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Audrey Galametz,
Andrea Grazian,
Adriano Fontana,
Henry C. Ferguson,
M. L. N. Ashby,
Guillermo Barro,
Marco Castellano,
Tomas Dahlen,
Jennifer L. Donley,
Sandy M. Faber, [......],
Ray A. Lucas,
Diego Paris,
Laura Pentericci,
Paola Santini,
Chris Simpson,
Veronica Sommariva,
Thomas Targett,
Benjamin J. Weiner,
Stijn Wuyts,
the CANDELS team
[show abstract]
[hide abstract]
ABSTRACT: We present the multiwavelength - ultraviolet to mid-infrared - catalog of the
UKIDSS Ultra-Deep Survey (UDS) field observed as part of the Cosmic Assembly
Near-infrared Deep Extragalactic Legacy Survey (CANDELS). Based on publicly
available data, the catalog includes: the CANDELS data from the Hubble Space
Telescope (near-infrared WFC3 F125W and F160W data and visible ACS F606W and
F814W data), u-band data from CFHT/Megacam, B, V, Rc, i' and z' band data from
Subaru/Suprime-Cam, Y and Ks band data from VLT/HAWK-I, J, H and K bands data
from UKIDSS (Data Release 8), and Spitzer/IRAC data (3.6, 4.5 from SEDS, 5.8
and 8.0um from SpUDS). The present catalog is F160W-selected and contains 35932
sources over an area of 201.7 square arcmin and includes radio and X-ray
detected sources and spectroscopic redshifts available for 210 sources.
05/2013;
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Robert Bassett,
Casey Papovich,
Jennifer M. Lotz,
Eric F. Bell,
Steven L. Finkelstein,
Jeffrey A. Newman,
Kim-Vy Tran,
Omar Almaini,
Caterina Lani,
Michael Cooper,
Darren Croton,
Avishai Dekel,
Henry C. Ferguson,
Dale D. Kocevski,
Anton M. Koekemoer, David C. Koo,
Elizabeth J. McGrath,
Daniel H. McIntosh,
Risa H. Wechsler
[show abstract]
[hide abstract]
ABSTRACT: We study the environmental dependence of color, stellar mass, and morphology
by comparing galaxies in a forming cluster to those in the field at z = 1:6
with Hubble Space Telescope near-infrared imaging in the CANDELS/UDS field. We
quantify the morphology of the galaxies using the effective radius, reff, and
S\'ersic index, n. In both the cluster and field, approximately half of the
bulge-dominated galaxies (n > 2) reside on the red sequence of the
color-magnitude diagram, and most disk-dominated galaxies (n < 2) have colors
expected for star-forming galaxies. There is weak evidence that cluster
galaxies have redder rest-frame U - B colors and higher stellar masses compared
to the field. Star-forming galaxies in both the cluster and field show no
significant differences in their morphologies. In contrast, there is evidence
that quiescent galaxies in the cluster have larger median effective radii and
smaller S\'ersic indices compared to the field with a significance of 2?. These
differences are most pronounced for galaxies at clustercentric distances 1 Mpc
< Rproj < 1.5 Mpc, which have low S\'ersic indices and possibly larger
effective radii, more consistent with star-forming galaxies at this epoch and
in contrast to other quiescent galaxies. We argue that star-forming galaxies
are processed under the influence of the cluster environment at distances
greater than the cluster-halo virial radius. Our results are consistent with
models where gas accretion onto these galaxies is suppressed from processes
associated with the cluster environment.
05/2013;
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F. S. Liu,
Yicheng Guo, David C. Koo,
Jonathan R. Trump,
Guillermo Barro,
Hassen Yesuf,
S. M. Faber,
M. Giavalisco,
P. Cassata,
A. M. Koekemoer, [......],
M. Castellano,
Edmond Cheung,
Shude Mao,
X. Y. Xia,
Norman A. Grogin,
Nimish P. Hathi,
Kuang-Han Huang,
Dale Kocevski,
Elizabeth J. McGrath,
Stijn Wuyts
[show abstract]
[hide abstract]
ABSTRACT: We have made a serendipitous discovery of a massive cD galaxy at z=1.096 in a
candidate rich cluster in the HUDF area of GOODS-South. This brightest cluster
galaxy is the most distant cD galaxy confirmed to date. Ultra-deep HST/WFC3
images reveal an extended envelope starting from ~10 kpc and reaching ~70 kpc
in radius along the semi-major axis. The spectral energy distributions indicate
that both its inner component and outer envelope are composed of an old,
passively-evolving stellar population. The cD galaxy lies on the same mass-size
relation as the bulk of quiescent galaxies at similar redshifts. The cD galaxy
has a higher stellar mass surface density but a similar velocity dispersion to
those of more-massive, nearby cDs. If the cD galaxy is one of the progenitors
of today's more massive cDs, its size and stellar mass have had to increase on
average by factors of $3.4\pm1.1$ and $3.3\pm1.3$ over the past ~8 Gyrs,
respectively. Such increases in size and stellar mass without being accompanied
by significant increases in velocity dispersion are consistent with
evolutionary scenarios driven by both major and minor dry mergers. If such cD
envelopes originate from dry mergers, our discovery of even one example proves
that some BCGs entered the dry merger phase at epochs earlier than z=1. Our
data match theoretical models which predict that the continuance of dry mergers
at z<1 can result in structures similar to those of massive cD galaxies seen
today. Moreover, our discovery is a surprise given that the extreme depth of
the HUDF is essential to reveal such an extended cD envelope at z>1 and, yet,
the HUDF covers only a minuscule region of sky. Adding that cDs are rare, Our
serendipitous discovery hints that such cDs may be more common than expected.
