Bounds on Resonantly-Produced Sterile Neutrinos from Phase Space Densities of Milky Way Dwarf Galaxies

TL;DR

This paper derives bounds on resonantly-produced sterile neutrino dark matter using phase-space densities of Milky Way dwarf galaxies, highlighting the importance of compact dSphs and future surveys in constraining dark matter models.

Contribution

It introduces a novel method to derive phase-space density bounds from stellar kinematics, avoiding simulation limitations, and emphasizes the significance of compact dwarf galaxies in dark matter constraints.

Findings

Compact dSphs provide strong constraints on sterile neutrino dark matter.

Future surveys can improve bounds by discovering more compact, dark matter-dominated systems.

Constraints are comparable to those from satellite count methods, impacting models explaining the 3.5 keV line.

Abstract

We examine the bounds on resonantly-produced sterile neutrino dark matter from phase-space densities of Milky Way dwarf spheroidal galaxies (dSphs). The bounds result from a derivation of the dark matter coarse-grained phase-space density from the stellar kinematics, which allows us to explore bounds from some of the most compact dSphs without suffering the resolution limitation from N-body simulations that conventional methods have. We find that the strongest constraints come from very compact dSphs, such as Draco II and Segue 1. We additionally forecast the constraining power of a few dSph candidates that do not yet have associated stellar kinematic data, and show that they can improve the bounds if they are confirmed to be highly dark matter dominated systems. Our results demonstrate that compact dSphs provide important constraints on sterile neutrino dark matter that are comparable to other methods using as Milky Way satellite counts. In particular, if more compact systems are discovered from current or future surveys such as LSST or HSC, it should be possible to test models that explain the 3.5 keV X-ray line signal with a 7.1 keV sterile neutrino particle decay.