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Boris Häußler,
Steven P. Bamford,
Marina Vika,
Alex L. Rojas,
Marco Barden,
Lee S. Kelvin,
Mehmet Alpaslan,
Aaron S. G. Robotham,
Simon P. Driver,
I. K. Baldry,
Sarah Brough,
Andrew M. Hopkins,
Jochen Liske,
Robert C. Nichol,
Cristina. C. Popescu,
Richard J. Tuffs
[show abstract]
[hide abstract]
ABSTRACT: In this paper, we demonstrate a new method for fitting galaxy profiles which
makes use of the full multi-wavelength data provided by modern large
optical-near-infrared imaging surveys. We present a new version of GALAPAGOS,
which utilises a recently-developed multi-wavelength version of GALFIT, and
enables the automated measurement of wavelength dependent S\'ersic profile
parameters for very large samples of galaxies. Our new technique is extensively
tested to assess the reliability of both pieces of software, GALFIT and
GALAPAGOS on both real ugrizY JHK imaging data from the GAMA survey and
simulated data made to the same specifications. We find that fitting galaxy
light profiles with multi-wavelength data increases the stability and accuracy
of the measured parameters, and hence produces more complete and meaningful
multi-wavelength photometry than has been available previously. The improvement
is particularly significant for magnitudes in low S/N bands and for structural
parameters like half-light radius re and S\'ersic index n for which a prior is
used by constraining these parameters to a polynomial as a function of
wavelength. This allows the fitting routines to push the magnitude of galaxies
for which sensible values can be derived to fainter limits. The technique
utilises a smooth transition of galaxy parameters with wavelength, creating
more physically meaningful transitions than single-band fitting and allows
accurate interpolation between passbands, perfect for derivation of rest-frame
values.
12/2012;
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[show abstract]
[hide abstract]
ABSTRACT: To automate source detection, two-dimensional light-profile Sersic modelling
and catalogue compilation in large survey applications, we introduce a new code
GALAPAGOS, Galaxy Analysis over Large Areas: Parameter Assessment by GALFITting
Objects from SExtractor. Based on a single setup, GALAPAGOS can process a
complete set of survey images. It detects sources in the data, estimates a
local sky background, cuts postage stamp images for all sources, prepares
object masks, performs Sersic fitting including neighbours and compiles all
objects in a final output catalogue. For the initial source detection GALAPAGOS
applies SExtractor, while GALFIT is incorporated for modelling Sersic profiles.
It measures the background sky involved in the Sersic fitting by means of a
flux growth curve. GALAPAGOS determines postage stamp sizes based on SExtractor
shape parameters. In order to obtain precise model parameters GALAPAGOS
incorporates a complex sorting mechanism and makes use of modern CPU's
multiplexing capabilities. It combines SExtractor and GALFIT data in a single
output table. When incorporating information from overlapping tiles, GALAPAGOS
automatically removes multiple entries from identical sources. GALAPAGOS is
programmed in the Interactive Data Language, IDL. We test the stability and the
ability to properly recover structural parameters extensively with artificial
image simulations. Moreover, we apply GALAPAGOS successfully to the STAGES data
set. For one-orbit HST data, a single 2.2 GHz CPU processes about 1000 primary
sources per 24 hours. Note that GALAPAGOS results depend critically on the
user-defined parameter setup. This paper provides useful guidelines to help the
user make sensible choices.
