50 research outputs found
Spatial matter density mapping of the STAGES Abell A901/2 supercluster field with 3D lensing
We present weak lensing data from the Hubble Space Telescope(HST)/Space Telescope A901/902 Galaxy Evolution Survey (STAGES) survey to study the three-dimensional spatial distribution of matter and galaxies in the Abell 901/902 supercluster complex. Our method improves over the existing 3D lensing mapping techniques by calibrating and removing redshift bias and accounting for the effects of the radial elongation of 3D structures. We also include the first detailed noise analysis of a 3D lensing map, showing that even with deep HST-quality data, only the most massive structures, for example M200âł 1015Mâh-1 at z⌠0.8, can be resolved in 3D with any reasonable redshift accuracy (Îzâ 0.15). We compare the lensing map to the stellar mass distribution and find luminous counterparts for all mass peaks detected with a peak significance >3Ï. We see structures in and behind the z= 0.165 foreground supercluster, finding structure directly behind the A901b cluster at z⌠0.6 and also behind the south-west (SW) group at z⌠0.7. This 3D structure viewed in projection has no significant impact on recent mass estimates of A901b or the SW group components SWa and SWb. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
GEMS: Galaxy fitting catalogues and testing parametric galaxy fitting codes
In the context of measuring structure and morphology of intermediate redshift
galaxies with recent HST/ACS surveys, we tune, test, and compare two widely
used fitting codes (GALFIT and GIM2D) for fitting single-component Sersic
models to the light profiles of both simulated and real galaxy data. We find
that fitting accuracy depends sensitively on galaxy profile shape. Exponential
disks are well fit with Sersic models and have small measurement errors,
whereas fits to de Vaucouleurs profiles show larger uncertainties owing to the
large amount of light at large radii. We find that both codes provide reliable
fits and little systematic error, when the effective surface brightness is
above that of the sky. Moreover, both codes return errors that significantly
underestimate the true fitting uncertainties, which are best estimated with
simulations. We find that GIM2D suffers significant systematic errors for
spheroids with close companions owing to the difficulty of effectively masking
out neighboring galaxy light; there appears to be no work around to this
important systematic in GIM2D's current implementation. While this crowding
error affects only a small fraction of galaxies in GEMS, it must be accounted
for in the analysis of deeper cosmological images or of more crowded fields
with GIM2D. In contrast, GALFIT results are robust to the presence of neighbors
because it can simultaneously fit the profiles of multiple companions thereby
deblending their effect on the fit to the galaxy of interest. We find GALFIT's
robustness to nearby companions and factor of >~20 faster runtime speed are
important advantages over GIM2D for analyzing large HST/ACS datasets. Finally
we include our final catalog of fit results for all 41,495 objects detected in
GEMS.Comment: Accepted for publication in ApJS October 2007, v172n2; 25 pages, 16
Figures, 9 Tables; for hi-resolution version, see
http://www.mpia.de/homes/bhaeussl/galaxy_fitting.pdf. For results, catalogues
and files for code-testing, see http://www.mpia.de/GEMS/fitting_paper.htm
Dry Mergers in GEMS: The Dynamical Evolution of Massive Early-Type Galaxies
We have used the 28'x 28' HST image mosaic from the GEMS (Galaxy Evolution
from Morphology and SEDs) survey in conjunction with the COMBO-17 photometric
redshift survey to constrain the incidence of major mergers between
spheroid-dominated galaxies with little cold gas (dry mergers) since z = 0.7. A
set of N-body merger simulations was used to explore the morphological
signatures of such interactions: they are recognizable either as < 5kpc
separation close pairs or because of broad, low surface brightness tidal
features and asymmetries. Data with the depth and resolution of GEMS are
sensitive to dry mergers between galaxies with M_V < -20.5 for z < 0.7; dry
mergers at higher redshifts are not easily recovered in single-orbit HST
imaging. Six dry mergers (12 galaxies) with luminosity ratios between 1:1 and
4:1 were found from a sample of 379 red early-type galaxies with M_V < -20.5
and 0.1 < z < 0.7. The simulations suggest that the morphological signatures of
dry merging are visible for ~250Myr and we use this timescale to convert the
observed merger incidence into a rate. On this basis we find that present day
spheroidal galaxies with M_V < -20.5 on average have undergone between 0.5 and
2 major dry mergers since z ~ 0.7. We have compared this result with the
predictions of a Cold Dark Matter based semi-analytic galaxy formation model.
