21cm signal sensitivity to dark matter decay

TL;DR

This paper investigates how the 21cm signal from the early Universe can be used to detect or constrain dark matter decay, showing that the HERA telescope could significantly improve current limits on dark matter decay properties.

Contribution

It provides the first Fisher matrix forecasts for HERA's sensitivity to dark matter decay, highlighting potential improvements over existing constraints.

Findings

HERA can improve constraints on dark matter decay lifetime by up to three orders of magnitude.

Even with extreme astrophysical scenarios, bounds on decay lifetime are significantly enhanced.

HERA's sensitivity is particularly strong for dark matter masses below 2 GeV/c^2 for certain decay channels.

Abstract

The redshifted 21cm signal from the Cosmic Dawn is expected to provide unprecedented insights into early Universe astrophysics and cosmology. Here we explore how dark matter can heat the intergalactic medium before the first galaxies, leaving a distinctive imprint in the 21cm power spectrum. We provide the first dedicated Fisher matrix forecasts on the sensitivity of the Hydrogen Epoch of Reionization Array (HERA) telescope to dark matter decays. We show that with 1000 hours of observation, HERA has the potential to improve current cosmological constraints on the dark matter decay lifetime by up to three orders of magnitude. Even in extreme scenarios with strong X-ray emission from early-forming, metal-free galaxies, the bounds on the decay lifetime would be improved by up to two orders of magnitude. Overall, HERA shall improve on existing limits for dark matter masses below $2$ GeV$/c^2$ for decays into $e^+e^-$ and below few MeV$/c^2$ for decays into photons.