Galaxy Clusters Discovered via the Thermal Sunyaev-Zel’dovich Effect in the 500-square-degree SPTpol Survey

We present a catalog of 689 galaxy cluster candidates detected at significance \(\xi>4\) via their thermal Sunyaev-Zel’dovich (SZ) effect signature in 95 and 150 GHz data from the 500-square-degree SPTpol survey. We use optical and infrared data from the Dark Energy Camera and the Wide-field Infrared Survey Explorer (WISE) and Spitzer satellites, to confirm 544 of these candidates as clusters with \(\sim94\%\) purity. The sample has an approximately redshift-independent mass threshold at redshift \(z>0.25\) and spans \(1.5 \times 10^{14} < M_{500c} < 9 \times 10^{14}\) \(M_\odot/h_{70}\) and \(0.03<z\lesssim1.6\) in mass and redshift, respectively; 21% of the confirmed clusters are at \(z>1\). We use external radio data from the Sydney University Molonglo Sky Survey (SUMSS) to estimate contamination to the SZ signal from synchrotron sources. The contamination reduces the recovered \(\xi\) by a median value of 0.032, or \(\sim0.8\%\) of the \(\xi=4\) threshold value, and \(\sim7\%\) of candidates have a predicted contamination greater than \(\Delta \xi = 1\). With the exception of a small number of systems \((<1\%)\), an analysis of clusters detected in single-frequency 95 and 150 GHz data shows no significant contamination of the SZ signal by emission from dusty or synchrotron sources. This cluster sample will be a key component in upcoming astrophysical and cosmological analyses of clusters. The SPTpol millimeter-wave maps and associated data products used to produce this sample are available at https://pole.uchicago.edu/public/data/sptpol_500d_clusters/index.html, and the NASA LAMBDA website. An interactive sky server with the SPTpol maps and Dark Energy Survey data release 2 images is also available at NCSA https://skyviewer.ncsa.illinois.edu.