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

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