Submitted to ApJ Preprint typeset using LATEX style emulateapj v. 08/22/09 COSMOLOGICAL CONSTRAINTS FROM SUNYAEV-ZEL’DOVICH-SELECTED CLUSTERS WITH X-RAY OBSERVATIONS IN THE FIRST 178 SQUARE DEGREES OF THE SOUTH POLE TELESCOPE SURVEY

We use measurements from the South Pole Telescope (SPT) Sunyaev Zel’dovich (SZ) cluster sur-vey 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-Newton. Assuming a spatially flat ΛCDM cosmological model, we find the SPT cluster sample constrains σ8(Ωm/0.25) 0.30 = 0.785 ± 0.037. In combination with measurements of the CMB power spectru