MAGIC observations of the diffuse γ-ray emission in the vicinity of the Galactic center
MAGIC observations of the diffuse γ-ray emission in the vicinity of the Galactic center
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DOI：
10.1051/0004-6361/201936896
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发表时间：
2020-10-20
影响因子：
6.5
通讯作者：
Zaric, D.
中科院分区：
文献类型：
--
作者：
Acciari, V. A.;Ansoldi, S.;Zaric, D.
目标。在有足够数量的目标物质存在的情况下，伽马射线可以被用作寻找银河宇宙射线（CR）源的示踪剂。在这里，我们提出了深银河系中心（GC）区域的观测与MAGIC望远镜，并使用它们来推断潜在的CR分布和研究所谓的PeV质子加速器在我们的银河系中心。我们使用了MAGIC望远镜在五年内（从2012年到2017年）对GC区域进行的大约100小时观测的数据。这些是在高天顶角（58-70度）收集的，导致更大的能量阈值，但与低天顶观测相比，有效收集面积也增加了。使用最近开发的软件工具，我们推导出的仪器响应和背景模型所需的提取该地区的漫发射。我们使用现有的测量的气体分布在GC区域推导出的基本分布的CR。我们提出了一个讨论的相关偏见和局限性，这样的方法。我们获得了用于拟合我们的数据的所有四个模型组件（Sgr A*，“弧”，G0.9+0.1和银河山脊的扩展组件）的显着检测。我们没有观察到直接GC周围的伽马射线光谱之间的显着差异，我们作为一个点源（Sgr A*）和银河山脊模型。后者可以被描述为指数为2的幂律和在20 TeV左右的指数截止，截止的重要性仅为2 sigma。导出的宇宙射线轮廓暗示在GC位置处有一个峰值，测量的轮廓指数为1.2 +/- 0.3，与1/r径向距离标度律一致，这支持了GC处CR加速器的假设。我们认为，该配置文件的测量目前是有限的，我们的知识在GC附近的气体分布。
Aims. In the presence of a sufficient amount of target material, gamma-rays can be used as a tracer in the search for sources of Galactic cosmic rays (CRs). Here we present deep observations of the Galactic center (GC) region with the MAGIC telescopes and use them to infer the underlying CR distribution and to study the alleged PeV proton accelerator at the center of our Galaxy.Methods. We used data from approximate to 100 h observations of the GC region conducted with the MAGIC telescopes over five years (from 2012 to 2017). Those were collected at high zenith angles (58-70 deg), leading to a larger energy threshold, but also an increased effective collection area compared to low zenith observations. Using recently developed software tools, we derived the instrument response and background models required for extracting the diffuse emission in the region. We used existing measurements of the gas distribution in the GC region to derive the underlying distribution of CRs. We present a discussion of the associated biases and limitations of such an approach.Results. We obtain a significant detection for all four model components used to fit our data (Sgr A*, "Arc", G0.9+0.1, and an extended component for the Galactic Ridge). We observe no significant difference between the gamma-ray spectra of the immediate GC surroundings, which we model as a point source (Sgr A*) and the Galactic Ridge. The latter can be described as a power-law with index 2 and an exponential cut-off at around 20 TeV with the significance of the cut-off being only 2 sigma. The derived cosmic-ray profile hints to a peak at the GC position and with a measured profile index of 1.2 +/- 0.3 is consistent with the 1/r radial distance scaling law, which supports the hypothesis of a CR accelerator at the GC. We argue that the measurements of this profile are presently limited by our knowledge of the gas distribution in the GC vicinity.