interferometric observations of the disk around the triple pre-main sequence system GW Ori, obtained with the Submillimeter Array, both in continuum and in the 12CO J = 2-1, 13CO J = 2-1, and C18O J = 2-1 lines. These new data reveal a huge, massive, and bright disk in the GW Ori system. The dust continuum emission suggests a disk radius of around 400 AU, but the 12CO J = 2-1 emission shows a much more extended disk with a size around 1300 AU. Owing to the spatial resolution ( 1''), we cannot detect the gap in the disk that is inferred from spectral energy distribution (SED) modeling. We characterize the dust and gas properties in the disk by comparing the observations with the predictions from the disk models with various parameters calculated with a Monte Carlo radiative transfer code RADMC-3D. The disk mass is around0.12 M⊙, and the disk inclination with respect to the line of sight is around 35°. The kinematics in the disk traced by the CO line emission strongly suggest that the circumstellar material in the disk is in Keplerian rotation around GW Ori.Tentatively substantial C18O depletion in gas phase is required to explain the characteristics of the line emission from the disk.

  20. Accretion by the Galaxy

    NARCIS (Netherlands)

    Binney, J.; Fraternali, F.; Reylé, C.; Robin, A.; Schultheis, M.

    Cosmology requires at least half of the baryons in the Universe to be in the intergalactic medium, much of which is believed to form hot coronae around galaxies. Star-forming galaxies must be accreting from their coronae. Hi observations of external galaxies show that they have Hi halos associated

  1. Disk Modeling: Arts and Phenomenology (United States)

    Gayley, K. G.; Porter, J. M.


    This article summarizes the focus session on disk modeling arts and phenomenology, which was devoted to the types of interesting physics a disk modeler may wish to include, and how best to include it. It is assumed that the modeling goal is to guide the process of falsification of various hypotheses with data accessible by existing and planned observations. Appropriate modeling choices depend on the conditions and aspects of the problem under study, but the expectation is that observations will yield to correct interpretation only when the key physics is properly understood, and effectively simulated in the models. This focus review first sketches several potentially relevant phenomena that disk modelers may wish to incorporate, especially in regard to the role of magnetic vs. inertial support of disks, and the source of disk angular momentum. It then concludes with some comments on effective numerical modeling strategies for incorporating these effects.


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    Li Zhaoyu [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Ho, Luis C. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Barth, Aaron J. [Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697-4575 (United States); Peng, Chien Y. [NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)


    The Carnegie-Irvine Galaxy Survey (CGS) is a comprehensive investigation of the physical properties of a complete, representative sample of 605 bright (B{sub T} {<=} 12.9 mag) galaxies in the southern hemisphere. This contribution describes the isophotal analysis of the broadband (BVRI) optical imaging component of the project. We pay close attention to sky subtraction, which is particularly challenging for some of the large galaxies in our sample. Extensive crosschecks with internal and external data confirm that our calibration and sky subtraction techniques are robust with respect to the quoted measurement uncertainties. We present a uniform catalog of one-dimensional radial profiles of surface brightness and geometric parameters, as well as integrated colors and color gradients. Composite profiles highlight the tremendous diversity of brightness distributions found in disk galaxies and their dependence on Hubble type. A significant fraction of S0 and spiral galaxies exhibit non-exponential profiles in their outer regions. We perform Fourier decomposition of the isophotes to quantify non-axisymmetric deviations in the light distribution. We use the geometric parameters, in conjunction with the amplitude and phase of the m = 2 Fourier mode, to identify bars and quantify their size and strength. Spiral arm strengths are characterized using the m = 2 Fourier profiles and structure maps. Finally, we utilize the information encoded in the m = 1 Fourier profiles to measure disk lopsidedness. The databases assembled here and in Paper I lay the foundation for forthcoming scientific applications of CGS.

  3. Are dSph galaxies Galactic building blocks?

    Directory of Open Access Journals (Sweden)

    Gilmore G.


    Full Text Available Dwarf spheroidal galaxies (dSph are frequently assumed to represent surviving examples of a vast now destroyed population of small systems in which many of the stars now forming the Milky Way were formed. Ongoing accretion and considerable sub-structure in the outer Galactic halo is direct evidence that there is some role for stars formed in small galaxies in populating the (outer galaxy. The evidence from stellar populations is however contradictory to this. dSph stellar populations are unlike any stars found in significant numbers in the Milky Way. The dSph are indeed small galaxies, formed over long times with low rates of star formation. Most of the stars in the Milky Way halo however seem to have formed quickly, at higher star formation rate, in gas mixed efficiently on kpc scales. The overwhelming majority of Milky Way stars, those in the Galactic thick disk and thin disk, seem to have nothing at all to do with dwarf galaxy origins.

  4. Ultraluminous Infrared Mergers: Elliptical Galaxies in Formation? (United States)

    Genzel, R.; Tacconi, L. J.; Rigopoulou, D.; Lutz, D.; Tecza, M.


    We report high-quality near-IR spectroscopy of 12 ultraluminous infrared galaxy mergers (ULIRGs). Our new VLT and Keck data provide ~0.5" resolution, stellar and gas kinematics of these galaxies, most of which are compact systems in the last merger stages. We confirm that ULIRG mergers are ``ellipticals in formation.'' Random motions dominate their stellar dynamics, but significant rotation is common. Gasdynamics and stellar dynamics are decoupled in most systems. ULIRGs fall on or near the fundamental plane of hot stellar systems, and especially on its less evolution-sensitive, reff-σ projection. The ULIRG velocity dispersion distribution, their location in the fundamental plane, and their distribution of vrotsini/σ closely resemble those of intermediate-mass (~L*), elliptical galaxies with moderate rotation. As a group ULIRGs do not resemble giant ellipticals with large cores and little rotation. Our results are in good agreement with other recent studies indicating that disky ellipticals with compact cores or cusps can form through dissipative mergers of gas-rich disk galaxies while giant ellipticals with large cores have a different formation history. Based on observations at the European Southern Observatory, Chile (ESO 65.N-0266, 65.N-0289), and on observations 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 Keck Observatory was made possible by the general financial support by the W. M. Keck Foundation.

  5. Constraints on the Size of the Circumplanetary Gas Disk (United States)

    Mosqueira, I.; Estrada, P. R.


    Based on the dynamical properties of the irregular satellites of Jupiter (Saha and Tremaine 1993; Cuk and Burns 2001) and the separation between the regular and irregular satellites of the giant planets of Jupiter, Saturn, and Uranus, Mosqueira and Estrada (a,b 2003, in press in Icarus) argued that the regular satellites of the giant planets formed in a disk extending out to the position of the irregulars at ˜ RH/5, where RH is the Hill radius of the planet, thus irregular satellites with smaller semi-major axis would have been lost due to gas drag. The recent discovery of irregular satellites of Neptune between 0.17-0.19 RH (Nicholson, personal communication) fits with this view (though observational issues cloud the picture to some extent). But what sets the size of the outer gas disk? One possibility is that the specific angular momentum of gas accreted by Jupiter determines it. Here we explore the alternative possibility that the circumplanetary gas disk once extended farther out, but the resonant tidal torque of the Sun on the circumplanetary gas disk reduced its size. If so, some of the angular momentum of accretion may end up in Jupiter's orbit instead of its spin angular momentum or the angular momentum of the gas-augmented satellite disk. To make progress we need to ask whether any resonant locations of the Sun fall within the disk. Due to the low frequency of the Sun's orbit the m = 2 horizontal Lindblad resonance falls far from the location of the irregulars at ˜ RH. An m = 2 vertical resonance (Lubow 1981) is located at ˜ RH/2, which may set the maximum allowable size for the circumplanetary gas disk, but is still well outside the location of the innermost irregulars. This leads us to consider resonances that arise from the eccentricity of the binary orbit, allowing for the possibility that the eccentricities of the giant planets were significantly larger in the past.

