174 research outputs found
The NICMOS Ultra Deep Field: Observations, Data Reduction, and Galaxy Photometry
This paper describes the observations and data reduction techniques for the
version 2.0 images and catalog of the NICMOS Ultra Deep Field Treasury program.
All sources discussed in this paper are based on detections in the combined
NICMOS F110W and F160W bands only. The NICMOS images are drizzled to 0.09 arc
second pixels and aligned to the ACS UDF F850LP image which was rebinned to the
same pixel scale. These form the NICMOS version 2.0 UDF images. The catalog
sources are chosen with a conservative detection limit to avoid the inclusion
of numerous spurious sources. The catalog contains 1293 objects in the 144 x
144 arc sececonds NICMOS subfield of the UDF. The 5 sigma signal to noise level
is an average 0.6 arc second diameter aperture AB magnitude of ~27.7 at 1.1 and
1.6 microns. The catalog sources, listed in order of right ascension, satisfy a
minimum signal to noise criterion of 1.4 sigma in at least 7 contiguous pixels
of the combined F110W and F160W imageComment: Accepted for publication in the Astronomical Journal. 33 Pages, 6
Figure
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
RELICS: High-Resolution Constraints on the Inner Mass Distribution of the z=0.83 Merging Cluster RXJ0152.7-1357 from strong lensing
Strong gravitational lensing (SL) is a powerful means to map the distribution
of dark matter. In this work, we perform a SL analysis of the prominent X-ray
cluster RXJ0152.7-1357 (z=0.83, also known as CL 0152.7-1357) in \textit{Hubble
Space Telescope} images, taken in the framework of the Reionization Lensing
Cluster Survey (RELICS). On top of a previously known galaxy multiply
imaged by RXJ0152.7-1357, for which we identify an additional multiple image,
guided by a light-traces-mass approach we identify seven new sets of multiply
imaged background sources lensed by this cluster, spanning the redshift range
[1.79-3.93]. A total of 25 multiple images are seen over a small area of ~0.4
, allowing us to put relatively high-resolution constraints on the
inner matter distribution. Although modestly massive, the high degree of
substructure together with its very elongated shape make RXJ0152.7-1357 a very
efficient lens for its size. This cluster also comprises the third-largest
sample of z~6-7 candidates in the RELICS survey. Finally, we present a
comparison of our resulting mass distribution and magnification estimates with
those from a Lenstool model. These models are made publicly available through
the MAST archive.Comment: 15 Pages, 7 Figures, 4 Tables Accepted for publication in Ap
The Majority of Compact Massive Galaxies at z~2 are Disk Dominated
We investigate the stellar structure of massive, quiescent galaxies at z~2,
based on Hubble Space Telescope/WFC3 imaging from the Early Release Science
program. Our sample of 14 galaxies has stellar masses of M* > 10^{10.8} Msol
and photometric redshifts of 1.5 < z < 2.5. In agreement with previous work,
their half-light radii are <2 kpc, much smaller than equally massive galaxies
in the present-day universe. A significant subset of the sample appears highly
flattened in projection, which implies, considering viewing angle statistics,
that a significant fraction of the galaxies in our sample have pronounced
disks. This is corroborated by two-dimensional surface brightness profile fits.
We estimate that 65% +/- 15% of the population of massive, quiescent z~2
galaxies are disk-dominated. The median disk scale length is 1.5 kpc,
substantially smaller than the disks of equally massive galaxies in the
present-day universe. Our results provide strong observational evidence that
the much-discussed ultra-dense high-redshift galaxies should generally be
thought of as disk-like stellar systems with the majority of stars formed from
gas that had time to settle into a disk.Comment: published versio
Reflecting on loss in Papua New Guinea
This article takes up the conundrum of conducting anthropological fieldwork with people who claim that they have 'lost their culture,' as is the case with Suau people in the Massim region of Papua New Guinea. But rather than claiming culture loss as a process of dispossession, Suau claim it as a consequence of their own attempts to engage with colonial interests. Suau appear to have responded to missionization and their close proximity to the colonial-era capital by jettisoning many of the practices characteristic of Massim societies, now identified as 'kastom.' The rejection of kastom in order to facilitate their relations with Europeans during colonialism, followed by the mourning for kastom after independence, both invite consideration of a kind of reflexivity that requires action based on the presumed perspective of another
Feedback from galactic stellar bulges and hot gaseous haloes of galaxies
We demonstrate that the feedback from stellar bulges can play an essential
role in shaping the halo gas of galaxies with substantial bulge components by
conducting 1-D hydrodynamical simulations. The feedback model we consider
consists of two distinct phases: 1) an early starburst during the bulge
formation and 2) a subsequent long-lasting mass and energy injection from
stellar winds of low-mass stars and Type Ia SNe. An energetic outward blastwave
is initiated by the starburst and is maintained and enhanced by the
long-lasting stellar feedback. For a MW-like galactic bulge, this blastwave
sweeps up the halo gas in the proto-galaxy and heats up the surrounding medium
to a scale much beyond the virial radius of the halo, thus the accretion of the
halo hot gas can be completely stopped. In addition, the long-lasting feedback
in the later phase powers a galactic bulge wind that is reverse-shocked at a
large radius in the presence of surrounding intergalactic medium and hence
maintains a hot gaseous halo. As the mass and energy injection decreases with
time, the feedback evolves to a subsonic and quasi-stable outflow, which is
enough to prevent halo gas from cooling. The two phases of the feedback thus
re-enforce each-other's impact on the gas dynamics. The simulation results
demonstrate that the stellar bulge feedback may provide a plausible solution to
the long-standing problems in understanding the MW type galaxies, such as the
"missing stellar feedback" problem and the "over-cooling" problem. The
