62 articles – 637 Notices  [english version]
 HAL : in2p3-00530044, version 1
 arXiv : 1003.0895
 Astrophysical Journal 720 (2010) 435-453
 The Fermi-LAT high-latitude Survey: Source Count Distributions and the Origin of the Extragalactic Diffuse Background
 Fermi-LAT Collaboration(s)
 (01/09/2010)
 This is the first of a series of papers aimed at characterizing the populations detected in the high-latitude sky of the {\it Fermi}-LAT survey. In this work we focus on the intrinsic spectral and flux properties of the source sample. We show that when selection effects are properly taken into account, {\it Fermi} sources are on average steeper than previously found (e.g. in the bright source list) with an average photon index of 2.40$\pm0.02$ over the entire 0.1--100\,GeV energy band. We confirm that FSRQs have steeper spectra than BL Lac objects with an average index of 2.48$\pm0.02$ versus 2.18$\pm0.02$. Using several methods we build the deepest source count distribution at GeV energies deriving that the intrinsic source (i.e. blazar) surface density at F$_{100}\geq10^{-9}$\,ph cm$^{-2}$ s$^{-1}$ is 0.12$^{+0.03}_{-0.02}$\,deg$^{-2}$. The integration of the source count distribution yields that point sources contribute 16$(\pm1.8)$\,\% ($\pm$7\,\% systematic uncertainty) of the GeV isotropic diffuse background. At the fluxes currently reached by LAT we can rule out the hypothesis that point-like sources (i.e. blazars) produce a larger fraction of the diffuse emission.
 Thème(s) : Physique/Astrophysique/Phénomènes cosmiques de haute energiePlanète et Univers/Astrophysique/Phénomènes cosmiques de haute energie
 Mot(s)-clé(s) : cosmology: observations – diffuse radiation – galaxies: active – galaxies: jets – gamma rays: diffuse background – surveys
 Lien vers le texte intégral : http://fr.arXiv.org/abs/1003.0895
 in2p3-00530044, version 1 http://hal.in2p3.fr/in2p3-00530044 oai:hal.in2p3.fr:in2p3-00530044 Contributeur : Virginie Mas <> Déposé pour le compte de : David Smith <> Soumis le : Mercredi 27 Octobre 2010, 11:57:30 Dernière modification le : Jeudi 28 Octobre 2010, 09:51:23