567 research outputs found
All-sky Relative Opacity Mapping Using Night Time Panoramic Images
An all-sky cloud monitoring system that generates relative opacity maps over
many of the world's premier astronomical observatories is described.
Photometric measurements of numerous background stars are combined with
simultaneous sky brightness measurements to differentiate thin clouds from sky
glow sources such as air glow and zodiacal light. The system takes a continuous
pipeline of all-sky images, and compares them to canonical images taken on
other nights at the same sidereal time. Data interpolation then yields
transmission maps covering almost the entire sky. An implementation of this
system is currently operating through the Night Sky Live network of CONCAM3s
located at Cerro Pachon (Chile), Mauna Kea (Hawaii), Haleakala (Hawaii), SALT
(South Africa) and the Canary Islands (Northwestern Africa).Comment: Accepted for publication in PAS
A Public Ks-selected Catalog in the COSMOS/UltraVISTA Field: Photometry, Photometric Redshifts and Stellar Population Parameters
We present a catalog covering 1.62 deg^2 of the COSMOS/UltraVISTA field with
PSF-matched photometry in 30 photometric bands. The catalog covers the
wavelength range 0.15um - 24um including the available GALEX, Subaru, CFHT,
VISTA and Spitzer data. Catalog sources have been selected from the DR1
UltraVISTA Ks band imaging that reaches a depth of K_{s,tot} = 23.4 AB (90%
completeness). The PSF-matched catalog is generated using position-dependent
PSFs ensuring accurate colors across the entire field. Also included is a
catalog of photometric redshifts (z_phot) for all galaxies computed with the
EAZY code. Comparison with spectroscopy from the zCOSMOS 10k bright sample
shows that up to z ~ 1.5 the z_phot are accurate to dz/(1 + z) = 0.013, with a
catastrophic outlier fraction of only 1.6%. The z_phot also show good agreement
with the z_phot from the NEWFIRM Medium Band Survey (NMBS) out to z ~ 3. A
catalog of stellar masses and stellar population parameters for galaxies
determined using the FAST spectral energy distribution fitting code is provided
for all galaxies. Also included are rest-frame U-V and V-J colors, L_2800 and
L_IR. The UVJ color-color diagram confirms that the galaxy bi-modality is
well-established out to z ~ 2. Star-forming galaxies also obey a star forming
"main sequence" out to z ~ 2.5, and this sequence evolves in a manner
consistent with previous measurements. The COSMOS/UltraVISTA Ks-selected
catalog covers a unique parameter space in both depth, area, and
multi-wavelength coverage and promises to be a useful tool for studying the
growth of the galaxy population out to z ~ 3 - 4.Comment: 20 pages, 14 figures. Accepted to the ApJSS. Catalog data products
available for download here:
http://www.strw.leidenuniv.nl/galaxyevolution/ULTRAVISTA
Stellar mass functions of galaxies at 4<z<7 from an IRAC-selected sample in COSMOS/UltraVISTA: limits on the abundance of very massive galaxies
We build a Spitzer IRAC complete catalog of objects, obtained by
complementing the -band selected UltraVISTA catalog with objects
detected in IRAC only. With the aim of identifying massive (i.e.,
) galaxies at , we consider the systematic effects
on the measured photometric redshifts from the introduction of an old and dusty
SED template and from the introduction of a bayesian prior taking into account
the brightness of the objects, as well as the systematic effects from different
star formation histories (SFHs) and from nebular emission lines in the recovery
of stellar population parameters. We show that our results are most affected by
the bayesian luminosity prior, while nebular emission lines and SFHs only
introduce a small dispersion in the measurements. Specifically, the number of
galaxies ranges from 52 to 382 depending on the adopted configuration.
Using these results we investigate, for the first time, the evolution of the
massive end of the stellar mass functions (SMFs) at . Given the rarity
of very massive galaxies in the early universe, major contributions to the
total error budget come from cosmic variance and poisson noise. The SMF
obtained without the introduction of the bayesian luminosity prior does not
show any evolution from to , implying that massive
galaxies could already be present when the Universe was ~Gyr old.
However, the introduction of the bayesian luminosity prior reduces the number
of galaxies with best fit masses by 83%, implying
a rapid growth of very massive galaxies in the first 1.5 Gyr of cosmic history.