[Abridged]
The Astrophysical Journal 04/2013; · 6.02 Impact Factor
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Jonathan R. Trump,
Nicholas P. Konidaris,
Guillermo Barro, David C. Koo,
Dale D. Kocevski,
Stephanie Juneau,
Benjamin J. Weiner,
S. M. Faber,
Ian S. McLean,
Renbin Yan,
Pablo G. Perez-Gonzalez,
Victor Villar
[show abstract]
[hide abstract]
ABSTRACT: We present some of the first science data with the new Keck/MOSFIRE
instrument to test the effectiveness of different AGN/SF diagnostics at z~1.5.
MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S
field, resulting in two hour exposures of 36 emission-line galaxies. We compare
X-ray data with the traditional emission-line ratio diagnostics and the
alternative mass-excitation and color-excitation diagrams, combining new
MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST
survey) and multiwavelength photometry. We demonstrate that a high [OIII]/Hb
ratio is insufficient as an AGN indicator at z>1. For the four X-ray detected
galaxies, the classic diagnostics ([OIII]/Hb vs. [NII]/Ha and [SII]/Ha) remain
consistent with X-ray AGN/SF classification. The X-ray data also suggest that
"composite" galaxies (with intermediate AGN/SF classification) host bona-fide
AGNs. Nearly 2/3 of the z~1.5 emission-line galaxies have nuclear activity
detected by either X-rays or the classic diagnostics. Compared to the X-ray and
line ratio classifications, the mass-excitation method remains effective at
z>1, but we show that the color-excitation method requires a new calibration to
successfully identify AGNs at these redshifts.
12/2012;
-
[show abstract]
[hide abstract]
ABSTRACT: We present the first quantified, statistical map of broad-line active
galactic nucleus (AGN) frequency with host galaxy color and stellar mass in
nearby (0.01 < z < 0.11) galaxies. Aperture photometry and z-band concentration
measurements from the Sloan Digital Sky Survey (SDSS) are used to dis- entangle
AGN and galaxy emission, resulting in estimates of uncontaminated galaxy
rest-frame color, luminosity, and stellar mass. Broad-line AGNs are distributed
throughout the blue cloud and green valley at a given stellar mass, and are
much rarer in quiescent (red sequence) galaxies. This is in contrast to the
published host galaxy properties of weaker narrow-line AGNs, indicating that
broad-line AGNs occur during a different phase in galaxy evolution. More
luminous broad-line AGNs have bluer host galaxies, even at fixed mass,
suggesting that the same processes that fuel nuclear activity also efficiently
form stars. The data favor processes that simultaneously fuel both star
formation activity and rapid supermassive black hole accretion. If AGNs cause
feedback on their host galaxies in the nearby universe, the evidence of
galaxy-wide quenching must be delayed until after the broad-line AGN phase.
12/2012;
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Edmond Cheung,
S. M. Faber, David C. Koo,
Aaron A. Dutton,
Luc Simard,
Elizabeth J. McGrath,
J. -S. Huang,
Eric F. Bell,
Avishai Dekel,
Jerome J. Fang, [......],
Susan A. Kassin,
Dale D. Kocevski,
Anton M. Koekemoer,
Lihwai Lin,
Jennifer M. Lotz,
J. A. Newman,
Andrew C. Phillips,
D. J. Rosario,
Benjamin J. Weiner,
C. N. A. Willmer
[show abstract]
[hide abstract]
ABSTRACT: The shutdown of star formation in galaxies is generally termed `quenching'.
Although quenching may occur through a variety of processes, the exact
mechanism(s) that is in fact responsible for quenching is still in question.
