A study is made of the 3EG Gamma Ray source catalogue [7] with particular regard to the nature of the so-called 'unidentified sources'.It is concluded that a case can be made for a significant number of them being pulsars,those at high latitudes being of the 'spun-up' variety.The present work examines gamma rays above 0.1 GeV,where the progenitor protons have a mean energy of about 2 GeV.The electron contribution is thought to be small(see [11] for details).A very useful set of data has come from the EGRET detector on the Gamma Ray Observatory,both with regard to the diffuse continuum [12] and so-called 'gamma ray sources' [7].It is with the latter that we are concerned here.At these low energies,a number of possibilities arise.These include:The irradiation of molecular clouds by the ambient cosmic ray flux(e.g.[8],Supernova remnants,both in isolation and associated with molecular clouds(MC),Pulsars(e.g.the early SAS II results),and Extragalactic sources(starburst galaxies,active galactic nuclei(AGN),etc.).
展开▼
