The Environmental Dependence of Properties of Galaxies around the RDCSJ0910+54 Cluster at z=1.1

TL;DR

This study investigates how galaxy properties vary with environment around a z=1.1 cluster, revealing large-scale structures and environment-dependent galaxy evolution, especially differences in red galaxy populations between rich and poor systems.

Contribution

It presents the discovery of a large-scale structure at z>1 and analyzes the environmental effects on galaxy stellar populations and luminosity functions at high redshift.

Findings

Large-scale structure of three galaxy clumps identified around the cluster.

Red galaxy fraction is higher in rich clusters and has remained stable since z~1.

Luminosity functions of red galaxies differ between rich and poor systems, indicating environment-dependent evolution.

Abstract

(Abridged) We report on the environmental dependence of properties of galaxies around the RDCSJ0910+54 cluster at z=1.1. We have obtained multi-band wide-field images of the cluster with Suprime-Cam and MOIRCS on Subaru and WFCAM on UKIRT. Also, an intensive spectroscopic campaign has been carried out using LRIS on Keck and FOCAS on Subaru. We discover a possible large-scale structure around the cluster in the form of three clumps of galaxies. This is potentially one of the largest structures found so far in the z>1 Universe. We then examine stellar populations of galaxies in the structure. Red galaxies have already become the dominant population in the cores of rich clusters at z~1, and the fraction of red galaxies has not strongly changed since then. The red fraction depends on richness of clusters in the sense that it is higher in rich clusters than in poor groups. The luminosity function of red galaxies in rich clusters is consistent with that in local clusters. On the other hand, luminosity function of red galaxies in poor groups shows a deficit of faint red galaxies. This confirms our earlier findings that galaxies follow an environment-dependent down-sizing evolution. There seems to be a large variation in the evolutionary phases of galaxies in groups with similar masses. Further studies of high-z clusters will be a promising way of addressing the role of nature and nurture effects on galaxy evolution.