It has long been speculated that supernova remnants represent a major source
of cosmic rays in the Galaxy. Observations over the past decade have
ceremoniously unveiled direct evidence of particle acceleration in SNRs to
energies approaching the knee of the cosmic ray spectrum. Nonthermal X-ray
emission from shell-type SNRs reveals multi-TeV electrons, and the dynamical
properties of several SNRs point to efficient acceleration of ions.
Observations of TeV gamma-ray emission have confirmed the presence of energetic
particles in several remnants as well, but there remains considerable debate as
to whether this emission originates with high energy electrons or ions. Equally
uncertain are the exact conditions that lead to efficient particle
acceleration.
Based on the catalog of EGRET sources, we know that there is a large
population of Galactic gamma-ray sources whose distribution is similar to that
of SNRs. With the increased resolution and sensitivity of GLAST, the gamma-ray
SNRs from this population will be identified. Their detailed emission
structure, along with their spectra, will provide the link between their
environments and their spectra in other wavebands to constrain emission models
and to potentially identify direct evidence of ion acceleration in SNRs. Here I
summarize recent observational and theoretical work in the area of cosmic ray
acceleration by SNRs, and discuss the contributions GLAST will bring to our
understanding of this problem.Comment: 5 pages, to be published in "The Proceedings of the First
International GLAST Symposium", February 5-8, 2007, Stanford University, AIP,
Eds. S. Ritz, P. F. Michelson, and C. Meega
