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Register a new userAn SZ-selected sample of the most massive galaxy clusters in the 2500-square-degree South Pole Telescope survey
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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-Zeldovich (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.
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(abridged) We present cosmological constraints obtained from galaxy clusters identified by their Sunyaev-Zeldovich effect signature in the 2500 square degree South Pole Telescope Sunyaev Zeldovich survey. We consider the 377 cluster candidates identified at z>0.25 with a detection significance greater than five, corresponding to the 95% purity threshold for the survey. We compute constraints on cosmological models using the measured cluster abundance as a function of mass and redshift. We include additional constraints from multi-wavelength observations, including Chandra X-ray data for 82 clusters and a weak lensing-based prior on the normalization of the mass-observable scaling relations. Assuming a LCDM cosmology, where the species-summed neutrino mass has the minimum allowed value (mnu = 0.06 eV) from neutrino oscillation experiments, we combine the cluster data with a prior on H0 and find sigma_8 = 0.797+-0.031 and Omega_m = 0.289+-0.042, with the parameter combination sigma_8(Omega_m/0.27)^0.3 = 0.784+-0.039. These results are in good agreement with constraints from the CMB from SPT, WMAP, and Planck, as well as with constraints from other cluster datasets. Adding mnu as a free parameter, we find mnu = 0.14+-0.08 eV when combining the SPT cluster data with Planck CMB data and BAO data, consistent with the minimum allowed value. Finally, we consider a cosmology where mnu and N_eff are fixed to the LCDM values, but the dark energy equation of state parameter w is free. Using the SPT cluster data in combination with an H0 prior, we measure w = -1.28+-0.31, a constraint consistent with the LCDM cosmological model and derived from the combination of growth of structure and geometry. When combined with primarily geometrical constraints from Planck CMB, H0, BAO and SNe, adding the SPT cluster data improves the w constraint from the geometrical data alone by 14%, to w = -1.023+-0.042.
We present a cosmic microwave background (CMB) lensing map produced from a linear combination of South Pole Telescope (SPT) and emph{Planck} temperature data. The 150 GHz temperature data from the $2500 {rm deg}^{2}$ SPT-SZ survey is combined with the emph{Planck} 143 GHz data in harmonic space, to obtain a temperature map that has a broader $ell$ coverage and less noise than either individual map. Using a quadratic estimator technique on this combined temperature map, we produce a map of the gravitational lensing potential projected along the line of sight. We measure the auto-spectrum of the lensing potential $C_{L}^{phiphi}$, and compare it to the theoretical prediction for a $Lambda$CDM cosmology consistent with the emph{Planck} 2015 data set, finding a best-fit amplitude of $0.95_{-0.06}^{+0.06}({rm Stat.})! _{-0.01}^{+0.01}({rm Sys.})$. The null hypothesis of no lensing is rejected at a significance of $24,sigma$. One important use of such a lensing potential map is in cross-correlations with other dark matter tracers. We demonstrate this cross-correlation in practice by calculating the cross-spectrum, $C_{L}^{phi G}$, between the SPT+emph{Planck} lensing map and Wide-field Infrared Survey Explorer (emph{WISE}) galaxies. We fit $C_{L}^{phi G}$ to a power law of the form $p_{L}=a(L/L_{0})^{-b}$ with $a=2.15 times 10^{-8}$, $b=1.35$, $L_{0}=490$, and find $eta^{phi G}=0.94^{+0.04}_{-0.04}$, which is marginally lower, but in good agreement with $eta^{phi G}=1.00^{+0.02}_{-0.01}$, the best-fit amplitude for the cross-correlation of emph{Planck}-2015 CMB lensing and emph{WISE} galaxies over $sim67%$ of the sky. The lensing potential map presented here will be used for cross-correlation studies with the Dark Energy Survey (DES), whose footprint nearly completely covers the SPT $2500 {rm deg}^2$ field.
The presence of non-thermal electrons and large scale magnetic fields in the intra-cluster medium (ICM) is known through the detection of mega-parsec (Mpc) scale diffuse radio synchrotron emission. Although a significant amount of progress in finding new diffuse radio sources has happened in the last decade, most of the investigation has been constrained towards massive low-redshift clusters. In this work, we explore clusters with redshift $z>0.3$ in search of diffuse radio emission, at 325 MHz with the Giant Metrewave Radio Telescope (GMRT). This campaign has resulted in the discovery of 2 new radio halos (SPT-CL J0013-4906 and SPT-CL J0304-4401) along with 2 other detections (SPT-CL J2031-4037 and SPT-CL J2248-4431), previously reported (at 325 MHz) in the literature. In addition, we detect a halo candidate in 1 cluster in our sample, and upper limits for halos are placed in 8 clusters where no diffuse emission is detected. In the $P_{1.4} - L_mathrm{X}$ plane, the detected halos follow the observed correlation, whereas the upper limits lie above the correlation line, indicating the possibility of future detection with sensitive observations.
We estimate total mass ($M_{500}$), intracluster medium (ICM) mass ($M_{mathrm{ICM}}$) and stellar mass ($M_{star}$) in a Sunyaev-Zeldovich effect (SZE) selected sample of 91 galaxy clusters with masses $M_{500}gtrsim2.5times10^{14}M_{odot}$ and redshift $0.2 < z < 1.25$ from the 2500 deg$^2$ South Pole Telescope SPT-SZ survey. The total masses $M_{500}$ are estimated from the SZE observable, the ICM masses $M_{mathrm{ICM}}$ are obtained from the analysis of $Chandra$ X-ray observations, and the stellar masses $M_{star}$ are derived by fitting spectral energy distribution templates to Dark Energy Survey (DES) $griz$ optical photometry and $WISE$ or $Spitzer$ near-infrared photometry. We study trends in the stellar mass, the ICM mass, the total baryonic mass and the cold baryonic fraction with cluster mass and redshift. We find significant departures from self-similarity in the mass scaling for all quantities, while the redshift trends are all statistically consistent with zero, indicating that the baryon content of clusters at fixed mass has changed remarkably little over the past $approx9$ Gyr. We compare our results to the mean baryon fraction (and the stellar mass fraction) in the field, finding that these values lie above (below) those in cluster virial regions in all but the most massive clusters at low redshift. Using a simple model of the matter assembly of clusters from infalling groups with lower masses and from infalling material from the low density environment or field surrounding the parent halos, we show that the measured mass trends without strong redshift trends in the stellar mass scaling relation could be explained by a mass and redshift dependent fractional contribution from field material. Similar analyses of the ICM and baryon mass scaling relations provide evidence for the so-called missing baryons outside cluster virial regions.
We present a detection-significance-limited catalog of 21 Sunyaev-Zeldovich 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 = 0.81 +- 0.09 and w = -1.07 +- 0.29, a ~50% improvement in precision on both parameters over WMAP7 alone.
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