The gamma-ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, and a residual all-sky emission component commonly called the isotropic diffuse gamma-ray background (IGRB). The IGRB comprises all extragalactic emissions too faint or too diffuse to be resolved in a given survey, as well as any residual Galactic foregrounds that are approximately isotropic. The first IGRB measurement with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) used 10 months of sky-survey data and considered an energy range between 200 MeV and 100 GeV. Improvements in event selection and characterization of cosmic-ray backgrounds, better understanding of the diffuse Galactic emission (DGE), and a longer data accumulation of 50 months allow for a refinement and extension of the IGRB measurement with the LAT, now covering the energy range from 100 MeV to 820 GeV. The IGRB spectrum shows a significant high-energy cutoff feature and can be well described over nearly four decades in energy by a power law with exponential cutoff having a spectral index of 2.32 +/- 0.02 and a break energy of (279 +/- 52) GeV using our baseline DGE model. The total intensity attributed to the IGRB is (7.2 +/- 0.6) x 10(-6) cm(-2) s(-1) sr(-1) above 100 MeV, with an additional +15%/-30% systematic uncertainty due to the Galactic diffuse foregrounds.
THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV / Ackermann M; Ajello M; Albert A; Atwood WB; Baldini L; Ballet J; Barbiellini G; Bastieri D; Bechtol K; Bellazzini R; Bissaldi E; Blandford RD; Bloom ED; Bottacini E; Brandt TJ; Bregeon J; Bruel P; Buehler R; Buson S; Caliandro GA; Cameron RA; Caragiulo M; Caraveo PA; Cavazzuti E; Cecchi C; Charles E; Chekhtman A; Chiang J; Chiaro G; Ciprini S; Claus R; Cohen-Tanugi J; Conrad J; Cuoco A; Cutini S; DAmmando F; de Angelis A; de Palma F; Dermer CD; Digel SW; Silva EDE; Drell PS; Favuzzi C; Ferrara EC; Focke WB; Franckowiak A; Fukazawa Y; Funk S; Fusco P; Gargano F; Gasparrini D; Germani S; Giglietto N; Giommi P; Giordano F; Giroletti M; Godfrey G; Gomez-Vargas GA; Grenier IA; Guiriec S; Gustafsson M; Hadasch D; Hayashi K; Hays E; Hewitt JW; Ippoliti P; Jogler T; Johannesson G; Johnson AS; Johnson WN; Kamae T; Kataoka J; Knodlseder J; Kuss M; Larsson S; Latronico L; Li J; Li L; Longo F; Loparco F; Lott B; Lovellette MN; Lubrano P; Madejski GM; Manfreda A; Massaro F; Mayer M; Mazziotta MN; McEnery JE; Michelson PF; Mitthumsiri W; Mizuno T; Moiseev AA; Monzani ME; Morselli A; Moskalenko IV; Murgia S; Nemmen R; Nuss E; Ohsugi T; Omodei N; Orlando E; Ormes JF; Paneque D; Panetta JH; Perkins JS; Pesce-Rollins M; Piron F; Pivato G; Porter TA; Raino S; Rando R; Razzano M; Razzaque S; Reimer A; Reimer O; Reposeur T; Ritz S; Romani RW; Sanchez-Conde M; Schaal M; Schulz A; Sgro C; Siskind EJ; Spandre G; Spinelli P; Strong AW; Suson DJ; Takahashi H; Thayer JG; Thayer JB; Tibaldo L; Tinivella M; Torres DF; Tosti G; Troja E; Uchiyama Y; Vianello G; Werner M; Winer BL; Wood KS; Wood M; Zaharijas G; Zimmer S. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - STAMPA. - 799:1(2015), pp. 86.86-86.109. [10.1088/0004-637X/799/1/86]
THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV
D'AMMANDO, FILIPPO;
2015
Abstract
The gamma-ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, and a residual all-sky emission component commonly called the isotropic diffuse gamma-ray background (IGRB). The IGRB comprises all extragalactic emissions too faint or too diffuse to be resolved in a given survey, as well as any residual Galactic foregrounds that are approximately isotropic. The first IGRB measurement with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) used 10 months of sky-survey data and considered an energy range between 200 MeV and 100 GeV. Improvements in event selection and characterization of cosmic-ray backgrounds, better understanding of the diffuse Galactic emission (DGE), and a longer data accumulation of 50 months allow for a refinement and extension of the IGRB measurement with the LAT, now covering the energy range from 100 MeV to 820 GeV. The IGRB spectrum shows a significant high-energy cutoff feature and can be well described over nearly four decades in energy by a power law with exponential cutoff having a spectral index of 2.32 +/- 0.02 and a break energy of (279 +/- 52) GeV using our baseline DGE model. The total intensity attributed to the IGRB is (7.2 +/- 0.6) x 10(-6) cm(-2) s(-1) sr(-1) above 100 MeV, with an additional +15%/-30% systematic uncertainty due to the Galactic diffuse foregrounds.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
