Molecular clouds as reservoir of cosmic rays

Abstract

Giant molecular clouds (GMCs) are emerging as a new population of -ray sources; with detections by instruments such as HESS and Fermi. These dense clouds are targets for cosmic rays (CRs) -- locally accelerated or not --. GMCs host very young star clusters where massive star formation takes place. Some of the early-type stars are usually ejected from the clusters; becoming runaway stars; that move through the cloud. These stars develop bowshocks where particles can be accelerated up to relativistic energies. As a result; the bowshocks present radio to -ray emission of leptonic origin; and inject relativistic protons in the cloud. These protons diffuse in the GMC interacting with the matter via inelastic collisions. This gives rise to extended -ray sources. We present a model for the non-thermal radiation produced by locally accelerated CRs in GMCs.