Constraints on Dark Matter Microphysics from the Milky Way Satellite Population

22 Apr 2019  ·  Ethan O. Nadler, Vera Gluscevic, Kimberly K. Boddy, Risa H. Wechsler ·

Alternatives to the cold, collisionless dark matter (DM) paradigm in which DM behaves as a collisional fluid generically suppress small-scale structure. Herein we use the observed population of Milky Way (MW) satellite galaxies to constrain the collisional nature of DM, focusing on DM--baryon scattering. We derive conservative analytic upper limits on the velocity-independent DM--baryon scattering cross section by translating the upper bound on the lowest mass of halos inferred to host satellites into a characteristic cutoff scale in the matter power spectrum. We confirm and improve these results through a detailed probabilistic inference of the MW satellite population that marginalizes over relevant astrophysical uncertainties, yielding $95\%$ confidence upper limits on the scattering cross section of $6\times10^{-30}\ \rm{cm}^2$ ($10^{-27}\ \rm{cm}^2$) for DM particle masses of $10\ \rm{keV}$ ($10\ \rm{GeV}$). These limits improve upon cosmological bounds derived from cosmic-microwave-background anisotropy measurements by more than three orders of magnitude over a wide range of DM masses, excluding regions of parameter space previously unexplored by other methods, including direct detection experiments. Our work reveals a mapping between DM--baryon scattering and other alternative DM models, and we discuss the implications of our results for warm and fuzzy DM scenarios.

PDF Abstract

Categories


Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology