Amanda Heiderman | The University of Texas at Austin (original) (raw)
Papers by Amanda Heiderman
Astrophysical Journal, 2010
[Abridged] The environment where galaxies are found heavily influences their evolution. Close gro... more [Abridged] The environment where galaxies are found heavily influences their evolution. Close groupings, like the cores of galaxy clusters or compact groups, evolve in ways far more dramatic than their isolated counterparts. We have conducted a multiwavelength study of HCG7, consisting of four giant galaxies: 3 spirals and 1 lenticular. We use Hubble Space Telescope (HST) imaging to identify and characterize the young and old star cluster populations. We find young massive clusters (YMC) mostly in the three spirals, while the lenticular features a large, unimodal population of globular clusters (GC) but no detectable clusters with ages less than ~Gyr. The spatial and approximate age distributions of the ~300 YMCs and ~150 GCs thus hint at a regular star formation history in the group over a Hubble time. While at first glance the HST data show the galaxies as undisturbed, our deep ground-based, wide-field imaging that extends the HST coverage reveals faint signatures of stellar material in the intra-group medium. We do not detect the intra-group medium in HI or Chandra X-ray observations, signatures that would be expected to arise from major mergers. We find that the HI gas content of the individual galaxies and the group as a whole are a third of the expected abundance. The appearance of quiescence is challenged by spectroscopy that reveals an intense ionization continuum in one galaxy nucleus, and post-burst characteristics in another. Our spectroscopic survey of dwarf galaxy members yields one dwarf elliptical in an apparent tidal feature. We therefore suggest an evolutionary scenario for HCG7, whereby the galaxies convert most of their available gas into stars without major mergers and result in a dry merger. As the conditions governing compact groups are reminiscent of galaxies at intermediate redshift, we propose that HCGs are appropriate for studying galaxy evolution at z~1-2.
We investigate the properties of bright (MV <= -18) barred and unbarred disks in the Abell 901/90... more We investigate the properties of bright (MV <= -18) barred and unbarred disks in the Abell 901/902 cluster system at z~0.165 with the STAGES HST ACS survey. To identify and characterize bars, we use ellipse-fitting. We use visual classification, a Sersic cut, and a color cut to select disk galaxies, and find that the latter two methods miss 31% and 51%, respectively of disk galaxies identified through visual classification. This underscores the importance of carefully selecting the disk sample in cluster environments. However, we find that the global optical bar fraction in the clusters is ~30% regardless of the method of disk selection. We study the relationship of the optical bar fraction to host galaxy properties, and find that the optical bar fraction depends strongly on the luminosity of the galaxy and whether it hosts a prominent bulge or is bulgeless. Within a given absolute magnitude bin, the optical bar fraction increases for galaxies with no significant bulge component. Within each morphological type bin, the optical bar fraction increases for brighter galaxies. We find no strong trend (variations larger than a factor of 1.3) for the optical bar fraction with local density within the cluster between the core and virial radius (R ~ 0.25 to 1.2 Mpc). We discuss the implications of our results for the evolution of bars and disks in dense environments.
We present an overview of and science highlights from the Space Telescope A901/902 Galaxy Evoluti... more We present an overview of and science highlights from the Space Telescope A901/902 Galaxy Evolution Survey. STAGES is a multiwavelength project designed to probe physical drivers of galaxy evolution across a wide range of environments and luminosity. A complex multi-cluster system at z=0.16 has been the subject of extensive multiwavelength observations ranging from the X-ray to radio, including an 80-orbit ACS/HST mosaic covering the full 0.5x0.5 degree span of the supercluster. Our survey goals include simultaneously linking galaxy morphology with other observables such as age, star-formation rate, nuclear activity, and stellar mass. In addition, with the unique multiwavelength dataset and new high resolution mass maps from gravitational lensing, we are able to disentangle the large-scale structure of the supercluster. By examining all aspects of environment we will determine the relative importance of the dark matter halos, the local galaxy density, and the hot X-ray gas in driving galaxy transformation. We acknowledge support from HST grant GO-10395.
