Dark Energy Survey Year 6 Results: Intra-Cluster Light from Redshift 0.2 to 0.5

TL;DR

This study uses six years of Dark Energy Survey data to analyze intra-cluster light in galaxy clusters from redshift 0.2 to 0.5, revealing its dependence on cluster mass, potential growth over time, and color gradients indicative of stellar stripping.

Contribution

It provides high signal-to-noise measurements of intra-cluster light profiles across a large sample, highlighting mass dependence and possible redshift evolution, supported by comparison with simulations.

Findings

Intra-cluster light brightness correlates strongly with cluster mass.

Evidence suggests intra-cluster light and central galaxy growth over time.

Color gradients indicate stellar stripping as a source of intra-cluster light.

Abstract

Using the full six years of imaging data from the Dark Energy Survey, we study the surface brightness profiles of galaxy cluster central galaxies and intra-cluster light. We apply a ``stacking'' method to over four thousand galaxy clusters identified by the redMaPPer cluster finding algorithm in the redshift range of 0.2 to 0.5. This yields high signal-to-noise radial profile measurements of the central galaxy and intra-cluster light out to 1 Mpc from the cluster center. Using redMaPPer richness as a cluster mass indicator, we find that the intra-cluster light brightness has a strong mass dependence throughout the 0.2 to 0.5 redshift range, and the dependence grows stronger at a larger radius. In terms of redshift evolution, we find some evidence that the central galaxy, as well as the diffuse light within the transition region between the cluster central galaxy and intra-cluster light within 80 kpc from the center, may be growing over time. At larger radii, more than 80 kpc away from the cluster center, we do not find evidence of additional redshift evolution beyond the cluster mass dependence, which is consistent with the findings from the IllustrisTNG hydrodynamic simulation. We speculate that the major driver of intra-cluster light growth, especially at large radii, is associated with cluster mass growth. Finally, we find that the color of the cluster central galaxy and intra-cluster light displays a radial gradient that becomes bluer at a larger radius, which is consistent with a stellar stripping and disruption origin of intra-cluster light as suggested by simulation studies.