An SZ-selected sample of the most massive galaxy clusters in the
  2500-square-degree South Pole Telescope survey
  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.
