| Abstract |
Cosmic rays were discovered nearly 100 years ago. These primarily
hadronic particles have been measured in the near Earth environment,
but we have not been able to determine their origin primarily because
magnetic fields deflect the cosmic rays in random directions.
However, gamma rays are produced by cosmic rays interacting near their
sources and as they propagate through the Galaxy, and the plane of the
Milky Way is a bright source of TeV gamma rays. Localized sources,
such as pulsar winds and supernova remnants, produce TeV gamma rays as
well as the interactions of cosmic rays with matter and radiation
fields. The Milagro observatory has measured this diffuse gamma ray
flux which is much larger than expected given the local cosmic ray
measurements. Deeper observations with current and future
observatories will remove more of the unresolved localized source
contributions and allow spectral measurements of the diffuse gamma-ray
emission. Different spectra as well as a different spatial
morphology are expected for different contributions to the gamma-ray
flux. For example, the higher the energy of the gamma rays the more
likely the gamma rays are produced by hadrons. The High Altitude
Water Cherenkov (HAWC) observatory, a next generation version of
Milagro, will have the sensitivity to observe these highest energy
gamma rays and shed light on the origin of cosmic rays.
|