Stellar bars are the most efficient internal drivers of disk evolution because they redistribute ... more Stellar bars are the most efficient internal drivers of disk evolution because they redistribute material and angular momentum within the galaxy and dark matter halo. Mounting evidence suggests that processes other than major mergers, such as minor mergers, secular processes driven by bars, and clump coalescence, as well as smooth accretion, play an important role in galaxy evolution since z = 2. As a key step toward characterizing this evolution and constraining theoretical models, we determine the frequency and properties of bars in the local Universe in both field and cluster environment, based on three of our studies: Marinova & Jogee (2007), Barazza, Jogee, & Marinova (2008) and Marinova et al. (2009). Among field spirals of intermediate Hubble types in the OSU survey, we find using ellipse fitting that the bar fraction is 44% in the optical and 60% in the NIR, giving an extinction correction factor of approximately 1.4 at z ˜ 0. Using data from the Abell 901/902 cluster system at z ˜ 0.165 from the HST ACS survey STAGES, we find that the optical bar fraction is a strong trend of both absolute magnitude and host bulge-to-total ratio, increasing for galaxies that are brighter and/or more disk-dominated. The latter trend is also found in the field from SDSS. For bright early types and faint late types the optical bar fraction in the cluster is similar to that in the field. We find that between the core region and the virial radii of the clusters the optical bar fraction is not a strong function of local environment density. We discuss the implications of our results in the context of theoretical models of the impact of bars on galaxy evolution.
We investigate galaxy mergers in the A901/902 supercluster at z ˜ 0.165, based on HST ACS F606W, ... more We investigate galaxy mergers in the A901/902 supercluster at z ˜ 0.165, based on HST ACS F606W, COMBO-17, Spitzer 24 μm, XMM-Newton X-ray, and gravitational lensing maps, as part of the STAGES survey. We utilize two methods to identify interacting galaxies in A901/902: visual classification and quantitative CAS parameters. In this article, we summarize our results for the frequency, distribution, color, and star formation rates of mergers, compared to non-interacting galaxies in A901/902. We also compare our results to other studies of clusters and groups, as well as theoretical predictions.
Astronomy & Astrophysics, 2009
We present a study of the population of bright early-type dwarf galaxies in the multiple-cluster ... more We present a study of the population of bright early-type dwarf galaxies in the multiple-cluster system Abell 901/902. We use data from the STAGES survey and COMBO-17 to investigate the relation between the color and structural properties of the dwarfs and their location in the cluster. The definition of the dwarf sample is based on the central surface brightness and includes galaxies in the luminosity range -16 >= M_B >~-19 mag. Using a fit to the color magnitude relation of the dwarfs, our sample is divided into a red and blue subsample. We find a color-density relation in the projected radial distribution of the dwarf sample: at the same luminosity dwarfs with redder colors are located closer to the cluster centers than their bluer counterparts. Furthermore, the redder dwarfs are on average more compact and rounder than the bluer dwarfs. These findings are consistent with theoretical expectations assuming that bright early-type dwarfs are the remnants of transformed late-type disk galaxies involving processes such as ram pressure stripping and galaxy harassment. This indicates that a considerable fraction of dwarf elliptical galaxies in clusters are the results of transformation processes related to interactions with their host cluster.
To study the rate at which stars form in distant galaxies and the connection between this and the... more To study the rate at which stars form in distant galaxies and the connection between this and their properties, a detailed analysis of data from the DEEP2 Redshift Survey is being performed. DEEP2 is studying a sample of 60,000 distant galaxies, 6-8 billion light years away, using DEIMOS, an instrument at the Keck II telescope. The amount of star formation in these galaxies is being investigated by measuring the equivalent width (EW) of [OII], or the amount of light emitted by ionized oxygen. Based on galaxies in the nearby Universe, correlations are expected to be found between the equivalent width values and the brightness of galaxies. Since DEEP2 is looking a distant galaxies, this is only a hypothesis, and conclusions will be established from the measured [OII] EW's. A similar trend is that nearby galaxies in dense clusters tend to have stopped star formation, while galaxies in less dense regions have higher oxygen equivalent widths and contain young stars. Further analysis of the DEEP2 data may lead to a better understanding of evolution and distribution of galaxies in the universe.
