Cosmic rays, from accelerators to galactic populations - A selected tour of the gamma-ray sky

Séminaire IPAG de Pierrick Martin (IPAG), jeudi 1er mars 2012 à 11h00, IPAG seminar room

Our Galaxy gives rise and hosts several populations of non-thermal particles, distributed over large scales from the centre to the periphery and halo. These Galactic cosmic rays span energies from less than 100MeV to more than 100TeV and it is now commonly accepted that they are accelerated in the strong shocks that accompany some of the most violent astrophysical phenomena, although some aspects of the process remain currently unclear. Far from being a side effect of stellar evolution, cosmic rays are an essential ingredient of the whole system and strongly influence the chemical and physical conditions of the Galaxy. In this talk, I will present the main facts about the acceleration of cosmic rays at astrophysical shocks, their propagation from sources to the interstellar medium, and the buildup and regulation of galactic populations. This will be illustrated by recent results obtained with gamma-ray telescopes, especially the LAT instrument onboard the Fermi satellite. The selection of objects will include the V407 Cygni nova, a bubble of cosmic rays in the Cygnus region, the Galactic interstellar medium, the Magellanic Clouds, and the starburst galaxies M82 and NGC253.