# Dwarf Galaxies as Cosmological Probes

Wednesday, December 12, 2018 — 11:30 AM EST

### Julio Navarro

Professor of Physics and Astronomy, University of Victoria

### Abstract

The Lambda Cold Dark Matter (LCDM) paradigm makes specific predictions for the non-linear clustering of dark matter on all scales. These predictions can be directly tested, in bright galaxies, by galaxy scaling laws such as the Tully-Fisher relation that links the stellar mass with the rotation speed of galactic discs. LCDM also makes specific predictions for the abundance, structure, substructure and clustering of dark matter halos that can be directly tested, in the low-mass halo regime, by dark matter-dominated dwarf galaxies. Indeed, a number of potential challenges to LCDM have been identified when confronting the expected properties of dwarfs with observation. I will review our understanding of a few of these issues, including the "missing satellites" and the "too-big-to-fail" problems, and argue that neither poses an insurmountable challenge to LCDM. Solving these problems requires that most dwarf galaxies inhabit halos spanning a narrow range in mass, and that there is a relatively sharp minimum halo mass threshold to form luminous galaxies. These predictions are eminently falsifiable. In particular, LCDM predicts a large number of "dark" low-mass halos, some of which should have retained enough primordial gas to be detectable in deep 21 cm or H$_\alpha$ surveys. Detecting this predicted population of "mini-halos" would be a major discovery and a resounding success for LCDM on small scales.

Location
PHY - Physics
308
200 University Avenue West

Waterloo, ON N2L 3G1
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