  6. Curious Case of a Stripped Elliptical Galaxy (United States)

    Kohler, Susanna


    direction.All of these features are signs that this galaxy is being ram-pressurestripped as it falls into the center of the cluster. The star-forming blobs, for example, are exhibiting classic ram-pressure-stripping behavior: as a galaxy falls into the cluster center, streams of ionized gas blow downwind, and stars (which dont respond as easily to the force of the wind) are left behind in a stream pointing upwind.Gas from a Merger?An example of a tidal tail drawn out from a disrupted late-type galaxy. The disrupted galaxy in Abell 2670 is, in contrast, an early-type, elliptical galaxy that should be gas-poor. [H. Ford, JHU/M. Clampin, STScI/G. Hartig, STScI/G. Illingworth, UCO, Lick/ACS Science Team/ESA/NASA]But if this is an elliptical galaxy, where did the gas come from for the tails and the galactic-center star formation? To rule out the obvious, the authors first check that this galaxy really is an early-type elliptical. The galaxys color (reddened), morphology (elliptical and no sign of a stellar disk), and stellar velocities (no sign of stellar rotation) all confirm this.The authors therefore speculate that the galaxy recently underwent a wet merger a merger with a companion galaxy that was gas-rich. Much of this gas was driven to the center of the elliptical galaxy in the merger, and its now responsible for the starbursts there.Well hopefully be able to draw stronger conclusions about this unusual galaxy after additional investigation into the amount of gas it contains and the galaxys star formation rate. In the meantime, this stripped elliptical makes for an intriguing puzzle!CitationYun-Kyeong Sheen et al 2017 ApJL 840 L7. doi:10.3847/2041-8213/aa6d79

  7. Resonant stripping as the origin of dwarf spheroidal galaxies (United States)

    D'Onghia, Elena; Besla, Gurtina; Cox, Thomas J.; Hernquist, Lars


    Dwarf spheroidal galaxies are the most dark-matter-dominated systems in the nearby Universe and their origin is one of the outstanding puzzles of how galaxies form. Dwarf spheroidals are poor in gas and stars, making them unusually faint, and those known as ultra-faint dwarfs have by far the lowest measured stellar content of any galaxy. Previous theories require that dwarf spheroidals orbit near giant galaxies like the Milky Way, but some dwarfs have been observed in the outskirts of the Local Group. Here we report simulations of encounters between dwarf disk galaxies and somewhat larger objects. We find that the encounters excite a process, which we term `resonant stripping', that transforms them into dwarf spheroidals. This effect is distinct from other mechanisms proposed to form dwarf spheroidals, including mergers, galaxy-galaxy harassment, or tidal and ram pressure stripping, because it is driven by gravitational resonances. It may account for some of the observed properties of dwarf spheroidals in the Local Group. Within this framework, dwarf spheroidals should form and interact in pairs, leaving detectable long stellar streams and tails.

  8. The Universe's Most Extreme Star-forming Galaxies (United States)

    Casey, Caitlin


    Dusty star-forming galaxies host the most intense stellar nurseries in the Universe. Their unusual characteristics (SFRs=200-2000Msun/yr, Mstar>1010 Msun) pose a unique challenge for cosmological simulations and galaxy formation theory, particularly at early times. Although rare today, they were factors of 1000 times more prevalent at z~2-5, contributing significantly to the buildup of the Universe's stellar mass and the formation of high-mass galaxies. At even earlier times (within 1Gyr post Big Bang) they could have played a pivotal role in enriching the IGM. However, an ongoing debate lingers as to their evolutionary origins at high-redshift, whether or not they are triggered by major mergers of gas-rich disk galaxies, or if they are solitary galaxies continually fed pristine gas from the intergalactic medium. Furthermore, their presence in early protoclusters, only revealed quite recently, pose intriguing questions regarding the collapse of large scale structure. I will discuss some of the latest observational programs dedicated to understanding dust-obscuration in and gas content of the early Universe, their context in the cosmic web, and future long-term observing campaigns that may reveal their relationship to `normal’ galaxies, thus teaching us valuable lessons on the physical mechanisms of galaxy growth and the collapse of large scale structure in an evolving Universe.

  9. The Physical Origin of Galaxy Morphologies and Scaling Laws (United States)

    Steinmetz, Matthia