A VLT/VIMOS view of two Planck multiple-cluster systems: Structure and galaxy properties

Abstract

We analysed spectroscopic data obtained with VLT/VIMOS for two multiple-cluster systems, PLCKG214.6+36.9 and PLCKG334.8-38.0, discovered by Planck via their thermal Sunyaev-Zela'dovich signal. Combining the optical spectroscopy for the redshift determination and photometric data from galaxy surveys (SDSS, WISE and DESI), we were able to study the structure of the two multiple-cluster systems to determine their nature and the properties of their member galaxies. We found that the two systems are mainly populated by passive galaxies and that PLCKG214.6+36.9 consists of a pair of clusters at redshift z = 0.445 and an isolated cluster in the background at z = 0.498, whereas the system PLCKG334.8-38.0 is a chance association of three independent clusters at redshifts of z = 0.367, z = 0.292, and z = 0.33. We also find evidence of remaining star formation activity in the highest redshift cluster of PLCKG214.6+36.9, at z = 0.498.