MATLAS (Mass Assembly of early-Type GaLAxies with their fine  Structures) investigates the mass assembly of Early-Type Galaxies (ETGs) and the build-up of their scaling relations, with extremely deep optical images. The stellar populations in the outermost regions of ETGs, the fine structures (tidal tails, stellar stream, and shells) around them, the Globular Cluster (GCs) and dwarf satellites, preserve a record of past merger events and more generally of the evolution and transformation of galaxies. 

This Large Programme of the Canada-France-Hawaii Telescope capitalizes on several developments (1) The unique capabilities of the MegaCam camera on the CFHT. Dedicated imaging procedures and a LSB-optimized pipeline allow us to detect low surface brightness structures and objects, as faint as 29 mag/arcsec2 in the g band. An exclusive image quality enables the identification of their associated globular cluster population (2) A stunning ancillary dataset provided by the ATLAS3D project giving complementary information on their dynamics, gas and stellar content of the host galaxy. (3) Numerical simulations that predict the various types of fine-structures and stellar halos depending on the mechanism driving the mass assembly: major or minor, wet or dry mergers; secular evolution.

The database collected as part of this Large Programme consists of deep multi-color images of 1 square degree fields centered on ETGs with distances below 42 Mpc, outside the Virgo cluster. The fields encompass 177 massive lenticular and elliptical galaxies, 55 massive spiral companions, about 2000 dwarf galaxy satellites, and among them about 100 ultra diffuse galaxies. The MATLAS database is complemented by images from the Next Generation Virgo Cluster Survey (NGVS) and Canada France Imaging Survey (CFIS), making the ETG Atlas3D / Megacam catalog a complete volume limited sample.


Census and classification of low-surface-brightness structures in nearby early-type galaxies from the MATLAS survey

Accounting for the morphology is an essential constraint for the theory of galaxy formation. The low-surface brightness regions of galaxies host multiple morphological features that any realistic model should consider; however they are still not fully explored because of observational difficulties. Here we present the results of our visual inspections of very deep images of …

Revealing the formation mechanism of the shell galaxy NGC474 with MUSE

Stellar shells around galaxies could provide precious insights into their assembly history. However, their formation mechanism remain poorly empirically constrained. We present MUSE@VLT data of the bright shell galaxy NGC 474, to constrain its formation history. We use a full spectra fitting method to determine the line-of-sight velocity and the age and metallicity of the …

A spectroscopic study of MATLAS-2019 with MUSE: an ultra-diffuse galaxy with an excess of old globular clusters

The MATLAS deep imaging survey has uncovered a plethora of dwarf galaxies in the low density environment it has mapped. A fraction of them are unusually extended and have a low-surface brightness. Among these so-called ultra-diffuse galaxies, a few seem to host an excess of globular clusters. With the integral-field unit spectrograph MUSE we have …