-
J. Song,
A. Zenteno,
B. Stalder,
S. Desai,
L. E. Bleem,
K. A. Aird,
R. Armstrong,
M. L. N. Ashby,
M. Bayliss,
G. Bazin, [......],
S. A. Stanford,
Z. Staniszewski,
A. A. Stark,
K. Story,
C. W. Stubbs,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
R. Williamson,
O. Zahn
[show abstract]
[hide abstract]
ABSTRACT: We present the results of the ground- and space-based optical and
near-infrared (NIR) follow-up of 224 galaxy cluster candidates detected with
the Sunyaev-Zel'dovich (SZ) effect in the 720 deg^2 of the South Pole Telescope
(SPT) survey completed in the 2008 and 2009 observing seasons. We use the
optical/NIR data to establish whether each candidate is associated with an
overdensity of galaxies and to estimate the cluster redshift. Most photometric
redshifts are derived through a combination of three different cluster redshift
estimators using red-sequence galaxies, resulting in an accuracy of \Delta
z/(1+z)=0.017, determined through comparison with a subsample of 57 clusters
for which we have spectroscopic redshifts. We successfully measure redshifts
for 158 systems and present redshift lower limits for the remaining candidates.
The redshift distribution of the confirmed clusters extends to z=1.35 with a
median of z_{med}=0.57. Approximately 18% of the sample with measured redshifts
lies at z>0.8. We estimate a lower limit to the purity of this SPT SZ-selected
sample by assuming that all unconfirmed clusters are noise fluctuations in the
SPT data. We show that the cumulative purity at detection significance \xi>5
(\xi>4.5) is >= 95 (>= 70%). We present the red brightest cluster galaxy (rBCG)
positions for the sample and examine the offsets between the SPT candidate
position and the rBCG. The radial distribution of offsets is similar to that
seen in X-ray-selected cluster samples, providing no evidence that SZ-selected
cluster samples include a different fraction of recent mergers than
X-ray-selected cluster samples.
07/2012;
-
S. Desai,
R. Armstrong,
J. J. Mohr,
D. R. Semler,
J. Liu, E. Bertin,
S. S. Alam,
W. A. Barkhouse,
G. Bazin,
E. J. Buckley-Geer,
M. C. Cooper,
S. M. Hansen,
F. W. High,
H. Lin,
Y. T. Lin,
C. -C. Ngeow,
A. Rest,
J. Song,
D. Tucker,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: The Blanco Cosmology Survey (BCS) is a 60 night imaging survey of $\sim$80
deg$^2$ of the southern sky located in two fields: ($\alpha$,$\delta$)= (5 hr,
$-55^{\circ}$) and (23 hr, $-55^{\circ}$). The survey was carried out between
2005 and 2008 in $griz$ bands with the Mosaic2 imager on the Blanco 4m
telescope. The primary aim of the BCS survey is to provide the data required to
optically confirm and measure photometric redshifts for Sunyaev-Zel'dovich
effect selected galaxy clusters from the South Pole Telescope and the Atacama
Cosmology Telescope. We process and calibrate the BCS data, carrying out PSF
corrected model fitting photometry for all detected objects. The median
10$\sigma$ galaxy (point source) depths over the survey in $griz$ are
approximately 23.3 (23.9), 23.4 (24.0), 23.0 (23.6) and 21.3 (22.1),
respectively. The astrometric accuracy relative to the USNO-B survey is
$\sim45$ milli-arcsec. We calibrate our absolute photometry using the stellar
locus in $grizJ$ bands, and thus our absolute photometric scale derives from
2MASS which has $\sim2$% accuracy. The scatter of stars about the stellar locus
indicates a systematics floor in the relative stellar photometric scatter in
$griz$ that is $\sim$1.9%, $\sim$2.2%, $\sim$2.7% and$\sim$2.7%, respectively.
A simple cut in the AstrOmatic star-galaxy classifier {\tt spread\_model}
produces a star sample with good spatial uniformity. We use the resulting
photometric catalogs to calibrate photometric redshifts for the survey and
demonstrate scatter $\delta z/(1+z)=0.054$ with an outlier fraction $\eta<5$%
to $z\sim1$. We highlight some selected science results to date and provide a
full description of the released data products.
