Evidence for the existence of abundant intracluster light at z= 1.24

TL;DR

This study detects significant intracluster light in a galaxy cluster at redshift 1.24, suggesting early formation of intracluster stars concurrent with cluster and brightest galaxy formation.

Contribution

First simultaneous measurement of spatial distribution, color, and quantity of intracluster light at such a high redshift, providing new insights into the timing of intracluster star formation.

Findings

Significant intracluster light detected at z=1.24

Indicates early formation of intracluster stars

Suggests ICL formation occurs during early cluster assembly

Abstract

Intracluster stars are believed to be unbound from their progenitor galaxies and diffused throughout the galaxy cluster, creating intracluster light (ICL). However, when and how these stars form are still in debate. To directly constrain the origin, one powerful method is to study clusters at the epoch when mature galaxy clusters began to appear. We report measurements of the spatial distribution, color, and quantity of diffuse intracluster stars for a massive galaxy cluster at a redshift of 1.24. This is the most distant galaxy cluster to date for which those three properties of the ICL have been quantified simultaneously. Our detection of the significant ICL fraction in this unprecedentedly high redshift regime strongly indicates that intracluster stars, contrary to most previous studies, might have formed during a short period and early in the history of the Virgo-like massive cluster formation and might be concurrent with the formation of the brightest cluster galaxy.