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arXiv 1408.0205astro-ph.HE
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银河脊X射线发射的6.4- keV线的起源

Origin of the 6.4-keV line of the Galactic Ridge X-ray Emission

T. G. Tsuru, H. Uchiyama, K. K. Nobukawa, M. Nobukawa, S. Nakashima, K. Koyama, K. Torii, Y. Fukui

摘要:

我们报告的第一个结果,从高统计观测的6.4 keV线的区域$l= +1.5^\circ$ $+3.5^\circ$(以下简称GC东),目的是揭示银河系脊X射线发射(GRXE)的起源。通过将这些数据与以前在$l=-1.5^\circ$到$-3.5^\circ$区域(以下简称GC West)的观测数据进行比较,我们发现6.4 keV线相对于银河系中心是不对称分布的,而6.7 keV线是对称分布的。6.4 keV谱线的分布遵循$^{13}$ CO谱线的分布,其通量与分子气体的柱密度成正比。这种相关性与$|l|>4^\circ$区域内6.4 keV谱线和冷星际介质(ISM)(H $_{\rm I}$ $+$ H $_2$)之间的相关性一致。这一结果表明,6.4 keV的发射是从冷ISM扩散荧光不仅在GC东,西,而且在整个银河系平面。这一观测结果表明,6.4 keV谱线的表面亮度与整个银河平面内冷ISM的柱密度成正比。对于电离粒子,我们考虑X射线和低能宇宙射线质子和电子。

英文摘要:

We report the first results from high-statistics observation of the 6.4-keV line in the region of $l= +1.5^\circ$ to $+3.5^\circ$ (hereafter referred to as GC East), with the goal to uncover the origin of the Galactic ridge X-ray emission (GRXE). By comparing this data with that from the previous observations in the region $l=-1.5^\circ$ to $-3.5^\circ$ (hereafter referred to as GC West), we discovered that the 6.4-keV line is asymmetrically distributed with respect to the Galactic center, whereas the 6.7-keV line is symmetrically distributed. The distribution of the 6.4-keV line follows that of $^{13}$CO and its flux is proportional to the column density of the molecular gas. This correlation agrees with that seen between the 6.4-keV line and the cold interstellar medium (ISM) (H$_{\rm I}$ $+$ H$_2$) in the region $|l|>4^\circ$. This result suggests that the 6.4-keV emission is diffuse fluorescence from the cold ISM not only in GC East and West but also in the entire Galactic plane. This observational result suggests that the surface brightness of the 6.4-keV line is proportional to the column density of the cold ISM in the entire Galactic plane. For the ionizing particles, we consider X-rays and low energy cosmic-ray protons and electrons .

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