Intra-Cluster Light at the Frontier: Abell 2744 (1405.2070v3)

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.