Probing the mass assembly of massive nearby galaxies with deep imaging

TL;DR

This study uses ultra-deep optical imaging to investigate the role of minor dry mergers in the mass assembly of nearby massive early-type galaxies, revealing faint tidal features and correlations with galaxy properties.

Contribution

It provides new observational evidence of minor dry mergers' impact on galaxy evolution through deep imaging of a complete sample of ETGs.

Findings

Detection of faint stellar tidal tails and extended halos.

Correlation between tidal perturbations and galaxy mass, size, and gas content.

Insights into the recent accretion history of ETGs.

Abstract

According to a popular scenario supported by numerical models, the mass assembly and growth of massive galaxies, in particular the Early-Type Galaxies (ETGs), is, below a redshift of 1, mainly due to the accretion of multiple gas--poor satellites. In order to get observational evidence of the role played by minor dry mergers, we are obtaining extremely deep optical images of a complete volume limited sample of nearby ETGs. These observations, done with the CFHT as part of the \AD, NGVS and MATLAS projects, reach a stunning 28.5)29 mag.arcsec-2 surface brightness limit in the g' band. They allow us to detect the relics of past collisions such as faint stellar tidal tails as well as the very extended stellar halos which keep the memory of the last episodes of galactic accretion. Images and preliminary results from this on-going survey are presented, in particular a possible correlation between the fine structure index (which parametrizes the amount of tidal perturbation) of the ETGs, their stellar mass, effective radius and gas content.