From the stellar-mass complete sample, we identify one candidate of a very
massive (), quiescent galaxy at , with
MIPS m detection suggesting the presence of a powerful obscured AGN.Comment: 23 pages, 18 figures. ApJ accepte
The Progenitors of Local Ultra-massive Galaxies Across Cosmic Time: from Dusty Star-bursting to Quiescent Stellar Populations
Using the UltraVISTA catalogs, we investigate the evolution in the 11.4~Gyr
since of the progenitors of local ultra-massive galaxies (; UMGs), providing a complete and consistent
picture of how the most massive galaxies at have assembled. By selecting
the progenitors with a semi-empirical approach using abundance matching, we
infer a growth in stellar mass of 0.56 dex,
0.45~dex, and 0.27 dex from , ,
and , respectively, to . At , the progenitors of UMGs constitute
a homogeneous population of only quiescent galaxies with old stellar
populations. At , the contribution from star-forming galaxies
progressively increases, with the progenitors at being dominated by
massive (M), dusty (1--2.2 mag), star-forming (SFR100--400~M yr)
galaxies with a large range in stellar ages. At , 15\% of the
progenitors are quiescent, with properties typical of post-starburst galaxies
with little dust extinction and strong Balmer break, and showing a large
scatter in color. Our findings indicate that at least half of the stellar
content of local UMGs was assembled at , whereas the remaining was
assembled via merging from to the present. Most of the quenching of
the star-forming progenitors happened between and , in good
agreement with the typical formation redshift and scatter in age of UMGs
as derived from their fossil records. The progenitors of local UMGs, including
the star-forming ones, never lived on the blue cloud since . We propose an
alternative path for the formation of local UMGs that refines previously
proposed pictures and that is fully consistent with our findings.Comment: 20 pages, 15 figures (6 of which in appendix); accepted for
publication in the Astrophysical Journa
The Evolution of the Stellar Mass Functions of Star-Forming and Quiescent Galaxies to z = 4 from the COSMOS/UltraVISTA Survey
We present measurements of the stellar mass functions (SMFs) of star-forming
and quiescent galaxies to z = 4 using a sample of 95 675 galaxies in the
COSMOS/UltraVISTA field. Sources have been selected from the DR1 UltraVISTA
K_{s}-band imaging which covers a unique combination of a wide area (1.62
deg^2), to a significant depth (K_{s,tot} = 23.4). The SMFs of the combined
population are in good agreement with previous measurements and show that the
stellar mass density of the universe was only 50%, 10% and 1% of its current
value at z ~ 0.75, 2.0, and 3.5, respectively. The quiescent population drives
most of the overall growth, with the stellar mass density of these galaxies
increasing by 2.71^{+0.93}_{-0.22} dex since z = 3.5. At z > 2.5, star-forming
galaxies dominate the total SMF at all stellar masses, although a nonzero
population of quiescent galaxies persists to z = 4. Comparisons of the
K_{s}-selected star-forming galaxy SMFs to UV-selected SMFs at 2.5 < z < 4 show
reasonable agreement and suggests UV-selected samples are representative of the
majority of the stellar mass density at z > 3.5. We estimate the average mass
growth of individual galaxies by selecting galaxies at fixed cumulative number
density. The average galaxy with Log(M_{*}/M_{sun}) = 11.5 at z = 0.3 has grown
in mass by only 0.2 dex (0.3 dex) since z = 2.0(3.5), whereas those with
Log(M_{*}/M_{sun}) = 10.5 have grown by > 1.0 dex since z = 2. At z < 2, the
time derivatives of the mass growth are always larger for lower-mass galaxies,
which demonstrates that the mass growth in galaxies since that redshift is
mass-dependent and primarily bottom-up. Lastly, we examine potential sources of
systematic uncertainties on the SMFs and find that those from photo-z
templates, SPS modeling, and the definition of quiescent galaxies dominate the
total error budget in the SMFs.Comment: 18 pages paper, 12 pages appendix, 23 figures. Accepted for
publication in the Ap
Spectroscopic Confirmation of Two Massive Red-Sequence-Selected Galaxy Clusters at z ~ 1.2 in the SpARCS-North Cluster Survey
The Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) is a deep z'-band imaging survey covering the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE) Legacy fields designed to create the first large homogeneously selected sample of massive clusters at z > 1 using an infrared adaptation of the cluster red-sequence method. We present an overview of the northern component of the survey which has been observed with Canada-France-Hawaii Telescope (CFHT)/MegaCam and covers 28.3 deg^2. The southern component of the survey was observed with Cerro Tololo Inter-American Observatory (CTIO)/MOSAICII, covers 13.6 deg^2, and is summarized in a companion paper by Wilson et al. We also present spectroscopic confirmation of two rich cluster candidates at z ~ 1.2. Based on Nod-and-Shuffle spectroscopy from GMOS-N on Gemini, there are 17 and 28 confirmed cluster members in SpARCS J163435+402151 and SpARCS J163852+403843 which have spectroscopic redshifts of 1.1798 and 1.1963, respectively. The clusters have velocity dispersions of 490 ± 140 km s^(–1) and 650 ± 160 km s^(–1), respectively, which imply masses (M_(200)) of (1.0 ± 0.9) × 10^(14) M_⊙ and (2.4 ± 1.8) × 10^(14) M_⊙. Confirmation of these candidates as bonafide massive clusters demonstrates that two-filter imaging is an effective, yet observationally efficient, method for selecting clusters at z > 1
Upregulation of peroxisome proliferator-activated receptor gamma coactivator gene ( PGC1A ) during weight loss is related to insulin sensitivity but not to energy expenditure
Aims/hypothesis: We investigated whether skeletal muscle peroxisome proliferator-activated receptor gamma coactivator-1 (PGC1A; also known as PPARGC1A) and its target mitofusin-2 (MFN2), as well as carnitine palmitoyltransferase-1 (CPT1; also known as carnitine palmitoyltransferase 1A [liver] [CPT1A]) and uncoupling protein (UCP)3, are involved in the improvement of insulin resistance and/or in the modification of energy expenditure during surgically induced massive weight loss. Materials and methods: Seventeen morbidly obese women (mean BMI: 45.9 ± 4kg/m2) were investigated before, and 3 and 12months after, Roux-en-Y gastric bypass (RYGB). We evaluated insulin sensitivity by the euglycaemic-hyperinsulinaemic clamp, energy expenditure and substrate oxidation by indirect calorimetry, and muscle mRNA expression by PCR. Results: Post-operatively, PGC1A was enhanced at 3 (p = 0.02) and 12months (p = 0.03) as was MFN2 (p = 0.008 and p = 0.03 at 3 and 12months respectively), whereas UCP3 was reduced (p = 0.03) at 12months. CPT1 did not change. The expression of PGC1A and MFN2 were strongly (p < 0.0001) related. Insulin sensitivity, which increased after surgery (p = 0.002 at 3, p = 0.003 at 12months), was significantly related to PGC1A and MFN2, but only MFN2 showed an independent influence in a multiple regression analysis. Energy expenditure was reduced at 3months post-operatively (p = 0.001 vs before RYGB), remaining unchanged thereafter until 12months. CPT1 and UCP3 were not significantly related to the modifications of energy expenditure or of lipid oxidation rate. Conclusions/interpretation: Weight loss upregulates PGC1A, which in turn stimulates MFN2 expression. MFN2 expression significantly and independently contributes to the improvement of insulin sensitivity. UCP3 and CPT1 do not seem to influence energy expenditure after RYG
Spectroscopic Confirmation of a Massive Red-Sequence-Selected Galaxy Cluster at z = 1.34 in the SpARCS-South Cluster Survey
The Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) is a
z'-passband imaging survey, consisting of deep (z' ~ 24 AB) observations made
from both hemispheres using the CFHT 3.6m and CTIO 4m telescopes. The survey
was designed with the primary aim of detecting galaxy clusters at z >~ 1. In
tandem with pre-existing 3.6um observations from the Spitzer Space Telescope
SWIRE Legacy Survey, SpARCS detects clusters using an infrared adaptation of
the two-filter red-sequence cluster technique. The total effective area of the
SpARCS cluster survey is 41.9 deg^2. In this paper, we provide an overview of
the 13.6 deg^2 Southern CTIO/MOSAICII observations. The 28.3 deg^2 Northern
CFHT/MegaCam observations are summarized in a companion paper by Muzzin et al.
(2008). In this paper, we also report spectroscopic confirmation of SpARCS
J003550-431224, a very rich galaxy cluster at z = 1.335, discovered in the
ELAIS-S1 field. To date, this is the highest spectroscopically confirmed
redshift for a galaxy cluster discovered using the red-sequence technique.
Based on nine confirmed members, SpARCS J003550-431224 has a preliminary
velocity dispersion of 1050 +/- 230 km/s. With its proven capability for
efficient cluster detection, SpARCS is a demonstration that we have entered an
era of large, homogeneously-selected z > 1 cluster surveys.Comment: 10 pages, 6 Figures, Submitted to the Ap
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