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Number of Authors: 134
2016 (English)In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 223, no 2, 26Article in journal (Refereed) Published
Abstract [en]

Most of the celestial. rays detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope originate from the interstellar medium when energetic cosmic rays interact with interstellar nucleons and photons. Conventional point-source and extended-source studies rely on the modeling of this diffuse emission for accurate characterization. Here, we describe the development of the Galactic Interstellar Emission Model (GIEM), which is the standard adopted by the LAT Collaboration and is publicly available. This model is based on a linear combination of maps for interstellar gas column density in Galactocentric annuli and for the inverse-Compton emission produced in the Galaxy. In the GIEM, we also include large-scale structures like Loop. I and the Fermi bubbles. The measured gas emissivity spectra confirm that the cosmic-ray proton density decreases with Galactocentric distance beyond 5 kpc from the Galactic Center. The measurements also suggest a softening of the proton spectrum with Galactocentric distance. We observe that the Fermi bubbles have boundaries with a shape similar to a catenary at latitudes below 20 degrees and we observe an enhanced emission toward their base extending in the north and south Galactic directions and located within similar to 4 degrees of the Galactic Center.

Place, publisher, year, edition, pages
2016. Vol. 223, no 2, 26
Keyword [en]
gamma rays: diffuse background, gamma rays: general, gamma rays: ISM
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-130885DOI: 10.3847/0067-0049/223/2/26ISI: 000375304600008OAI: diva2:933885
Available from: 2016-06-07 Created: 2016-06-07 Last updated: 2016-06-07Bibliographically approved

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Conrad, JanSanchez-Conde, MiguelZimmer, Stephan
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Department of PhysicsThe Oskar Klein Centre for Cosmo Particle Physics (OKC)
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