Stellar Halos of Bright Central Galaxies: A View from the FEGA Semi-Analytic Model of Galaxy Formation and VEGAS Survey

TL;DR

This paper combines a semi-analytic galaxy formation model with observational data to predict properties of stellar halos around central galaxies, revealing how these halos transition into intracluster light across different halo masses.

Contribution

It introduces a novel application of the FEGA semi-analytic model to predict stellar halo characteristics and compares these predictions with VEGAS survey observations.

Findings

Transition radius increases with halo mass (20-250 kpc).

Stellar halo mass is 7-18% of total stellar mass.

Stellar halo-to-intracluster light ratio remains constant.

Abstract

We present theoretical predictions and extrapolations from observed data of the stellar halos surrounding central group/cluster galaxies and the transition radius between them and the intracluster or diffuse light. Leveraging the state-of-the-art semi-analytic model of galaxy formation, {\small FEGA} (\citealt{contini2024c}), applied to two dark matter-only cosmological simulations, we derive both the stellar halo mass and its radius. Using theoretical assumptions about the diffuse light distribution and halo concentration, we extrapolate the same information for observed data from the {\small VEGAS} survey (\citealt{capaccioli2015,iodice2021}). Our model, supported by observational data and independent simulation results, predicts an increasing transition radius with halo mass, a constant stellar halo-to-intracluster light ratio, and a stable stellar halo mass fraction with increasing halo mass. Specifically, we find that the transition radius between the stellar halo and the diffuse light ranges from 20 to 250 kpc, from Milky Way-like halos to large clusters, while the stellar halo mass comprises only a small fraction, between 7\% and 18\%, of the total stellar mass within the virial radius. These results support the idea that the stellar halo can be viewed as a transition region between the stars bound to the galaxy and those belonging to the intracluster light, consistent with recent observations and theoretical predictions.