Hickson Compact Groups (HCGs) provide a unique environment to study the role of gas in galaxy evo... more Hickson Compact Groups (HCGs) provide a unique environment to study the role of gas in galaxy evolution. We use new Spitzer IRAC (3.6, 4.5, 5.8, and 8.0 microns) and MIPS (24 micron) data in combination with archival VLA HI observations to examine star formation and HI gas content in HCG 07 and HCG 19. The HI observations show that gas is confined to the individual galaxies, which are HI deficient compared to isolated galaxies. The gas kinematics are fairly regular, indicating that these systems are at an early stage of the proposed evolutionary scenario for compact groups. We examine the relationship between the HI deficiency and the infrared spectral energy distributions of the individual galaxies to help understand how the cold gas content and star formation activity evolve in compact groups.
We report on our analysis of our BVI ACS images of Hickson Compact Group (HCG) 7, one of twelve t... more We report on our analysis of our BVI ACS images of Hickson Compact Group (HCG) 7, one of twelve that we will obtain as part of a Cycle 15 HST program. HCG 7 is at an early stage of compact group evolution, as evidenced by HI gas that is confined to the individual galaxies in the group. Nonetheless, it has evidence of considerable amounts of star formation in three of the four giant galaxies, one of which is significantly disturbed. This star formation is evident from our 3.6-24 micron Spitzer images of the group. We will present the point source and extended source photometry based on the ACS images, and will use these results to consider the early evolutionary history of this group.
The VIXENS project is an integral field unit (IFU) survey of 15 nearby infrared bright (LIR > 3×1... more The VIXENS project is an integral field unit (IFU) survey of 15 nearby infrared bright (LIR > 3×1010L⊙) starburst/interacting galaxies, chosen to cover a range of interaction stages (from early to late phase mergers), star formation rates, and gas surface densities. The main goal of VIXENS is to investigate the relation between the star formation rate (SFR) and gas surface densities on spatially resolved scales of 0.2-0.9 kpc by comparing various tracers of star formation and gas content. More specifically, we use the Hα from our IFU data, 24μm, and far-UV data to investigate star formation and archival CO and HI maps, as well as maps of dense gas as traced by HCN(1–0). VIXENS will provide 2D maps of ionized gas, SFRs, stellar and gas kinematics, and metallicities. This unique data set will enable us to test theoretical predictions at the high star formation rate and gas surface density regime of the Kennicutt-Schmidt relation.
Arxiv preprint arXiv: …, Jan 1, 2010
The Astrophysical …, Jan 1, 2009
Arxiv preprint arXiv: …, Jan 1, 2010
VENGA is a large-scale extragalactic IFU survey, which maps the bulges, bars and large parts of t... more VENGA is a large-scale extragalactic IFU survey, which maps the bulges, bars and large parts of the outer disks of 32 nearby normal spiral galaxies. The targets are chosen to span a wide range in Hubble types, star formation activities, morphologies, and inclinations, at the same time of having vast available multi-wavelength coverage from the far-UV to the mid-IR, and available CO and 21cm mapping. The VENGA dataset will provide 2D maps of the SFR, stellar and gas kinematics, chemical abundances, ISM density and ionization states, dust extinction and stellar populations for these 32 galaxies. The uniqueness of the VIRUS-P large field of view permits these large-scale mappings to be performed. VENGA will allow us to correlate all these important quantities throughout the different environments present in galactic disks, allowing the conduction of a large number of studies in star formation, structure assembly, galactic feedback and ISM in galaxies.
Bulletin of the …, Jan 1, 2007
Abstract The cluster environment is host to an array of processes such as galaxy-galaxy interacti... more Abstract The cluster environment is host to an array of processes such as galaxy-galaxy interactions and ram pressure stripping, which can dramatically influence the evolution of galaxies. In order to constrain the frequency of these environmental processes and their consequences, we analyze the morphological properties of galaxies in the Abell 901/902 Supercluster at z= 0.17. As part of the STAGES (Space Telescope Abell 901/902 Galaxy Evolution Survey) collaboration, we have a panoramic multi-wavelength dataset that ...
