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THE HUBBLE SPACE TELESCOPE WIDE FIELD CAMERA 3 EARLY RELEASE SCIENCE DATA: PANCHROMATIC FAINT OBJECT COUNTS FROM 0.2{2 MICRONS WAVELENGTH
We describe the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) Early Re- lease Science (ERS) observations in the Great Observatories Origins Deep Survey (GOODS) South eld. The new WFC3 ERS data provide calibrated, drizzled mosaics in the mid-UV lters F225W, F275W, and F336W, as well as in the near-IR lters F098W (Ys), F125W (J), and F160W (H) in 1{2 HST orbits per lter. Together with the existing HST Advanced Camera for Surveys (ACS) GOODS-South mosaics in the BVi\u27z\u27 lters, these panchromatic 10-band ERS data cover 40{50 square arcmin from from 0.2-1.7 m in wavelength at 00:007{ 000 :15 FWHM resolution and 000 :090 multidrizzled pixels to depths of AB\u3c 26.0{27.0 mag (5-sigma) for point sources, and AB\u3c 25.5{26.5 mag for compact galaxies. In this paper, we describe: a) the scientic rationale, and the data taking plus reduction procedures of the panchromatic 10-band ERS mosaics; b) the procedure of generating object catalogs across the 10 dierent ERS lters, and the specic star-galaxy separation techniques used; and c) the reliability and completeness of the object catalogs from the WFC3 ERS mosaics. The excellent 00:007{00:015 FWHM resolution of HST/WFC3 and ACS makes star- galaxy separation rather straightforward over a factor of 10 in wavelength to AB\u3c 25{26 mag from the UV to the near-IR, respectively. Our main scientic results are: 1) We present the resulting Galactic star counts and galaxy counts in 10 dierent lters. From the ERS data, these could be accurately determined from AB\u2719 mag to AB\u3c 26 from the mid-UV to the near-IR, respectively. 2) Both the Galactic stars counts and the galaxy counts show mild but signicant trends of decreasing count slopes from the mid{UV to the near-IR over a factor of 10 in wavelength. 3) We combine the 10-band ERS counts with the panchromatic GAMA counts at the bright end (10\u3c AB\u3c 20 mag), and with the ultradeep BVizYJH HUDF counts and other avail- able HST UV counts at the faint end (24\u3c AB\u3c 30 mag). The galaxy counts are now well measured over the entire magnitude range 10\u3c AB\u3c 30 mag from 0.2{2 m in wavelength. 4)We t simple galaxy evolution models to these panchromatic galaxy counts over this entire ux range, using the best available 10-band local galaxy luminosity functions (LFs) from the GAMA survey, as well as simple prescriptions of luminosity and/or density evolution. While these models can explain each of the 10-band counts from 10\u3c AB\u3c 30 mag well, no single one of these simple models can explain the counts over this entire ux range in all 10 lters simultaneously. 5) The 10-band panchromatic ERS data base is very rich in structural information at all rest-frame wavelengths where young or older stars shine during the peak epoch in the cosmic star-formation rate (z\u271{2), and constitutes a unique new HST data base for the community to explore in the future
The Size Evolution of Passive Galaxies: Observations from the Wide Field Camera 3 Early Release Science Program
We present results on the size evolution of passively evolving galaxies at
1<z<2 drawn from the Wide Field Camera 3 Early Release Science program. Our
sample was constructed using an analog to the passive BzK selection criterion,
which isolates galaxies with little or no on-going star formation at z>1.5. We
identify 30 galaxies in ~40 square arcmin to H<25 mag. We supplement
spectroscopic redshifts from the literature with photometric redshifts
determined from the 15-band photometry from 0.22-8 micron. We determine
effective radii from Sersic profile fits to the H-band image using an empirical
PSF. We find that size evolution is a strong function of stellar mass, with the
most massive (M* ~ 10^11 Msol) galaxies undergoing the most rapid evolution
from z~2 to the present. Parameterizing the size evolution as (1+z)^{-alpha},
we find a tentative scaling between alpha and stellar mass of alpha ~ -1.8+1.4
log(M*/10^9 Msol). We briefly discuss the implications of this result for our
understanding of the dynamical evolution of the red galaxies.Comment: 11 pages, 7 figures, 4 tables. Submitted to Ap
The Size Evolution of Passive Galaxies: Observations From the Wide-Field Camera 3 Early Release Science Program
We present the size evolution of passively evolving galaxies at z approximately 2 identified in Wide-Field Camera 3 imaging from the Early Release Science program. Our sample was constructed using an analog to the passive BzK galaxy selection criterion, which isolates galaxies with little or no ongoing star formation at z greater than approximately 1.5. We identify 30 galaxies in approximately 40 arcmin(sup 2) to H less than 25 mag. By fitting the 10-band Hubble Space Telescope photometry from 0.22 micrometers less than approximately lambda (sub obs) 1.6 micrometers with stellar population synthesis models, we simultaneously determine photometric redshift, stellar mass, and a bevy of other population parameters. Based on the six galaxies with published spectroscopic redshifts, we estimate a typical redshift uncertainty of approximately 0.033(1+z).We determine effective radii from Sersic profile fits to the H-band image using an empirical point-spread function. By supplementing our data with published samples, we propose a mass-dependent size evolution model for passively evolving galaxies, where the most massive galaxies (M(sub ) approximately 10(sup 11) solar mass) undergo the strongest evolution from z approximately 2 to the present. Parameterizing the size evolution as (1 + z)(sup - alpha), we find a tentative scaling of alpha approximately equals (0.6 plus or minus 0.7) + (0.9 plus or minus 0.4) log(M(sub )/10(sup 9 solar mass), where the relatively large uncertainties reflect the poor sampling in stellar mass due to the low numbers of highredshift systems. We discuss the implications of this result for the redshift evolution of the M(sub )-R(sub e) relation for red galaxies
Hubble Space Telescope Observations of Field Ultracool Dwarfs at High Galactic Latitude
We present a sample of 17 newly discovered ultracool dwarf candidates later
than ~M8, drawn from 231.90 arcmin2 of {\it Hubble Space Telescope} Wide Field
Camera 3 infrared imaging. By comparing the observed number counts for
17.5<J_125<25.5 AB mag to an exponential disk model, we estimate a vertical
scale height of z_scl=290 +- 25 (random) +- 30 (systematic) pc for a binarity
fraction of f_b=0. While our estimate is roughly consistent with published
results, we suggest that the differences can be attributed to sample
properties, with the present sample containing far more substellar objects than
previous work. We predict the object counts should peak at J_{125}~24 AB mag
due to the exponentially-declining number density at the edge of the disc. We
conclude by arguing that trend in scale height with spectral type may breakdown
for brown dwarfs since they do not settle onto the main sequence.Comment: 9 pages, 6 figures, 3 tables, accepted to ApJ (v2 is consistent with
Referee changes
Do the Most Massive Black Holes at z = 2 Grow via Major Mergers?
The most frequently proposed model for the origin of quasars holds that the
high accretion rates seen in luminous active galactic nuclei are primarily
triggered during major mergers between gas-rich galaxies. While plausible for
decades, this model has only begun to be tested with statistical rigor in the
past few years. Here we report on a Hubble Space Telescope study to test this
hypothesis for quasars with high super-massive black hole masses
(), which dominate cosmic black hole
growth at this redshift. We compare Wide Field Camera 3 (rest-frame
-band) imaging of 19 point source-subtracted quasar hosts to a matched
sample of 84 inactive galaxies, testing whether the quasar hosts have greater
evidence for strong gravitational interactions. Using an expert ranking
procedure, we find that the quasar hosts are uniformly distributed within the
merger sequence of inactive galaxies, with no preference for quasars in
high-distortion hosts. Using a merger/non-merger cutoff approach, we recover
distortion fractions of for quasar hosts and
for inactive galaxies (distribution modes, 68%
confidence intervals), with both measurements subjected to the same
observational conditions and limitations. The slight enhancement in distorted
fraction for quasar hosts over inactive galaxies is not significant, with a
probability that the quasar fraction is higher of
(), in line with
results for lower mass and lower AGN. We find no evidence that major
mergers are the primary triggering mechanism for the massive quasars that
dominate accretion at the peak of cosmic quasar activity.Comment: 30 pages, accepted for publication to Ap
Limits to Rest-Frame Ultraviolet Emission From Far-Infrared-Luminous z~6 Quasar Hosts
We report on a Hubble Space Telescope search for rest-frame ultraviolet
emission from the host galaxies of five far-infrared-luminous
quasars and the hot-dust free quasar SDSS J0005-0006. We perform 2D
surface brightness modeling for each quasar using a Markov-Chain Monte-Carlo
estimator, to simultaneously fit and subtract the quasar point source in order
to constrain the underlying host galaxy emission. We measure upper limits for
the quasar host galaxies of mag and mag, corresponding to
stellar masses of . These stellar mass limits are
consistent with the local - relation. Our flux limits
are consistent with those predicted for the UV stellar populations of
host galaxies, but likely in the presence of significant dust
( mag). We also detect a total of up
to 9 potential quasar companion galaxies surrounding five of the six
quasars, separated from the quasars by 1.4''-3.2'', or 8.4-19.4 kpc, which may
be interacting with the quasar hosts. These nearby companion galaxies have UV
absolute magnitudes of -22.1 to -19.9 mag, and UV spectral slopes of
-2.0 to -0.2, consistent with luminous star-forming galaxies at .
