Optical validation and characterization of Planck PSZ1 sources at the Canary Islands observatories

I. First year of ITP13 observations

¹ Instituto de Astrofísica de Canarias, C/ Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
e-mail: rbarrena@iac.es
² Universidad de La Laguna, Departamento de Astrofísica, 38206 La Laguna, Tenerife, Spain
³ University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban 4000, South Africa
⁴ Universidad Andrés Bello, Departamento de Ciencias Físicas, 7591538 Santiago de Chile, Chile
⁵ Tartu Observatory, University of Tartu, 61602 Tõravere, Tartumaa, Estonia
⁶ Institut d’Astrophysique Spatiale, Université Paris-Sud, CNRS, UMR8617, 91405 Orsay Cedex, France
⁷ IRFU, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
⁸ Université Paris Diderot, AIM, Sorbonne Paris Cité, CEA, CNRS, 91191 Gif-sur-Yvette, France
⁹ Max-Planck-Institut für Extraterrestrische Physik, 85748 Garching, Germany
¹⁰ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029, Blindern, 0315 Oslo, Norway
¹¹ Astrophysics Group, Cavendish Laboratory, JJ Thomson Av., Cambridge 3 Θ HE, UK
¹² Kavli Institute for Cosmology, Madingley Road, Cambridge 3 Θ HA, UK
¹³ Dipartimento di Fisica, Università degli Studi di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Roma, Italy
¹⁴ Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysique et Planétologie (IRAP), 31400 Toulouse, France
¹⁵ CNRS, IRAP, 9 avenue Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
¹⁶ IASF-Milano, Istituto Nazionale di Astrofisica, Via Bassini 15, 20133 Milano, Italy
¹⁷ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany

Received: 17 November 2017
Accepted: 27 March 2018

Abstract

We have identified new clusters and characterized previously unknown Planck Sunyaev–Zeldovich (SZ) sources from the first Planck catalogue of SZ sources (PSZ1). The results presented here correspond to an optical follow-up observational programme developed during approximately one year (2014) at Roque de los Muchachos Observatory, using the 2.5 m Isaac Newton telescope, the 3.5 m Telescopio Nazionale Galileo, the 4.2 m William Herschel telescope and the 10.4 m Gran Telescopio Canarias. We have characterized 115 new PSZ1 sources using deep optical imaging and spectroscopy. We adopted robust criteria in order to consolidate the SZ counterparts by analysing the optical richness, the 2D galaxy distribution, and velocity dispersions of clusters. Confirmed counterparts are considered to be validated if they are rich structures, well aligned with the Planck PSZ1 coordinate and show relatively high velocity dispersion. Following this classification, we confirm 53 clusters, which means that 46% of this PSZ1 subsample has been validated and characterized with this technique. Sixty-two SZ sources (54% of this PSZ1 subset) remain unconfirmed. In addition, we find that the fraction of unconfirmed clusters close to the galactic plane (at |b| < 25°) is greater than that at higher galactic latitudes (|b| > 25°), which indicates contamination produced by radio emission of galactic dust and gas clouds on these SZ detections. In fact, in the majority of the cases, we detect important galactic cirrus in the optical images, mainly in the SZ target located at low galactic latitudes, which supports this hypothesis.