Dark Matter Detection with Hard X-ray Telescopes

TL;DR

This paper explores how future hard X-ray telescopes could improve the detection of dark matter signatures in galaxy clusters by observing inverse Compton emissions, with potential sensitivity gains over current gamma-ray constraints.

Contribution

It assesses the potential of upcoming hard X-ray telescopes to detect dark matter signals, highlighting the importance of orbit background levels for sensitivity.

Findings

Hard X-ray observations can complement gamma-ray searches for dark matter.

NuSTAR and ASTRO-H will have sensitivities close to current constraints.

ATHENA's WFI could significantly improve detection if placed in a low-background orbit.

Abstract

We analyze the impact of future hard X-ray observations on the search for indirect signatures of particle dark matter in large extragalactic systems such as nearby clusters or groups of galaxies. We argue that the hard X-ray energy band falls squarely at the peak of the inverse Compton emission from electrons and positrons produced by dark matter annihilation or decay for a large class of dark matter models. Specifically, the most promising are low-mass models with a hard electron-positron annihilation final state spectrum and intermediate-mass models with a soft electron-positron spectrum. We find that constraints on dark matter models similar to the current constraints from the Fermi Gamma-Ray Space Telescope will be close to the sensitivity limit of the near-term hard X-ray telescopes NuSTAR and ASTRO-H for relatively long observations. An instrument like the Wide Field Imager (WFI) proposed for ATHENA would instead give a significant gain in sensitivity to dark matter if placed in a low background orbit similar to NuSTAR's; however, given the higher expected background level for ATHENA's proposed orbit at L2, its sensitivity will be similar to that of NuSTAR.