Complex Spectra of the Galactic Ridge X-Rays Observed with ASCA
Complex Spectra of the Galactic Ridge X-Rays Observed with ASCA
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ASCA 观测到的银河脊 X 射线的复杂光谱
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
N. Yamasaki
中科院分区：
文献类型：
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作者：
H. Kaneda;K. Makishima;S. Yamauchi;K. Koyama;K. Matsuzaki;N. Yamasaki
使用ASCA GIS和SIS在0.7-10 keV能量范围内获得了盾牌臂区域银河山脊发射的X射线谱。所观察到的光谱基本上是从薄的热等离子体的热发射，和个别K类氦的Mg，Si，S，和Fe离子的发射线被确认在GIS和SIS光谱。这意味着银河脊的X射线辐射不能用单温电离平衡等离子体模型来解释。然而，它不能被复制，即使引入非平衡电离模型，因此需要多个等离子体组件。用双温非平衡电离等离子体模型（kT ~ 0.8keV和kT ~ 7 keV）对GIS光谱进行了较好的拟合。较软的组分被发现是在一个非常低的电离状态，与净~ 109 cm-3 s，而较硬的组分是在一个相对较高的电离状态，虽然还没有在一个完全平衡。用GIS获得的GRXE特性通过SIS的高分辨谱线特征进行了仔细的重新检查。软组分和硬组分分别被0.7 × 1022 cm-2和4.6 × 1022 cm-2的当量氢柱吸收。在B ~ 0°处，软、硬组分的表面亮度分别为1.9 × 10 ~（-6）和5.3 × 10 ~（-7）ergscm ~（-2）s ~（-1）sr ~（-1），均在0.5-10 keV波段。较软部分的表面亮度比较硬部分向更高的银河系纬度（约2°）延伸，尽管如果考虑到它们可观测深度的差异，它们的实际尺度高度可能在约100 pc处相似。这两个组件的光谱特性被认为是取决于纬度，最显着的效果是快速减少铁K线的等效宽度中看到的硬组件。试图解释这两个组成部分的弥漫热等离子体填充星际空间。
X-ray spectra of the Galactic ridge emission in the Scutum arm region have been obtained with ASCA GIS and SIS in the energy range 0.7-10 keV. The observed spectra are basically of thermal emission from thin hot plasmas, and individual K emission lines from helium-like Mg, Si, S, and Fe ions are confirmed in both the GIS and SIS spectra. This means that the Galactic ridge X-ray emission cannot be explained by a single-temperature ionization-equilibrium plasma model. It cannot, however, be reproduced even if a nonequilibrium ionization model is introduced; thus multiple plasma components are required. The GIS spectra are fairly well fitted by a double-temperature nonequilibrium ionization plasma model with temperatures of kT ~ 0.8 keV and kT ~ 7 keV. The softer component is found to be in an extremely low ionization state, with net ~ 109 cm-3 s, while the harder component is in a relatively high ionization state, though not yet in a full equilibrium. The GRXE properties obtained with the GIS are carefully reexamined by the highly resolved spectral-line features with the SIS. The soft and hard components are absorbed by equivalent hydrogen columns of 0.7 × 1022 cm-2 and 4.6 × 1022 cm-2, respectively. The surface brightness of the soft and hard components at b ~ 0° are estimated to be 1.9 × 10-6 and 5.3 × 10-7 ergs cm-2 s-1 sr-1 respectively, both in the 0.5-10 keV band. The surface brightness of the softer component extends toward significantly higher (~2°) Galactic latitudes than the harder component, although their actual scale heights may be similar at ~100 pc if the differences in their observable depths are taken into account. Spectral properties of the two components are seen to depend on the latitude; the most noticeable effect is a rapid decrease in the Fe K line equivalent width seen in the hard component. Attempts are made to interpret the two components in terms of diffuse hot plasmas filling the interstellar space.