Gamma rays from the ρ-Ophiuchus cloud complex (sic)

Abstract

A serious problem in gamma -ray astronomy is to distinguish between gamma rays from unresolved discrete sources and those from cosmic-ray interactions in the interstellar medium. Most of the resolved gamma -ray sources have not been identified optically and the possibility arises that they represent molecular clouds illuminated by the ambient cosmic-ray flux. The rho Ophiuchi cloud complex is a good candidate for study as it is in a region where good gamma -ray contrast is possible. There is evidence from the COS-B satellite for a significant flux of gamma rays of energy above 100 MeV from the direction of the object and this flux can be compared with expectation based on the cosmic-ray irradiation hypothesis. Other workers have concluded that the measured flux is in excess of expectation for the hypothesis. The authors argue that, although the uncertainties are large, there is no evidence for an excess in flux over expectation for the irradiation hypothesis.