03/2012;
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Carlos Hoyos,
Alfonso Aragón-Salamanca,
Meghan E. Gray,
David T. Maltby,
Eric F. Bell,
Fabio D. Barazza,
Asmus Böhm, Boris Häußler,
Knud Jahnke,
Shardha Jogee,
Kyle P. Lane,
Daniel H. McIntosh,
Christian Wolf
[show abstract]
[hide abstract]
ABSTRACT: We present a new automatic method to identify galaxy mergers using the morphological information contained in the residual images of galaxies after the subtraction of a smooth Sérsic model. The removal of the bulk signal from the host galaxy light is done with the aim of detecting the much fainter and elusive minor mergers. The specific morphological parameters that are used in the merger diagnostic suggested here are the residual flux fraction (RFF) and the asymmetry of the residuals [A(Res)]. The new diagnostic has been calibrated and optimized so that the resulting merger sample is very complete. However, the contamination by non-mergers is also high. If the same optimization method is adopted for combinations of other structural parameters such as the Concentration, Asymmetry, clumpineSs (CAS) system, the merger indicator we introduce yields merger samples of equal or higher statistical quality than the samples obtained through the use of other structural parameters. We investigate the ability of the method presented here to select minor mergers by identifying a sample of visually classified mergers that would not have been picked up by the use of the CAS system, when using its usual limits. However, given the low prevalence of mergers among the general population of galaxies and the optimization used here, we find that the merger diagnostic introduced in this work is best used as a negative merger test, that is, it is very effective at selecting non-merging galaxies. In common with all the currently available automatic methods, the sample of merger candidates selected is heavily contaminated by non-mergers, and further steps are needed to produce a clean merger sample. This merger diagnostic has been developed using the Hubble Space Telescope/ACS F606W images of the A901/902 multiple cluster system (z= 0.165) obtained by the Space Telescope A901/902 Galaxy Evolution Survey team. In particular, we have focused on a mass- and magnitude-limited sample (log M/M⊙ > 9.0, RVega, Total≤ 23.5 mag) which includes 905 cluster galaxies and 655 field galaxies of all morphological types.
Monthly Notices of the Royal Astronomical Society 11/2011; 419(3):2703 - 2724. · 4.90 Impact Factor
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Shardha Jogee,
Sarah H. Miller,
Kyle Penner,
Rosalind E. Skelton,
Christopher J. Conselice,
Rachel S. Somerville,
Eric F. Bell,
Xian Zhong Zheng,
Hans-Walter Rix,
Aday R. Robaina, [......],
Chien Y. Peng,
Catherine Heymans,
Daniel H. McIntosh, Boris Häußler,
Knud Jahnke,
Klaus Meisenheimer,
Sebastian F. Sanchez,
Lutz Wisotzki,
Christian Wolf,
and Casey Papovich
[show abstract]
[hide abstract]
ABSTRACT: We perform a comprehensive estimate of the frequency of galaxy mergers and their impact on star formation over z~ 0.24-0.80 (lookback time T b~ 3-7 Gyr) using ~3600 (M≥ 1 × 109 M ☉) galaxies with GEMS Hubble Space Telescope, COMBO-17, and Spitzer data. Our results are as follows. (1) Among ~790 high-mass (M≥ 2.5 × 1010 M ☉) galaxies, the visually based merger fraction over z~ 0.24-0.80, ranges from 9% ± 5% to 8% ± 2%. Lower limits on the major merger and minor merger fraction over this interval range from 1.1% to 3.5%, and 3.6% to 7.5%, respectively. This is the first, albeit approximate, empirical estimate of the frequency of minor mergers over the last 7 Gyr. Assuming a visibility timescale of ~0.5 Gyr, it follows that over T b~ 3-7 Gyr, ~68% of high-mass systems have undergone a merger of mass ratio >1/10, with ~16%, 45%, and 7% of these corresponding respectively to major, minor, and ambiguous "major or minor" mergers. The average merger rate is ~ a few ×10–4 galaxies Gyr–1 Mpc–3. Among ~2840 blue-cloud galaxies of mass M≥ 1.0 × 109 M ☉, similar results hold. (2) We compare the empirical merger fraction and merger rate for high-mass galaxies to three Λ cold dark matter-based models: halo occupation distribution models, semi-analytic models, and hydrodynamic SPH simulations. We find qualitative agreement between observations and models such that the (major+minor) merger fraction or rate from different models bracket the observations, and show a factor of 5 dispersion. Near-future improvements can now start to rule out certain merger scenarios. (3) Among ~3698 M≥ 1.0 × 109 M ☉ galaxies, we find that the mean star formation rate (SFR) of visibly merging systems is only modestly enhanced compared to non-interacting galaxies over z~ 0.24-0.80. Visibly merging systems only account for a small fraction (<30%) of the cosmic SFR density over T b~ 3-7 Gyr. This complements the results of Wolf et al. over a shorter time interval of T b~ 6.2-6.8 Gyr, and suggests that the behavior of the cosmic SFR density over the last 7 Gyr is predominantly shaped by non-interacting galaxies.