simulations also show that the properties of the hot gas in the subsonic
outflow state depend sensitively on the environment and the formation history
of the bulge. This dependence and variance may explain the large dispersion in
the X-ray to B-band luminosity ratio of the low Es.Comment: v2, discussions added, accepted for publication in MNRA
âIt Takes Two Hands to Clapâ: How Gaddi Shepherds in the Indian Himalayas Negotiate Access to Grazing
This article examines the effects of state intervention on the workings of informal institutions that coordinate the communal use and management of natural resources. Specifically it focuses on the case of the nomadic Gaddi
shepherds and official attempts to regulate their access to grazing pastures in the Indian Himalayas. It is often predicted that the increased presence of the modern state critically undermines locally appropriate and community-based resource management arrangements. Drawing on the work of Pauline Peters and Francis Cleaver, I identify key instances of socially embedded âcommonâ management institutions and explain the evolution of these arrangements
through dynamic interactions between individuals, communities and the agents of the state. Through describing the âliving spaceâ of Gaddi shepherds across the annual cycle of nomadic migration with their flocks I explore the
ways in which they have been able to creatively reinterpret external interventions, and suggest how contemporary arrangements for accessing pasture at different moments of the annual cycle involve complex combinations of the
formal and the informal, the âtraditionalâ and the âmodernâ
ALMA 26 Arcmin Survey of GOODS-S at One-millimeter (ASAGAO): Average Morphology of High- Dusty Star-Forming Galaxies is an Exponential-Disk ()
We present morphological properties of dusty star-forming galaxies at z=1-3
determined with high-resolution (FWHM~0"19) Atacama Large
Milllimeter/submilimeter Array (ALMA) 1-mm band maps of our ASAGAO survey
covering a 26-arcmin^2 area in GOODS-S. In conjunction with the ALMA archival
data, the present sample consists of 42 ALMA sources with a wide rest-frame
far-infrared (FIR) luminosity L_FIR range of ~10^11-10^13 Lo. To obtain an
average rest-frame FIR profile, we perform individual measurements and careful
stacking of the ALMA sources using the uv-visibility method that includes
positional-uncertainty and smoothing-effect evaluations through Monte-Carlo
simulations. We find that the dusty star-forming galaxies have the average
FIR-wavelength Sersic index and effective radius of n_FIR=1.2+/-0.2 and
R_e,FIR=1.0-1.3 kpc, respectively, additionally with a point source at the
center, indicative of the existence of AGN. The average FIR profile agrees with
a morphology of an exponential-disk clearly distinguished from a spheroidal
profile (Sersic index of 4). We also examine the rest-frame optical Sersic
index n_opt and effective radius R_e,opt with the deep Hubble Space Telescope
(HST) images. Interestingly, we obtain n_opt=0.9+/-0.3 (~n_FIR) and
R_e,opt=3.2+/-0.6 kpc (>R_e,FIR), suggesting that the FIR-emitting disk is
embedded within a larger stellar disk. The rest-frame UV and FIR data of HST
and ALMA provide us a radial surface density profile of the total
star-formation rate (SFR), where the FIR SFR dominates over the UV SFR at the
center. Under the simple assumption of a constant SFR, a compact stellar
distribution found in z~1-2 compact quiescent galaxies (cQGs) is well
reproduced, while a spheroidal stellar morphology of cQGs (n_opt=4) cannot,
suggestive of other important mechanisms such as dynamical dissipation.Comment: 13 pages, 6 figures, ApJ in pres
Association of maternal serum concentrations of 2,2', 4,4'5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p'-DDE) levels with birth weight, gestational age and preterm births in Inuit and European populations
<p>Abstract</p> <p>Background</p> <p>Epidemiological studies on the association between maternal exposure to persistent organic pollutants (POPs) and fetal growth alteration report inconsistent findings which weights in favor of additional studies.</p> <p>Methods</p> <p>Blood samples were collected from interviewed pregnant women in Greenland (572), Kharkiv (611) and Warsaw (258) and were analyzed for CB-153 and p,p'-DDE by gas chromatography-mass spectrometry. Data on birth weight, gestational age and preterm birth were obtained for 1322 singleton live births. We examined the association between natural log-transformed serum POPs concentration and birth weight and gestational age using multiple linear regression and the association with prematurity using logistic regression controlling for potential confounding factors.</p> <p>Results</p> <p>The median serum concentrations of CB-153 and p,p'-DDE were for Inuit mothers 105.6 and 298.9, for Kharkiv mothers 27.0 and 645.4 and for Warsaw mothers 10.7 and 365.2 ng/g lipids, respectively. Increase in CB-153 concentration by one unit on the log scale in Inuit mothers serum was associated with significant decrease in infant birth weight of -59 g and gestational age by -0.2 week. Decreases observed in the cohorts in Kharkiv (-10 g and -0.1 week) and in Warsaw (-49 g and -0.2 week) were not statistically significant. Increase in p,p'-DDE concentration by one unit on the log scale was associated with a statistically significant decrease in infant birth weight of -39.4 g and -104.3 g and shortening of gestational age of -0.2 week and -0.6 week in the Inuit and Warsaw cohorts, respectively. In the Kharkiv cohort decrease in birth weight (-30.5 g) was not significant, however a shortening of gestational age of -0.2 week per increase in p,p'-DDE concentration by one unit on the log scale was of the borderline significance. There was no significant association between CB-153 and p,p'-DDE concentrations and risk of preterm birth however, in all cohorts the odds ratio was above 1.</p> <p>Conclusions</p> <p><it>In utero </it>exposure to POPs may reduce birth weight and gestational age of newborns however, new insights as to why results vary across studies were not apparent.</p
CANDELS: The progenitors of compact quiescent galaxies at z~2
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.Comment: Submitted to the Astrophysical Journal Letters, 6 pages, 4 figure
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