Diffuse Light in Galaxy Clusters

TL;DR

Diffuse intracluster light (ICL) in galaxy clusters reveals insights into cluster formation, galaxy evolution, and baryonic matter distribution, with recent observations and simulations providing new understanding of its origin and properties.

Contribution

This paper reviews recent observational detections of ICL, discusses its significance in understanding cluster evolution, and highlights how simulations are used to predict ICL properties.

Findings

ICL constitutes 10-30% of stellar mass in clusters.

In dense cores like Coma, ICL can reach 40-50%.

Simulations are beginning to predict ICL kinematics and origin.

Abstract

Diffuse intracluster light (ICL) has now been observed in nearby and in intermediate redshift clusters. Individual intracluster stars have been detected in the Virgo and Coma clusters and the first color-magnitude diagram and velocity measurements have been obtained. Recent studies show that the ICL contains of the order of 10% and perhaps up to 30% of the stellar mass in the cluster, but in the cores of some dense and rich clusters like Coma, the local ICL fraction can be high as 40%-50%. What can we learn from the ICL about the formation of galaxy clusters and the evolution of cluster galaxies? How and when did the ICL form? What is the connection to the central brightest cluster galaxy? Cosmological N-body and hydrodynamical simulations are beginning to make predictions for the kinematics and origin of the ICL. The ICL traces the evolution of baryonic substructures in dense environments and can thus be used to constrain some aspects of cosmological simulations that are most uncertain, such as the modeling of star formation and the mass distribution of the baryonic component in galaxies.