The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV

M. Ackermann, M. Ajello, A. Albert, W. B. Atwood, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, E. Bissaldi, R. D. Blandford, E. D. Bloom, E. Bottacini, T. J. Brandt, J. Bregeon, P. Bruel, R. Buehler, S. Buson, G. A. CaliandroR. A. Cameron, M. Caragiulo, P. A. Caraveo, E. Cavazzuti, C. Cecchi, E. Charles, A. Chekhtman, J. Chiang, G. Chiaro, S. Ciprini, R. Claus, J. Cohen-Tanugi, J. Conrad, A. Cuoco, S. Cutini, F. D'Ammando, A. De Angelis, F. De Palma, C. D. Dermer, S. W. Digel, E. Do Couto E Silva, P. S. Drell, C. Favuzzi, E. C. Ferrara, W. B. Focke, A. Franckowiak, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, S. Germani, N. Giglietto, P. Giommi, F. Giordano, M. Giroletti, G. Godfrey, G. A. Gomez-Vargas, I. A. Grenier, S. Guiriec, M. Gustafsson, D. Hadasch, K. Hayashi, E. Hays, J. W. Hewitt, P. Ippoliti, T. Jogler, G. Jóhannesson, A. S. Johnson, W. N. Johnson, T. Kamae, Jun Kataoka, J. Knödlseder, M. Kuss, S. Larsson, L. Latronico, J. Li, L. Li, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, G. M. Madejski, A. Manfreda, F. Massaro, M. Mayer, M. N. Mazziotta, J. E. McEnery, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, R. Nemmen, E. Nuss, T. Ohsugi, N. Omodei, E. Orlando, J. F. Ormes, D. Paneque, J. H. Panetta, J. S. Perkins, M. Pesce-Rollins, F. Piron, G. Pivato, T. A. Porter, S. Rainò, R. Rando, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, T. Reposeur, S. Ritz, R. W. Romani, M. Sánchez-Conde, M. Schaal, A. Schulz, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, A. W. Strong, D. J. Suson, H. Takahashi, J. G. Thayer, J. B. Thayer, L. Tibaldo, M. Tinivella, D. F. Torres, G. Tosti, E. Troja, Y. Uchiyama, G. Vianello, M. Werner, B. L. Winer, K. S. Wood, M. Wood, G. Zaharijas, S. Zimmer

    Research output: Contribution to journalArticle

    309 Citations (Scopus)

    Abstract

    The γ-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 γ-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.

    Original languageEnglish
    Article number86
    JournalAstrophysical Journal
    Volume799
    Issue number1
    DOIs
    Publication statusPublished - 2015 Jan 20

    Fingerprint

    gamma rays
    energy
    cosmic ray
    sky
    rays
    cut-off
    telescopes
    Fermi Gamma-ray Space Telescope
    radiation distribution
    cosmic rays
    power law
    coverings
    gases
    gas
    interactions

    Keywords

    • Diffuse radiation
    • Gamma rays: Diffuse background

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    Ackermann, M., Ajello, M., Albert, A., Atwood, W. B., Baldini, L., Ballet, J., ... Zimmer, S. (2015). The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV. Astrophysical Journal, 799(1), [86]. https://doi.org/10.1088/0004-637X/799/1/86

    The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV. / Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; 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.; D'Ammando, F.; De Angelis, A.; De Palma, F.; Dermer, C. D.; Digel, S. W.; Do Couto E Silva, E.; Drell, P. S.; Favuzzi, C.; Ferrara, E. C.; Focke, W. B.; 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, G. A.; Grenier, I. A.; Guiriec, S.; Gustafsson, M.; Hadasch, D.; Hayashi, K.; Hays, E.; Hewitt, J. W.; Ippoliti, P.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Kataoka, Jun; Knödlseder, J.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Manfreda, A.; Massaro, F.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nemmen, R.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Perkins, J. S.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Reposeur, T.; Ritz, S.; Romani, R. W.; Sánchez-Conde, M.; Schaal, M.; Schulz, A.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Strong, A. W.; Suson, D. J.; Takahashi, H.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Vianello, G.; Werner, M.; Winer, B. L.; Wood, K. S.; Wood, M.; Zaharijas, G.; Zimmer, S.

    In: Astrophysical Journal, Vol. 799, No. 1, 86, 20.01.2015.

