-
C. L. Reichardt,
B. Stalder,
L. E. Bleem,
T. E. Montroy,
K. A. Aird,
K. Andersson, R. Armstrong,
M. L. N. Ashby,
M. Bautz,
M. Bayliss, [......],
K. Story,
C. W. Stubbs,
R. Suhada,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R. Williamson,
O. Zahn,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We present a catalog of 224 galaxy cluster candidates, selected through their
Sunyaev-Zel'dovich (SZ) effect signature in the first 720 deg2 of the South
Pole Telescope (SPT) survey. This area was mapped with the SPT in the 2008 and
2009 austral winters to a depth of 18 uK-arcmin at 150 GHz; 550 deg2 of it was
also mapped to 44 uK-arcmin at 95 GHz. Based on optical imaging of all
candidates and near-infrared imaging of the majority of candidates, we have
found optical and/or infrared counterparts for 158 clusters. Of these, 135 were
first identified as clusters in SPT data, including 117 new discoveries
reported in this work. This catalog triples the number of confirmed galaxy
clusters discovered through the SZ effect. We report photometrically derived
(and in some cases spectroscopic) redshifts for confirmed clusters and redshift
lower limits for the remaining candidates. The catalog extends to high redshift
with a median redshift of z = 0.55 and maximum redshift of z = 1.37. Based on
simulations, we expect the catalog to be nearly 100% complete above M500 ~ 5e14
Msun h_{70}^-1 at z > 0.6. There are 121 candidates detected at signal-to-noise
greater than five, at which the catalog purity is measured to be 95%. From this
high-purity subsample, we exclude the z < 0.3 clusters and use the remaining
100 candidates to improve cosmological constraints following the method
presented by Benson et al., 2011. Adding the cluster data to CMB+BAO+H0 data
leads to a preference for non-zero neutrino masses while only slightly reducing
the upper limit on the sum of neutrino masses to sum mnu < 0.38 eV (95% CL).
For a spatially flat wCDM cosmological model, the addition of this catalog to
the CMB+BAO+H0+SNe results yields sigma8=0.807+-0.027 and w = -1.010+-0.058,
improving the constraints on these parameters by a factor of 1.4 and 1.3,
respectively. [abbrev]
03/2012;
-
L. E. Bleem,
A. van Engelen,
G. P. Holder,
K. A. Aird, R. Armstrong,
M. L. N. Ashby,
M. R. Becker,
B. A. Benson,
T. Biesiadzinski,
M. Brodwin, [......],
Z. Staniszewski,
A. A. Stark,
D. Stern,
K. Story,
A. Vallinotto,
K. Vanderlinde,
J. D. Vieira,
R. H. Wechsler,
R. Williamson,
O. Zahn
[show abstract]
[hide abstract]
ABSTRACT: We compare cosmic microwave background lensing convergence maps derived from
South Pole Telescope (SPT) data with galaxy survey data from the Blanco
Cosmology Survey, the Wide-field Infrared Survey Explorer, and a new large
Spitzer/IRAC field designed to overlap with the SPT survey. Using optical and
infrared catalogs covering between 17 and 68 square degrees of sky, we detect
correlation between the SPT convergence maps and each of the galaxy density
maps at >4 sigma, with zero cross-correlation robustly ruled out in all cases.
The amplitude and shape of the cross-power spectra are in good agreement with
theoretical expectations and the measured galaxy bias is consistent with
previous work. The detections reported here utilize a small fraction of the
full 2500 square degree SPT survey data and serve as both a proof of principle
of the technique and an illustration of the potential of this emerging
cosmological probe.
