High - Latitude Molecular Clouds as γ - ray Sources for GLAST 1

For about two decades, a population of relative small and nearby molecular clouds has been known to exist at high Galactic latitudes. Lying more than 10◦ from the Galactic plane, these clouds have typical distances of ∼150 pc, angular sizes of ∼1◦, and masses of order tens of solar masses. These objects are passive sources of high-energy γ-rays through cosmic ray-gas interactions. Using a new wide-angle CO survey of the northern sky, we show that typical high-latitude clouds are not bright enough in γ-rays to have been detected by EGRET, but that of order 100 of them will be detectable by the Large Area Telescope (LAT) on GLAST. Thus, we predict a new steady population of γ-ray sources at high Galactic latitudes, perhaps the most numerous after active galactic nuclei. Subject headings: gamma rays: observations, gamma rays: theory, ISM: clouds, ISM: cosmic rays