The Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived From First-Year Fermi Large Area Telescope Data

A. A. Abdo Markus Ackermann Marco Ajello W. B. Atwood Luca Baldini Jean Ballet 1 Guido Barbiellini D. Bastieri B. M. Baughman K. Bechtol R. Bellazzini 1 B. Berenji R. D. Blandford E. D. Bloom E. Bonamente A.W. Borgland J. Bregeon 2 A. Brez M. Brigida Pascal Bruel 3 T. H. Burnett S. Buson G. A. Caliandro R. A. Cameron P. A. Caraveo J. M. Casandjian 1 E. Cavazzuti C. Cecchi E. Charles 1 A. Chekhtman C. C. Cheung J. Chiang S. Ciprini R. Claus J. Cohen-Tanugi 4 L. R. Cominsky J. Conrad S. Cutini C. D. Dermer A. de Angelis F. de Palma S.W. Digel G. Di Bernardo E. Do Couto E Silva P. S. Drell A. Drlica-Wagner R. Dubois D. Dumora 2 C. Farnier 4 C. Favuzzi S. J. Fegan 3 W. B. Focke P. Fortin 3 M. Frailis Y. Fukazawa S. Funk P. Fusco D. Gaggero F. Gargano D. Gasparrini N. Gehrels S. Germani B. Giebels 3 N. Giglietto P. Giommi F. Giordano T. Glanzman G. Godfrey I. A. Grenier 1 M.-H. Grondin 2 J. E. Grove L. Guillemot 2 S. Guiriec 4 M. Gustafsson Y. Hanabata A. K. Harding M. Hayashida R. E. Hughes R. Itoh M. S. Jackson G. Johannesson A. S. Johnson R. P. Johnson T. J. Johnson W. N. Johnson T. Kamae H. Katagiri J. Kataoka N. Kawai M. Kerr J. Knodlseder 5 M. L. Kocian F. Kuehn M. Kuss J. Lande L. Latronico M. Lemoine-Goumard 2 F. Longo F. Loparco B. Lott 2 M. N. Lovellette P. Lubrano G. M. Madejski A. Makeev M. N. Mazziotta W. Mcconville J. E. Mcenery C. Meurer P. F. Michelson W. Mitthumsiri T. Mizuno A. A. Moiseev C. Monte M. E. Monzani A. Morselli I.V. Moskalenko S. Murgia P. L. Nolan J. P. Norris E. Nuss 4 T. Ohsugi N. Omodei E. Orlando J. F. Ormes D. Paneque J. H. Panetta D. Parent 2 V. Pelassa 4 M. Pepe M. Pesce-Rollins F. Piron 4 T.A. Porter S. Raino R. Rando M. Razzano A. Reimer O. Reimer T. Reposeur 2 S. Ritz L. S. Rochester A.Y. Rodriguez M. Roth F. Ryde H. F.-W. Sadrozinski D. Sanchez 3 A. Sander P. M. Saz Parkinson J. D. Scargle A. Sellerholm C. Sgro 3 M. S. Shaw E. J. Siskind David Stanley Smith 2 P. D. Smith G. Spandre P. Spinelli Jean-Luc Starck 1 M. S. Strickman A.W. Strong D. J. Suson H. Tajima H. Takahashi T. Takahashi T. Tanaka J. B. Thayer J. G. Thayer D. J. Thompson L. Tibaldo 1 D. F. Torres G. Tosti A. Tramacere Y. Uchiyama T. L. Usher V. Vasileiou N. Vilchez 5 V. Vitale A. P. Waite P. Wang B. L. Winer K. S. Wood T. Ylinen M. Ziegler
Abstract : We report on the first Fermi Large Area Telescope (LAT) measurements of the so-called "extra-galactic" diffuse gamma-ray emission (EGB). This component of the diffuse gamma-ray emission is generally considered to have an isotropic or nearly isotropic distribution on the sky with diverse contributions discussed in the literature. The derivation of the EGB is based on detailed modelling of the bright foreground diffuse Galactic gamma-ray emission (DGE), the detected LAT sources and the solar gamma-ray emission. We find the spectrum of the EGB is consistent with a power law with differential spectral index g = 2.41+/-0.05 and intensity, I(> 100 MeV) = (1.03+/-0.17) 10^-5 cm^-2 s^-1 sr^-1, where the error is systematics dominated. Our EGB spectrum is featureless, less intense, and softer than that derived from EGRET data.
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Submitted on : Friday, April 16, 2010 - 11:07:29 AM
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A. A. Abdo, Markus Ackermann, Marco Ajello, W. B. Atwood, Luca Baldini, et al.. The Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived From First-Year Fermi Large Area Telescope Data. Physical Review Letters, American Physical Society, 2010, 104, pp.101101. ⟨10.1103/PhysRevLett.104.101101⟩. ⟨in2p3-00473713⟩

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