The Astrophysical …, Jan 1, 2009
The Astrophysical …, Jan 1, 2009
Astrophysical Journal, 2010
[Abridged] The environment where galaxies are found heavily influences their evolution. Close gro... more [Abridged] The environment where galaxies are found heavily influences their evolution. Close groupings, like the cores of galaxy clusters or compact groups, evolve in ways far more dramatic than their isolated counterparts. We have conducted a multiwavelength study of HCG7, consisting of four giant galaxies: 3 spirals and 1 lenticular. We use Hubble Space Telescope (HST) imaging to identify and characterize the young and old star cluster populations. We find young massive clusters (YMC) mostly in the three spirals, while the lenticular features a large, unimodal population of globular clusters (GC) but no detectable clusters with ages less than ~Gyr. The spatial and approximate age distributions of the ~300 YMCs and ~150 GCs thus hint at a regular star formation history in the group over a Hubble time. While at first glance the HST data show the galaxies as undisturbed, our deep ground-based, wide-field imaging that extends the HST coverage reveals faint signatures of stellar material in the intra-group medium. We do not detect the intra-group medium in HI or Chandra X-ray observations, signatures that would be expected to arise from major mergers. We find that the HI gas content of the individual galaxies and the group as a whole are a third of the expected abundance. The appearance of quiescence is challenged by spectroscopy that reveals an intense ionization continuum in one galaxy nucleus, and post-burst characteristics in another. Our spectroscopic survey of dwarf galaxy members yields one dwarf elliptical in an apparent tidal feature. We therefore suggest an evolutionary scenario for HCG7, whereby the galaxies convert most of their available gas into stars without major mergers and result in a dry merger. As the conditions governing compact groups are reminiscent of galaxies at intermediate redshift, we propose that HCGs are appropriate for studying galaxy evolution at z~1-2.
We investigate the properties of bright (MV <= -18) barred and unbarred disks in the Abell 901/90... more We investigate the properties of bright (MV <= -18) barred and unbarred disks in the Abell 901/902 cluster system at z~0.165 with the STAGES HST ACS survey. To identify and characterize bars, we use ellipse-fitting. We use visual classification, a Sersic cut, and a color cut to select disk galaxies, and find that the latter two methods miss 31% and 51%, respectively of disk galaxies identified through visual classification. This underscores the importance of carefully selecting the disk sample in cluster environments. However, we find that the global optical bar fraction in the clusters is ~30% regardless of the method of disk selection. We study the relationship of the optical bar fraction to host galaxy properties, and find that the optical bar fraction depends strongly on the luminosity of the galaxy and whether it hosts a prominent bulge or is bulgeless. Within a given absolute magnitude bin, the optical bar fraction increases for galaxies with no significant bulge component. Within each morphological type bin, the optical bar fraction increases for brighter galaxies. We find no strong trend (variations larger than a factor of 1.3) for the optical bar fraction with local density within the cluster between the core and virial radius (R ~ 0.25 to 1.2 Mpc). We discuss the implications of our results for the evolution of bars and disks in dense environments.
We present an overview of and science highlights from the Space Telescope A901/902 Galaxy Evoluti... more We present an overview of and science highlights from the Space Telescope A901/902 Galaxy Evolution Survey. STAGES is a multiwavelength project designed to probe physical drivers of galaxy evolution across a wide range of environments and luminosity. A complex multi-cluster system at z=0.16 has been the subject of extensive multiwavelength observations ranging from the X-ray to radio, including an 80-orbit ACS/HST mosaic covering the full 0.5x0.5 degree span of the supercluster. Our survey goals include simultaneously linking galaxy morphology with other observables such as age, star-formation rate, nuclear activity, and stellar mass. In addition, with the unique multiwavelength dataset and new high resolution mass maps from gravitational lensing, we are able to disentangle the large-scale structure of the supercluster. By examining all aspects of environment we will determine the relative importance of the dark matter halos, the local galaxy density, and the hot X-ray gas in driving galaxy transformation. We acknowledge support from HST grant GO-10395.
