Presentation
Galaxy formation and evolution is a fundamental Astrophysical problem. Its study requires “travelling back in time”, for which there are two complementary approaches. One is to analyse galaxy properties as a function of red-shift. Our team focuses on the other approach, called “Galactic Archaeology”. It is based on the determination of galaxy properties from the study of their resolved stars. Depending on their mass, stars can live on longer than a Hubble time, thus allowing us to study in exquisite detail how galaxies have evolved from the early Universe to the present time. Galactic Archaeology is one of the main drivers of major international projects, both observational (such as the Gaia mission, WHT/WEAVE, LSST, VISTA/4MOST, DESI, E-ELT/HARMONI, to name a few), and theoretical (such as NIHAO, CLUES, MaGICC and Auriga hydrodynamical cosmological simulations), in some of which members of our team are involved.
The objective of our group is to understand the formation and evolution of galaxies of different morphological types, using the many local examples that can be resolved into individual stars, and which, therefore, can be studied in a detail impossible elsewhere. In particular, the Local Group and its immediate surroundings contain more than 100 galaxies of different morphological types. Among these, the largest are spiral galaxies (the Milky Way, M31 and M33), a dozen of them are (dwarf) irregulars and the rest are early-type dwarf systems. Thus, we can study galaxies of different morphological types, from the Milky Way down to the smallest galactic scales, which are those challenging our understanding of what a "galaxy" is.
We aim to derive their evolutionary history using a set of complementary techniques: i) using deep photometry reaching the old main sequence turn-offs, it is possible to derive the full star formation history over the entire galaxy's life; ii) spectroscopic studies of individual stars add direct information on the kinematics and chemical abundances of the different stellar populations; iii) for the most nearby systems, the inclusion of accurate astrometric measurements yields information on the distance (and thus absolute brightness), the orbital motion and can even deliver the full 6D phase-space information of sub-samples of stars; iv) the study of variable stars such as Cepheids and RR Lyrae provide independent constraints on metallicities and ages of the populations they belong to. These observations offer invaluable, rich information that can be interpreted using hydrodynamic cosmological simulations of galaxy formation that model a wide range of important physical processes.