-
M. McDonald,
B. A. Benson,
A. Vikhlinin,
B. Stalder,
L. E. Bleem,
H. W. Lin,
K. A. Aird,
M. L. N. Ashby,
M. W. Bautz,
M. Bayliss, [......],
S. A. Stanford,
Z. Staniszewski,
A. A. Stark,
K. Story,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
R. Williamson,
O. Zahn,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We present first results on the cooling properties derived from Chandra X-ray
observations of 83 high-redshift (0.3 < z < 1.2) massive galaxy clusters
selected by their Sunyaev-Zel'dovich signature in the South Pole Telescope
data. We measure each cluster's central cooling time, central entropy, and mass
deposition rate, and compare to local cluster samples. We find no significant
evolution from z~0 to z~1 in the distribution of these properties, suggesting
that cooling in cluster cores is stable over long periods of time. We also find
that the average cool core entropy profile in the inner ~100 kpc has not
changed dramatically since z ~ 1, implying that feedback must be providing
nearly constant energy injection to maintain the observed "entropy floor" at
~10 keV cm^2. While the cooling properties appear roughly constant over long
periods of time, we observe strong evolution in the gas density profile, with
the normalized central density (rho_0/rho_crit) increasing by an order of
magnitude from z ~ 1 to z ~ 0. When using metrics defined by the inner surface
brightness profile of clusters, we find an apparent lack of classical, cuspy,
cool-core clusters at z > 0.75, consistent with earlier reports for clusters at
z > 0.5 using similar definitions. Our measurements indicate that cool cores
have been steadily growing over the 8 Gyr spanned by our sample, consistent
with a constant, ~150 Msun/yr cooling flow that is unable to cool below
entropies of 10 keV cm^2 and, instead, accumulates in the cluster center. We
estimate that cool cores began to assemble in these massive systems at z ~ 1,
which represents the first constraints on the onset of cooling in galaxy
cluster cores. We investigate several potential biases which could conspire to
mimic this cool core evolution and are unable to find a bias that has a similar
redshift dependence and a substantial amplitude.
05/2013;
-
D. R. Semler,
R. Šuhada,
K. A. Aird,
M. L. N. Ashby,
M. Bautz,
M. Bayliss,
G. Bazin,
S. Bocquet,
B. A. Benson,
L. E. Bleem, [......],
A. A. Stark,
K. Story,
C. W. Stubbs,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R. Williamson,
O. Zahn,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We report the first investigation of cool-core properties of galaxy clusters
selected via their Sunyaev--Zel'dovich (SZ) effect. We use 13 galaxy clusters
uniformly selected from 178 deg^2 observed with the South Pole Telescope (SPT)
and followed up by the Chandra X-ray Observatory. They form an approximately
mass-limited sample (> 3 x 10^14 M_sun h^-1_70) spanning redshifts 0.3 < z <
1.1. Using previously published X-ray-selected cluster samples, we compare two
proxies of cool-core strength: surface brightness concentration (cSB) and
cuspiness ({\alpha}). We find that cSB is better constrained. We measure cSB
for the SPT sample and find several new z > 0.5 cool-core clusters, including
two strong cool cores. This rules out the hypothesis that there are no z > 0.5
clusters that qualify as strong cool cores at the 5.4{\sigma} level. The
fraction of strong cool-core clusters in the SPT sample in this redshift regime
is between 7% and 56% (95% confidence). Although the SPT selection function is
significantly different from the X-ray samples, the high-z cSB distribution for
the SPT sample is statistically consistent with that of X-ray-selected samples
at both low and high redshifts. The cool-core strength is inversely correlated
with the offset between the brightest cluster galaxy and the X-ray centroid,
providing evidence that the dynamical state affects the cool-core strength of
the cluster. Larger SZ-selected samples will be crucial in understanding the
evolution of cluster cool cores over cosmic time.
