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# A new estimate of the extragalactic $\gamma$-ray background as seen by EGRET

Abstract : Large amounts of dark gas, not accounted for in the HI and CO surveys, have been found in infrared and gamma rays above 100 MeV at the interface between the atomic and molecular clouds in the solar neighbourhood. The local measurements imply a total dark-gas mass in the Milky Way at least comparable to the molecular mass detected in CO. The column-densities and large angular extent of the local dark clouds imply severe revisions of the gamma-ray interstellar emission model to high latitudes. A new estimate of the extragalactic gamma-ray background intensity is presented, but we point out large systematic uncertainties due to our limited knowledge of the foreground emissions, in particular the contributions from the nearby radio loops and the local inverse Compton (IC) emission.
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http://hal.in2p3.fr/in2p3-00085931
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Submitted on : Monday, July 17, 2006 - 12:52:39 PM
Last modification on : Wednesday, November 17, 2021 - 12:30:20 PM
Long-term archiving on: : Tuesday, April 6, 2010 - 12:12:04 AM

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• HAL Id : in2p3-00085931, version 1

### Citation

I.A. Grenier, J.M. Casandjian, R. Terrier. A new estimate of the extragalactic $\gamma$-ray background as seen by EGRET. 29th International Cosmic Ray Conference - ICRC 2005, Aug 2005, Pune, India. pp.13-16. ⟨in2p3-00085931⟩

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