Extragalactic Gamma Ray Excess from Coma Supercluster Direction

Abstract

The origin of extragalactic diffuse gamma ray is not accu- rately known, especially because our suggestions are related to many models that need to be considered either to compute the galactic diffuse gamma ray intensity or to consider the contribution of other extragalac- tic structures while surveying a specific portion of the sky. More precise analysis of EGRET data however, makes it possible to estimate the diffuse gamma ray in Coma supercluster (i.e., Coma\A1367 supercluster) direc- tion with a value of I (E > 30 MeV) � 1.9 × 10 −6 cm −2 s −1 ,w hich is considered to be an upper limit for the diffuse gamma ray due to Coma supercluster. The related total intensity (on average) is calculated to be ∼5% of the actual diffuse extragalactic background. The calculated inten- sity makes it possible to estimate the origin of extragalactic diffuse gamma ray.