08/2012;
-
M McDonald,
M Bayliss,
B A Benson,
R J Foley,
J Ruel,
P Sullivan,
S Veilleux,
K A Aird,
M L N Ashby,
M Bautz, [......],
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: In the cores of some clusters of galaxies the hot intracluster plasma is dense enough that it should cool radiatively in the cluster's lifetime, leading to continuous 'cooling flows' of gas sinking towards the cluster centre, yet no such cooling flow has been observed. The low observed star-formation rates and cool gas masses for these 'cool-core' clusters suggest that much of the cooling must be offset by feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical and infrared observations of the galaxy cluster SPT-CLJ2344-4243 (ref. 11) at redshift z = 0.596. These observations reveal an exceptionally luminous (8.2 × 10(45) erg s(-1)) galaxy cluster that hosts an extremely strong cooling flow (around 3,820 solar masses a year). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (formation of around 740 solar masses a year), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool-core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star-formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form through accretion of the intracluster medium, rather than (as is currently thought) assembling entirely via mergers.
Nature 08/2012; 488(7411):349-52. · 36.28 Impact Factor
-
M. McDonald,
M. Bayliss,
B. A. Benson,
R. J. Foley,
J. Ruel,
P. Sullivan,
S. Veilleux,
K. A. Aird,
M. L. N. Ashby,
M. Bautz, [......],
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: In the cores of some galaxy clusters the hot intracluster plasma is dense
enough that it should cool radiatively in the cluster's lifetime, leading to
continuous "cooling flows" of gas sinking towards the cluster center, yet no
such cooling flow has been observed. The low observed star formation rates and
cool gas masses for these "cool core" clusters suggest that much of the cooling
must be offset by astrophysical feedback to prevent the formation of a runaway
cooling flow. Here we report X-ray, optical, and infrared observations of the
galaxy cluster SPT-CLJ2344-4243 at z = 0.596. These observations reveal an
exceptionally luminous (L_2-10 keV = 8.2 x 10^45 erg/s) galaxy cluster which
hosts an extremely strong cooling flow (dM/dt = 3820 +/- 530 Msun/yr). Further,
the central galaxy in this cluster appears to be experiencing a massive
starburst (740 +/- 160 Msun/yr), which suggests that the feedback source
responsible for preventing runaway cooling in nearby cool core clusters may not
yet be fully established in SPT-CLJ2344-4243. This large star formation rate
implies that a significant fraction of the stars in the central galaxy of this
cluster may form via accretion of the intracluster medium, rather than the
current picture of central galaxies assembling entirely via mergers.
08/2012;
-
B. Stalder,
J. Ruel,
R. Suhada,
M. Brodwin,
K. A. Aird,
K. Andersson,
R. Armstrong,
M. L. N. Ashby,
M. Bautz,
M. Bayliss, [......],
A. A. Stark,
K. Story,
C. W. Stubbs,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R. Williamson,
O. Zahn,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: The galaxy cluster SPT-CL J0205-5829 currently has the highest
spectroscopically-confirmed redshift, z=1.322, in the South Pole Telescope
Sunyaev-Zel'dovich (SPT-SZ) survey. XMM-Newton observations measure a
core-excluded temperature of Tx=8.7keV producing a mass estimate that is
consistent with the Sunyaev-Zel'dovich derived mass. The combined SZ and X-ray
mass estimate of M500=(4.9+/-0.8)e14 h_{70}^{-1} Msun makes it the most massive
known SZ-selected galaxy cluster at z>1.2 and the second most massive at z>1.
Using optical and infrared observations, we find that the brightest galaxies in
SPT-CL J0205-5829 are already well evolved by the time the universe was <5 Gyr
old, with stellar population ages >3 Gyr, and low rates of star formation
(<0.5Msun/yr). We find that, despite the high redshift and mass, the existence
of SPT-CL J0205-5829 is not surprising given a flat LambdaCDM cosmology with
Gaussian initial perturbations. The a priori chance of finding a cluster of
similar rarity (or rarer) in a survey the size of the 2500 deg^2 SPT-SZ survey
is 69%.
