THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV
THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV
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DOI：
10.1088/0004-637x/799/1/86
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发表时间：
2015-01-20
影响因子：
4.9
通讯作者：
Zimmer, S.
中科院分区：
文献类型：
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作者：
Ackermann, M.;Ajello, M.;Zimmer, S.
伽玛射线天空可以分解为单独探测到的源，归因于银河系宇宙射线与气体和辐射场相互作用的漫射发射，以及通常称为各向同性漫射伽玛射线背景（IGRB）的残余全天空发射成分。IGRB包括所有的星系外辐射，这些辐射要么太微弱，要么太分散，以至于无法在给定的调查中解决，以及任何残留的银河系前景，它们几乎是各向同性的。Fermi伽玛射线空间望远镜（Fermi）上的大面积望远镜（LAT）首次测量了IGRB，使用了10个月的巡天数据，并认为能量范围在200 MeV到100 GeV之间。事件选择和宇宙射线背景特征的改进，对漫射星系发射（DGE）的更好理解，以及50个月的更长的数据积累，使得LAT可以改进和扩展IGRB的测量，现在覆盖了100 MeV到820 GeV的能量范围。IGRB光谱显示出明显的高能截止特征，可以用幂律很好地描述近40年的能量，指数截止的光谱指数为2.32 +/- 0.02，使用我们的基线DGE模型的断裂能量为（279 +/- 52）GeV。归因于IGRB的总强度为（7.2 +/- 0.6）× 10(-6) cm(-2) s(-1) sr(-1)，高于100 MeV，由于银河系漫射前景，系统不确定性增加了+15%/-30%。
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.