The Astrophysical Journal 05/2009; 697(2):1971. · 6.02 Impact Factor
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Rachel S. Somerville,
Marco Barden,
Hans-Walter Rix,
Eric F. Bell,
Steven V. W. Beckwith,
Andrea Borch,
John A. R. Caldwell, Boris Häußler,
Catherine Heymans,
Knud Jahnke,
Shardha Jogee,
Daniel H. McIntosh,
Klaus Meisenheimer,
Chien Y. Peng,
Sebastian F. Sánchez,
Lutz Wisotzki,
and Christian Wolf
[show abstract]
[hide abstract]
ABSTRACT: Surveys of distant galaxies with the Hubble Space Telescope and from the ground have shown that there is only mild evolution in the relationship between radial size and stellar mass for galactic disks from z ~ 1 to the present day. Using a sample of nearby disk-dominated galaxies from the Sloan Digital Sky Survey (SDSS) and high-redshift data from the GEMS (Galaxy Evolution from Morphology and SEDs) survey, we investigate whether this result is consistent with theoretical expectations within the hierarchical paradigm of structure formation. The relationship between virial radius and mass for dark matter halos in the ΛCDM model evolves by about a factor of 2 over this interval. However, N-body simulations have shown that halos of a given mass have less centrally concentrated mass profiles at high redshift. When we compute the expected disk size-stellar mass distribution, accounting for this evolution in the internal structure of dark matter halos and the adiabatic contraction of the dark matter by the self-gravity of the collapsing baryons, we find that the predicted evolution in the mean size at fixed stellar mass since z ~ 1 is about 15%-20%, in good agreement with the observational constraints from GEMS. At redshift z ~ 2, the model predicts that disks at fixed stellar mass were on average only 60% as large as they are today. Similarly, we predict that the rotation velocity at a given stellar mass (essentially the zero point of the Tully-Fisher relation) is only about 10% larger at z ~ 1 (20% at z ~ 2) than at the present day.
The Astrophysical Journal 12/2008; 672(2):776. · 6.02 Impact Factor
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Fitting 20,000 galaxies: Galfit meets GEMS, ASP, 199-199 (2003).
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Ignacio Trujillo,
Natascha M. Förster Schreiber,
Gregory Rudnick,
Marco Barden,
Marijn Franx,
Hans-Walter Rix,
J. A. R. Caldwell,
Daniel H. McIntosh,
Andrew Zirm, Boris Häußler,
Pieter G. van Dokkum,
Ivo Labbé,
Alan Moorwood,
Huub Röttgering,
Arjen van der Wel,
Paul van der Werf,
Lottie van Starkenburg
[show abstract]
[hide abstract]
ABSTRACT: We present the evolution of the luminosity size and stellar mass size relations of luminous (LV > 3.4×1010h70 -2Lo) and of massive (M* >3×1010h70 -2Mo) galaxies in the lastË11 Gyr. We use very deep near infrared images of the Hubble Deep Field South and the MS1054-03 field in the Js, H and Ks bands from FIRES to retrieve the sizes in the optical rest frame for galaxies with z >1.
Island Universes - Structure and Evolution of Disk Galaxies, 481-486 (2007).
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David T. Maltby,
Alfonso Aragón-Salamanca,
Meghan E. Gray,
Marco Barden, Boris Häußler,
Christian Wolf,
Chien Y. Peng,
Knud Jahnke,
Daniel H. McIntosh,
Asmus Böhm,
Van Eelco Kampen
[show abstract]
[hide abstract]
ABSTRACT: ABSTRACT We present the stellar-mass-size relations for elliptical, lenticular and spiral galaxies in the field and cluster environments using Hubble Space Telescope/Advanced Camera for Surveys imaging and data from the Space Telescope A901/2 Galaxy Evolution Survey. We use a large sample of ~1200 field and cluster galaxies and a sub-sample of cluster core galaxies, and quantify the significance of any putative environmental dependence on the stellar-mass-size relation. For elliptical, lenticular and high-mass (logM*/Msolar > 10) spiral galaxies we find no evidence to suggest any such environmental dependence, implying that internal drivers are governing their size evolution. For intermediate-/low-mass spirals (logM*/Msolar < 10) we find evidence, significant at the 2ÃÆ level, for a possible environmental dependence on galaxy sizes: the mean effective radius for lower mass spirals is ~15-20 per cent larger in the field than in the cluster. This is due to a population of low-mass large-ae field spirals that are largely absent from the cluster environments. These large-ae field spirals contain extended stellar discs not present in their cluster counterparts. This suggests that the fragile extended stellar discs of these spiral galaxies may not survive the environmental conditions in the cluster. Our results suggest that internal physical processes are the main drivers governing the size evolution of galaxies, with the environment possibly playing a role affecting only the discs of intermediate-/low-mass spirals.