05/2012;
-
F. W. High,
H. Hoekstra,
N. Leethochawalit,
T. de Haan,
L. Abramson,
K. A. Aird,
R. Armstrong,
M. L. N. Ashby,
M. Bautz,
M. Bayliss, [......],
C. W. Stubbs,
R. Suhada,
S. Tokarz,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R. Williamson,
O. Zahn,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We use weak gravitational lensing to measure the masses of five galaxy
clusters selected from the South Pole Telescope (SPT) survey, with the primary
goal of comparing these with the SPT Sunyaev--Zel'dovich (SZ) and X-ray based
mass estimates. The clusters span redshifts 0.28 < z < 0.43 and have masses
M_500 > 2 x 10^14 h^-1 M_sun, and three of the five clusters were discovered by
the SPT survey. We observed the clusters in the g'r'i' passbands with the
Megacam imager on the Magellan Clay 6.5m telescope. We measure a mean ratio of
weak lensing (WL) aperture masses to inferred aperture masses from the SZ data,
both within an aperture of R_500,SZ derived from the SZ mass, of 1.04 +/- 0.18.
We measure a mean ratio of spherical WL masses evaluated at R_500,SZ to
spherical SZ masses of 1.07 +/- 0.18, and a mean ratio of spherical WL masses
evaluated at R_500,WL to spherical SZ masses of 1.10 +/- 0.24. We explore
potential sources of systematic error in the mass comparisons and conclude that
all are subdominant to the statistical uncertainty, with dominant terms being
cluster concentration uncertainty and N-body simulation calibration bias.
Expanding the sample of SPT clusters with WL observations has the potential to
significantly improve the SPT cluster mass calibration and the resulting
cosmological constraints from the SPT cluster survey. These are the first WL
detections using Megacam on the Magellan Clay telescope.
05/2012;
-
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;
-
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;
-
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
-
K. Andersson,
B. A. Benson,
P. A. R. Ade,
K. A. Aird,
B. Armstrong,
M. Bautz,
L. E. Bleem,
M. Brodwin,
J. E. Carlstrom,
C. L. Chang, [......],
Z. Staniszewski,
A. A. Stark,
C. W. Stubbs,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R. Williamson,
Y. Yang,
O. Zahn,
and A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We present results of X-ray observations of a sample of 15 clusters selected via their imprint on the cosmic microwave background from the thermal Sunyaev-Zel'dovich (SZ) effect. These clusters are a subset of the first SZ-selected cluster catalog, obtained from observations of 178 deg2 of sky surveyed by the South Pole Telescope (SPT). Using X-ray observations with Chandra and XMM-Newton, we estimate the temperature, TX , and mass, Mg , of the intracluster medium within r 500 for each cluster. From these, we calculate YX = MgTX and estimate the total cluster mass using an M 500-YX scaling relation measured from previous X-ray studies. The integrated Comptonization, Y SZ, is derived from the SZ measurements, using additional information from the X-ray-measured gas density profiles and a universal temperature profile. We calculate scaling relations between the X-ray and SZ observables and find results generally consistent with other measurements and the expectations from simple self-similar behavior. Specifically, we fit a Y SZ-YX relation and find a normalization of 0.82 ± 0.07, marginally consistent with the predicted ratio of Y SZ/YX = 0.91 ± 0.01 that would be expected from the density and temperature models used in this work. Using the YX -derived mass estimates, we fit a Y SZ-M 500 relation and find a slope consistent with the self-similar expectation of Y SZM 5/3 with a normalization consistent with predictions from other X-ray studies. We find that the SZ mass estimates, derived from cosmological simulations of the SPT survey, are lower by a factor of 0.78 ± 0.06 relative to the X-ray mass estimates. This offset is at a level of 1.3σ when considering the ~15% systematic uncertainty for the simulation-based SZ masses. Overall, the X-ray measurements confirm that the scaling relations of the SZ-selected clusters are consistent with the properties of other X-ray-selected samples of massive clusters, even allowing for the broad redshift range (0.29 < z < 1.08) of the sample.
