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

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.

Optical validation and characterization of Planck PSZ2 sources at the Canary Islands observatories

“…While we confirm about 10 % of the clusters at z < 0.4, this rate is ∼ 20 % for z > 0.4. Moreover, we confirmed in Barrena et al (2018) the most distant Planck SZ cluster in the northern hemisphere: the PSZ2 G123.35+25.39, at z phot = 0.95. Burenin (2017) presented an extension for the PSZ2 catalogue using SDSS and WISE.…”

“…We use colour-magnitude diagrams to identify likely clusters members and fit the RS to make an estimate of the photometric redshift using the methodology explained in Barrena et al (2018), Sect. 3 and in Planck Collaboration int.…”

Optical validation and characterization of Planck PSZ2 sources at the Canary Islands observatories

“…We identified, validated and characterized galaxy clusters using the same criteria already adopted in our previous papers (Planck Collaboration XXXVI 2016; Barrena et al 2018;Streblyanska et al 2018). In the next subsection, we will describe again those criteria, when applied to our LP15 sample.…”

“…XXVI 2015; Liu et al 2015;van der Burg et al 2016;Burenin et al 2018;Boada et al 2019). Telescopes at Canary Islands Observatories have actively participated in these validation and characterization efforts of Planck catalogues (Planck Collaboration XXXVI 2016; Barrena et al 2018). The first two catalogues, ESZ and PSZ1, have been partially observed and validated through the International Time Programme 2 ITP12-2 and ITP13-08 (e.g.…”

“…The first two catalogues, ESZ and PSZ1, have been partially observed and validated through the International Time Programme 2 ITP12-2 and ITP13-08 (e.g. Planck Collaboration XXXVI 2016; Barrena et al 2018Barrena et al , 2019. As a result, we retrieved physical properties and confirmed almost 200 previously unknown clusters with 0.08 < z < 0.85.…”