Galactic Cosmic Rays: From Earth to Sources
For over 100 years we have known that cosmic rays come from outer space, yet proof of their origin, as well as a comprehensive understanding of their acceleration, remains elusive. Direct detection of high energy (up to 10^15eV), charged nuclei with experiments such as the balloon-born, antarctic Trans-Iron Galactic Element Recorder (TIGER) and the recently flown SuperTIGER have provided insight into these mysteries through measurements of cosmic ray abundances. The abundance of rare heavy elements with respect to certain intrinsic properties suggests that cosmic rays include a component of massive star ejecta.
Supernovae and their remnants (SNe & SNRs), often occurring at the end of a massive star's life or in an environment including massive star material, are one of the most likely candidates for sources accelerating galactic comic ray nuclei up to the requisite high energies. The Fermi Gamma-ray Space Telescope Large Area Detector (Fermi LAT) has improved our understanding of such sources by widening the window of observable energies and thus our view into potential sources' energetic processes. Since Fermi LAT surveys the whole sky, we have created the first systematic study of GeV emission in all regions containing known SNRs. Not only does this catalog, in combination with the wealth of multiwavelength data available, allow us to constrain SNRs' ability to accelerate cosmic rays, but it also provides statistically-motivated insight into the inner workings of GeV-emitting SNRs.