On the Mass Distribution of the Intra-Cluster Light in Galaxy Groups and Clusters

TL;DR

This study uses a semi-analytic model to analyze the mass distribution of intra-cluster light in galaxy groups and clusters, revealing it is more concentrated than dark matter but less so than previous models, and varies with redshift and halo mass.

Contribution

It introduces a modified NFW profile for ICL distribution linked to dark matter, calibrated against observations, and explores its dependence on redshift and halo mass.

Findings

ICL fraction increases with redshift and $\gamma$

ICL distribution is more concentrated than dark matter

Modified NFW describes ICL distribution well

Abstract

We take advantage of a semi-analytic model with a state-of-art implementation of the formation of the intra-cluster light (ICL) to study the mass distribution of the ICL in galaxy groups and clusters, at different redshifts. We assume the ICL to follow a NFW profile with a different concentration, linked to that of the dark matter by the relation $c_{ICL}=\gamma c_{DM}$, where the parameter $\gamma$ is set to reproduce the observed relation between the stellar mass in the brightest cluster galaxy (BCG) and ICL in the innermost 100 kpc and the halo mass ($M^*_{100}-M_{500}$), at $z=0$. The model is then tested against several theoretical and observational results, from the present time to $z\sim1.5$. Our analysis shows that the fraction of stellar mass in the BCG and ICL within the innermost 100 kpc is an increasing function of redshift, parameter $\gamma$, and a decreasing function of the halo mass. The value of $\gamma$ required to match the observed $M^*_{100}-M_{500}$ is $\gamma=3$ at $z=0$, but there are hints that it might be a function of redshift and halo mass. This result indicates that the distribution of the ICL is more concentrated than the dark matter one, but less concentrated than previously found by other studies. We suggest that a modified version of the NFW is a good description of the distribution of the diffuse light in groups and clusters, which makes the ICL a reliable tracer of the dark matter, in good agreement with recent observational findings.