Gaggero D, Grasso D, Marinelli A, Taoso M, Urbano A
GRAPPA, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands.
INFN Pisa and Pisa University, Largo B. Pontecorvo 3, I-56127 Pisa, Italy.
Phys Rev Lett. 2017 Jul 21;119(3):031101. doi: 10.1103/PhysRevLett.119.031101. Epub 2017 Jul 17.
We present a novel interpretation of the γ-ray diffuse emission measured by Fermi-LAT and H.E.S.S. in the Galactic center (GC) region and the Galactic ridge (GR). In the first part we perform a data-driven analysis based on PASS8 Fermi-LAT data: We extend down to a few GeV the spectra measured by H.E.S.S. and infer the primary cosmic-ray (CR) radial distribution between 0.1 and 3 TeV. In the second part we adopt a CR transport model based on a position-dependent diffusion coefficient. Such behavior reproduces the radial dependence of the CR spectral index recently inferred from the Fermi-LAT observations. We find that the bulk of the GR emission can be naturally explained by the interaction of the diffuse steady-state Galactic CR sea with the gas present in the central molecular zone. Although we confirm the presence of a residual radial-dependent emission associated with a central source, the relevance of the large-scale diffuse component prevents to claim a solid evidence of GC pevatrons.
我们对费米大面积望远镜（Fermi-LAT）和高能立体视野望远镜（H.E.S.S.）在银河系中心（GC）区域和银河系脊（GR）测量到的伽马射线漫射发射提出了一种全新的解释。在第一部分中，我们基于PASS8费米大面积望远镜数据进行了数据驱动分析：我们将高能立体视野望远镜测量的光谱延伸至几个GeV，并推断出0.1至3 TeV之间的初级宇宙射线（CR）径向分布。在第二部分中，我们采用了基于位置相关扩散系数的宇宙射线传输模型。这种行为再现了最近从费米大面积望远镜观测中推断出的宇宙射线光谱指数的径向依赖性。我们发现，银河系脊发射的大部分可以自然地解释为漫射稳态银河系宇宙射线海与中央分子区存在的气体之间的相互作用。虽然我们证实了与中央源相关的残余径向依赖性发射的存在，但大规模漫射成分的相关性使得无法声称有确凿证据证明银河系中心存在皮瓦级天体（pevatrons）。
