Decaying dark matter in Draco

TL;DR

This study uses Chandra X-ray data of the Draco dwarf galaxy to search for signals of decaying dark matter, specifically sterile neutrinos, and sets constraints on their properties based on the absence of detectable line emission.

Contribution

It demonstrates that dwarf spheroidals like Draco are optimal for dark matter X-ray searches and compares different flux derivation methods affecting the constraints.

Findings

Dwarf spheroidals have low baryonic noise, ideal for dark matter X-ray studies.

No significant line emission detected, constraining sterile neutrino parameters.

Constraints vary depending on the flux derivation method used.

Abstract

Context. The sterile neutrino is an excellent dark matter candidate, which can be searched for in a wide range of astrophysical sites. It has previously been shown that the optimal search strategy is to consider dwarf galaxies belonging to the Milky Way. Aims. We search for line emission from decaying dark matter. Methods. We analyse publicly available Chandra X-ray observations of the dwarf galaxy Draco. Results. The Draco and blank sky (background) spectra are nearly identical in shape, which allows us to conclude: i) Dwarf spheroidals are ideal for studying dark matter X-ray emission since the baryonic noise is impressively low, ii) there is very little room for line emission, which leads to constraints in the mass-mixing angle parameter space of the sterile neutrino. We compare the standard flux derivation method to a very conservative rebinning approach. The resulting constraints are strongly dependent on the chosen method.