Intracluster light in the core of z∼2 galaxy proto-clusters

Abstract Intracluster light is thought to originate from stars that were ripped away their parent galaxies by gravitational tides and galaxy interactions during the build up of cluster. The such will accumulate over time, so semi-analytic models suggest abundance intracluster negligible in young proto-clusters at z ∼ 2 grows around a quarter stellar mass oldest, most mature clusters. In contrast these theoretical expectations, we report on detection within two = using deep HST images. We use colour estimate its mass-to-light ratio annuli brightest cluster (BCG), radius 100 kpc. find 54 ± 5% 71 3% regions located more than 10 kpc BCGs proto-clusters. This low concentration similar lower redshift clusters, distinct other massive proto-cluster galaxies. suggests are already present core compare observations Hydrangea hydrodynamical simulations predicted be generic feature group-sized halos 2. These gradually move further BCG as assembles into