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, PLCKG$214.6+36.9$ and PLCKG$334.8-38.0$, discovered via their thermal Sunyaev-Zel'dovich signal by $Planck$. Combining the Optical spectroscopy, for the redshift determination, and photometric data from galaxy surveys (SDSS, WISE, 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 populated mainly with passive galaxies and that PLCKG$214.6+36.9$ consists of a pair of clusters at redshift $z=0.445$ and a background isolated cluster at $z=0.498$, whereas the system PLCKG$334.8-38.0$ is a chance association of three independent clusters at redshifts $z=0.367$, $z=0.292$, and $z=0.33$. We also find evidence for remaining star formation activity in the highest-redshift cluster of PLCKG$214.6+36.9$, at $z=0.498$.

12 pages, 9 Figures, 5 Tables. Submitted to A&A, comments are welcome