Local Group dSph radio survey with ATCA (III): Constraints on Particle Dark Matter

TL;DR

This study uses deep radio observations of dwarf spheroidal galaxies to set constraints on WIMP dark matter properties, exploring the impact of astrophysical uncertainties and future detection prospects with SKA.

Contribution

It provides new bounds on WIMP annihilation/decay rates from radio data and discusses how astrophysical assumptions affect these constraints.

Findings

No extended radio emission detected in dSphs.

Constraints on WIMP annihilation rates below thermal relic levels for masses up to a few TeV.

Future radio surveys with SKA could fully probe WIMP parameter space.

Abstract

We performed a deep search for radio synchrotron emissions induced by weakly interacting massive particles (WIMPs) annihilation or decay in six dwarf spheroidal (dSph) galaxies of the Local Group. Observations were conducted with the Australia Telescope Compact Array (ATCA) at 16 cm wavelength, with an rms sensitivity better than 0.05 mJy/beam in each field. In this work, we first discuss the uncertainties associated with the modeling of the expected signal, such as the shape of the dark matter (DM) profile and the dSph magnetic properties. We then investigate the possibility that point-sources detected in the proximity of the dSph optical center might be due to the emission from a DM cuspy profile. No evidence for an extended emission over a size of few arcmin (which is the DM halo size) has been detected. We present the associated bounds on the WIMP parameter space for different annihilation/decay final states and for different astrophysical assumptions. If the confinement of electrons and positrons in the dSph is such that the majority of their power is radiated within the dSph region, we obtain constraints on the WIMP annihilation rate which are well below the thermal value for masses up to few TeV. On the other hand, for conservative assumptions on the dSph magnetic properties, the bounds can be dramatically relaxed. We show however that, within the next 10 years and regardless of the astrophysical assumptions, it will be possible to progressively close in on the full parameter space of WIMPs by searching for radio signals in dSphs with SKA and its precursors.