    Research output: Contribution to journalArticle

    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, D'Ammando, F, De Angelis, A, De Palma, F, Dermer, CD, Digel, SW, Do Couto E Silva, E, 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, Jóhannesson, G, Johnson, AS, Johnson, WN, Kamae, T, Kataoka, J, Knödlseder, 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, Rainò, S, Rando, R, Razzano, M, Razzaque, S, Reimer, A, Reimer, O, Reposeur, T, Ritz, S, Romani, RW, Sánchez-Conde, M, Schaal, M, Schulz, A, Sgrò, 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 2015, 'The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV', Astrophysical Journal, vol. 799, no. 1, 86. https://doi.org/10.1088/0004-637X/799/1/86
    Ackermann M, Ajello M, Albert A, Atwood WB, Baldini L, Ballet J et al. The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV. Astrophysical Journal. 2015 Jan 20;799(1). 86. https://doi.org/10.1088/0004-637X/799/1/86
    Ackermann, M. ; Ajello, M. ; Albert, A. ; Atwood, W. B. ; Baldini, L. ; Ballet, J. ; Barbiellini, G. ; Bastieri, D. ; Bechtol, K. ; Bellazzini, R. ; Bissaldi, E. ; Blandford, R. D. ; Bloom, E. D. ; Bottacini, E. ; Brandt, T. J. ; Bregeon, J. ; Bruel, P. ; Buehler, R. ; Buson, S. ; Caliandro, G. A. ; Cameron, R. A. ; Caragiulo, M. ; Caraveo, P. A. ; 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. ; D'Ammando, F. ; De Angelis, A. ; De Palma, F. ; Dermer, C. D. ; Digel, S. W. ; Do Couto E Silva, E. ; Drell, P. S. ; Favuzzi, C. ; Ferrara, E. C. ; Focke, W. B. ; 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, G. A. ; Grenier, I. A. ; Guiriec, S. ; Gustafsson, M. ; Hadasch, D. ; Hayashi, K. ; Hays, E. ; Hewitt, J. W. ; Ippoliti, P. ; Jogler, T. ; Jóhannesson, G. ; Johnson, A. S. ; Johnson, W. N. ; Kamae, T. ; Kataoka, Jun ; Knödlseder, J. ; Kuss, M. ; Larsson, S. ; Latronico, L. ; Li, J. ; Li, L. ; Longo, F. ; Loparco, F. ; Lott, B. ; Lovellette, M. N. ; Lubrano, P. ; Madejski, G. M. ; Manfreda, A. ; Massaro, F. ; Mayer, M. ; Mazziotta, M. N. ; McEnery, J. E. ; Michelson, P. F. ; Mitthumsiri, W. ; Mizuno, T. ; Moiseev, A. A. ; Monzani, M. E. ; Morselli, A. ; Moskalenko, I. V. ; Murgia, S. ; Nemmen, R. ; Nuss, E. ; Ohsugi, T. ; Omodei, N. ; Orlando, E. ; Ormes, J. F. ; Paneque, D. ; Panetta, J. H. ; Perkins, J. S. ; Pesce-Rollins, M. ; Piron, F. ; Pivato, G. ; Porter, T. A. ; Rainò, S. ; Rando, R. ; Razzano, M. ; Razzaque, S. ; Reimer, A. ; Reimer, O. ; Reposeur, T. ; Ritz, S. ; Romani, R. W. ; Sánchez-Conde, M. ; Schaal, M. ; Schulz, A. ; Sgrò, C. ; Siskind, E. J. ; Spandre, G. ; Spinelli, P. ; Strong, A. W. ; Suson, D. J. ; Takahashi, H. ; Thayer, J. G. ; Thayer, J. B. ; Tibaldo, L. ; Tinivella, M. ; Torres, D. F. ; Tosti, G. ; Troja, E. ; Uchiyama, Y. ; Vianello, G. ; Werner, M. ; Winer, B. L. ; Wood, K. S. ; Wood, M. ; Zaharijas, G. ; Zimmer, S. / The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV. In: Astrophysical Journal. 2015 ; Vol. 799, No. 1.