The model reproduces the observed declining major merger fraction of bright
galaxies and the space density of luminous early-type galaxies reasonably well.
The predicted dry merger fraction is consistent with our observational result.
Hence, hierarchical models predict and observations now show that major dry
mergers are an important driver of the evolution of massive early-type galaxies
in recent epochs.Comment: ApJ, in press. The paper has been extensively modified, detailing the
automated+visual selection and dry merger classification. 11 pages emulateapj
with 9 reduced-quality figures. A high quality copy is available at
http://www.mpia-hd.mpg.de/homes/bell/papers/dry.ps.g
Obscured star formation in intermediate-density environments:A Spitzer study of the Abell 901/902 supercluster
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 m photometry to estimate both the unobscured and obscured star formation in galaxies with M-* > 10(10) M-circle dot. 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 Sersicindices, 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 greater than or similar to 40% 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 size evolution of galaxies since z~3: combining SDSS, GEMS and FIRES
We present the evolution of the luminosity-size and stellar mass-size
relations of luminous (L_V>3.4x10^10h_70^-2L_sun) and of massive
(M_*>3x10^10h_70^-2M_sun) galaxies in the last ~11 Gyr. We use very deep
near-infrared images of the Hubble Deep Field-South and the MS1054-03 field in
the J_s, H and K_s bands from FIRES to retrieve the sizes in the optical
rest-frame for galaxies with z>1. We combine our results with those from GEMS
at 0.2<z<1 and SDSS at z~0.1 to achieve a comprehensive picture of the optical
rest-frame size evolution from z=0 to z=3. Galaxies are differentiated
according to their light concentration using the Sersic index n. For less
concentrated objects, the galaxies at a given luminosity were typically ~3+-0.5
(+-2 sigma) times smaller at z~2.5 than those we see today. The stellar
mass-size relation has evolved less: the mean size at a given stellar mass was
\~2+-0.5 times smaller at z~2.5, evolving proportional to (1+z)^{-0.40+-0.06}.
Simple scaling relations between dark matter halos and baryons in a
hierarchical cosmogony predict a stronger (although consistent within the error
bars) than observed evolution of the stellar mass-size relation. The observed
luminosity-size evolution out to z~2.5 matches well recent infall model
predictions for Milky-Way type objects. For low-n galaxies, the evolution of
the stellar mass-size relation would follow naturally if the individual
galaxies grow inside-out. For highly concentrated objects, the situation is as
follows: at a given luminosity, these galaxies were ~2.7+-1.1 times smaller at
z~2.5 (or put differently, were typically ~2.2+-0.7 mag brighter at a given
size than they are today), and at a given stellar mass the size has evolved
proportional to (1+z)^{-0.45+-0.10}.Comment: Accepted for publication in ApJ. The new version includes several
improvements: much accurate size estimations and a better completeness and
robustness analysis. Tables of data are included. 29 pages and 14 figures
(one low resolution
GEMS: Galaxy Evolution from Morphologies and SEDs
GEMS, Galaxy Evolution from Morphologies and SEDs, is a large-area (800
arcmin2) two-color (F606W and F850LP) imaging survey with the Advanced Camera
for Surveys on HST. Centered on the Chandra Deep Field South, it covers an area
of ~28'x28', or about 120 Hubble Deep Field areas, to a depth of
m_AB(F606W)=28.3 (5sigma and m_AB(F850LP)=27.1 (5sigma) for compact sources. In
its central ~1/4, GEMS incorporates ACS imaging from the GOODS project.
