# Closing in on Resonantly Produced Sterile Neutrino Dark Matter

## TL;DR

This study thoroughly explores the resonant production of sterile neutrino dark matter, combining astrophysical constraints to narrow down viable mass and asymmetry ranges, and assessing the 3.55 keV X-ray line as a potential signal.

## Contribution

It provides the first comprehensive analysis of the resonant sterile neutrino production parameter space using multiple observational constraints.

## Key findings

- Sterile neutrino masses between 7.0 keV and 36 keV are consistent with constraints.
- Models with lepton asymmetries below 15 x 10^-6 are largely ruled out.
- The 3.55 keV X-ray line is disfavored as a sterile neutrino decay signal at 93% confidence.

## Abstract

We perform an exhaustive scan of the allowed resonant production regime for sterile neutrino dark matter in order to improve constraints for dark matter structures which arise from the non-thermal sterile neutrino energy spectra. Small-scale structure constraints are particularly sensitive to large lepton asymmetries/small mixing angles which result in relatively warmer sterile neutrino momentum distributions. We revisit Milky Way galaxy subhalo count constraints and combine them with recent searches for X-ray emission from sterile neutrino decays. Together they rule out models outside the mass range 7.0 keV < m_nu_s < 36 keV and lepton asymmetries smaller than 15 x 10-6 per unit entropy density at 95 percent CI or greater. We also find that while a portion of the parameter space remains unconstrained, the combination of subhalo counts and X-ray data indicate the candidate 3.55 keV X-ray line signal potentially originating from a 7.1 keV sterile neutrino decay to be disfavored at 93 percent CI.