Monthly Notices of the Royal Astronomical Society, v.402 (2010).
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[show abstract]
[hide abstract]
ABSTRACT: We present first measurements of the evolution of the scatter of the cosmic average early-type galaxy color-magnitude relation (CMR) from z = 1 to the present day, finding that it is consistent with models in which galaxies are constantly being added to the red sequence through truncation of star formation in blue cloud galaxies. We used a sample of over 700 red sequence, structurally selected early-type galaxies (defined to have Sérsic index >2.5) with redshifts 0 < z < 1 taken from the Extended Chandra Deep Field South (173 galaxies) and the Sloan Digital Sky Survey (550 galaxies), constructing rest-frame U -- V colors accurate to <0.04 mag. We find that the scatter of the CMR of cosmic average early-type galaxies is ~0.1 mag in rest-frame U -- V color at 0.05 < z < 0.75, and somewhat higher at z = 1. We compared these observations with a model in which new red-sequence galaxies are being constantly added at the rate required to match the observed number density evolution, and found that this model predicts the correct CMR scatter and its evolution. Furthermore, this model predicts approximately the correct number density of "blue spheroids"---structurally early-type galaxies with blue colors---albeit with considerable model dependence. Thus, we conclude that both the evolution of the number density and colors of the early-type galaxy population paint a consistent picture in which the early-type galaxy population grows significantly between z = 1 and the present day through the quenching of star formation in blue cloud galaxies.
The Astrophysical Journal, v.695, 1058-1069 (2009).
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Boris Häußler,
Eric F. Bell,
Marco Barden,
Daniel H. McIntosh,
Hans-Walter Rix,
Andrea Borch,
Steven V. Beckwith,
John A. Caldwell,
Catherine Heymans,
Knud Jahnke,
Shardha Jogee,
Sergey E. Koposov,
Klaus Meisenheimer,
Chien Peng,
Sebastian F. Sánchez,
Rachel S. Somerville,
Lutz Wisotzki,
Christian Wolf
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Catherine Heymans,
Michael L. Brown,
Marco Barden,
John A. R. Caldwell,
Knud Jahnke,
Hans-Walter Rix,
Andy N. Taylor,
Steve Beckwith,
Eric Bell,
Andrea Borch, Boris Häußler,
Sharda Jogee,
Daniel H. McIntosh,
Klaus Meisenheimer,
Chen Peng,
Sebastian F. Sánchez,
Rachel Somerville,
Lutz Wisotzki,
Christian Wolf
[show abstract]
[hide abstract]
ABSTRACT: We present our cosmic shear analysis of the Galaxy Evolution from Morphology and SEDs (GEMS) survey. Imaged with the Advanced Camera for Surveys (ACS) on HST, GEMS provides high resolution imaging spanning some 800 square arcmins in the Chandra Deep Field South (CDFS). We discuss the benefits of using space-based data for weak lensing studies and show that the ACS is a very powerful instrument in this regard. We find that we are not limited by systematic errors arising from the anisotropic ACS point spread function distortion and use our cosmic shear results to place joint constraints on the matter density parameter Omegam and the amplitude of the matter power spectrum sigma8, finding sigma8(Omegam/0.3)0.62=0.73 ± 0.12.
New Astronomy Review, v.225, 392-395 (2005).
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Boris Häußler,
Eric F. Bell,
Marco Barden,
Daniel H. McIntosh,
Hans-Walter Rix,
Andrea Borch,
Steven V. W. Beckwith,
John A. R. Caldwell,
Catherine Heymans,
Knud Jahnke,
Shardha Jogee,
Sergey E. Koposov,
Klaus Meisenheimer,
Chien Y. Peng,
Sebastian F. Sánchez,
Rachel S. Somerville,
Lutz Wisotzki,
Christian Wolf
Combes, F.;Palous, J.: Galaxy Evolution Across the Hubble Time, Cambridge Univ. Press, 102-102 (2007).
