Stellar halos of bright central galaxies A view from the FEGA semi-analytic model of galaxy formation and VEGAS survey

Aims. We present theoretical predictions and extrapolations from observed data of the stellar halos surrounding central group and cluster galaxies, and the transition radius between them and the intracluster or diffuse light. Methods. Leveraging the state-of-the-art semi-analytic model of galaxy formation, FEGA (Formation and Evolution of GAlaxies), applied to two dark matter-only cosmological simulations, we derived both the stellar halo mass and its radius. Using theoretical assumptions about the diffuse light distribution and halo concentration, we extrapolated the same information for observed data from the VEGAS survey. Results. 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. Conclusions. These results support the idea that the stellar halo can be viewed as a transition region between the stars bound to a galaxy and those belonging to the intracluster light and are consistent with recent observations and theoretical predictions.