Intra-Cluster Light at the Frontier: Abell 2744

TL;DR

This study uses deep HST data to analyze the stellar populations of intra-cluster light in Abell 2744, revealing its recent formation, metallicity, and contribution to the cluster's total stellar mass.

Contribution

It provides detailed stellar population properties of ICL at intermediate redshift, highlighting its recent formation and origin from disrupted Milky Way-like galaxies.

Findings

ICL is bluer and younger than main galaxy populations.

ICL accounts for at least 6% of total stellar mass.

ICL likely formed from disruption of Milky Way-like galaxies.

Abstract

The ultra-deep multiwavelength HST Frontier Fields coverage of the Abell Cluster 2744 is used to derive the stellar population properties of its intra-cluster light (ICL). The restframe colors of the ICL of this intermediate redshift (z=0.3064) massive cluster are bluer (g-r=0.68+-0.04; i-J=0.56+-0.01) than those found in the stellar populations of its main galaxy members (g-r=0.83+-0.01; i-J=0.75+-0.01). Based on these colors, we derive the following mean metallicity Z=0.018+-0.007 for the ICL. The ICL age is 6+-3 Gyr younger than the average age of the most massive galaxies of the cluster. The fraction of stellar mass in the ICL component comprises at least 6% of the total stellar mass of the galaxy cluster. Our data is consistent with a scenario where the bulk of the ICL of Abell 2744 has been formed relatively recently (z<1). The stellar population properties of the ICL suggest that this diffuse component is mainly the result of the disruption of infalling galaxies with similar characteristics in mass (M*~ 3x10^10 Msolar) and metallicity than our own Milky Way. The amount of ICL mass in the central part of the cluster (<400 kpc) is equivalent to the disruption of 4-6 Milky Way-type galaxies.