Investigating the merger origin of Early-Type Galaxies using ultra-deep optical images

TL;DR

This study uses ultra-deep optical imaging and simulations to investigate the faint structures around Early-Type Galaxies, shedding light on their merger-driven formation history.

Contribution

It presents new ultra-deep optical images of ETGs' outskirts and interprets these with numerical simulations to understand galaxy assembly mechanisms.

Findings

Detection of faint structures at 29 mag arcsec-2 levels

Initial analysis of two galaxies' outskirts

Evidence supporting merger-driven formation processes

Abstract

The mass assembly of galaxies leaves various imprints on their surroundings, such as shells, streams and tidal tails. The frequency and properties of these fine structures depend on the mechanism driving the mass assembly: e.g. a monolithic collapse, rapid cold-gas accretion followed by violent disk instabilities, minor mergers or major dry / wet mergers. Therefore, by studying the outskirts of galaxies, one can learn about their main formation mechanism. I present here our on-going work to characterize the outskirts of Early-Type Galaxies (ETGs), which are powerful probes at low redshift of the hierarchical mass assembly of galaxies. This work relies on ultra-deep optical images obtained at CFHT with the wide-field of view MegaCam camera of field and cluster ETGs obtained as part of the Atlas-3D and NGVS projects. State of the art numerical simulations are used to interpret the data. The images reveal a wealth of unknown faint structures at levels as faint as 29 mag arcsec-2 in the g-band. Initial results for two galaxies are presented here.