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Abstract:
We derive cosmological constraints using a galaxy cluster sample selected from the 2500 deg2 SPT-SZ survey. The sample spans the redshift range 0.25 < z < 1.75 and contains 343 clusters with SZ detection significance ξ > 5. The sample is supplemented with optical weak gravitational lensing measurements of 32 clusters with 0.29 < z < 1.13 (from Magellan and Hubble Space Telescope) and X-ray measurements of 89 clusters with 0.25 < z < 1.75 (from Chandra). We rely on minimal modeling assumptions: (i) weak lensing provides an accurate means of measuring halo masses, (ii) the mean SZ and X-ray observables are related to the true halo mass through power-law relations in mass and dimensionless Hubble parameter E(z) with a priori unknown parameters, and (iii) there is (correlated, lognormal) intrinsic scatter and measurement noise relating these observables to their mean relations. We simultaneously fit for these astrophysical modeling parameters and for cosmology. Assuming a flat νΛCDM model, in which the sum of neutrino masses is a free parameter, we measure Ωm = 0.276 ± 0.047, σ 8 = 0.781 ± 0.037, and σ 8(Ωm/0.3)0.2 = 0.766 ±0.025. The redshift evolutions of the X-ray Y X–mass and M gas–mass relations are both consistent with self-similar evolution to within 1σ. The mass slope of the Y X–mass relation shows a 2.3σ deviation from self-similarity. Similarly, the mass slope of the M gas–mass relation is steeper than self-similarity at the 2.5σ level. In a νwCDM cosmology, we measure the dark energy equation-of-state parameter w = −1.55 ± 0.41 from the cluster data. We perform a measurement of the growth of structure since redshift z ~ 1.7 and find no evidence for tension with the prediction from general relativity. This is the first analysis of the SPT cluster sample that uses direct weak-lensing mass calibration and is a step toward using the much larger weak-lensing data set from DES. We provide updated redshift and mass estimates for the SPT sample.
