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http://hdl.handle.net/20.500.12386/26764
Title: | Reconciling the diffuse Galactic γ-ray and the cosmic ray spectra | Authors: | Nava, Lara Benyamin, David Piran, Tsvi Shaviv, Nir J. |
Issue Date: | 2017 | Journal: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Number: | 466 | Issue: | 3 | First Page: | 3674 | Abstract: | Most of the diffuse Galactic GeV γ-ray emission is produced via collisions of cosmic ray (CR) protons with ISM protons. As such the observed spectra of the γ-rays and the CRs should be strongly linked. Recent observations of Fermi-LAT exhibit a hardening of the γ-ray spectrum at around a hundred GeV, between the Sagittarius and Carina tangents, and a further hardening at a few degrees above and below the Galactic plane. However, standard CR propagation models that assume a time-independent source distribution and a location-independent diffusion cannot give rise to a spatially dependent CR (and hence γ-ray) spectral slopes. Here, we consider a dynamic spiral arm model in which the distribution of CR sources is concentrated in the (dynamic) spiral arms, and we study the effects of this model on the π<SUP>0</SUP>-decay-produced γ-ray spectra. Within this model, near the Galactic arms the observed γ-ray spectral slope is not trivially related to the CR injection spectrum and energy dependence of the diffusion coefficient. We find unique signatures that agree with the Fermi-LAT observations. This model also provides a physical explanation for the difference between the local CR spectral slope and the CR slope inferred from the average γ-ray spectrum. | URI: | http://hdl.handle.net/20.500.12386/26764 | URL: | https://academic.oup.com/mnras/article/466/3/3674/2736302 | ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stw3346 | Bibcode ADS: | 2017MNRAS.466.3674N | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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stw3346.pdf | PDF editoriale | 2.94 MB | Adobe PDF | View/Open |
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