04/2012;
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S. Desai,
R. Armstrong,
M. L. N. Ashby,
B. Bayliss,
G. Bazin,
B. Benson, E. Bertin,
L. Bleem,
M. Brodwin,
A. Clochiatti, [......],
J. Liu,
J. Mohr,
A. Rest,
J. Ruel,
A. Saro,
J. Song,
B. Stalder,
A. Stanford,
C. Stubbs,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: The South Pole Telescope (SPT) is a 10 meter telescope operating at mm
wavelengths. It has recently completed a three-band survey covering 2500 sq.
degrees. One of the survey's main goals is to detect galaxy clusters using
Sunyaev-Zeldovich effect and use these clusters for a variety of cosmological
and astrophysical studies such as the dark energy equation of state, the
primordial non-gaussianity and the evolution of galaxy populations. Since 2005,
we have been engaged in a comprehensive optical and near-infrared followup
program (at wavelengths between 0.4 and 5 {\mu}m) to image high-significance
SPT clusters, to measure their photometric redshifts, and to estimate the
contamination rate of the candidate lists. These clusters are then used for
various cosmological and astrophysical studies.
01/2012;
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E. J. Buckley-Geer,
H. Lin,
E. R. Drabek,
S. S. Allam,
D. L. Tucker,
R. Armstrong,
W. A. Barkhouse, E. Bertin,
M. Brodwin,
S. Desai,
J. A. Frieman,
S. M. Hansen,
F. W. High,
J. J. Mohr,
Y.-T. Lin,
C.-C. Ngeow,
A. Rest,
R. C. Smith,
J. Song,
and A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We report on the serendipitous discovery in the Blanco Cosmology Survey (BCS) imaging data of a z = 0.9057 galaxy that is being strongly lensed by a massive galaxy cluster at a redshift of z = 0.3838. The lens (BCS J2352–5452) was discovered while examining i- and z-band images being acquired in 2006 October during a BCS observing run. Follow-up spectroscopic observations with the Gemini Multi-Object Spectrograph instrument on the Gemini-South 8 m telescope confirmed the lensing nature of this system. Using weak-plus-strong lensing, velocity dispersion, cluster richness N 200, and fitting to a Navarro-Frenk-White (NFW) cluster mass density profile, we have made three independent estimates of the mass M 200 which are all very consistent with each other. The combination of the results from the three methods gives M 200 = (5.1 ± 1.3) × 1014 M ☉, which is fully consistent with the individual measurements. The final NFW concentration c 200 from the combined fit is c 200 = 5.4+1.4 – 1.1. We have compared our measurements of M 200 and c 200 with predictions for (1) clusters from ΛCDM simulations, (2) lensing-selected clusters from simulations, and (3) a real sample of cluster lenses. We find that we are most compatible with the predictions for ΛCDM simulations for lensing clusters, and we see no evidence based on this one system for an increased concentration compared to ΛCDM. Finally, using the flux measured from the [O II]3727 line we have determined the star formation rate of the source galaxy and find it to be rather modest given the assumed lens magnification.
The Astrophysical Journal 11/2011; 742(1):48. · 6.02 Impact Factor
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R. Šuhada,
J Song,
H. Böhringer,
J. J. Mohr,
G. Chon,
A. Finoguenov,
R. Fassbender,
S Desai,
R. Armstrong,
A. Zenteno, [......],
E. J. Buckley-Geer,
S. M. Hansen,
F. W. High,
H Lin,
M. Mühlegger,
C. -C. Ngeow,
D. Pierini,
G. W. Pratt,
M. Verdugo,
D. L. Tucker
[show abstract]
[hide abstract]
ABSTRACT: The XMM-Newton - Blanco Cosmology Survey project (XMM-BCS) is a coordinated
X-ray, optical and mid-infrared cluster survey in a field also covered by
Sunyaev-Zel'dovich effect surveys by the South Pole Telescope and the Atacama
Cosmology Telescope. The aim of the project is to study the cluster population
in a 14 deg$^2$ field.