This paper addresses quenching by searching for traces of possible quenching
processes through their effects on galaxy structural parameters such as surface
stellar mass density and Sersic index (n). We analyze the rest-frame U-B color
correlations versus these structural parameters using a sample of galaxies in
the redshift range 0.5< z<0.8 from the DEEP2/AEGIS survey. We find that Sersic
index (n) has the smallest overlap region among all tested parameters and
resembles a step-function with a threshold value of n=2.3. There exists,
however, a significant population of outliers with blue colors yet high n
values that seem to contradict this behavior. We hypothesize that their Sersic
values may be distorted by bursts of star formation, AGNs, and/or poor fits,
leading us to consider central surface stellar mass density as an alternative
to Sersic index. Not only does it correct the outliers, it also forms a tight
relationship with color, suggesting that the innermost structure of galaxies is
most physically linked with quenching. Furthermore, at z~0.65, the majority of
the blue cloud galaxies cannot simply fade onto the red sequence since their
GIM2D bulge masses are only half as large on average as the bulge masses of
similar red sequence galaxies, thus demonstrating that stellar mass must
absolutely increase at the centers of galaxies as they quench. We discuss a
two-stage model for quenching in which galaxy star formation rates are
controlled by their dark halos while they are still in the blue cloud and a
second quenching process sets in later, associated with the central stellar
mass build-up.
10/2012;
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Susan A. Kassin,
Benjamin J. Weiner,
S. M. Faber,
Jonathan P. Gardner,
C. N. A. Willmer,
Alison L. Coil,
Michael C. Cooper,
Julien Devriendt,
Aaron A. Dutton,
Puragra Guhathakurta, David C. Koo,
A. J. Metevier,
Kai G. Noeske,
Joel R. Primack
[show abstract]
[hide abstract]
ABSTRACT: We present evidence from a sample of 544 galaxies from the DEEP2 Survey for
evolution of the internal kinematics of blue galaxies with stellar masses
ranging 8.0 < log M* (M_Sun) < 10.7 over 0.2<z<1.2. DEEP2 provides galaxy
spectra and Hubble imaging from which we measure emission-line kinematics and
galaxy inclinations, respectively. Our large sample allows us to overcome
scatter intrinsic to galaxy properties in order to examine trends in
kinematics. We find that at a fixed stellar mass galaxies systematically
decrease in disordered motions and increase in rotation velocity and potential
well depth with time. Massive galaxies are the most well-ordered at all times
examined, with higher rotation velocities and less disordered motions than less
massive galaxies. We quantify disordered motions with an integrated gas
velocity dispersion corrected for beam smearing (sigma_g). It is unlike the
typical pressure-supported velocity dispersion measured for early type galaxies
and galaxy bulges. Because both seeing and the width of our spectral slits
comprise a significant fraction of the galaxy sizes, sigma_g integrates over
velocity gradients on large scales which can correspond to non-ordered gas
kinematics. We compile measurements of galaxy kinematics from the literature
over 1.2<z<3.8 and do not find any trends with redshift, likely for the most
part because these datasets are biased toward the most highly star-forming
systems. In summary, over the last ~8 billion years since z=1.2, blue galaxies
evolve from disordered to ordered systems as they settle to become the
rotation-dominated disk galaxies observed in the Universe today, with the most
massive galaxies being the most evolved at any time.
07/2012;
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Guillermo Barro,
S. M. Faber,
Pablo G. Perez-Gonzalez, David C. Koo,
Christina C. Williams,
Dale D. Kocevski,
Jonathan R. Trump,
Mark Mozena,
Elizabeth McGrath,
Arjen van der Wel, [......],
Kuang-Han Huang,
Anton M. Koekemoer,
Jeyhan S. Kartaltepe,
Kyoung-Soo Lee,
Jeffrey A. Newman,
Lauren A. Porter,
Joel R. Primack,
Russell E. Ryan,
David Rosario,
Rachel S. Somerville
[show abstract]
[hide abstract]
ABSTRACT: We combine high-resolution HST/WFC3 images with multi-wavelength photometry
to track the evolution of structure and activity of massive (log(M*) > 10)
galaxies at redshifts z = 1.4 - 3 in two fields of the Cosmic Assembly
Near-infrared Deep Extragalactic Legacy Survey (CANDELS). We detect compact,
star-forming galaxies (cSFGs) whose number densities, masses, sizes, and star
formation rates qualify them as likely progenitors of compact, quiescent,
massive galaxies (cQGs) at z = 1.5 - 3. At z > 2 most cSFGs have specific
star-formation rates (sSFR = 10^-9 yr^-1) half that of typical, massive SFGs at
the same epoch, and host X-ray luminous AGN 30 times (~30%) more frequently.
These properties suggest that cSFGs are formed by gas-rich processes (mergers
or disk-instabilities) that induce a compact starburst and feed an AGN, which,
in turn, quench the star formation on dynamical timescales (few 10^8 yr). The
cSFGs are continuously being formed at z = 2 - 3 and fade to cQGs by z = 1.5.
After this epoch, cSFGs are rare, thereby truncating the formation of new cQGs.
Meanwhile, down to z = 1, existing cQGs continue to enlarge to match local QGs
in size, while less-gas-rich mergers and other secular mechanisms shepherd
(larger) SFGs as later arrivals to the red sequence. In summary, we propose two
evolutionary scenarios of QG formation: an early (z > 2), fast-formation path
of rapidly-quenched cSFGs that evolve into cQGs that later enlarge within the
quiescent phase, and a slow, late-arrival (z < 2) path for SFGs to form QGs
without passing through a compact state.
