South Pole Telescope Detections of the Previously Unconfirmed Planck Early SZ Clusters in the Southern Hemisphere

TL;DR

This paper reports the confirmation of five galaxy clusters in the southern hemisphere using South Pole Telescope observations, optical data, and X-ray measurements, validating their status as real clusters and providing their properties.

Contribution

It presents the first confirmation of previously unconfirmed Planck ESZ cluster candidates through combined SPT, optical, and X-ray observations, expanding the catalog of known galaxy clusters.

Findings

All five candidates are confirmed as galaxy clusters.

Redshifts range from 0.24 to 0.46.

Measured properties are consistent with known cluster samples.

Abstract

We present South Pole Telescope (SPT) observations of the five galaxy cluster candidates in the southern hemisphere which were reported as unconfirmed in the Planck Early Sunyaev-Zel'dovich (ESZ) sample. One cluster candidate, PLCKESZ G255.62-46.16, is located in the 2500-square-degree SPT SZ survey region and was reported previously as SPT-CL J0411-4819. For the remaining four candidates, which are located outside of the SPT SZ survey region, we performed short, dedicated SPT observations. Each of these four candidates was strongly detected in maps made from these observations, with signal-to-noise ratios ranging from 6.3 to 13.8. We have observed these four candidates on the Magellan-Baade telescope and used these data to estimate cluster redshifts from the red sequence. Resulting redshifts range from 0.24 to 0.46. We report measurements of Y_0.75', the integrated Comptonization within a 0.75' radius, for all five candidates. We also report X-ray luminosities calculated from ROSAT All-Sky Survey catalog counts, as well as optical and improved SZ coordinates for each candidate. The combination of SPT SZ measurements, optical red-sequence measurements, and X-ray luminosity estimates demonstrates that these five Planck ESZ cluster candidates do indeed correspond to real galaxy clusters with redshifts and observable properties consistent with the rest of the ESZ sample.