Detecting axion dark matter through the radio signal from Omega Centauri

Abstract

As a well-motivated dark matter candidate, axions can be detected through the axion-photon resonant conversion in the magnetospheres of magnetic white dwarf stars or neutron stars. In this work, we utilize Omega Centauri, which is the largest globular cluster in the Milky Way and is suggested to be the remnant core of a dwarf galaxy, to probe the axion dark matter through radio signals that originate from all the neutron stars and magnetic white dwarf stars in it. With 100 h of observation, the combination of the radio telescopes Square Kilometer Array phase 1 and Low-Frequency Array can effectively probe the parameter space of the axion-photon coupling ${g}_{a\ensuremath{\gamma}}$ up to ${10}^{\ensuremath{-}14}\ensuremath{\sim}{10}^{\ensuremath{-}15}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$ for the axion mass range of $0.1\ensuremath{\sim}30\text{ }\text{ }\ensuremath{\mu}\mathrm{eV}$. Depending on the choice of neutron star evolution model, this limitation is 2 or 3.5 orders of magnitude higher than that of the single neutron star or magnetic white dwarf.