06/2012;
-
Brian F. Gerke,
Jeffrey A. Newman,
Marc Davis,
Alison L. Coil,
Michael C. Cooper,
Aaron A. Dutton,
S. M. Faber,
Puragra Guhathakurta,
Nicholas Konidaris, David C. Koo,
Lihwai Lin,
Kai Noeske,
Andrew C. Phillips,
David J. Rosario,
Benjamin J. Weiner,
Christopher N. A. Willmer,
Renbin Yan
[show abstract]
[hide abstract]
ABSTRACT: We present a public catalog of galaxy groups constructed from the
spectroscopic sample of galaxies in the fourth data release from the DEEP2
Galaxy Redshift Survey, including the Extended Groth Strip (EGS). The catalog
contains 1165 groups with two or more members in the EGS over the redshift
range 0<z<1.5 and 1295 groups at z>0.6 in the rest of DEEP2. 25% of EGS
galaxies and 14% of high-z DEEP2 galaxies are assigned to galaxy groups. The
groups were detected using the Voronoi-Delaunay Method, after it has been
optimized on mock DEEP2 catalogs following similar methods to those employed in
Gerke et al. (2005). In the optimization effort, we have taken particular care
to ensure that the mock catalogs resemble the data as closely as possible, and
we have fine-tuned our methods separately on mocks constructed for the EGS and
the rest of DEEP2. We have also probed the effect of the assumed cosmology on
our inferred group-finding efficiency by performing our optimization on three
different mock catalogs with different background cosmologies, finding large
differences in the group-finding success we can achieve for these different
mocks. Using the mock catalog whose background cosmology is most consistent
with current data, we estimate that the DEEP2 group catalog is 72% complete and
61% pure (74% and 67% for the EGS) and that the group-finder correctly
classifies 70% of galaxies that truly belong to groups, with an additional 46%
of interloper galaxies contaminating the catalog (66% and 43% for the EGS).
(Abridged)
03/2012;
-
Jeffrey A. Newman,
Michael C. Cooper,
Marc Davis,
S. M. Faber,
Alison L. Coil,
Puragra Guhathakurta, David C. Koo,
Andrew C. Phillips,
Charlie Conroy,
Aaron A. Dutton, [......],
Nick Kaiser,
Evan N. Kirby,
Brian C. Lemaux,
Lihwai Lin,
Jennifer M. Lotz,
Gerard A. Luppino,
Christian Marinoni,
Daniel J. Matthews,
Anne Metevier,
Ricardo P. Schiavon
[show abstract]
[hide abstract]
ABSTRACT: We describe the design and data sample from the DEEP2 Galaxy Redshift Survey,
the densest and largest precision-redshift survey of galaxies at z ~ 1
completed to date. The survey has conducted a comprehensive census of massive
galaxies, their properties, environments, and large-scale structure down to
absolute magnitude M_B = -20 at z ~ 1 via ~90 nights of observation on the
DEIMOS spectrograph at Keck Observatory. DEEP2 covers an area of 2.8 deg^2
divided into four separate fields, observed to a limiting apparent magnitude of
R_AB=24.1. Objects with z < 0.7 are rejected based on BRI photometry in three
of the four DEEP2 fields, allowing galaxies with z > 0.7 to be targeted ~2.5
times more efficiently than in a purely magnitude-limited sample. Approximately
sixty percent of eligible targets are chosen for spectroscopy, yielding nearly
53,000 spectra and more than 38,000 reliable redshift measurements. Most of the
targets which fail to yield secure redshifts are blue objects that lie beyond z
~ 1.45. The DEIMOS 1200-line/mm grating used for the survey delivers high
spectral resolution (R~6000), accurate and secure redshifts, and unique
internal kinematic information. Extensive ancillary data are available in the
DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into
one of the richest multiwavelength regions on the sky. DEEP2 surpasses other
deep precision-redshift surveys at z ~ 1 in terms of galaxy numbers, redshift
accuracy, sample number density, and amount of spectral information. We also
provide an overview of the scientific highlights of the DEEP2 survey thus far.
