http://arxiv.org/abs/2303.13689
Supernova remnants act as particle accelerators, providing the cosmic-ray protons that permeate the interstellar medium and initiate the ion-molecule reactions that drive interstellar chemistry. Enhanced fluxes of cosmic-ray protons in close proximity to supernova remnants have been inferred from observations tracing particle interactions with nearby molecular gas. Here I present observations of H$_3^+$ and CO absorption, molecules that serve as tracers of the cosmic-ray ionization rate and gas density, respectively, in sight lines toward the W28 and Vela supernova remnants. Cosmic-ray ionization rates inferred from these observations range from about 2–10 times the average value in Galactic diffuse clouds ($\sim 3\times10^{-16}$ s$^{-1}$), suggesting that the gas being probed is experiencing an elevated particle flux. While it is difficult to constrain the line-of-sight location of the absorbing gas with respect to the supernova remnants, these results are consistent with a scenario where cosmic rays are diffusing away from the acceleration site and producing enhanced ionization rates in the surrounding medium.
N. Indriolo
Mon, 27 Mar 23
37/59
Comments: 26 pages, 6 figures, 4 tables; accepted for publication in ApJ
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