Circum-Galactic Gas and the Isotropic Gamma Ray Background

Abstract

Interactions of cosmic rays with the interstellar gas and radiation fields of the Milky Way provide the majority of the gamma rays observed by the Fermi Gamma Ray Space Telescope. In addition to the gas which is densely concentrated along the Galactic Disk, hydrodynamical simulations and observational evidence favor the presence of a halo of hot (T~10^6 K) ionized hydrogen (H_II), extending with non-negligible densities out to the virial radius of the Milky Way. We show that cosmic ray collisions with this circum-galactic gas should be expected to provide a significant flux of gamma rays, on the order of 10% of the observed isotopic gamma ray background at energies above 1 GeV. In addition, gamma rays originating from the extended H_II halos of other galaxies along a given line-of-sight should contribute to this background at a similar level.

6 pages, 3 figures, submitted to APJ, comments welcome

References in corpus (15)

• The Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived From First-Year Fermi Large Area Telescope Data
• The Search for the Missing Baryons at Low Redshift
• Global cosmic-ray related luminosity and energy budget of the Milky Way
• Environmental Dependence of the Kennicutt-Schmidt Relation in Galaxies
• Do Hot Haloes Around Galaxies Contain the Missing Baryons?
• The Starburst Contribution to the Extra-Galactic Gamma-Ray Background
• X-ray coronae in simulations of disc galaxy formation
• All-sky Galactic radiation at 45 MHz and spectral index between 45 and 408 MHz
• Where are the ``Missing'' Galactic Baryons?
• The Source of Ionization along the Magellanic Stream
• Fermi Large Area Telescope observations of Local Group galaxies: Detection of M31 and search for M33
• Joint anisotropy and source count constraints on the contribution of blazars to the diffuse gamma-ray background
• How Universal is the SFR - H2 Relation?
• Reconstructing Deconstruction: High-Velocity Cloud Distance Through Disruption Morphology
• Atomic Hydrogen Properties of AGN Host Galaxies: HI in 16 NUclei of GAlaxies (NUGA) Sources

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