03/2012;
-
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;
-
B. A. Benson,
T. de Haan,
J. P. Dudley,
C. L. Reichardt,
K. A. Aird,
K. Andersson, R. Armstrong,
M. Bautz,
M. Bayliss,
G. Bazin, [......],
K. Story,
C. W. Stubbs,
R. Suhada,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R. Williamson,
O. Zahn,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We use measurements from the South Pole Telescope (SPT) Sunyaev Zel'dovich
(SZ) cluster survey in combination with X-ray measurements to constrain
cosmological parameters. We present a statistical method that fits for the
scaling relations of the SZ and X-ray cluster observables with mass while
jointly fitting for cosmology. The method is generalizable to multiple cluster
observables, and self-consistently accounts for the effects of the cluster
selection and uncertainties in cluster mass calibration on the derived
cosmological constraints. We apply this method to a data set consisting of an
SZ-selected catalog of 18 galaxy clusters at z > 0.3 from the first 178 deg2 of
the 2500 deg2 SPT-SZ survey, with 14 clusters having X-ray observations from
either Chandra or XMM. Assuming a spatially flat LCDM cosmological model, we
find the SPT cluster sample constrain sigma_8 (Omega_m/0.25)^0.30 = 0.785 +-
0.037. In combination with measurements of the CMB power spectrum from the SPT
and the seven-year WMAP data, the SPT cluster sample constrain sigma_8 = 0.795
+- 0.016 and Omega_m = 0.255 +- 0.016, a factor of 1.5 improvement on each
parameter over the CMB data alone. We consider several extensions beyond the
LCDM model by including the following as free parameters: the dark energy
equation of state (w), the sum of the neutrino masses (sum mnu), the effective
number of relativistic species (Neff), and a primordial non-Gaussianity (fNL).
We find that adding the SPT cluster data significantly improves the constraints
on w and sum mnu beyond those found when using measurements of the CMB,
supernovae, baryon acoustic oscillations, and the Hubble constant. Considering
each extension independently, we best constrain w=-0.973 +- 0.063 and the sum
of neutrino masses sum mnu < 0.28 eV at 95% confidence, a factor of 1.25 and
1.4 improvement, respectively, over the constraints without clusters. [abbrev.]
12/2011;
-
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
-
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
-
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;
-
K. Story,
K. A. Aird,
K. Andersson, R. Armstrong,
G. Bazin,
B. A. Benson,
L. E. Bleem,
M. Bonamente,
M. Brodwin,
J. E. Carlstrom, [......],
J Song,
H. G. Spieler,
B. Stalder,
Z. Staniszewski,
A. A. Stark,
C. W. Stubbs,
K. Vanderlinde,
J. D. Vieira,
R Williamson,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We present South Pole Telescope (SPT) observations of the five galaxy cluster
candidates in the southern hemisphere which were reported as unconfirmed in the
Planck Early Sunyaev-Zel'dovich (ESZ) sample. One cluster candidate, PLCKESZ
G255.62-46.16, is located in the 2500-square-degree SPT SZ survey region and
was reported previously as SPT-CL J0411-4819. For the remaining four
candidates, which are located outside of the SPT SZ survey region, we performed
short, dedicated SPT observations. Each of these four candidates was strongly
detected in maps made from these observations, with signal-to-noise ratios
ranging from 6.3 to 13.8. We have observed these four candidates on the
Magellan-Baade telescope and used these data to estimate cluster redshifts from
the red sequence. Resulting redshifts range from 0.24 to 0.46. We report
measurements of Y_0.75', the integrated Comptonization within a 0.75' radius,
for all five candidates. We also report X-ray luminosities calculated from
ROSAT All-Sky Survey catalog counts, as well as optical and improved SZ
coordinates for each candidate. The combination of SPT SZ measurements, optical
red-sequence measurements, and X-ray luminosity estimates demonstrates that
these five Planck ESZ cluster candidates do indeed correspond to real galaxy
clusters with redshifts and observable properties consistent with the rest of
the ESZ sample.
