Optical Confirmation and Redshift Estimation of the Planck Cluster Candidates overlapping the Pan-STARRS Survey

TL;DR

This study uses Pan-STARRS imaging to confirm and estimate redshifts of Planck galaxy cluster candidates, achieving high accuracy and identifying new clusters, thereby improving the catalog of galaxy clusters detected via the Sunyaev-Zel'dovich effect.

Contribution

The paper presents a new optical confirmation method for Planck SZE cluster candidates and provides redshift estimates, expanding the known sample of galaxy clusters.

Findings

Confirmed 60 new galaxy clusters with redshifts.

Achieved redshift measurement accuracy of ~0.022.

Estimated that about 12 unconfirmed candidates are likely real clusters.

Abstract

We report results of a study of Planck Sunyaev-Zel'dovich effect (SZE) selected galaxy cluster candidates using the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) imaging data. We first examine 150 Planck confirmed galaxy clusters with spectroscopic redshifts to test our algorithm for identifying optical counterparts and measuring their redshifts; our redshifts have a typical accuracy of $\sigma_{z/(1+z)} \sim 0.022$ for this sample. Using 60 random sky locations, we estimate that our chance of contamination through a random superposition is ~ 3 per cent. We then examine an additional 237 Planck galaxy cluster candidates that have no redshift in the source catalogue. Of these 237 unconfirmed cluster candidates we are able to confirm 60 galaxy clusters and measure their redshifts. A further 83 candidates are so heavily contaminated by stars due to their location near the Galactic plane that we do not attempt to identify counterparts. For the remaining 94 candidates we find no optical counterpart but use the depth of the Pan-STARRS1 data to estimate a redshift lower limit $z_{\text{lim}(10^{15})}$ beyond which we would not have expected to detect enough galaxies for confirmation. Scaling from the already published Planck sample, we expect that $\sim$12 of these unconfirmed candidates may be real clusters.