Assembly history of massive galaxies

Abstract

In this paper we present the new deep images from the VEGAS survey of three massive (M* ≃ 1012 M⊙) galaxies from the MUSE Most Massive Galaxies (M3G) project, with distances in the range 151 ≤ D ≤ 183 Mpc: PGC007748, PGC015524, and PGC049940. The long integration time and the wide field of view of the OmegaCam at the VST allowed us to map the light and color distributions down to μg ≃ 30 mag arcsec−2 and out to ∼2Re. The deep data are crucial for estimating the contribution of the different galaxy components, in particular the accreted fraction in the stellar halo. The available integral field observations with MUSE cover a limited portion of each galaxy (out to ∼1Re), but from the imaging analysis, we find that they map the kinematics and stellar population beyond the first transition radius, where the contribution of the accreted component starts to dominate. The main goal of this work is to correlate the scales of the different components derived from the image analysis with the kinematics and stellar population profiles from the MUSE data. The results were used to address the assembly history of the three galaxies with the help of theoretical predictions. Our results suggest that PGC049940 has the lowest accreted mass fraction of 77%. The higher accreted mass fraction estimated for PGC007748 and PGC015524 (86% and 89%, respectively) combined with the flat λR profiles suggest that a great majority of the mass has been acquired through major mergers, which have also shaped the shallower metallicity profiles that are observed at larger radii.