The role of the eROSITA all-sky survey in searches for sterile neutrino dark matter

TL;DR

This paper explores how the upcoming eROSITA X-ray survey can detect sterile neutrino dark matter through angular correlation analysis, potentially confirming or refuting the 3.56-keV line hypothesis.

Contribution

It introduces a novel method using auto- and cross-correlation power spectra with eROSITA data to search for sterile neutrino dark matter signals.

Findings

Cross-correlation enhances sterile neutrino decay signals.

eROSITA can set stringent constraints on decay lifetime.

Shot-noise in galaxy catalogs limits detection sensitivity.

Abstract

We investigate for the first time the potential of angular auto- and cross-correlation power spectra in identifying sterile neutrino dark matter in the cosmic X-ray background. We take as reference the performance of the soon-to-be-launched eROSITA satellite. The main astrophysical background sources against sterile neutrino decays are active galactic nuclei, galaxies powered by X-ray binaries, and clusters of galaxies. While sterile neutrino decays are always subdominant in the auto-correlation power spectra, they can be efficiently enhanced when cross-correlating with tracers of the dark matter distribution such as galaxies in the 2MASS catalogues. We show that the planned four-years eROSITA all-sky survey will provide a large enough photon statistics to potentially yield very stringent constraints on the decay lifetime, enabling to firmly test the recently claimed 3.56-keV X-ray line found towards several clusters and galaxies and its decaying dark matter interpretation. However, we also show that in order to fully exploit the potential of eROSITA for dark matter searches, it is vital to overcome the shot-noise limitations inherent to galaxy catalogues as tracers for the dark matter distribution.