Stellar bars are the most efficient internal drivers of disk evolution because they redistribute ... more Stellar bars are the most efficient internal drivers of disk evolution because they redistribute material and angular momentum within the galaxy and dark matter halo. Mounting evidence suggests that processes other than major mergers, such as minor mergers, secular processes driven by bars, and clump coalescence, as well as smooth accretion, play an important role in galaxy evolution since z = 2. As a key step toward characterizing this evolution and constraining theoretical models, we determine the frequency and properties of bars in the local Universe in both field and cluster environment, based on three of our studies: Marinova & Jogee (2007), Barazza, Jogee, & Marinova (2008) and Marinova et al. (2009). Among field spirals of intermediate Hubble types in the OSU survey, we find using ellipse fitting that the bar fraction is 44% in the optical and 60% in the NIR, giving an extinction correction factor of approximately 1.4 at z ˜ 0. Using data from the Abell 901/902 cluster system at z ˜ 0.165 from the HST ACS survey STAGES, we find that the optical bar fraction is a strong trend of both absolute magnitude and host bulge-to-total ratio, increasing for galaxies that are brighter and/or more disk-dominated. The latter trend is also found in the field from SDSS. For bright early types and faint late types the optical bar fraction in the cluster is similar to that in the field. We find that between the core region and the virial radii of the clusters the optical bar fraction is not a strong function of local environment density. We discuss the implications of our results in the context of theoretical models of the impact of bars on galaxy evolution.
We investigate galaxy mergers in the A901/902 supercluster at z ˜ 0.165, based on HST ACS F606W, ... more We investigate galaxy mergers in the A901/902 supercluster at z ˜ 0.165, based on HST ACS F606W, COMBO-17, Spitzer 24 μm, XMM-Newton X-ray, and gravitational lensing maps, as part of the STAGES survey. We utilize two methods to identify interacting galaxies in A901/902: visual classification and quantitative CAS parameters. In this article, we summarize our results for the frequency, distribution, color, and star formation rates of mergers, compared to non-interacting galaxies in A901/902. We also compare our results to other studies of clusters and groups, as well as theoretical predictions.
Astronomy & Astrophysics, 2009
We present a study of the population of bright early-type dwarf galaxies in the multiple-cluster ... more We present a study of the population of bright early-type dwarf galaxies in the multiple-cluster system Abell 901/902. We use data from the STAGES survey and COMBO-17 to investigate the relation between the color and structural properties of the dwarfs and their location in the cluster. The definition of the dwarf sample is based on the central surface brightness and includes galaxies in the luminosity range -16 >= M_B >~-19 mag. Using a fit to the color magnitude relation of the dwarfs, our sample is divided into a red and blue subsample. We find a color-density relation in the projected radial distribution of the dwarf sample: at the same luminosity dwarfs with redder colors are located closer to the cluster centers than their bluer counterparts. Furthermore, the redder dwarfs are on average more compact and rounder than the bluer dwarfs. These findings are consistent with theoretical expectations assuming that bright early-type dwarfs are the remnants of transformed late-type disk galaxies involving processes such as ram pressure stripping and galaxy harassment. This indicates that a considerable fraction of dwarf elliptical galaxies in clusters are the results of transformation processes related to interactions with their host cluster.
To study the rate at which stars form in distant galaxies and the connection between this and the... more To study the rate at which stars form in distant galaxies and the connection between this and their properties, a detailed analysis of data from the DEEP2 Redshift Survey is being performed. DEEP2 is studying a sample of 60,000 distant galaxies, 6-8 billion light years away, using DEIMOS, an instrument at the Keck II telescope. The amount of star formation in these galaxies is being investigated by measuring the equivalent width (EW) of [OII], or the amount of light emitted by ionized oxygen. Based on galaxies in the nearby Universe, correlations are expected to be found between the equivalent width values and the brightness of galaxies. Since DEEP2 is looking a distant galaxies, this is only a hypothesis, and conclusions will be established from the measured [OII] EW's. A similar trend is that nearby galaxies in dense clusters tend to have stopped star formation, while galaxies in less dense regions have higher oxygen equivalent widths and contain young stars. Further analysis of the DEEP2 data may lead to a better understanding of evolution and distribution of galaxies in the universe.
