Are lines from unassociated gamma-ray sources evidence for dark matter annihilation?

Abstract

Very recently, it was pointed out that there exists a population of gamma-ray sources without associations at other wavelengths which exhibit spectral features consistent with mono-energetic lines at energies of approximately 111 and 129 GeV. Given recent evidence of similar gamma-ray lines from the Inner Galaxy, it is tempting to interpret these unassociated sources as nearby dark matter subhalos, powered by ongoing annihilations. In this paper, we study the spectrum, luminosity, and angular distribution of these sources, with the intention of testing the hypothesis that they are, in fact, dark matter subhalos. We find that of the 12 sources containing at least one prospective line photon, only 2 exhibit an overall gamma-ray spectrum which is consistent with that predicted from dark matter annihilations (2FGL J2351.6-7558 and 2FGL J0555.9-4348). After discounting the 10 clearly non-dark matter sources, the statistical significance of the remaining two prospective line photons is negligible. That being said, we cannot rule out the possibility that either or both of these sources are dark matter subhalos; their overall luminosity and galactic latitude distribution are not inconsistent with a dark matter origin.