Gamma-ray lines from cosmic-ray interactions with interstellar dust grains

Abstract

As pointed out by Lingenfelter and Ramaty (1977), the shapes of some gamma-ray lines produced by cosmic-ray interactions with the interstellar medium potentially contain valuable information on the physical properties of dust grains, including their compositions and size distributions. The most promising of such lines are at 847, 1369, 1779 and 6129 keV, from 56-Fe*, 24-Mg*, 28-Si* and 16-O*, respectively. We performed detailed calculations of their profiles using, in particular, available laboratory measurements combined with optical model calculations to evaluate the energy distributions of the recoiling excited nuclei. We show that the line shapes are mainly sensitive to relatively large interstellar grains, with radii greater than 0.25 microns. Line fluxes from the inner Galaxy are then predicted.

arXiv comment7 pages, 4 figures, to be published in New Astronomy Reviews (proceedings of the Workshop "Astronomy with Radioactivities IV and Filling the Sensitivity Gap in MeV Astronomy", Seeon, Germany, May 26-30, 2003)

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Cited by in corpus (10)

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• Gamma rays as probes of cosmic-ray propagation and interactions in galaxies
• Radio spectra and sizes of ALMA-identified submillimetre galaxies: evidence of age-related spectral curvature and cosmic ray diffusion?
• Spectrum and ionization rate of low energy Galactic cosmic rays
• Nuclear Interaction Gamma-Ray Lines from the Galactic Center Region
• Measurement and analysis of nuclear $\gamma$-ray production cross sections in proton interactions with Mg, Si and Fe nuclei abundant in astrophysical sites over the incident energy range $E=30-66$ MeV
• Gamma-ray emission in proton-induced nuclear reactions on natC and Mylar targets over the incident energy range of Ep = 30-200 MeV. Astrophysical implications
• Exploring the MeV Sky with a Combined Coded Mask and Compton Telescope: The Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO)
• Gamma ray production cross sections in proton induced reactions on natural Mg, Si and Fe targets over the proton energy range 30 up to 66 MeV