Constraining sterile neutrino dark matter by phase-space density observations

TL;DR

This paper uses phase-space density constraints to establish lower bounds on sterile neutrino dark matter mass, analyzing different production mechanisms and their compatibility with observational limits.

Contribution

It introduces a novel application of phase-space density considerations to constrain sterile neutrino dark matter mass across various production scenarios.

Findings

Non-resonant production is disfavored by combined bounds.

Resonant production bounds are comparable to Lyman-alpha constraints.

Heavy particles could constitute warm dark matter in decay scenarios.

Abstract

We apply phase-space density considerations to obtain lower bounds on the mass of sterile neutrino as dark matter candidate. The bounds are different for non-resonant production, resonant production in the presence of lepton asymmetry and production in decays of heavier particles. In the former case our bound is comparable to, but independent of the Lyman-alpha bound, and together with X-ray upper limit it disfavors non-resonantly produced sterile neutrino dark matter. An interesting feature of the latter case is that warm dark matter may be composed of heavy particles.