Planck 2015 results. XXVII. The Second Planck Catalogue of Sunyaev-Zeldovich Sources

TL;DR

The paper presents the largest all-sky Sunyaev-Zeldovich (SZ) galaxy cluster catalog from Planck data, including detailed analysis of its completeness, reliability, and multi-wavelength counterpart identification, revealing new low-redshift X-ray under-luminous clusters.

Contribution

It introduces the second Planck SZ catalog (PSZ2) with over 1600 detections, detailed survey analysis, and multi-wavelength counterpart identification, expanding the known galaxy cluster sample.

Findings

Contains 1653 SZ detections, 1203 confirmed clusters.

Achieves at least 83% purity in the catalog.

Identifies low-redshift X-ray under-luminous clusters.

Abstract

We present the all-sky Planck catalogue of Sunyaev-Zeldovich (SZ) sources detected from the 29 month full-mission data. The catalogue (PSZ2) is the largest SZ-selected sample of galaxy clusters yet produced and the deepest all-sky catalogue of galaxy clusters. It contains 1653 detections, of which 1203 are confirmed clusters with identified counterparts in external data-sets, and is the first SZ-selected cluster survey containing > $10^3$ confirmed clusters. We present a detailed analysis of the survey selection function in terms of its completeness and statistical reliability, placing a lower limit of 83% on the purity. Using simulations, we find that the Y5R500 estimates are robust to pressure-profile variation and beam systematics, but accurate conversion to Y500 requires. the use of prior information on the cluster extent. We describe the multi-wavelength search for counterparts in ancillary data, which makes use of radio, microwave, infra-red, optical and X-ray data-sets, and which places emphasis on the robustness of the counterpart match. We discuss the physical properties of the new sample and identify a population of low-redshift X-ray under- luminous clusters revealed by SZ selection. These objects appear in optical and SZ surveys with consistent properties for their mass, but are almost absent from ROSAT X-ray selected samples.