On the assembly history of massive galaxies. A pilot project with VEGAS
  deep imaging and M3G integral field spectroscopy
  In this paper we present the new deep images from the VEGAS survey of three
massive ($M_{*} \simeq 10^{12}$~M$_\odot$) galaxies from the MUSE Most Massive
Galaxies (M3G) project, with distances in the range $151\leq D \leq 183$ Mpc:
PGC007748, PGC015524 and PGC049940. The long integration time and the wide
field of view of OmegaCam@VST allowed us to map the light and color
distributions down to $\mu_g\simeq30$~mag/arcsec$^2$ and out to $\sim 2R_e$.
The deep data are crucial to estimate the contribution of the different
galaxy's 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 $\sim 1R_e$), 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. Results were used to address the
assembly history of the three galaxies with the help of the 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 $\lambda_R$
profiles suggest that a great majority of the mass has been acquired through
major mergers, which have also shaped the shallower metallicity profiles
observed at larger radii.