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Christian Wolf,
Aragón-Salamanca,
Alfonso,
Michael Balogh,
Marco Barden,
Eric F. Bell,
Meghan E. Gray,
Chien Y. Peng,
David Bacon,
Fabio D. Barazza, [......],
Shardha Jogee,
Eelco van Kampen,
Kyle Lane,
Daniel H. McIntosh,
Klaus Meisenheimer,
Casey Papovich,
Sebastian F. Sánchez,
Andy Taylor,
Lutz Wisotzki,
Xianzhong Zheng
[show abstract]
[hide abstract]
ABSTRACT: We investigate the properties of optically passive spirals and dusty red galaxies in the A901/2 cluster complex at redshift ~0.17 using rest-frame near-ultraviolet-optical spectral energy distributions, 24-mum infrared data and Hubble Space Telescope morphologies from the STAGES data set. The cluster sample is based on COMBO-17 redshifts with an rms precision of sigmacz ~ 2000kms-1. We find that `dusty red galaxies' and `optically passive spirals' in A901/2 are largely the same phenomenon, and that they form stars at a substantial rate, which is only four times lower than that in blue spirals at fixed mass. This star formation is more obscured than in blue galaxies and its optical signatures are weak. They appear predominantly in the stellar mass range of logM*/Msolar = [10, 11] where they constitute over half of the star-forming galaxies in the cluster; they are thus a vital ingredient for understanding the overall picture of star formation quenching in clusters. We find that the mean specific star formation rate (SFR) of star-forming galaxies in the cluster is clearly lower than in the field, in contrast to the specific SFR properties of blue galaxies alone, which appear similar in cluster and field. Such a rich red spiral population is best explained if quenching is a slow process and morphological transformation is delayed even more. At logM*/Msolar < 10, such galaxies are rare, suggesting that their quenching is fast and accompanied by morphological change. We note that edge-on spirals play a minor role; despite being dust reddened they form only a small fraction of spirals independent of environment.
Monthly Notices of the Royal Astronomical Society, v.393, 1302-1323 (2009).
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Irina Marinova,
Shardha Jogee,
Amanda Heiderman,
Fabio D. Barazza,
Meghan E. Gray,
Marco Barden,
Christian Wolf,
Chien Y. Peng,
David Bacon,
Michael Balogh, [......],
Knud Jahnke,
Eelco van Kampen,
Kyle Lane,
Daniel H. McIntosh,
Klaus Meisenheimer,
Sebastian F. Sánchez,
Rachel Somerville,
Andy Taylor,
Lutz Wisotzki,
Xianzhong Zheng
[show abstract]
[hide abstract]
ABSTRACT: We present a study of bar and host disk evolution in a dense cluster environment, based on a sample of ~800 bright (M V <= --18) galaxies in the Abell 901/2 supercluster at z~ 0.165. We use Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) F606W imaging from the STAGES survey, and data from Spitzer, XMM-Newton, and COMBO-17. We identify and characterize bars through ellipse-fitting, and other morphological features through visual classification. We find the following results. (1) To define the optical fraction of barred disk galaxies, we explore three commonly used methods for selecting disk galaxies. We find 625, 485, and 353 disk galaxies, respectively, via visual classification, a single component Sérsic cut (n <= 2.5), and a blue-cloud cut. In cluster environments, the latter two methods suffer from serious limitations, and miss 31% and 51%, respectively, of visually identified disks, particularly the many red, bulge-dominated disk galaxies in clusters. (2) For moderately inclined disks, the three methods of disk selection, however, yield a similar global optical bar fraction (f bar-opt) of 34%+10% --3% (115/340), 31%+10% --3% (58/189), and 30%+10% --3% (72/241), respectively. (3) We explore f bar-opt as a function of host galaxy properties and find that it rises in brighter galaxies and those which appear to have no significant bulge component. Within a given absolute magnitude bin, f bar-opt is higher in visually selected disk galaxies that have no bulge as opposed to those with bulges. Conversely, for a given visual morphological class, f bar-opt rises at higher luminosities. Both results are similar to trends found in the field. (4) For bright early-types, as well as faint late-type systems with no evident bulge, the optical bar fraction in the Abell 901/2 clusters is comparable within a factor of 1.1-1.4 to that of field galaxies at lower redshifts (z < 0.04). (5) Between the core and the virial radius of the cluster (R~ 0.25-1.2 Mpc) at intermediate environmental densities (log(Sigma10) ~ 1.7-2.3), the optical bar fraction does not appear to depend strongly on the local environment density tracers (kappa, Sigma10, and intracluster medium (ICM) density), and varies at most by a factor of ~1.3. Inside the cluster core, we are limited by number statistics, projection effects, and different trends from different indicators, but overall f bar-opt does not show evidence for a variation larger than a factor of 1.5. We discuss the implications of our results for the evolution of bars and disks in dense environments.
