We present constraints on cosmological parameters based on a sample of Sunyaev-Zel ’ dovich-selected galaxy clusters detected in a millimeter-wave survey by the Atacama Cosmology Telescope .
The cluster sample used in this analysis consists of 9 optically-confirmed high-mass clusters comprising the high-significance end of the total cluster sample identified in 455 square degrees of sky surveyed during 2008 at 148 GHz .
We focus on the most massive systems to reduce the degeneracy between unknown cluster astrophysics and cosmology derived from SZ surveys .
We describe the scaling relation between cluster mass and SZ signal with a 4-parameter fit .
Marginalizing over the values of the parameters in this fit with conservative priors gives \sigma _ { 8 } = 0.851 \pm 0.115 and w = -1.14 \pm 0.35 for a spatially-flat wCDM cosmological model with WMAP 7-year priors on cosmological parameters .
This gives a modest improvement in statistical uncertainty over WMAP 7-year constraints alone .
Fixing the scaling relation between cluster mass and SZ signal to a fiducial relation obtained from numerical simulations and calibrated by X-ray observations , we find \sigma _ { 8 } = 0.821 \pm 0.044 and w = -1.05 \pm 0.20 .
These results are consistent with constraints from WMAP 7 plus baryon acoustic oscillations plus type Ia supernoava which give \sigma _ { 8 } = 0.802 \pm 0.038 and w = -0.98 \pm 0.053 .
A stacking analysis of the clusters in this sample compared to clusters simulated assuming the fiducial model also shows good agreement .
These results suggest that , given the sample of clusters used here , both the astrophysics of massive clusters and the cosmological parameters derived from them are broadly consistent with current models .