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Supernova enhanced cosmic ray ionization and induced chemistry in a molecular cloud of W51C | C. Ceccarelli
; P. Hily-Blant
; T.Montmerle
; G.Dubus
; Y.Gallant
; A.Fiasson
; | Date: |
18 Aug 2011 | Abstract: | Cosmic rays pervade the Galaxy and are thought to be accelerated in supernova
shocks. The interaction of cosmic rays with dense interstellar matter has two
important effects: 1) high energy (>1 GeV) protons produce {gamma}-rays by
{pi}0-meson decay; 2) low energy (< 1 GeV) cosmic rays (protons and electrons)
ionize the gas. We present here new observations towards a molecular cloud
close to the W51C supernova remnant and associated with a recently discovered
TeV {gamma}-ray source. Our observations show that the cloud ionization degree
is highly enhanced, implying a cosmic ray ionization rate ~ 10-15 s-1, i.e. 100
times larger than the standard value in molecular clouds. This is consistent
with the idea that the cloud is irradiated by an enhanced flux of freshly
accelerated low-energy cosmic rays. In addition, the observed high cosmic ray
ionization rate leads to an instability in the chemistry of the cloud, which
keeps the electron fraction high, ~ 10-5, in a large fraction (Av geq 6mag) of
the cloud and low, ~ 10-7, in the interior. The two states have been predicted
in the literature as high- and low-ionization phases (HIP and LIP). This is the
observational evidence of their simultaneous presence in a cloud. | Source: | arXiv, 1108.3600 | Services: | Forum | Review | PDF | Favorites |
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