A Multiband Study of the Galaxy Populations of the First Four Sunyaev--Zeldovich Effect selected Galaxy Clusters

TL;DR

This study examines the optical properties of galaxy populations in four Sunyaev--Zeldovich effect selected clusters, comparing their characteristics with those of clusters selected by optical and X-ray methods to identify potential differences.

Contribution

It provides the first detailed analysis of galaxy populations in SZE-selected clusters, revealing similarities with optically and X-ray selected clusters and offering insights into their structure and evolution.

Findings

Galaxy distributions follow NFW profiles with concentration 3-6.

Luminosity functions are consistent with passively evolving populations from z=3.

Halo occupation numbers align with X-ray selected clusters.

Abstract

We present first results of an examination of the optical properties of the galaxy populations in SZE selected galaxy clusters. Using clusters selected by the South Pole Telescope survey and deep multiband optical data from the Blanco Cosmology Survey, we measure the radial profile, the luminosity function, the blue fraction and the halo occupation number of the galaxy populations of these four clusters with redshifts ranging from 0.3 to 1. Our goal is to understand whether there are differences among the galaxy populations of these SZE selected clusters and previously studied clusters selected in the optical and the X-ray. The radial distributions of galaxies in the four systems are consistent with NFW profiles with a galaxy concentration of 3 to 6. We show that the characteristic luminosities in $griz$ bands are consistent with passively evolving populations emerging from a single burst at redshift $z=3$. The faint end power law slope of the luminosity function is found to be on average $\alpha \approx -1.2$ in griz. Halo occupation numbers (to $m^*+2$) for these systems appear to be consistent with those based on X-ray selected clusters. The blue fraction estimated to $0.36L^*$, for the three lower redshift systems, suggests an increase with redshift, although with the current sample the uncertainties are still large. Overall, this pilot study of the first four clusters provides no evidence that the galaxy populations in these systems differ significantly from those in previously studied cluster populations selected in the X-ray or the optical.