This paper is intended as a handbook for users of the DEEP2 Data Release 4,
which includes all DEEP2 spectra and redshifts, as well as for the
publicly-available DEEP2 DEIMOS data reduction pipelines. [Abridged]
03/2012;
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Stijn Wuyts,
Natascha M. Forster Schreiber,
Reinhard Genzel,
Yicheng Guo,
Guillermo Barro,
Eric F. Bell,
Avishai Dekel,
Sandra M. Faber,
Henry C. Ferguson,
Mauro Giavalisco, [......], David C. Koo,
Jennifer Lotz,
Dieter Lutz,
Elizabeth McGrath,
Jeffrey A. Newman,
David Rosario,
Amelie Saintonge,
Linda J. Tacconi,
Benjamin J. Weiner,
Arjen van der Wel
[show abstract]
[hide abstract]
ABSTRACT: We perform a detailed analysis of the resolved colors and stellar populations
of a complete sample of 323 star-forming galaxies at 0.5 < z < 1.5, and 326
star-forming galaxies at 1.5 < z < 2.5 in the ERS and CANDELS-Deep region of
GOODS-South. Galaxies were selected to be more massive than 10^10 Msun and have
specific star formation rates above 1/t_H. We model the 7-band optical ACS +
near-IR WFC3 spectral energy distributions of individual bins of pixels,
accounting simultaneously for the galaxy-integrated photometric constraints
available over a longer wavelength range. We analyze variations in rest-frame
color, stellar surface mass density, age, and extinction as a function of
galactocentric radius and local surface brightness/density, and measure
structural parameters on luminosity and stellar mass maps. We find evidence for
redder colors, older stellar ages, and increased dust extinction in the nuclei
of galaxies. Big star-forming clumps seen in star formation tracers are less
prominent or even invisible on the inferred stellar mass distributions.
Off-center clumps contribute up to ~20% to the integrated SFR, but only 7% or
less to the integrated mass of all massive star-forming galaxies at z ~ 1 and z
~ 2, with the fractional contributions being a decreasing function of
wavelength used to select the clumps. The stellar mass profiles tend to have
smaller sizes and M20 coefficients, and higher concentration and Gini
coefficients than the light distribution. Our results are consistent with an
inside-out disk growth scenario with brief (100 - 200 Myr) episodic local
enhancements in star formation superposed on the underlying disk.
Alternatively, the young ages of off-center clumps may signal inward clump
migration, provided this happens efficiently on the order of an orbital
timescale.
03/2012;
-
Roger L. Griffith,
Michael C. Cooper,
Jeffrey A. Newman,
Leonidas A. Moustakas,
Daniel Stern,
Julia M. Comerford,
Marc Davis,
Jennifer M. Lotz,
Marco Barden,
Christopher J. Conselice, [......],
S. M. Faber,
J. Davy Kirkpatrick,
Anton M. Koekemoer, David C. Koo,
Kai G. Noeske,
Nick Scoville,
Kartik Sheth,
Patrick Shopbell,
Christopher N. A. Willmer,
Benjamin Weiner
[show abstract]
[hide abstract]
ABSTRACT: We present the Advanced Camera for Surveys General Catalog (ACS-GC), a
photometric and morphological database using publicly available data obtained
with the Advanced Camera for Surveys (ACS) instrument on the Hubble Space
Telescope. The goal of the ACS-GC database is to provide a large statistical
sample of galaxies with reliable structural and distance measurements to probe
the evolution of galaxies over a wide range of look-back times. The ACS-GC
includes approximately 470,000 astronomical sources (stars + galaxies) derived
from the AEGIS, COSMOS, GEMS, and GOODS surveys. Galapagos was used to
construct photometric (SExtractor) and morphological (Galfit) catalogs. The
analysis assumes a single S\'ersic model for each object to derive quantitative
structural parameters. We include publicly available redshifts from the DEEP2,
COMBO-17, TKRS, PEARS, ACES, CFHTLS,and zCOSMOS surveys to supply redshifts
(spectroscopic and photometric) for a considerable fraction (~74%) of the
imaging sample. The ACS-GC includes color postage stamps, Galfit residual
images, and photometry, structural parameters, and redshifts combined into a
single catalog.
03/2012;
-
Joanna Woo,
Avishai Dekel,
S. M. Faber,
Kai Noeske, David C. Koo,
Brian F. Gerke,
Michael C. Cooper,
Samir Salim,
Aaron A. Dutton,
Jeffrey Newman,
Benjamin J. Weiner,
Kevin Bundy,
Christopher N. A. Willmer,
Marc Davis,
Renbin Yan
[show abstract]
[hide abstract]
ABSTRACT: We study the dependence of star-formation quenching on galaxy mass and
environment, in the SDSS (z~0.1) and the AEGIS (z~1). It is crucial that we
define quenching by low star-formation rate rather than by red colour, given
that one third of the red galaxies are star forming. We address stellar mass
M*, halo mass Mh, density over the nearest N neighbours deltaN, and distance to
the halo centre D. The fraction of quenched galaxies appears more strongly
correlated with Mh at fixed M* than with M* at fixed Mh, while for satellites
quenching also depends on D. We present the M*-Mh relation for centrals at z~1.
