The Stellar Halos of Nearby Galaxies: Decoding the Merger History of Galaxies

Thursday, 06 September 2018 9 a.m. — 10 a.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
ANTONELA MONACHESI (Universidad de La Serena and Gemini South Visiting Astronomer)

Stellar halos around galaxies are predicted to be the visible collisionless tracers of merging and accretion histories of galaxies.

Thus, they are the best place to look at in order to gain insight into the growth history of galaxies. However, due to their very low surface brightnesses it is extremely challenging to observe them.  In this talk, I will present the latest results from the GHOSTS survey, which has observed the resolved stellar populations in the outskirts of nearby galaxies using the Hubble Space Telescope, mainly the diversity in stellar halo properties (mass, density, metallicity, shape, size) of six nearby Milky Way-like galaxies.  I will also present the results from the stellar halos of the Auriga simulations, a suite of forty cosmological magneto-hydrodynamical zoom-in simulations of Milky Way-mass galaxies. The Auriga simulations represent one of the largest and highest resolution sample of simulated Milky Way-mass galaxies with which it is possible to investigate in detail the properties of individual stellar halos and interpret the observed data. I will compare the results from the Auriga simulations with those obtained from observations. I will end by discussing observational signatures that allow us to decode the accretion and merger history of observed galaxies.