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    title = "The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV",
    abstract = "The γ-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 γ-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.",
    keywords = "Diffuse radiation, Gamma rays: Diffuse background",
    author = "M. Ackermann and M. Ajello and A. Albert and Atwood, {W. B.} and L. Baldini and J. Ballet and G. Barbiellini and D. Bastieri and K. Bechtol and R. Bellazzini and E. Bissaldi and Blandford, {R. D.} and Bloom, {E. D.} and E. Bottacini and Brandt, {T. J.} and J. Bregeon and P. Bruel and R. Buehler and S. Buson and Caliandro, {G. A.} and Cameron, {R. A.} and M. Caragiulo and Caraveo, {P. A.} and E. Cavazzuti and C. Cecchi and E. Charles and A. Chekhtman and J. Chiang and G. Chiaro and S. Ciprini and R. Claus and J. Cohen-Tanugi and J. Conrad and A. Cuoco and S. Cutini and F. D'Ammando and {De Angelis}, A. and {De Palma}, F. and Dermer, {C. D.} and Digel, {S. W.} and {Do Couto E Silva}, E. and Drell, {P. S.} and C. Favuzzi and Ferrara, {E. C.} and Focke, {W. B.} and A. Franckowiak and Y. Fukazawa and S. Funk and P. Fusco and F. Gargano and D. Gasparrini and S. Germani and N. Giglietto and P. Giommi and F. Giordano and M. Giroletti and G. Godfrey and Gomez-Vargas, {G. A.} and Grenier, {I. A.} and S. Guiriec and M. Gustafsson and D. Hadasch and K. Hayashi and E. Hays and Hewitt, {J. W.} and P. Ippoliti and T. Jogler and G. J{\'o}hannesson and Johnson, {A. S.} and Johnson, {W. N.} and T. Kamae and Jun Kataoka and J. Kn{\"o}dlseder and M. Kuss and S. Larsson and L. Latronico and J. Li and L. Li and F. Longo and F. Loparco and B. Lott and Lovellette, {M. N.} and P. Lubrano and Madejski, {G. M.} and A. Manfreda and F. Massaro and M. Mayer and Mazziotta, {M. N.} and McEnery, {J. E.} and Michelson, {P. F.} and W. Mitthumsiri and T. Mizuno and Moiseev, {A. A.} and Monzani, {M. E.} and A. Morselli and Moskalenko, {I. V.} and S. Murgia and R. Nemmen and E. Nuss and T. Ohsugi and N. Omodei and E. Orlando and Ormes, {J. F.} and D. Paneque and Panetta, {J. H.} and Perkins, {J. S.} and M. Pesce-Rollins and F. Piron and G. Pivato and Porter, {T. A.} and S. Rain{\`o} and R. Rando and M. Razzano and S. Razzaque and A. Reimer and O. Reimer and T. Reposeur and S. Ritz and Romani, {R. W.} and M. S{\'a}nchez-Conde and M. Schaal and A. Schulz and C. Sgr{\`o} and Siskind, {E. J.} and G. Spandre and P. Spinelli and Strong, {A. W.} and Suson, {D. J.} and H. Takahashi and Thayer, {J. G.} and Thayer, {J. B.} and L. Tibaldo and M. Tinivella and Torres, {D. F.} and G. Tosti and E. Troja and Y. Uchiyama and G. Vianello and M. Werner and Winer, {B. L.} and Wood, {K. S.} and M. Wood and G. Zaharijas and S. Zimmer",
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    TY - JOUR