Focusing on the redshift range 0.2<=z<=1.1, GEMS provides morphologies and
structural parameters for nearly 10,000 galaxies where redshift estimates,
luminosities and SEDs exist from COMBO-17. At the same time, GEMS contains
detectable host galaxy images for several hundred faint AGN. This paper
provides an overview of the science goals, the experiment design, the data
reduction and the science analysis plan for GEMS.Comment: 24 pages, TeX with 6 eps Figures; to appear in ApJ Supplement. Low
resolution figures only. Full resolution at
http://zwicky.as.arizona.edu/~rix/Misc/GEMS.ps.g
Recommended from our members
CANDELS Observations Of The Structural Properties Of Cluster Galaxies At Z=1.62
We discuss the structural and morphological properties of galaxies in a z = 1.62 proto-cluster using near-IR imaging data from Hubble Space Telescope Wide Field Camera 3 data of the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS). The cluster galaxies exhibit a clear color-morphology relation: galaxies with colors of quiescent stellar populations generally have morphologies consistent with spheroids, and galaxies with colors consistent with ongoing star formation have disk-like and irregular morphologies. The size distribution of the quiescent cluster galaxies shows a deficit of compact (less than or similar to 1 kpc), massive galaxies compared to CANDELS field galaxies at z = 1.6. As a result, the cluster quiescent galaxies have larger average effective sizes compared to field galaxies at fixed mass at greater than 90% significance. Combined with data from the literature, the size evolution of quiescent cluster galaxies is relatively slow from z similar or equal to 1.6 to the present, growing as (1 + z)(-0.6 +/- 0.1). If this result is generalizable, then it implies that physical processes associated with the denser cluster region seem to have caused accelerated size growth in quiescent galaxies prior to z = 1.6 and slower subsequent growth at z < 1.6 compared to galaxies in the lower density field. The quiescent cluster galaxies at z = 1.6 have higher ellipticities compared to lower redshift samples at fixed mass, and their surface-brightness profiles suggest that they contain extended stellar disks. We argue that the cluster galaxies require dissipationless (i.e., gas-poor or "dry") mergers to reorganize the disk material and to match the relations for ellipticity, stellar mass, size, and color of early-type galaxies in z < 1 clusters.NASA NAS5-26555HST GO-12060NASA through from the Space Telescope Science Institute GO-12060European Research CouncilRoyal SocietyTexas AM UniversityGeorge P. and Cynthia Woods Institute for Fundamental Physics and AstronomyAstronom
Stellar Half-Mass Radii of Galaxies: Comparison with JWST/NIRCam Half-Light Radii
We use CEERS JWST/NIRCam imaging to measure rest-frame near-IR light profiles
of 500 galaxies in the redshift range .
We compare the resulting rest-frame 1.5-2m half-light radii
() with stellar half-mass radii (\rmass) derived with multi-color
light profiles from CANDELS HST imaging. In general agreement with previous
work, we find that and \rmass~are up to 40\%~smaller than the
rest-frame optical half-light radius . The agreement between
and \rmass~is excellent, with negligible systematic offset
(0.03 dex) up to for quiescent galaxies and up to for
star-forming galaxies. We also deproject the profiles to estimate \rmassd, the
radius of a sphere containing 50\% of the stellar mass. We present the
distribution of galaxies at , comparing ,
\rmass~and \rmassd. The slope is significantly flatter for \rmass~and \rmassd~
compared to , mostly due to downward shifts in size for massive
star-forming galaxies, while \rmass~and \rmassd~do not show markedly different
trends. Finally, we show rapid size evolution ()
for massive () quiescent galaxies between and
, again comparing , \rmass~and \rmassd. We conclude that
the main tenets of the size evolution narrative established over the past 20
years, based on rest-frame optical light profile analysis, still hold in the
era of JWST/NIRCam observations in the rest-frame near-IR.Comment: Submitted to ApJ. Comments welcom
Integrated Molecular Characterization of Uterine Carcinosarcoma
SummaryWe performed genomic, epigenomic, transcriptomic, and proteomic characterizations of uterine carcinosarcomas (UCSs). Cohort samples had extensive copy-number alterations and highly recurrent somatic mutations. Frequent mutations were found in TP53, PTEN, PIK3CA, PPP2R1A, FBXW7, and KRAS, similar to endometrioid and serous uterine carcinomas. Transcriptome sequencing identified a strong epithelial-to-mesenchymal transition (EMT) gene signature in a subset of cases that was attributable to epigenetic alterations at microRNA promoters. The range of EMT scores in UCS was the largest among all tumor types studied via The Cancer Genome Atlas. UCSs shared proteomic features with gynecologic carcinomas and sarcomas with intermediate EMT features. Multiple somatic mutations and copy-number alterations in genes that are therapeutic targets were identified