At z~1, the dependence of quenching on M* at fixed Mh is somewhat more
pronounced than at z~0, but the quenched fraction is low (10%) and the haloes
are less massive. For satellites, M*-dependent quenching is noticeable at high
D, suggesting a quenching dependence on sub-halo mass for recently captured
satellites. At small D, where satellites likely fell in more than a few Gyr
ago, quenching strongly depends on Mh, and not on M*. The Mh-dependence of
quenching is consistent with theoretical wisdom where virial shock heating in
massive haloes shuts down accretion and triggers ram-pressure stripping,
causing quenching. The interpretation of deltaN is complicated by the fact that
it depends on the number of observed group members compared to N, motivating
the use of D as a better measure of local environment.
03/2012;
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Karina I. Caputi,
James S. Dunlop,
Ross J. McLure,
Jiasheng Huang,
Giovanni G. Fazio,
Matthew L. N. Ashby,
Marco Castellano,
Adriano Fontana,
Michele Cirasuolo,
Omar Almaini, [......],
Sandra M. Faber,
Henry C. Ferguson,
Mauro Giavalisco,
Norman A. Grogin,
Dale D. Kocevski,
Anton M. Koekemoer, David C. Koo,
Kamson Lai,
Jeffrey A. Newman,
Rachel S. Somerville
[show abstract]
[hide abstract]
ABSTRACT: We have analysed a sample of 25 extremely red H-[4.5]>4 galaxies, selected
using 4.5 micron data from the Spitzer SEDS survey and deep H-band data from
the Hubble Space Telescope (HST) CANDELS survey, over ~180 square arcmin of the
UKIDSS Ultra Deep Survey (UDS) field. Our aim is to investigate the nature of
this rare population of mid-infrared (mid-IR) sources that display such extreme
near-to-mid-IR colours. Using up to 17-band photometry (U through 8.0 microns),
we have studied in detail their spectral energy distributions, including
possible degeneracies in the photometric redshift/internal extinction
(zphot-Av) plane. Our sample appears to include sources of very different
nature. Between 45% and 75% of them are dust-obscured, massive galaxies at
3<zphot<5. All of the 24 micron-detected sources in our sample are in this
category. Two of these have S(24 micron)>300 microJy, which at 3<zphot<5
suggests that they probably host a dust-obscured active galactic nucleus (AGN).
Our sample also contains four highly obscured (Av>5) sources at zphot<1.
Finally, we analyse in detail two zphot~6 galaxy candidates, and discuss their
plausibility and implications. Overall, our red galaxy sample contains the tip
of the iceberg of a larger population of z>3 galaxies to be discovered with the
future James Webb Space Telescope.
02/2012;
-
[show abstract]
[hide abstract]
ABSTRACT: We construct a fully self-consistent mass model for the lens galaxy J2141 at
z=0.14, and use it to improve on previous studies by modelling its
gravitational lensing effect, gas rotation curve and stellar kinematics
simultaneously. We adopt a very flexible axisymmetric mass model constituted by
a generalized NFW dark matter halo and a stellar mass distribution obtained by
deprojecting the MGE fit to the high-resolution K'-band LGSAO imaging data of
the galaxy, with the (spatially constant) M/L ratio as a free parameter. We
model the stellar kinematics by solving the anisotropic Jeans equations. We
find that the inner logarithmic slope of the dark halo is weakly constrained
(gamma = 0.82^{+0.65}_{-0.54}), and consistent with an unmodified NFW profile.
We infer the galaxy to have (i) a dark matter fraction within 2.2 disk radii of
0.28^{+0.15}_{-0.10}, independent of the galaxy stellar population, implying a
maximal disk for J2141; (ii) an apparently uncontracted dark matter halo, with
concentration c_{-2} = 7.7_{-2.5}^{+4.2} and virial velocity v_{vir} =
242_{-39}^{+44} km/s, consistent with LCDM predictions; (iii) a slightly oblate
halo (q_h = 0.75^{+0.27}_{-0.16}), consistent with predictions from
baryon-affected models. Comparing the stellar mass inferred from the combined
analysis (log_{10} Mstar/Msun = 11.12_{-0.09}^{+0.05}) with that inferred from
SPS modelling of the galaxies colours, and accounting for a cold gas fraction
of 20+/-10%, we determine a preference for a Chabrier IMF over Salpeter IMF by
a Bayes factor of 5.7 (substantial evidence). We infer a value beta_{z} = 1 -
sigma^2_{z}/sigma^2_{R} = 0.43_{-0.11}^{+0.08} for the orbital anisotropy
parameter in the meridional plane, in agreement with most studies of local disk
galaxies, and ruling out at 99% CL that the dynamics of this system can be
described by a two-integral distribution function. [Abridged]
01/2012;
-
[show abstract]
[hide abstract]
ABSTRACT: We present gravitational lens models for 20 strong gravitational lens systems
observed as part of the Sloan WFC Edge-on Late-type Lens Survey (SWELLS)
project. Fifteen of the lenses are taken from paper I while five are newly
discovered systems. The systems are galaxy-galaxy lenses where the foreground
deflector has an inclined disc, with a wide range of morphological types, from
late-type spiral to lenticular. For each system, we compare the total mass
inside the critical curve inferred from gravitational lens modelling to the
stellar mass inferred from stellar population synthesis (SPS) models, computing
the stellar mass fraction f* = M(SPS)/M(lens). We find that, for the lower mass
SWELLS systems, adoption of a Salpeter stellar initial mass function (IMF)
leads to estimates of f* that exceed 1. This is unphysical, and provides strong
evidence against the Salpeter IMF being valid for these systems. Taking the
lower mass end of the SWELLS sample sigma(SIE) < 230 km/s, we find that the IMF
is lighter (in terms of stellar mass-to-light ratio) than Salpeter with 98%
probability, and consistent with the Chabrier IMF and IMFs between the two.
