Astrophysical constraints on resonantly produced sterile neutrino dark matter

TL;DR

This paper critically examines the viability of resonantly produced sterile neutrinos as warm dark matter by comparing theoretical predictions with observational constraints from structure formation, especially Lyman-alpha data and Milky-Way satellites.

Contribution

It introduces a new method to extend Lyman-alpha constraints from thermal relics to resonant sterile neutrino dark matter, providing updated bounds on their parameter space.

Findings

Lyman-alpha constraints exclude the entire parameter space allowed by X-ray data.

Milky-Way satellite counts are less restrictive, leaving room for 7.1 keV sterile neutrino dark matter.

Resonant sterile neutrinos remain a viable dark matter candidate within certain parameters.

Abstract

Resonantly produced sterile neutrinos are considered an attractive dark matter (DM) candidate only requiring a minimal, well motivated extension to the standard model of particle physics. With a particle mass restricted to the keV range, sterile neutrinos are furthermore a prime candidate for warm DM, characterised by suppressed matter perturbations at the smallest observable scales. In this paper we take a critical look at the validity of the resonant scenario in the context of constraints from structure formation. We compare predicted and observed number of Milky-Way satellites and we introduce a new method to generalise existing Lyman-$\alpha$ limits based on thermal relic warm DM to the case of resonant sterile neutrino DM. The tightest limits come from the Lyman-$\alpha$ analysis, excluding the entire parameter space (at 2-$\sigma$ confidence level) still allowed by X-ray observations. Constraints from Milky-Way satellite counts are less stringent, leaving room for resonant sterile neutrino DM most notably around the suggested line signal at 7.1 keV.