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arXiv 2202.04574astro-ph.HE
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弥漫银河系发射光谱在0.5和8.0之间MeV

Diffuse Galactic emission spectrum between 0.5 and 8.0 MeV

Thomas Siegert, Joanna Berteaud, Francesca Calore, Pasquale D. Serpico, Christoph Weinberger

摘要:

最近一次测量银河系在兆电子伏光子能量范围内的漫射发射光谱是在20多年前由CGRO/COMPTEL进行的。我们报告了一个新的分析与光谱仪SPI船上INTEGRAL在0.5-8.0 MeV的频带,最终取代了历史观测的信噪比。这是可能的,这要归功于精心制作的仪器背景模型和对所选数据的仔细考虑,这些数据受到太阳活动的强烈影响。我们的分析基于银河系中心周围$Δl \times Δb = 95^\circ \times 95^\circ$区域的能量依赖空间模板拟合。我们的通量估计是一致的COMPTEL测量,并显示没有'兆电子伏颠簸'。该光谱遵循幂律的形状与指数$-1.39 \pm 0.09_{\rm stat} \pm 0.10_{\rm syst}$和$(5.7 \pm 0.8_{\rm stat} \pm 1.7_{\rm syst}) \times 10^{-8}\,\mathrm{erg\,cm^{-2}\,s^{-1}}$的综合通量之间的0.5和8.0兆电子伏。我们发现,宇宙射线电子和传播模型与最新的费米/LAT,旅行者1号和AMS-02数据一致,与推断的逆康普顿谱形状大致一致。然而,一个不匹配的2-3倍的标准化相对于基线的预期可能指向增强的目标光子密度和/或电子源光谱在银河系内部,稍微修改的扩散特性,或存在一个未解决的人口MeV的$γ$ -射线源。

英文摘要:

The last measurement of the diffuse emission spectrum of the Milky Way in the megaelectronvolt (MeV) photon energy range was performed by CGRO/COMPTEL more than 20 years ago. We report a new analysis with the spectrometer SPI aboard INTEGRAL in the band 0.5-8.0 MeV, finally superseding the signal-to-noise ratio of the historic observations. This is possible thanks to an elaborate instrumental background model and careful considerations of the selected data, which are strongly affected by solar activity. We base our analysis on energy-dependent spatial template fitting in a region of $Δl \times Δb = 95^\circ \times 95^\circ$ around the Galactic centre. Our flux estimates are consistent with COMPTEL measurements and show no `MeV bump'. The spectrum follows a power-law shape with index $-1.39 \pm 0.09_{\rm stat} \pm 0.10_{\rm syst}$ and an integrated flux of $(5.7 \pm 0.8_{\rm stat} \pm 1.7_{\rm syst}) \times 10^{-8}\,\mathrm{erg\,cm^{-2}\,s^{-1}}$ between 0.5 and 8.0 MeV. We find that cosmic-ray electrons and propagation models consistent with the latest Fermi/LAT, Voyager 1, and AMS-02 data are broadly in agreement with the inferred inverse Compton spectral shape. However, a mismatch of a factor of 2-3 in normalisation with respect to baseline expectations may point to enhanced target photon densities and/or electron source spectra in the inner Galaxy, slightly modified diffusion properties, or the presence of an unresolved population of MeV $γ$-ray sources.

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