This result is consistent with previous studies of spiral galaxies based on
independent techniques. In combination with recent studies of massive
early-type galaxies that have favoured a heavier Salpeter-like IMF, this result
strengthens the evidence against a universal stellar IMF.
01/2012;
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Jonathan R Trump,
Benjamin J Weiner,
Claudia Scarlata,
Dale D Kocevski,
Eric F Bell,
Elizabeth J Mcgrath, David C Koo,
S M Faber,
Elise S Laird,
Mark Mozena, [......],
Norman A Grogin,
Nimish P Hathi,
Stéphanie Juneau,
Jeyhan S Kartaltepe,
Anton M Koekemoer,
Kirpal Nandra,
Jeffrey A Newman,
Steven A Rodney,
Amber N Straughn,
Harry I Teplitz
[show abstract]
[hide abstract]
ABSTRACT: We present Hubble Space Telescope Wide Field Camera 3 (WFC3) slitless grism spectroscopy of 28 emission-line galaxies at z ∼ 2, in the GOODS-S region of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. The high sensitivity of these grism observations, with >1σ detections of emission lines to f > 2.5 × 10 −18 erg s −1 cm −2 , means that the galaxies in the sample are typically ∼7 times less massive (median M * = 10 9.5 M) than previously studied z ∼ 2 emission-line galaxies. Despite their lower mass, the galaxies have [O iii]/Hβ ratios which are very similar to previously studied z ∼ 2 galaxies and much higher than the typical emission-line ratios of local galaxies. The WFC3 grism allows for unique studies of spatial gradients in emission lines, and we stack the two-dimensional spectra of the galaxies for this purpose. In the stacked data the [O iii] emission line is more spatially concentrated than the Hβ emission line with 98.1% confidence. We additionally stack the X-ray data (all sources are individually undetected), and find that the average L [O iii] /L 0.5–10 keV ratio is intermediate between typical z ∼ 0 obscured active galaxies and star-forming galaxies. Together the compactness of the stacked [O iii] spatial profile and the stacked X-ray data suggest that at least some of these low-mass, low-metallicity galaxies harbor weak active galactic nuclei.
The Astrophysical Journal 12/2011; 743(144). · 6.02 Impact Factor
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Anton M. Koekemoer,
S. M. Faber,
Henry C. Ferguson,
Norman A. Grogin,
Dale D. Kocevski, David C. Koo,
Kamson Lai,
Jennifer M. Lotz,
Ray A. Lucas,
Elizabeth J. McGrath, [......],
Carolin Villforth,
Cory R. Wagner,
Pat Wandro,
Risa H. Wechsler,
Benjamin J. Weiner,
Tommy Wiklind,
Vivienne Wild,
Grant Wilson,
Stijn Wuyts,
and Min S. Yun
[show abstract]
[hide abstract]
ABSTRACT: This paper describes the Hubble Space Telescope imaging data products and data reduction procedures for the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). This survey is designed to document the evolution of galaxies and black holes at z 1.5-8, and to study Type Ia supernovae at z > 1.5. Five premier multi-wavelength sky regions are selected, each with extensive multi-wavelength observations. The primary CANDELS data consist of imaging obtained in the Wide Field Camera 3 infrared channel (WFC3/IR) and the WFC3 ultraviolet/optical channel, along with the Advanced Camera for Surveys (ACS). The CANDELS/Deep survey covers ~125 arcmin2 within GOODS-N and GOODS-S, while the remainder consists of the CANDELS/Wide survey, achieving a total of ~800 arcmin2 across GOODS and three additional fields (Extended Groth Strip, COSMOS, and Ultra-Deep Survey). We summarize the observational aspects of the survey as motivated by the scientific goals and present a detailed description of the data reduction procedures and products from the survey. Our data reduction methods utilize the most up-to-date calibration files and image combination procedures. We have paid special attention to correcting a range of instrumental effects, including charge transfer efficiency degradation for ACS, removal of electronic bias-striping present in ACS data after Servicing Mission 4, and persistence effects and other artifacts in WFC3/IR. For each field, we release mosaics for individual epochs and eventual mosaics containing data from all epochs combined, to facilitate photometric variability studies and the deepest possible photometry. A more detailed overview of the science goals and observational design of the survey are presented in a companion paper.
