The SPTpol Extended Cluster Survey

Abstract

We describe the observations and resultant galaxy cluster catalog from the 2770 deg${}^2$ SPTpol Extended Cluster Survey (SPT-ECS). Clusters are identified via the Sunyaev-Zel'dovich (SZ) effect, and confirmed with a combination of archival and targeted follow-up data, making particular use of data from the Dark Energy Survey (DES). With incomplete followup we have confirmed as clusters 244 of 266 candidates at a detection significance $\hat{I}¾\ge 5$ and an additional 204 systems at $4<\hat{I}¾<5$. The confirmed sample has a median mass of $M_{500c}\sim 4.4\times 10^{14}{M}_{\odot }{h}_{70}^{-1}$, a median redshift of $z=0.49$, and we have identified 44 strong gravitational lenses in the sample thus far. Radio data are used to characterize contamination to the SZ signal; the median contamination for confirmed clusters is predicted to be $\sim$1% of the SZ signal at the $\hat{I}¾>4$ threshold, and $<4\%$ of clusters have a predicted contamination $>10\%$ of their measured SZ flux. We associate SZ-selected clusters, from both SPT-ECS and the SPT-SZ survey, with clusters from the DES redMaPPer sample, and find an offset distribution between the SZ center and central galaxy in general agreement with previous work, though with a larger fraction of clusters with significant offsets. Adopting a fixed Planck-like cosmology, we measure the optical richness-to-SZ-mass ($\hat{I}»-M$) relation and find it to be 28% shallower than that from a weak-lensing analysis of the DES data---a difference significant at the 4 $\ddot{I}ƒ$ level---with the relations intersecting at $\hat{I}»=60$ . The SPT-ECS cluster sample will be particularly useful for studying the evolution of massive clusters and, in combination with DES lensing observations and the SPT-SZ cluster sample, will be an important component of future cosmological analyses.

49 pages, 14 figures, 10 tables. Minor changes to match accepted version in ApJS