Does the virial mass drive the intra-cluster light? The relationship between the ICL and M$_{vir}$ from VEGAS

TL;DR

This study investigates the relationship between intra-cluster light (ICL) and virial mass in galaxy groups and clusters, finding no significant correlation with mass but a weak link to galaxy morphology, based on extensive VEGAS survey data.

Contribution

It provides the largest homogeneous ICL dataset for local galaxy systems and clarifies the lack of correlation between ICL fraction and virial mass.

Findings

No significant trend between ICL fraction and virial mass.

A weak correlation exists between ICL fraction and the fraction of early-type galaxies.

Large scatter suggests intrinsic variation in ICL fractions.

Abstract

In this Letter we revisit the relationship between the fraction of the intra-cluster light (ICL) and both the virial mass and the fraction of Early Type Galaxies in the host halo. This is based on a statistically significant and homogeneous sample of 22 groups and clusters of galaxies in the local Universe ($z \leq 0.05$), obtained with the VST Early-type GAlaxy Survey (VEGAS). Taking advantage of the long integration time and large area of the VEGAS images, we are able to map the galaxy outskirts and ICL down to $\mu_g$ $\geq$ 29-30 mag/arcsec$^2$ and out to hundreds of kpc. With this data-set, we have expanded the sample of ICL measurements, doubling the previous measures available from the literature for z $\leq$ 0.05. The main result of this work is the lack of any significant trend between the fraction of ICL and the virial mass of the host environment, covering a wide range of virial masses ( $\sim$ $10^{12.5} \leq M_{vir} \leq 10^{15.5} M_{\odot}$), in agreement with some theoretical studies. Since the new data points are all derived with the same methodology and from the same observational setup, and all have comparable depth, the large observed scatter indicates an intrinsic variation in the ICL fraction.On the other hand, there is a weak relation between the fraction of ICL and the fraction of Early Type Galaxies in the host halo, where a larger fraction of ICL is found in groups and clusters of galaxies dominated by earlier morphological types, indicating a connection between the ICL and the dynamical state of the host system.