In this work, we present a catalog of 46 X-ray selected clusters from the
initial 6 deg$^2$ survey core. We describe the XMM-BCS source detection
pipeline and derive physical properties of the clusters. We provide photometric
redshift estimates derived from the BCS imaging data and spectroscopic redshift
measurements for a low redshift subset of the clusters. We derive the cluster
log N - log S relation using an approximation to the survey selection function
and find it in good agreement with previous studies. We carry out an initial
comparison between X-ray luminosity derived masses and masses from optical
estimators from the Southern Cosmology Survey for a subset of the cluster
sample. Optical masses based on cluster richness and total optical luminosity
are found to be significantly higher than the X-ray values.
(abridged)
11/2011;
-
I. Sevilla,
R. Armstrong, E. Bertin,
A. Carlson,
G. Daues,
S Desai,
M. Gower,
R. Gruendl,
W. Hanlon,
M. Jarvis, [......],
J. Marriner,
J. Mohr,
D. Petravick,
E. Sheldon,
M. E. C. Swanson,
T. Tomashek,
D. Tucker,
Y Yang,
B. Yanny,
for the DES Collaboration
[show abstract]
[hide abstract]
ABSTRACT: The Dark Energy Survey (DES) is a project with the goal of building,
installing and exploiting a new 74 CCD-camera at the Blanco telescope, in order
to study the nature of cosmic acceleration. It will cover 5000 square degrees
of the southern hemisphere sky and will record the positions and shapes of 300
million galaxies up to redshift 1.4. The survey will be completed using 525
nights during a 5-year period starting in 2012. About O(1 TB) of raw data will
be produced every night, including science and calibration images. The DES data
management system has been designed for the processing, calibration and
archiving of these data. It is being developed by collaborating DES
institutions, led by NCSA. In this contribution, we describe the basic
functions of the system, what kind of scientific codes are involved and how the
Data Challenge process works, to improve simultaneously the Data Management
system algorithms and the Science Working Group analysis codes.
09/2011;
-
R. Williamson,
B. A. Benson,
F. W. High,
K. Vanderlinde,
P. A. R. Ade,
K. A. Aird,
K. Andersson,
R. Armstrong,
M. L. N. Ashby,
M. Bautz, [......],
H. G. Spieler,
B. Stalder,
S. A. Stanford,
Z. Staniszewski,
A. A. Stark,
K. Story,
C. W. Stubbs,
J. D. Vieira,
A. Vikhlinin,
and A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: The South Pole Telescope (SPT) is currently surveying 2500 deg2 of the southern sky to detect massive galaxy clusters out to the epoch of their formation using the Sunyaev-Zel'dovich (SZ) effect. This paper presents a catalog of the 26 most significant SZ cluster detections in the full survey region. The catalog includes 14 clusters which have been previously identified and 12 that are new discoveries. These clusters were identified in fields observed to two differing noise depths: 1500 deg2 at the final SPT survey depth of 18 μK arcmin at 150 GHz and 1000 deg2 at a depth of 54 μK arcmin. Clusters were selected on the basis of their SZ signal-to-noise ratio (S/N) in SPT maps, a quantity which has been demonstrated to correlate tightly with cluster mass. The S/N thresholds were chosen to achieve a comparable mass selection across survey fields of both depths. Cluster redshifts were obtained with optical and infrared imaging and spectroscopy from a variety of ground- and space-based facilities. The redshifts range from 0.098 ≤ z ≤ 1.132 with a median of z med = 0.40. The measured SZ S/N and redshifts lead to unbiased mass estimates ranging from 9.8 × 1014 M ☉ h –1 70 ≤ M 200(ρmean) ≤ 3.1 × 1015 M ☉ h –1 70. Based on the SZ mass estimates, we find that none of the clusters are individually in significant tension with the ΛCDM cosmological model. We also test for evidence of non-Gaussianity based on the cluster sample and find the data show no preference for non-Gaussian perturbations.
