Dark Matter Search Using XMM-Newton Observations of Willman 1

TL;DR

This study uses XMM-Newton observations of Willman 1 to search for dark matter decay signals, improving constraints on sterile neutrino parameters and not confirming previous tentative detections.

Contribution

It provides new constraints on sterile neutrino dark matter using XMM-Newton data and advanced analysis methods, improving upon previous Chandra results.

Findings

No confirmation of the 2.5 keV emission line.

Improved limits on sterile neutrino mass and mixing angle.

Enhanced analysis techniques for extended X-ray sources.

Abstract

We report the results of a search for an emission line from radiatively decaying dark matter in the ultra-faint dwarf spheroidal galaxy Willman 1 based on analysis of spectra extracted from XMM-Newton X-ray Observatory data. The observation follows up our analysis of Chandra data of Willman 1 that resulted in line flux upper limits over the Chandra bandpass and evidence of a 2.5 keV feature at a significance below the 99% confidence threshold used to define the limits. The higher effective area of the XMM-Newton detectors, combined with application of recently developing methods for extended-source analysis, allow us to derive improved constraints on the combination of mass and mixing angle of the sterile neutrino dark matter candidate. We do not confirm the Chandra evidence for a 2.5 keV emission line.