06 October 2021Séminaire – Martin Rey (Oxford)

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The diversity of galaxies in the low surface brightness Universe 


Recent advances in imaging capabilities have transformed our understanding of galaxies at the low surface brightnesses frontier, unveiling a new population of ever smaller “ultra-faint” dwarf galaxies, and more and more faint and diffuse structures in the outskirts of galaxies. Such low-mass, feeble objects are highly sensitive to the physical processes that shape galaxies in our Universe, providing an ideal laboratory for testing cosmological galaxy formation models. This same sensitivity, however, also generates extended scatter in their properties, which will be essential to quantify to interpret findings in the next generation of deep, wide sky, surveys (e.g. LSST, the Euclid and Nancy Roman Telescopes). To begin this quantification, I present results from “genetically modified” cosmological simulations of galaxies, which allow us to uniquely separate the role of cosmological assemblies and physical models in a given galaxy’s final observables. I will show how this combination of abilities enables us to extract the expected diversity in the stellar and gaseous properties of the faintest galaxies in our Universe, making testable predictions for near-future photometric and radio surveys. I will then present results disentangling how different merger scenarios and galaxy formation models contribute to the build-up of the diffuse halo of stars around Milky-Way-like galaxies, opening a new pathway to interpret galactic and extragalactic observations of stellar halos.