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Dark matter and galaxy formation in the Local Group

The standard cosmological paradigm, wherein luminous galaxies trace the underlying cosmic web of dark matter, reproduces a wide variety of large-scale observations spectacularly well.  However, basic questions remain within the model, including the nature of dark matter and of the small-scale physics that are important to galaxy formation.  Our cosmic neighborhood, the Local Group (LG), is one of the best laboratories for answering these vital questions, largely because tiny, faint dwarf galaxies -- which have historically presented tensions to the model -- are only observationally accessible within the LG.  I discuss lessons from (and the status of) two well-known small-scale problems:  missing satellites and too-big-to-fail, with a focus on the physical processes that can eliminate the problems within the standard paradigm and their observational signatures.  I culminate by presenting state-of-the-art simulations, run with the "bottom-up" FIRE prescriptions for star formation and stellar feedback, that resolve dwarf galaxy formation in the LG environment.  While these runs do not suffer from the classic small-scale problems, I highlight a potential new tension related to the wide variety of dwarf galaxies in the LG.  Finally, I present evidence that dwarf galaxy formation varies between environments, reinforcing the need to simulate dwarfs in LG-like regions that are chosen to contain a pair of Milky Way analogues.

Speaker: Shea Garrison-Kimmel (Caltech)

Monday, 04/08/19


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Varian Physics Building

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Room 355
Stanford, CA 94305