On the progressive hardening of the cosmic-ray proton spectrum in the inner Galaxy
On the progressive hardening of the cosmic-ray proton spectrum in the inner Galaxy
复制标题
关于银河系内部宇宙射线质子光谱的逐渐硬化
DOI：
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发表时间：
2018
影响因子：
6.4
通讯作者：
C. Weniger
中科院分区：
文献类型：
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作者：
M. Pothast;D. Gaggero;E. Storm;C. Weniger
漫射银河系宇宙射线海中强子成分的平均性质的空间变化，特别是光谱斜率和归一化，可能揭示它们在银河系中的约束机制的关键信息。在本文的第一部分中，我们使用SkyFACT软件包对Fermi LAT伽玛射线数据进行了分析，该软件包将图像重建技术与标准模板拟合相结合，分离出强子发射并将其分解为银河系中心环。我们发现分子环的强子谱指数明显变硬。我们研究了这种硬化在不同的能量范围内，并评估其弹性相对于不同的处方在分析设置。在第二部分中，我们用专门的蒙特卡罗模拟量化了来自未解析点源的漫射伽马射线通量的贡献，并考虑了第一部分中所描述的趋势是否可以被银河系内部与该成分相关的逐渐增加的通量所模仿。我们发现观测到的强子谱指数的硬化不可能是由于亚tev能量范围内的未解析源，特别是在分子环外，给出了对未解析源种群的合理假设。
Spatial variations of the average properties that characterize the hadronic component of the diffuse Galactic cosmic-ray sea, in particular the spectral slope and normalization, may unveil critical information about their confinement mechanism in the Galaxy. In the first part of this paper we perform an analysis of the Fermi LAT gamma-ray data with the SkyFACT package, which combines image reconstruction techniques with standard template fitting, isolate the hadronic emission and decompose it into Galactocentric rings. We find a significant hardening of the hadronic spectral index towards the molecular ring. We study this hardening in different energy ranges, and assess its resilience with respect to different prescriptions in the analysis setup. In the second part we quantify the contribution to the diffuse gamma-ray flux coming from unresolved point sources with a dedicated Monte Carlo simulation, and consider whether the trend characterized in the first part can be mimicked by a progressively more relevant flux associated to this component in the inner Galaxy. We find that the observed hardening of the hadronic spectral index cannot be due to unresolved sources in the sub-TeV energy range, especially outside the molecular ring, given reasonable assumptions about the unresolved source population.