Intragroup and Intracluster Light

TL;DR

This paper reviews the formation and evolution of intracluster light (ICL) in galaxy clusters and groups, highlighting observational signatures, simulation predictions, and the challenges in tracking ICL growth over cosmic time.

Contribution

It synthesizes current observational and simulation studies of ICL, emphasizing the early stages in groups and the growth in clusters, and discusses the difficulties in measuring ICL evolution.

Findings

ICL is formed through galaxy interactions and mergers in clusters.

Nearby Virgo Cluster shows diverse accretion signatures in ICL.

Early ICL formation is observable in diffuse tidal streams in groups.

Abstract

The largest stellar halos in the universe are found in massive galaxy clusters, where interactions and mergers of galaxies, along with the cluster tidal field, all act to strip stars from their host galaxies and feed the diffuse intracluster light (ICL) and extended halos of brightest cluster galaxies (BCGs). Studies of the nearby Virgo Cluster reveal a variety of accretion signatures imprinted in the morphology and stellar populations of its ICL. While simulations suggest the ICL should grow with time, attempts to track this evolution across clusters spanning a range of mass and redshift have proved difficult due to a variety of observational and definitional issues. Meanwhile, studies of nearby galaxy groups reveal the earliest stages of ICL formation: the extremely diffuse tidal streams formed during interactions in the group environment.