Hunting dark matter in galaxy clusters with non-thermal electrons

TL;DR

This paper proposes a new indirect method to compare observed and dark matter predicted electron spectra in galaxy clusters, leveraging spectral features of synchrotron emissions to improve constraints on dark matter properties.

Contribution

It introduces a novel spectral comparison technique using synchrotron emission features to distinguish dark matter signals from astrophysical electrons in galaxy clusters.

Findings

Method yields stronger dark matter constraints than current VLA data.

Constraints surpass Fermi-LAT dwarf galaxy searches across multiple channels.

Future ngVLA observations can validate and enhance this approach.

Abstract

The electron population inferred to be responsible for the mini-halo within the Ophiuchus galaxy cluster is a steep power-law in energy with a slope of $3.8$. This is substantially different to that predicted by dark matter annihilation models. In this work we present a method of indirect comparison between the observed electron spectrum and that predicted for indirect dark matter emissions. This method utilises differences in the consequences of a given electron distribution on the subsequent spectral features of synchrotron emissions. To fully exploit this difference, by leveraging the fact that the peak and cut-off synchrotron frequencies are substantially different to hard power-law cases for WIMP masses above $\sim 50$ GeV, we find that we need $\mu$Jy sensitivities at frequencies above 10 GHz while being sensitive to arcminute scales. We explore the extent to which this electron spectrum comparison can be validated with the up-coming ngVLA instrument. We show that, with the ngVLA, this method allows us to produce far stronger constraints than existing VLA data, indeed these exceed the Fermi-LAT dwarf searches in a wide variety of annihilation channels and for all studied magnetic field scenarios.