The Astrophysical Journal, v.698, 1639-1658 (2009).
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Amanda Heiderman,
Shardha Jogee,
Irina Marinova,
Eelco van Kampen,
Marco Barden,
Chien Y. Peng,
Catherine Heymans,
Meghan E. Gray,
Eric F. Bell,
David Bacon, [......],
Knud Jahnke,
Kyle Lane,
Daniel H. Mc Intosh,
Klaus Meisenheimer,
Sebastian F. Sánchez,
Rachel S. Somerville,
Andy Taylor,
Lutz Wisotzki,
Christian Wolf,
Xianzhong Zheng
[show abstract]
[hide abstract]
ABSTRACT: We present a study of galaxy mergers and the influence of environment in the Abell 901/902 supercluster at z~ 0.165, based on 893 bright (R Vega<= 24) intermediate-mass (M * >= 109 M sun) galaxies. We use HST ACS F606W data from the Space Telescope A901/902 Galaxy Evolution Survey, COMBO-17, Spitzer 24 mum, and XMM-Newton X-ray data. Our analysis utilizes both a physically driven visual classification system and quantitative CAS parameters to identify systems which show evidence of a recent or ongoing merger of mass ratio >1/10 (i.e., major and minor mergers). Our results are (1) after visual classification and minimizing the contamination from false projection pairs, we find that the merger fraction f merge is 0.023 ± 0.007. The estimated fractions of likely major mergers, likely minor mergers, and ambiguous cases are 0.01 ± 0.004, 0.006 ± 0.003, and 0.007 ± 0.003, respectively. (2) All the mergers lie outside the cluster core of radius R< 0.25 Mpc: the lack of mergers in the core is likely due to the large galaxy velocity dispersion in the core. The mergers, instead, populate the region (0.25 Mpc <R<= 2 Mpc) between the core and the cluster outskirt. In this region, the estimated frequency of mergers is similar to those seen at typical group overdensities in N-body simulations of accreting groups in the A901/902 clusters. This suggests the ongoing growth of the clusters via accretion of group and field galaxies. (3) We compare our observed merger fraction with those reported in other clusters and groups out to z~ 0.4. Existing data points on the merger fraction for L <= L* galaxies in clusters allow for a wide spectrum of scenarios, ranging from no evolution to evolution by a factor of ~5 over z~ 0.17-0.4. (4) In A901/902, the fraction of interacting galaxies, which lie on the blue cloud is 80% ± 18% (16/20) versus 34% ± 7% or (294/866) for non-interacting galaxies, implying that interacting galaxies are preferentially blue. (5) The average star formation rate (SFR), based on UV or a combination of UV+IR data, is enhanced by a factor of ~1.5-2 in mergers compared to non-interacting galaxies. However, mergers in the A901/902 clusters contribute only a small fraction (between 10% and 15%) of the total SFR density, while the rest of the SFR density comes from non-interacting galaxies.
The Astrophysical Journal, v.705, 1433-1455 (2009).
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Meghan E. Gray,
Christian Wolf,
Marco Barden,
Chien Y. Peng, Boris Häußler,
Eric F. Bell,
Daniel H. McIntosh,
Yicheng Guo,
John A. R. Caldwell,
David Bacon, [......],
Sebastian F. Sánchez,
Andy Taylor,
Lutz Wisotzki,
Xianzhong Zheng,
David A. Green,
R. J. Beswick,
D. J. Saikia,
Rachel Gilmour,
Benjamin D. Johnson,
Casey Papovich
[show abstract]
[hide abstract]
ABSTRACT: We present an overview of the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). STAGES is a multiwavelength project designed to probe physical drivers of galaxy evolution across a wide range of environments and luminosity. A complex multicluster system at z ~ 0.165 has been the subject of an 80-orbit F606W Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) mosaic covering the full span of the supercluster. Extensive multiwavelength observations with XMM-Newton, GALEX, Spitzer, 2dF, Giant Metrewave Radio Telescope and the 17-band COMBO-17 photometric redshift survey complement the HST imaging. 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 multiwavelength data set and new high-resolution mass maps from gravitational lensing, we are able to disentangle the large-scale structure of the system. By examining all aspects of an environment we will be able to evaluate the relative importance of the dark matter haloes, the local galaxy density and the hot X-ray gas in driving galaxy transformation. This paper describes the HST imaging, data reduction and creation of a master catalogue. We perform the Sérsic fitting on the HST images and conduct associated simulations to quantify completeness. In addition, we present the COMBO-17 photometric redshift catalogue and estimates of stellar masses and star formation rates for this field. We define galaxy and cluster sample selection criteria, which will be the basis for forthcoming science analyses, and present a compilation of notable objects in the field. Finally, we describe the further multiwavelength observations and announce public access to the data and catalogues.