02/2011;
-
R. J. Foley,
K. Andersson,
G. Bazin,
T. de Haan,
J. Ruel,
P. A. R. Ade,
K. A. Aird, R. Armstrong,
M. L. N. Ashby,
M. Bautz, [......],
S. A. Stanford,
Z. Staniszewski,
A. A. Stark,
K. Story,
C. W. Stubbs,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R Williamson,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: Using the South Pole Telescope (SPT), we have discovered the most massive
known galaxy cluster at z > 1, SPT-CL J2106-5844. In addition to producing a
strong Sunyaev-Zel'dovich effect signal, this system is a luminous X-ray source
and its numerous constituent galaxies display spatial and color clustering, all
indicating the presence of a massive galaxy cluster. VLT and Magellan
spectroscopy of 18 member galaxies shows that the cluster is at z =
1.132^+0.002_-0.003. Chandra observations obtained through a combined HRC-ACIS
GTO program reveal an X-ray spectrum with an Fe K line redshifted by z = 1.18
+/- 0.03. These redshifts are consistent with galaxy colors in extensive
optical, near-infrared, and mid-infrared imaging. SPT-CL J2106-5844 displays
extreme X-ray properties for a cluster, having a core-excluded temperature of
kT = 11.0^+2.6_-1.9 keV and a luminosity (within r_500) of L_X (0.5 - 2.0 keV)
= (13.9 +/- 1.0) x 10^44 erg/s. The combined mass estimate from measurements of
the Sunyaev-Zel'dovich effect and X-ray data is M_200 = (1.27 +/- 0.21) x 10^15
M_sun. The discovery of such a massive gravitationally collapsed system at high
redshift provides an interesting laboratory for galaxy formation and evolution,
and is a powerful probe of extreme perturbations of the primordial matter
density field. We discuss the latter, determining that, under the assumption of
LambdaCDM cosmology with only Gaussian perturbations, there is only a 7% chance
of finding a galaxy cluster similar to SPT-CL J2106-5844 in the 2500 deg^2 SPT
survey region, and that only one such galaxy cluster is expected in the entire
sky.
01/2011;
-
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
-
R. Suhada,
J Song,
H. Boehringer,
B. A. Benson,
J. Mohr,
R. Fassbender,
A. Finoguenov,
D. Pierini,
G. W. Pratt,
K. Andersson, R. Armstrong,
S Desai
[show abstract]
[hide abstract]
ABSTRACT: We report on the discovery of two galaxy clusters, SPT-CL J2332-5358 and SPT-CL J2342-5411, in X-rays. These clusters were also independently detected through their Sunyaev-Zel'dovich effect by the South Pole Telescope, and confirmed in the optical band by the Blanco Cosmology Survey. They are thus the first clusters detected under survey conditions by all major cluster search approaches. The X-ray detection is made within the frame of the XMM-BCS cluster survey utilizing a novel XMM-Newton mosaic mode of observations. The present study makes the first scientific use of this operation mode. We estimate the X-ray spectroscopic temperature of SPT-CL J2332-5358 (at redshift z=0.32) to T = 9.3 (+3.3/-1.9) keV, implying a high mass, M_{500} = 8.8 +/- 3.8 \times 10^{14} M_{sun}. For SPT-CL J2342-5411, at z=1.08, the available X-ray data doesn't allow us to directly estimate the temperature with good confidence. However, using our measured luminosity and scaling relations we estimate that T = 4.5 +/- 1.3 keV and M_{500} = 1.9 +/- 0.8 \times 10^{14} M_{sun}. We find a good agreement between the X-ray masses and those estimated from the Sunyaev-Zel'dovich effect. Comment: Submitted to A&A, 8 pages, 5 figures, 1 table
03/2010;
-
R. Šuhada,
J Song,
H. Böhringer,
B. A. Benson,
J. Mohr,
R. Fassbender,
A. Finoguenov,
D. Pierini,
G. W. Pratt,
K. Andersson, R. Armstrong,
S Desai
http://dx.doi.org/10.1051/0004-6361/201014434.
