Planck Intermediate Results. XXXVI. Optical identification and redshifts of Planck SZ sources with telescopes in the Canary Islands Observatories

TL;DR

This study reports three years of optical follow-up observations of Planck SZ sources using Canary Islands telescopes, successfully identifying counterparts and determining redshifts for most sources, including new redshifts for previously uncatalogued clusters.

Contribution

It provides the first extensive optical identification and redshift measurements for Planck SZ sources, including new redshifts for 27 previously unconfirmed clusters.

Findings

Optical counterparts identified for 73 of 78 SZ sources.

53 spectroscopic redshifts obtained, including 27 new cluster redshifts.

Effective use of 37.5 clear nights for observations.

Abstract

We present the results of approximately three years of observations of Planck Sunyaev-Zeldovich (SZ) sources with telescopes at the Canary Islands observatories as part of the general optical follow-up programme undertaken by the Planck collaboration. In total, 78 SZ sources are discussed. Deep-imaging observations were obtained for most of these sources; spectroscopic observations in either in long-slit or multi-object modes were obtained for many. We effectively used 37.5 clear nights. We found optical counterparts for 73 of the 78 candidates. This sample includes 53 spectroscopic redshift determinations, 20 of them obtained with a multi-object spectroscopic mode. The sample contains new redshifts for 27 Planck clusters that were not included in the first Planck SZ source catalogue (PSZ1).