Strong limits on keV-scale galactic sterile neutrino dark matter with stray light from NuSTAR after 11 years of operation

TL;DR

This study uses 11 years of NuSTAR stray light data to set stringent limits on keV-scale sterile neutrino dark matter decay signals, constraining theoretical models and narrowing the parameter space for sterile neutrinos as dark matter candidates.

Contribution

The paper provides the first strong observational limits on keV sterile neutrino decay using NuSTAR's stray light, significantly constraining dark matter models.

Findings

Limits reach the bottom of theoretical predictions for sterile neutrino models.

Only a small parameter space remains where sterile neutrinos could account for all dark matter.

NuSTAR data effectively constrains sterile neutrino decay emission in the 3-20 keV range.

Abstract

Using tremendous photon statistics gained with the stray light aperture of the NuSTAR telescope over 11 years of operation, we set strong limits on the emission of close to monochromatic photons from the radiative decays of putative dark matter sterile neutrinos in the Milky Way. In the energy range of 3-20 keV covered by the NuSTAR, the obtained limits reach the bottom edge of theoretical predictions of realistic models where sterile neutrinos are produced in the early Universe. Only a small region is left to explore, if the sterile neutrinos form the entire dark matter component.