The Astrophysical Journal Supplement Series 12/2011; 197(2):36. · 13.46 Impact Factor
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Lihwai Lin,
Mark Dickinson,
Hung-Yu Jian,
A. I. Merson,
C. M. Baugh,
Douglas Scott,
Sebastien Foucaud,
Wei-Hao Wang,
Chi-Hung Yan,
Hao-Jing Yan, [......],
John Helly,
Franz Kirsten, David C. Koo,
Claudia del P. Lagos,
Nicole Meger,
Alexandra Pope,
Luc Simard,
Norman A. Grogin,
Hugo Messias,
Shiang-Yu Wang
[show abstract]
[hide abstract]
ABSTRACT: Using a sample of BzK-selected galaxies at z~2 identified from the
CFHT/WIRCAM near-infrared survey of GOODS-North, we discuss the relation
between star formation rate (SFR), specific star formation rate (SSFR), and
stellar mass (M_{*}), and the clustering of galaxies as a function of these
parameters. For star-forming galaxies (sBzKs), the UV-based SFR, corrected for
extinction, scales with the stellar mass as SFR ~ M_{*}^{alpha} with alpha =
0.74+/-0.20 down to M_{*} ~ 10^{9} M_{solar}, indicating a weak dependence on
the stellar mass of the SSFR. We also measure the angular correlation function
and hence infer the correlation length for sBzK galaxies as a function of
M_{*}, SFR, and SSFR, as well as K-band apparent magnitude. We show that
passive galaxies (pBzKs) are more strongly clustered than sBzK galaxies at a
given stellar mass, mirroring the color-density relation seen at lower
redshifts. We also find that the correlation length of sBzK galaxies ranges
from 4 to 20 h^{-1}Mpc, being a strong function of M_{K}, M_{*}, and SFR. On
the other hand, the clustering dependence on SSFR changes abruptly at 2x10^{-9}
yr^{-1}, which is the typical value for "main sequence" star-forming galaxies
at z~2. We show that the correlation length reaches a minimum at this
characteristic value, and is larger for galaxies with both smaller and larger
SSFRs; a dichotomy that is only marginally implied from the predictions of the
semi-analytical models. Our results suggest that there are two types of
environmental effects at work at z~2. Stronger clustering for relatively
quiescent galaxies implies that the environment has started to play a role in
quenching star formation. At the same time, stronger clustering for galaxies
with elevated SSFRs ("starbursts") might be attributed to an increased
efficiency for galaxy interactions and mergers in dense environments.
11/2011;
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[show abstract]
[hide abstract]
ABSTRACT: The degeneracy among the disc, bulge and halo contributions to galaxy rotation curves prevents an understanding of the distribution of baryons and dark matter in disc galaxies. In an attempt to break this degeneracy, we present an analysis of the strong gravitational lens SDSS J2141−0001, discovered as part of the Sloan Lens ACS survey. The lens galaxy is a high-inclination, disc-dominated system. We present new Hubble Space Telescope multicolour imaging, gas and stellar kinematics data derived from long-slit spectroscopy and K-band laser guide star adaptive optics imaging, both from the Keck telescopes. We model the galaxy as a sum of concentric axisymmetric bulge, disc and halo components and infer the contribution of each component, using information from gravitational lensing and gas kinematics. This analysis yields a best-fitting total (disc plus bulge) stellar mass of log10(M*/M⊙) = 10.99+0.11− 0.25. The photometric data combined with stellar population synthesis models yield log10(M*/M⊙) = 10.97 ± 0.07 and 11.21 ± 0.07 for the Chabrier and Salpeter initial mass functions (IMFs), respectively. Assuming no cold gas, a Salpeter IMF is marginally disfavoured, with a Bayes factor of 2.7. Accounting for the expected gas fraction of ≃ 20 per cent reduces the lensing plus kinematics stellar mass by 0.10 ± 0.05 dex, resulting in a Bayes factor of 11.9 in favour of a Chabrier IMF. The dark matter halo is roughly spherical, with minor to major axis ratio q3, h= 0.91+0.15− 0.13. The dark matter halo has a maximum circular velocity of Vmax= 276+17− 18 km s−1, and a central density parameter of log10ΔV/2= 5.9+0.9− 0.5. This is higher than predicted for uncontracted dark matter haloes in Λ cold dark matter cosmologies, log10ΔV/2= 5.2, suggesting that either the halo has contracted in response to galaxy formation, or that the halo has a higher than average concentration. Larger samples of spiral galaxy strong gravitational lenses are needed in order to distinguish between these two possibilities. At 2.2 disc scalelengths the dark matter fraction is fDM= 0.55+0.20− 0.15, suggesting that SDSS J2141−0001 is submaximal.
Monthly Notices of the Royal Astronomical Society 10/2011; 417(3):1621 - 1642. · 4.90 Impact Factor
