Modelling the Galactic very-high-energy γ-ray source population
Modelling the Galactic very-high-energy γ-ray source population
复制标题
银河系极高能 γ 射线源群建模
DOI：
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发表时间：
2020
影响因子：
6.5
通讯作者：
K. Egberts
中科院分区：
文献类型：
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作者：
C. Steppa;K. Egberts
上下文高能体视系统银河平面巡天（High Energy Stereoscopic System Galactic Plane Survey，HGPS）是迄今为止对极高能（VHE; 100 GeV ≤ E ≤ 100 TeV）银河γ射线源最全面的普查。 由于这次调查的灵敏度有限，78个探测到的γ射线源只占总人口的一小部分，而且有偏差。大部分是目前尚未解决的来源，这些来源造成大规模的扩散排放，其数量仍不确定。
目标。我们研究了银河系中的VHE γ源布居。为此目的，人口合成模型的基础上来源的位置，范围和亮度的分布。
方法.比较了几种方位对称和螺旋臂模型的空间源分布。根据HGPS数据集的源特性导出了星群的光度和半径函数，并对HGPS的灵敏度偏差进行了校正。基于这些模型，VHE源群体进行了模拟，并根据HGPS源检测的源的子集进行了比较。
结果光度和半径函数的幂律指数被确定为光度在-1.6和-1.9之间，半径在-1.1和-1.6之间。VHE源的空间分布不考虑具有中心杆的双臂螺旋结构，而方位对称分布和遵循无杆的四臂螺旋结构的分布则较好地描述了HGPS数据。银河系VHE源的总数预计在800到7000之间，总光度和通量分别为（1.6 − 6.3）× 1036 ph s−1和（3 − 15）× 10−10 ph cm−2 s−1。
结论.根据模型的不同，HGPS样本占扫描区域人口排放量的（68−87）%。 这表明，未解决的来源是一个关键的组成部分，扩散排放可测量的HGPS。随着切伦科夫望远镜阵列的灵敏度预计将大幅提升，可探测到的辐射源数量预计将增加5到9倍。
Context. The High Energy Stereoscopic System Galactic plane survey (HGPS) is to date the most comprehensive census of Galactic γ-ray sources at very high energies (VHE; 100 GeV ≤ E ≤ 100 TeV). As a consequence of the limited sensitivity of this survey, the 78 detected γ-ray sources comprise only a small and biased subsample of the overall population. The larger part consists of currently unresolved sources, which contribute to large-scale diffuse emission to a still uncertain amount.
Aims. We study the VHE γ-ray source population in the Milky Way. For this purpose population-synthesis models are derived based on the distributions of source positions, extents, and luminosities.
Methods. Several azimuth-symmetric and spiral-arm models are compared for spatial source distribution. The luminosity and radius function of the population are derived from the source properties of the HGPS data set and are corrected for the sensitivity bias of the HGPS. Based on these models, VHE source populations are simulated and the subsets of sources detectable according to the HGPS are compared with HGPS sources.
Results. The power-law indices of luminosity and radius functions are determined to range between −1.6 and −1.9 for luminosity and −1.1 and −1.6 for radius. A two-arm spiral structure with central bar is discarded as spatial distribution of VHE sources, while azimuth-symmetric distributions and a distribution following a four-arm spiral structure without bar describe the HGPS data reasonably well. The total number of Galactic VHE sources is predicted to be in the range from 800 to 7000 with a total luminosity and flux of (1.6 − 6.3) × 1036 ph s−1 and (3 − 15) × 10−10 ph cm−2 s−1, respectively.
Conclusions. Depending on the model, the HGPS sample accounts for (68 − 87)% of the emission of the population in the scanned region. This suggests that unresolved sources represent a critical component of the diffuse emission measurable in the HGPS. With the foreseen jump in sensitivity of the Cherenkov Telescope Array, the number of detectable sources is predicted to increase by a factor between 5 and 9.