Mr Luigi Tibaldo (university & INFN Parma)
Supernova remnants are generally considered as the accelerators of the Galactic cosmic rays. The majority of supernovae have massive star progenitors and explode in a highly turbulent medium sustained by stellar winds and intense ionizing radiation in and around the parent stellar clusters. The early evolution of cosmic rays after their injection in the turbulent medium and the potential trapping and reacceleration of the particles in this environment have escaped observations so far. CRs can be traced in gamma rays as they interact with ambient interstellar gas and radiation. We present an analysis of the Fermi Large Area Telescope (LAT) observations of the Cygnus X region: gamma-ray emission above 1 GeV reveals a 50-pc wide cocoon of freshly-accelerated cosmic rays following the cavities carved by Cyg OB2 and other young stellar clusters. We will discuss the cocoon properties and its relationship with the nearby gamma-ray bright supernova remnant gamma Cygni.