Monthly Notices of the Royal Astronomical Society, v.393, 1275-1301 (2009).
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Anna Gallazzi,
Eric F. Bell,
Christian Wolf,
Meghan E. Gray,
Casey Papovich,
Marco Barden,
Chien Y. Peng,
Klaus Meisenheimer,
Catherine Heymans,
Eelco van Kampen, [......],
John A. R. Caldwell, Boris Häußler,
Knud Jahnke,
Shardha Jogee,
Kyle Lane,
Aday R. Robaina,
Sebastian F. Sanchez,
Andy Taylor,
Lutz Wisotzki,
Xianzhong Zheng
[show abstract]
[hide abstract]
ABSTRACT: We explore the amount of obscured star formation as a function of environment in the Abell 901/902 (A901/902) supercluster at z = 0.165 in conjunction with a field sample drawn from the A901 and CDFS fields, imaged with the Hubble Space Telescope as part of the Space Telescope A901/902 Galaxy Evolution Survey and Galaxy Evolution from Morphology and Spectral Energy Distributions (SEDs) Survey. We combine the COMBO-17 near-UV/optical SED with Spitzer 24 mu photometry to estimate both the unobscured and obscured star formation in galaxies with M * > 1010 M sun. We find that the star formation activity in massive galaxies is suppressed in dense environments, in agreement with previous studies. Yet, nearly 40% of the star-forming (SF) galaxies have red optical colors at intermediate and high densities. These red systems are not starbursting; they have star formation rates (SFRs) per unit stellar mass similar to or lower than blue SF galaxies. More than half of the red SF galaxies have low infrared-to-ultraviolet (IR-to-UV) luminosity ratios, relatively high Sérsic indices, and they are equally abundant at all densities. They might be gradually quenching their star formation, possibly but not necessarily under the influence of gas-removing environmental processes. The other gsim40% of the red SF galaxies have high IR-to-UV luminosity ratios, indicative of high dust obscuration. They have relatively high specific SFRs and are more abundant at intermediate densities. Our results indicate that while there is an overall suppression in the SF galaxy fraction with density, the small amount of star formation surviving the cluster environment is to a large extent obscured, suggesting that environmental interactions trigger a phase of obscured star formation, before complete quenching.
The Astrophysical Journal, v.690, 1883-1900 (2009).
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Catherine Heymans,
Meghan E. Gray,
Chien Y. Peng,
Ludovic Van Waerbeke,
Eric F. Bell,
Christian Wolf,
David Bacon,
Michael Balogh,
Fabio D. Barazza,
Marco Barden, [......],
Shardha Jogee,
Eelco van Kampen,
Kyle Lane,
Daniel H. McIntosh,
Klaus Meisenheimer,
Yannick Mellier,
Sebastian F. Sánchez,
Andy N. Taylor,
Lutz Wisotzki,
Xianzhong Zheng
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ABSTRACT: We present a high-resolution dark matter reconstruction of the z = 0.165 Abell 901/902 supercluster from a weak lensing analysis of the Hubble Space Telescope STAGES survey. We detect the four main structures of the supercluster at high significance, resolving substructure within and between the clusters. We find that the distribution of dark matter is well traced by the cluster galaxies, with the brightest cluster galaxies marking out the strongest peaks in the dark matter distribution. We also find a significant extension of the dark matter distribution of Abell 901a in the direction of an infalling X-ray group Abell 901alpha. We present mass, mass-to-light and mass-to-stellar mass ratio measurements of the structures and substructures that we detect. We find no evidence for variation of the mass-to-light and mass-to-stellar mass ratio between the different clusters. We compare our space-based lensing analysis with an earlier ground-based lensing analysis of the supercluster to demonstrate the importance of space-based imaging for future weak lensing dark matter `observations'.
Monthly Notices of the Royal Astronomical Society, v.385, 1431-1442 (2008).
