Constraining Sterile Neutrino Warm Dark Matter with Chandra Observations of the Andromeda Galaxy

TL;DR

This study uses Chandra X-ray data from the Andromeda galaxy to set the tightest limits yet on sterile neutrino dark matter decay, constraining their mass and production scenarios.

Contribution

It provides the most stringent constraints on sterile neutrino mass using X-ray observations, reducing uncertainties by focusing on a specific galaxy region.

Findings

Sterile neutrino mass < 2.2 keV at 95% confidence level.

Constraints on sterile neutrino production scenarios at small mixing angles.

Improved limits by excluding baryon-rich central galaxy regions.

Abstract

We use the Chandra unresolved X-ray emission spectrum from a 12'-28' (2.8-6.4 kpc) annular region of the Andromeda galaxy to constrain the radiative decay of sterile neutrino warm dark matter. By excising the most baryon-dominated, central 2.8 kpc of the galaxy, we reduce the uncertainties in our estimate of the dark matter mass within the field of view and improve the signal-to-noise ratio of prospective sterile neutrino decay signatures relative to hot gas and unresolved stellar emission. Our findings impose the most stringent limit on the sterile neutrino mass to date in the context of the Dodelson-Widrow model, m_s < 2.2 keV (95% C.L.). Our results also constrain alternative sterile neutrino production scenarios at very small active-sterile neutrino mixing angles.