Searching for dark matter X-ray lines from the Large Magellanic Cloud with eROSITA

Abstract

We perform a search for an X-ray monochromatic line arising from dark matter (DM) decay in the halo of the Large Magellanic Cloud. An emission line can be expected from two well-motivated DM candidates: sterile neturinos and axion-like particles (ALPs). We analyze the eROSITA-DE DR1 datasets in the energy range between 1 and 9 keV. No evidence for a DM line is found, and we set lower limits on the DM lifetime. We then recast these bounds into upper limits on the active-sterile neutrino mixing angle $\sin^2(2\theta)$ and on the ALP to photon coupling $g_{a\gamma}$, for DM masses between 2 and 18 keV. These results set new strong constraints for masses below 5 keV.