Supernova remnants (SNRs) have long been considered the primary sites for
the acceleration of cosmic rays up to 10³ TeV. The evidence lending
support to this belief is based on several strong arguments. First,
supernova blast shock are one of the few galactic sites capable of
sustaining the cosmic ray population against loss by escape and nuclear interactions.
Second, shock acceleration models provide a plausible mechanism for
converting this explosive energy into accelerated particles with
energies ~10² - 10³ TeV. Finally, recent detections of non-thermal
X-ray emission in
SN 1006 ), IC 443 and CAS A suggests the presence of electrons accelerated to
10 - 100 TeV. However, observations of electrons accelerated by
strong shocks only provide indirect evidence of cosmic ray production.
If SNRs do contain significant accelerated proton
populations these will inevitably interact with the
swept up interstellar medium in the remnants to
produce pi° gamma-rays .
One critical test of the shock acceleration model
for the origin of cosmic rays is the observation of gamma-rays.
VERITAS will be
able to make crucial measurements in this area as
good angular resolution is required to map the
emission region and good energy resolution is required
to differentiate contributions to the gamma-ray flux
by other mechanisms such as bremsstrahlung and inverse Compton.
VERITAS :A new major ground-based gamma-ray observatory with an array of four 12m optical reflectors for gamma-ray astronomy