Constraining Sterile Neutrino Dark Matter in the Milky Way Halo with Swift-XRT

TL;DR

This study uses Swift-XRT data to search for sterile neutrino dark matter decay signals in the Milky Way halo, finding no emission lines but setting new constraints on sterile neutrino properties and the 3.5 keV line profile.

Contribution

It provides the first comprehensive analysis of the entire Swift-XRT archive for sterile neutrino decay signals, improving existing constraints and analyzing the galactic 3.5 keV line profile.

Findings

No detection of decay lines in 3--6 keV range.

Constraints on sterile neutrino parameter space are strengthened.

The 3.5 keV line profile constraints are the most stringent to date.

Abstract

We present a search for sterile neutrino dark matter decay signals in the Milky Way's dark matter halo by considering the entirety of the Swift-XRT data archive. After filtering the raw archive, we analyze a $\sim$77 Ms data set containing the full field of view, as well as a $\sim$41 Ms data set with point-sources excised using the Swift-XRT Point Source catalog. We report non-detections of emission lines across the 3--6 keV continuum in both data sets, including at and around 3.5 keV. The point-sources excised data set is found to have higher sensitivity to faint dark matter decay signals due to its freedom from point-source contamination and is thus used to set constraints. Non-detections across the total data set's continuum are used to constrain the sterile neutrino dark matter parameter space, marginally strengthening existing X-ray constraints. Non-detections at $\sim$3.5 keV in data subsets grouped by angular distance from the galactic center are used to constrain the 3.5 keV line's galactic intensity profile, providing the strongest constraints to date across $\sim$1/4 of the galaxy.