Hickson Compact Groups (HCGs) provide a unique environment to study the role of gas in galaxy evo... more Hickson Compact Groups (HCGs) provide a unique environment to study the role of gas in galaxy evolution. We use new Spitzer IRAC (3.6, 4.5, 5.8, and 8.0 microns) and MIPS (24 micron) data in combination with archival VLA HI observations to examine star formation and HI gas content in HCG 07 and HCG 19. The HI observations show that gas is confined to the individual galaxies, which are HI deficient compared to isolated galaxies. The gas kinematics are fairly regular, indicating that these systems are at an early stage of the proposed evolutionary scenario for compact groups. We examine the relationship between the HI deficiency and the infrared spectral energy distributions of the individual galaxies to help understand how the cold gas content and star formation activity evolve in compact groups.
We report on our analysis of our BVI ACS images of Hickson Compact Group (HCG) 7, one of twelve t... more We report on our analysis of our BVI ACS images of Hickson Compact Group (HCG) 7, one of twelve that we will obtain as part of a Cycle 15 HST program. HCG 7 is at an early stage of compact group evolution, as evidenced by HI gas that is confined to the individual galaxies in the group. Nonetheless, it has evidence of considerable amounts of star formation in three of the four giant galaxies, one of which is significantly disturbed. This star formation is evident from our 3.6-24 micron Spitzer images of the group. We will present the point source and extended source photometry based on the ACS images, and will use these results to consider the early evolutionary history of this group.
The VIXENS project is an integral field unit (IFU) survey of 15 nearby infrared bright (LIR > 3×1... more The VIXENS project is an integral field unit (IFU) survey of 15 nearby infrared bright (LIR > 3×1010L⊙) starburst/interacting galaxies, chosen to cover a range of interaction stages (from early to late phase mergers), star formation rates, and gas surface densities. The main goal of VIXENS is to investigate the relation between the star formation rate (SFR) and gas surface densities on spatially resolved scales of 0.2-0.9 kpc by comparing various tracers of star formation and gas content. More specifically, we use the Hα from our IFU data, 24μm, and far-UV data to investigate star formation and archival CO and HI maps, as well as maps of dense gas as traced by HCN(1–0). VIXENS will provide 2D maps of ionized gas, SFRs, stellar and gas kinematics, and metallicities. This unique data set will enable us to test theoretical predictions at the high star formation rate and gas surface density regime of the Kennicutt-Schmidt relation.
Arxiv preprint arXiv: …, Jan 1, 2010
The Astrophysical …, Jan 1, 2009
Arxiv preprint arXiv: …, Jan 1, 2010
VENGA is a large-scale extragalactic IFU survey, which maps the bulges, bars and large parts of t... more VENGA is a large-scale extragalactic IFU survey, which maps the bulges, bars and large parts of the outer disks of 32 nearby normal spiral galaxies. The targets are chosen to span a wide range in Hubble types, star formation activities, morphologies, and inclinations, at the same time of having vast available multi-wavelength coverage from the far-UV to the mid-IR, and available CO and 21cm mapping. The VENGA dataset will provide 2D maps of the SFR, stellar and gas kinematics, chemical abundances, ISM density and ionization states, dust extinction and stellar populations for these 32 galaxies. The uniqueness of the VIRUS-P large field of view permits these large-scale mappings to be performed. VENGA will allow us to correlate all these important quantities throughout the different environments present in galactic disks, allowing the conduction of a large number of studies in star formation, structure assembly, galactic feedback and ISM in galaxies.
Bulletin of the …, Jan 1, 2007
Abstract The cluster environment is host to an array of processes such as galaxy-galaxy interacti... more Abstract The cluster environment is host to an array of processes such as galaxy-galaxy interactions and ram pressure stripping, which can dramatically influence the evolution of galaxies. In order to constrain the frequency of these environmental processes and their consequences, we analyze the morphological properties of galaxies in the Abell 901/902 Supercluster at z= 0.17. As part of the STAGES (Space Telescope Abell 901/902 Galaxy Evolution Survey) collaboration, we have a panoramic multi-wavelength dataset that ...
The Astrophysical …, Jan 1, 2009
The Astrophysical …, Jan 1, 2009