The Astrophysical Journal 08/2011; 738(2):139. · 6.02 Impact Factor
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B. M. Rossetto,
B. X. Santiago,
L. Girardi,
J. I. B. Camargo,
E. Balbinot,
L. N. da Costa,
B. Yanny,
M. A. G. Maia,
M. Makler,
R. L. C. Ogando,
P. S. Pellegrini,
B. Ramos,
F. de Simoni,
R. Armstrong, E. Bertin,
S Desai,
N. Kuropatkin,
H Lin,
J. J. Mohr,
D. L. Tucker
[show abstract]
[hide abstract]
ABSTRACT: Wide angle and deep surveys, regardless of their primary purpose, always
sample a large number of stars in the Galaxy and in its satellite system. We
here make a forecast of the expected stellar sample resulting from the Dark
Energy Survey and the perspectives that it will open for studies of Galactic
structure and resolved stellar populations in general. An estimated 1.2x10^8
stars will be sampled in DES grizY filters. This roughly corresponds to 20% of
all DES sources. Most of these stars belong to the stellar thick disk and halo
of the Galaxy. DES will probe low-mass stellar and sub-stellar objects at
depths from 3 to 8 times larger than SDSS. The faint end of the main-sequence
will be densely sampled beyond 10 kpc. The slope of the low mass end of the
stellar IMF will be constrained to within a few hundredth dex, even in the
thick disk and halo. In the sub-stellar mass regime, the IMF slope will be
potentially constrained to within dlog \phi(m) / dlog m ~ 0.1$. About 3x10^4
brown dwarf and at least 7.6x10^5 white dwarf candidates will be selected, the
latter embedded into the thick disk and halo. The stellar halo flattening will
also be constrained to within a few percent. DES will probe the main sequence
of new Milky Way satellites and halo clusters for distances out to ~ 120 kpc,
therefore yielding stellar surface density contrasts 1.6-1.7 times larger than
those attainable with SDSS. It will also allow detection of these objects in
the far reaches of the stellar halo, substantially increasing the number and
quality of probes to the Galactic potential. Combined with northern samples,
such as the SDSS, the DES stellar sample will yield constraints on the
structure and stellar populations of Galactic components in unprecedented
detail. In particular, the combined sample from both hemispheres will allow
detailed studies of halo and thick disk asymmetries and triaxiality.
The Astronomical Journal 04/2011; 141(6). · 4.03 Impact Factor
-
A. Zenteno,
J Song,
S Desai,
R. Armstrong,
J. J. Mohr,
C. -C. Ngeow,
W. A. Barkhouse,
S. S. Allam,
K. Andersson,
G. Bazin, [......],
F. W. High,
H Lin,
Y T Lin,
J Liu,
A. Rest,
R. C. Smith,
B. Stalder,
A. A. Stark,
D. L. Tucker,
Y Yang
[show abstract]
[hide abstract]
ABSTRACT: We present first results of an examination of the optical properties of the
galaxy populations in SZE selected galaxy clusters. Using clusters selected by
the South Pole Telescope survey and deep multiband optical data from the Blanco
Cosmology Survey, we measure the radial profile, the luminosity function, the
blue fraction and the halo occupation number of the galaxy populations of these
four clusters with redshifts ranging from 0.3 to 1. Our goal is to understand
whether there are differences among the galaxy populations of these SZE
selected clusters and previously studied clusters selected in the optical and
the X-ray. The radial distributions of galaxies in the four systems are
consistent with NFW profiles with a galaxy concentration of 3 to 6. We show
that the characteristic luminosities in $griz$ bands are consistent with
passively evolving populations emerging from a single burst at redshift $z=3$.
The faint end power law slope of the luminosity function is found to be on
average $\alpha \approx -1.2$ in griz. Halo occupation numbers (to $m^*+2$) for
these systems appear to be consistent with those based on X-ray selected
clusters. The blue fraction estimated to $0.36L^*$, for the three lower
redshift systems, suggests an increase with redshift, although with the current
sample the uncertainties are still large. Overall, this pilot study of the
first four clusters provides no evidence that the galaxy populations in these
systems differ significantly from those in previously studied cluster
populations selected in the X-ray or the optical.
