Diffuse X-Ray Emission from the Northern Arc of Loop I Observed with Suzaku
Diffuse X-Ray Emission from the Northern Arc of Loop I Observed with Suzaku
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DOI：
10.3847/1538-4357/aacd08
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发表时间：
2018-07-20
影响因子：
4.9
通讯作者：
Nakashima, Shinya
中科院分区：
文献类型：
--
作者：
Akita, Masahiro;Kataoka, Jun;Nakashima, Shinya
发现费米气泡后，从无线电到 X 射线监测观察到的巨型结构已被广泛讨论，作为银河系中心 (GC) 过去活动的可能证据。我们在此报告对指向巨型环 I 弧周围的所有朱雀档案数据的分析。来自环 I 弧北部的漫射 X 射线发射由三分量模型很好地表示：(1) 来自局部热气泡 (LHB) 和/或太阳风电荷交换 (SWCX) 的 kT 相似或等于 0.1 keV 的未吸收热等离子体，(2) 被视为来自环 I 和银河晕 (GH) 的贡献的吸收热等离子体，以及 (3) 代表宇宙 X 射线背景 (CXB) 的吸收幂律分量。所吸收的热等离子体的温度沿着环路 I（“ON”区域）狭窄地聚集在 0.30 +/- 0.02 keV 的范围内，而邻近气泡和环路 I（“关闭”区域）的腔体中的温度略低，为 0.24 +/- 0.03 keV。发射测量（EM）沿银河纬度 b 变化很大，并且与 ROSAT 全天图测量的 0.75 keV 计数率变化密切相关。尽管中性气体的量并没有对环路 I 的距离提供任何有用的限制，但观测到的电磁值显然拒绝了该结构靠近太阳的假设；我们认为环 I 是 GH 中一个遥远的千秒差距结构。我们讨论了费米气泡和 Loop I 弧形态明显不匹配的根源，表明 GC 中存在两步爆炸过程。
After discovery of the Fermi bubbles, giant structures observed from radio to X-ray monitoring have been widely discussed as possible evidence of past activities in the Galactic center (GC). We report here on the analysis of all the Suzaku archival data pointing around the giant-scale Loop I arc. The diffuse X-ray emission from the northern Loop I arc was well represented by the three-component model: (1) an unabsorbed thermal plasma with kT similar or equal to 0.1 keV either from the local hot bubble (LHB) and/or solar wind charge exchange (SWCX), (2) an absorbed thermal plasma regarded as a contribution from the Loop I and the Galactic halo (GH), and (3) an absorbed power-law component representing the cosmic X-ray background (CXB). The temperature of the absorbed thermal plasma was narrowly clustered in a range of 0.30 +/- 0.02 keV along Loop I ("ON" regions), whereas the temperature was a little lower in the cavity adjacent to the bubbles and Loop I ("OFF" regions) with 0.24 +/- 0.03 keV. The emission measure (EM) largely varied along the Galactic latitude b, and was well correlated with the count rate variation as measured with the ROSAT all-sky map in 0.75 keV. Although the amount of neutral gas does not provide any useful constraints on the distance to Loop I, the observed EM values clearly reject a hypothesis that the structure is close to the Sun; we argue that Loop I is a distant, kiloparsec structure in the GH. We discuss the origin of apparent mismatch in the morphologies of the Fermi bubbles and the Loop I arc, suggesting a two-step explosion process in the GC.