Giant Molecular Clouds as probes of of Galactic Cosmic Rays with Fermi-LAT

Direct measurements of Cosmic Rays (CRs) can not extend much further than the Solar System. In order to probe the so-called “sea” of Galactic Cosmic Rays, one should rely on secondary emission. Gamma rays produced in the interstellar gas, when hit by high energy particles, trace the energy distribution of the parent CRs. Giant Molecular Clouds, being huge reservoirs of hydrogen, serve as perfect targets for interaction with CRs. The high particle density in these objects enables to have enhanced  emission from small isolated location, and hence to derive information about single spots of the Milky Way. We analyzed more than 9 years data of Fermi -LAT from 18 molecular clouds, located in different regions from 100 pc to more than 10 kpc from us, allowing us to have the most comprehensive study on Galactic Cosmic Rays from Molecular Clouds ever.