These results suggest that the quasars are in dense environments typical of
luminous galaxies. However, we cannot rule out the possibility that
some of these companions are foreground interlopers. Infrared observations with
the James Webb Space Telescope will be needed to detect the quasar
host galaxies and better constrain their stellar mass and dust content.Comment: 22 pages, 13 figures. Accepted for publication in Ap
The Hubble Space Telescope Wide Field Camera 3 Early Release Science data: Panchromatic Faint Object Counts for 0.2-2 microns wavelength
We describe the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) Early
Release Science (ERS) observations in the Great Observatories Origins Deep
Survey (GOODS) South field. The new WFC3 ERS data provide calibrated, drizzled
mosaics in the UV filters F225W, F275W, and F336W, as well as in the near-IR
filters F098M (Ys), F125W (J), and F160W (H) with 1-2 HST orbits per filter.
Together with the existing HST Advanced Camera for Surveys (ACS) GOODS-South
mosaics in the BViz filters, these panchromatic 10-band ERS data cover 40-50
square arcmin at 0.2-1.7 {\mu}m in wavelength at 0.07-0.15" FWHM resolution and
0.090" Multidrizzled pixels to depths of AB\simeq 26.0-27.0 mag (5-{\sigma})
for point sources, and AB\simeq 25.5-26.5 mag for compact galaxies.
In this paper, we describe: a) the scientific rationale, and the data taking
plus reduction procedures of the panchromatic 10-band ERS mosaics; b) the
procedure of generating object catalogs across the 10 different ERS filters,
and the specific star-galaxy separation techniques used; and c) the reliability
and completeness of the object catalogs from the WFC3 ERS mosaics. The
excellent 0.07-0.15" FWHM resolution of HST/WFC3 and ACS makes star- galaxy
separation straightforward over a factor of 10 in wavelength to AB\simeq 25-26
mag from the UV to the near-IR, respectively.Comment: 51 pages, 71 figures Accepted to ApJS 2011.01.2
On the observability of individual Population III stars and their stellar-mass black hole accretion disks through cluster caustic transits
Large scale structure and cosmolog
Major Mergers Are Not the Dominant Trigger for High-accretion AGNs at z âŒÂ 2
Research over the past decade has shown diminishing evidence for major galaxy mergers being a dominant mechanism for the growth of supermassive black holes (BHs) in galaxies and the triggering of optically or X-ray- selected active galactic nuclei (AGNs). For the first time we test whether such a connection exists at least in the most âplausibleâ part of parameter space: the highest specific accretion rate broad-line AGNs at the peak epoch of BH activity around z = 2. To that end we analyze two samplesâ21 AGNs with L/L edd > 0.7 and 92 stellar mass- and redshift-matched inactive galaxiesâobserved with HST/WFC3. We remove the AGN point sources from their host galaxies and avoid bias in visual classification by adding and then subtracting mock point sources to and from the comparison galaxies, producing matched residual structures for both sets. The resulting samples are joined and visually ranked according to distortion strength by 10 experts. The ensuing individual rankings are combined into a consensus sequence and from this we derive the merger fractions for both samples. With the merger fractions f m,agn = 0.24 ± 0.09 for the AGN host galaxy sample and f m,ina = 0.19 ± 0.04 for the inactive galaxies, we find no significant difference between the samples. This finding is consistent with previous studies for different AGN populations, and we conclude that even BH growth at the highest specific accretion rates and at the peak of cosmic AGN activity is not predominantly caused by major mergers