Evolution in cluster cores since z~1

TL;DR

This study detects and measures intracluster light in galaxy clusters at redshift ~1, revealing a significant increase in ICL fraction since then, which impacts understanding of cluster evolution and galaxy interactions.

Contribution

First measurement of intracluster light flux at z~1, showing its growth over time and implications for cluster evolution models.

Findings

ICL fraction has increased by factors of 2-4 since z~1

ICL growth suggests stripping dominates over merging in cluster cores

Results challenge previous notions of BCG mass and size stability

Abstract

A large fraction of the stellar mass in galaxy clusters is thought to be contained in the diffuse low surface brightness intracluster light (ICL). Being bound to the gravitational potential of the cluster rather than any individual galaxy, the ICL contains much information about the evolution of its host cluster and the interactions between the galaxies within. However due its low surface brightness it is notoriously difficult to study. We present the first detection and measurement of the flux contained in the ICL at z~1. We find that the fraction of the total cluster light contained in the ICL may have increased by factors of 2-4 since z~1, in contrast to recent findings for the lack of mass and scale size evolution found for brightest cluster galaxies. Our results suggest that late time buildup in cluster cores may occur more through stripping than merging and we discuss the implications of our results for hierarchical simulations.