Gamma-Rays from Dark Matter Mini-Spikes in M31

Abstract

The existence of a population of wandering Intermediate Mass Black Holes (IMBHs) is a generic prediction of scenarios that seek to explain the formation of Supermassive Black Holes in terms of growth from massive seeds. The growth of IMBHs may lead to the formation of DM overdensities called "mini-spikes", recently proposed as ideal targets for indirect DM searches. Current ground-based gamma-ray experiments, however, cannot search for these objects due to their limited field of view, and it might be challenging to discriminate mini-spikes in the Milky Way from the many astrophysical sources that GLAST is expected to observe. We show here that gamma-ray experiments can effectively search for IMBHs in the nearby Andromeda galaxy (also known as M31), where mini-spikes would appear as a distribution of point-sources, isotropically distributed in a \thickapprox 3^{\circ} circle around the galactic center. For a neutralino-like DM candidate with a mass m_χ=150 GeV, up to 20 sources would be detected with GLAST (at 5σ, in 2 months). With Air Cherenkov Telescopes such as MAGIC and VERITAS, up to 10 sources might be detected, provided that the mass of neutralino is in the TeV range or above.