    T1 - The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV

    AU - Ackermann, M.

    AU - Ajello, M.

    AU - Albert, A.

    AU - Atwood, W. B.

    AU - Baldini, L.

    AU - Ballet, J.

    AU - Barbiellini, G.

    AU - Bastieri, D.

    AU - Bechtol, K.

    AU - Bellazzini, R.

    AU - Bissaldi, E.

    AU - Blandford, R. D.

    AU - Bloom, E. D.

    AU - Bottacini, E.

    AU - Brandt, T. J.

    AU - Bregeon, J.

    AU - Bruel, P.

    AU - Buehler, R.

    AU - Buson, S.

    AU - Caliandro, G. A.

    AU - Cameron, R. A.

    AU - Caragiulo, M.

    AU - Caraveo, P. A.

    AU - Cavazzuti, E.

    AU - Cecchi, C.

    AU - Charles, E.

    AU - Chekhtman, A.

    AU - Chiang, J.

    AU - Chiaro, G.

    AU - Ciprini, S.

    AU - Claus, R.

    AU - Cohen-Tanugi, J.

    AU - Conrad, J.

    AU - Cuoco, A.

    AU - Cutini, S.

    AU - D'Ammando, F.

    AU - De Angelis, A.

    AU - De Palma, F.

    AU - Dermer, C. D.

    AU - Digel, S. W.

    AU - Do Couto E Silva, E.

    AU - Drell, P. S.

    AU - Favuzzi, C.

    AU - Ferrara, E. C.

    AU - Focke, W. B.

    AU - Franckowiak, A.

    AU - Fukazawa, Y.

    AU - Funk, S.

    AU - Fusco, P.

    AU - Gargano, F.

    AU - Gasparrini, D.

    AU - Germani, S.

    AU - Giglietto, N.

    AU - Giommi, P.

    AU - Giordano, F.

    AU - Giroletti, M.

    AU - Godfrey, G.

    AU - Gomez-Vargas, G. A.

    AU - Grenier, I. A.

    AU - Guiriec, S.

    AU - Gustafsson, M.

    AU - Hadasch, D.

    AU - Hayashi, K.

    AU - Hays, E.

    AU - Hewitt, J. W.

    AU - Ippoliti, P.

    AU - Jogler, T.

    AU - Jóhannesson, G.

    AU - Johnson, A. S.

    AU - Johnson, W. N.

    AU - Kamae, T.

    AU - Kataoka, Jun

    AU - Knödlseder, J.

    AU - Kuss, M.

    AU - Larsson, S.

    AU - Latronico, L.

    AU - Li, J.

    AU - Li, L.

    AU - Longo, F.

    AU - Loparco, F.

    AU - Lott, B.

    AU - Lovellette, M. N.

    AU - Lubrano, P.

    AU - Madejski, G. M.

    AU - Manfreda, A.

    AU - Massaro, F.

    AU - Mayer, M.

    AU - Mazziotta, M. N.

    AU - McEnery, J. E.

    AU - Michelson, P. F.

    AU - Mitthumsiri, W.

    AU - Mizuno, T.

    AU - Moiseev, A. A.

    AU - Monzani, M. E.

    AU - Morselli, A.

    AU - Moskalenko, I. V.

    AU - Murgia, S.

    AU - Nemmen, R.

    AU - Nuss, E.

    AU - Ohsugi, T.

    AU - Omodei, N.

    AU - Orlando, E.

    AU - Ormes, J. F.

    AU - Paneque, D.

    AU - Panetta, J. H.

    AU - Perkins, J. S.

    AU - Pesce-Rollins, M.

    AU - Piron, F.

    AU - Pivato, G.

    AU - Porter, T. A.

    AU - Rainò, S.

    AU - Rando, R.

    AU - Razzano, M.

    AU - Razzaque, S.

    AU - Reimer, A.

    AU - Reimer, O.

    AU - Reposeur, T.

    AU - Ritz, S.

    AU - Romani, R. W.

    AU - Sánchez-Conde, M.

    AU - Schaal, M.

    AU - Schulz, A.

    AU - Sgrò, C.

    AU - Siskind, E. J.

    AU - Spandre, G.

    AU - Spinelli, P.

    AU - Strong, A. W.

    AU - Suson, D. J.

    AU - Takahashi, H.

    AU - Thayer, J. G.

    AU - Thayer, J. B.

    AU - Tibaldo, L.

    AU - Tinivella, M.

    AU - Torres, D. F.

    AU - Tosti, G.

    AU - Troja, E.

    AU - Uchiyama, Y.

    AU - Vianello, G.

    AU - Werner, M.

    AU - Winer, B. L.

    AU - Wood, K. S.

    AU - Wood, M.

    AU - Zaharijas, G.

    AU - Zimmer, S.

    PY - 2015/1/20

    Y1 - 2015/1/20

    N2 - The γ-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 γ-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.

    AB - The γ-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 γ-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.

    KW - Diffuse radiation

    KW - Gamma rays: Diffuse background

    UR - http://www.scopus.com/inward/record.url?scp=84921629099&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=84921629099&partnerID=8YFLogxK

    U2 - 10.1088/0004-637X/799/1/86

    DO - 10.1088/0004-637X/799/1/86

    M3 - Article

    AN - SCOPUS:84921629099

    VL - 799

    JO - Astrophysical Journal

    JF - Astrophysical Journal

    SN - 0004-637X

    IS - 1

    M1 - 86

    ER -