GeV Gamma Rays from Supernova Remnants Interacting with Molecular Clouds
Proceedings of 25th Texas Symposium on Relativistic Astrophysics — PoS(Texas 2010)(2011)
摘要
We report the current status of the observations of supernova remnants (SNRs)
with the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope,
focusing on middle-aged SNRs that appear to be interacting with molecular
clouds. Observations with the Fermi LAT in an energy range from 0.2 to 100 GeV
have unveiled the presence of luminous GeV gamma-ray emission in middle-aged
SNRs, providing a new insight into the shock-acceleration theory and the origin
of galactic cosmic rays. The middle-aged SNRs detected by the Fermi LAT are
generally much brighter in GeV than in TeV in terms of energy flux, which
emphasizes the importance of the GeV observations. Spectral steepening in the
Fermi-LAT band is commonly found for the GeV-luminous SNRs. Remarkably, most
(if not all) of them are known to be interacting with molecular clouds, and
they are also the strong sources of synchrotron radio emission. We discuss
possible scenarios to explain the enhanced GeV gamma-ray emission in the
cloud-interacting SNRs. Particular emphasis is placed on a scenario in which
shock-accelerated cosmic-rays are adiabatically compressed and energized as
result of radiative cooling behind the cloud shock.
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关键词
space telescope,cosmic ray,energy flux,high energy astrophysics,gamma ray,molecular clouds
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