Dark matter annihilation in $\ddot{I}‰$ Centauri: Astrophysical implications derived from the MWA radio data

Abstract

We present an analysis of Murchison Widefield Array radio telescope data from $\ddot{I}‰$ Cen, possibly a stripped dwarf spheroidal galaxy core captured by our Galaxy. Recent interpretations of Fermi-LAT ${\hat{I}}^3$-ray data by Brown {\it et al.} (2019) and Reynoso-Cordova {\it et al.} (2019) suggest that $\ddot{I}‰$ Cen may contain significant Dark Matter. We utilise their best-fit Dark Matter annihilation models, and an estimate of the magnetic field strength in $\ddot{I}‰$ Cen, to calculate the expected radio synchrotron signal from annihilation, and show that one can usefully rule out significant parts of the magnetic field - diffusion coefficient plane using our current observational limits on the radio emission. Improvement by a factor of 10-100 on these limits could constrain the models even more tightly.

Accepted in Physics of the Dark Universe, 7 pages, 4 figures, 1 table