Sterile neutrinos as subdominant warm dark matter

TL;DR

This paper explores the constraints on sterile neutrinos as a subdominant component of warm dark matter produced via the Dodelson-Widrow mechanism, using X-ray and Lyman-alpha data to limit their abundance and parameter space.

Contribution

It reinterprets existing observational limits for sterile neutrinos as a fraction of dark matter and constrains their production parameters, establishing an upper limit on their contribution.

Findings

Sterile neutrinos can constitute at most 70% of dark matter at 2 sigma.

The combined X-ray and Lyman-alpha data exclude sterile neutrinos as the dominant dark matter component.

The study provides a framework for assessing sterile neutrino dark matter scenarios with partial contributions.

Abstract

In light of recent findings which seem to disfavor a scenario with (warm) dark matter entirely constituted of sterile neutrinos produced via the Dodelson-Widrow (DW) mechanism, we investigate the constraints attainable for this mechanism by relaxing the usual hypothesis that the relic neutrino abundance must necessarily account for all of the dark matter. We first study how to reinterpret the limits attainable from X-ray non-detection and Lyman-alpha forest measurements in the case that sterile neutrinos constitute only a fraction fs of the total amount of dark matter. Then, assuming that sterile neutrinos are generated in the early universe solely through the DW mechanism, we show how the X-ray and Lyman-alpha results jointly constrain the mass-mixing parameters governing their production. Furthermore, we show how the same data allow us to set a robust upper limit fs < 0.7 at the 2 sigma level, rejecting the case of dominant dark matter (fs = 1) at the ~ 3 sigma level.