The Astrophysical Journal 08/2011; 738(1):48. · 6.02 Impact Factor
-
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
-
M. Brodwin,
J. Ruel,
P. A. R. Ade,
K. A. Aird,
K. Andersson,
M. L. N. Ashby,
M. Bautz,
G. Bazin,
B. A. Benson,
L. E. Bleem, [......],
Z. Staniszewski,
A. A. Stark,
C. W. Stubbs,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R Williamson,
Y Yang,
O. Zahn,
A. Zenteno
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ABSTRACT: We report the spectroscopic confirmation of SPT-CL J0546-5345 at = 1.067. To date this is the most distant cluster to be spectroscopically confirmed from the 2008 South Pole Telescope (SPT) catalog, and indeed the first z > 1 cluster discovered by the Sunyaev-Zel'dovich Effect (SZE). We identify 21 secure spectroscopic members within 0.9 Mpc of the SPT cluster position, 18 of which are quiescent, early-type galaxies. From these quiescent galaxies we obtain a velocity dispersion of 1179^{+232}_{-167} km/s, ranking SPT-CL J0546-5345 as the most dynamically massive cluster yet discovered at z > 1. Assuming that SPT-CL J0546-5345 is virialized, this implies a dynamical mass of M_200 = 1.0^{+0.6}_{-0.4} x 10^{15} Msun, in agreement with the X-ray and SZE mass measurements. Combining masses from several independent measures leads to a best-estimate mass of M_200 = (7.95 +/- 0.92) x 10^{14} Msun. The spectroscopic confirmation of SPT-CL J0546-5345, discovered in the wide-angle, mass-selected SPT cluster survey, marks the onset of the high redshift SZE-selected galaxy cluster era. Comment: ApJ, in press
06/2010;
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K. Vanderlinde,
T. M. Crawford,
T. de Haan, J P Dudley,
L. Shaw,
P. A. R. Ade,
K. A. Aird,
B. A. Benson,
L. E. Bleem,
M. Brodwin, [......],
B. Stalder,
Z. Staniszewski,
A. A. Stark,
C. W. Stubbs,
A. van Engelen,
J. D. Vieira,
R Williamson,
Y Yang,
O. Zahn,
A. Zenteno
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[hide abstract]
ABSTRACT: We present a detection-significance-limited catalog of 21 Sunyaev-Zel'dovich selected galaxy clusters. These clusters, along with 1 unconfirmed candidate, were identified in 178 deg^2 of sky surveyed in 2008 by the South Pole Telescope to a depth of 18 uK-arcmin at 150 GHz. Optical imaging from the Blanco Cosmology Survey (BCS) and Magellan telescopes provided photometric (and in some cases spectroscopic) redshift estimates, with catalog redshifts ranging from z=0.15 to z>1, with a median z = 0.74. Of the 21 confirmed galaxy clusters, three were previously identified as Abell clusters, three were presented as SPT discoveries in Staniszewski et al, 2009, and three were first identified in a recent analysis of BCS data by Menanteau et al, 2010; the remaining 12 clusters are presented for the first time in this work. Simulated observations of the SPT fields predict the sample to be nearly 100% complete above a mass threshold of M_200 ~ 5x10^14 M_sun/h at z = 0.6. This completeness threshold pushes to lower mass with increasing redshift, dropping to ~4x10^14 M_sun/h at z=1. The size and redshift distribution of this catalog are in good agreement with expectations based on our current understanding of galaxy clusters and cosmology. In combination with other cosmological probes, we use the cluster catalog to improve estimates of cosmological parameters. Assuming a standard spatially flat wCDM cosmological model, the addition of our catalog to the WMAP 7-year analysis yields sigma_8 = 0.80 +- 0.09 and w = -1.05 +- 0.29, a ~50% improvement in precision on both parameters over WMAP7 alone. Comment: 19 pages, 9 figures, 4 appendices; submitted to ApJ
03/2010;