03/2011;
-
R Williamson,
B. A. Benson,
F. W. High,
K. Vanderlinde,
P. A. R. Ade,
K. A. Aird,
K. Andersson,
R. Armstrong,
M. L. N. Ashby,
M. Bautz, [......],
H. G. Spieler,
B. Stalder,
S. A. Stanford,
Z. Staniszewski,
A. A. Stark,
K. Story,
C. W. Stubbs,
J. D. Vieira,
A. Vikhlinin,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: The South Pole Telescope (SPT) is currently surveying 2500 deg^2 of the
southern sky to detect massive galaxy clusters out to the epoch of their
formation using the Sunyaev-Zel'dovich (SZ) effect. This paper presents a
catalog of the 26 most significant SZ cluster detections in the full survey
region. The catalog includes 14 clusters which have been previously identified
and 12 that are new discoveries. These clusters were identified in fields
observed to two differing noise depths: 1500 deg^2 at the final SPT survey
depth of 18 uK-arcmin at 150 GHz, and 1000 deg^2 at a depth of 54 uK-arcmin.
Clusters were selected on the basis of their SZ signal-to-noise ratio (S/N) in
SPT maps, a quantity which has been demonstrated to correlate tightly with
cluster mass. The S/N thresholds were chosen to achieve a comparable mass
selection across survey fields of both depths. Cluster redshifts were obtained
with optical and infrared imaging and spectroscopy from a variety of ground-
and space-based facilities. The redshifts range from 0.098 \leq z \leq 1.132
with a median of z_med = 0.40. The measured SZ S/N and redshifts lead to
unbiased mass estimates ranging from 9.8 \times 10^14 M_sun/h_70 \leq
M_200(rho_mean) \leq 3.1 \times 10^15 M_sun/h_70. Based on the SZ mass
estimates, we find that none of the clusters are individually in significant
tension with the LambdaCDM cosmological model. We also test for evidence of
non-Gaussianity based on the cluster sample and find the data show no
preference for non-Gaussian perturbations.
01/2011;
-
F. W. High,
B. Stalder,
J. Song,
P. A. R. Ade,
K. A. Aird,
S. S. Allam,
R. Armstrong,
W. A. Barkhouse,
B. A. Benson, E. Bertin, [......],
A. A. Stark,
C. W. Stubbs,
D. L. Tucker,
K. Vanderlinde,
J. D. Vieira,
R. Williamson,
W. M. Wood-Vasey,
Y. Yang,
O. Zahn,
and A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We present redshifts and optical richness properties of 21 galaxy clusters uniformly selected by their Sunyaev-Zel'dovich (SZ) signature. These clusters, plus an additional, unconfirmed candidate, were detected in a 178 deg2 area surveyed by the South Pole Telescope (SPT) in 2008. Using griz imaging from the Blanco Cosmology Survey and from pointed Magellan telescope observations, as well as spectroscopy using Magellan facilities, we confirm the existence of clustered red-sequence galaxies, report red-sequence photometric redshifts, present spectroscopic redshifts for a subsample, and derive R 200 radii and M 200 masses from optical richness. The clusters span redshifts from 0.15 to greater than 1, with a median redshift of 0.74; three clusters are estimated to be at z>1. Redshifts inferred from mean red-sequence colors exhibit 2% rms scatter in σ z /(1 + z) with respect to the spectroscopic subsample for z < 1. We show that the M 200 cluster masses derived from optical richness correlate with masses derived from SPT data and agree with previously derived scaling relations to within the uncertainties. Optical and infrared imaging is an efficient means of cluster identification and redshift estimation in large SZ surveys, and exploiting the same data for richness measurements, as we have done, will be useful for constraining cluster masses and radii for large samples in cosmological analysis.
The Astrophysical Journal 10/2010; 723(2):1736. · 6.02 Impact Factor
