Diffuse cosmic gamma rays at 1–20 MeV: a trace of the dark matter?

Abstract

Several independent observations of the galactic core suggest hitherto unexplained sources ofenergy. The most well known case is the 511 keV line which has proven very difficult to explainwith conventional astrophysical positron sources. A similar, but less well known mystery isthe excess of gamma ray photons detected by COMPTEL across a broad energy range∼1–20 MeV. Such photons are found to be very difficult to produce via known astrophysicalsources. We show in this work that dark matter in the form of dense antimatterdroplets provides a natural explanation for the observed flux of gamma rays in the∼1–20 MeV range. We argue that such photons must always accompany the 511 keV line as they areproduced by the same mechanism within our framework. We calculate the spectrum and intensity ofthe ∼1–20 MeV gamma rays, and find it to be consistent with the COMPTEL data.