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arXiv 1908.06561astro-ph.HE
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IGR ~ J17448-3232扩散X射线辐射的特征:一种视线合并活动的暗示

Characterization of diffuse X-ray emission from IGR~J17448-3232: an implication of a line of sight merging activity

Shoko Watanabe, Shigeo Yamauchi, Kumiko K. Nobukawa, Hiroki Akamatsu

摘要:

本文给出了对星系团IGR J17448-3232的光谱分析结果。中心区(r<300”,320 kpc)的团内介质(ICM)具有kTe~13-15 keV的高电子温度等离子体,由Fe XXVI Ly α/Fe XXV He α线强度比估算的电离温度低于电子温度,表明ICM处于非电离平衡态。中心区域的光谱也可以用双组分模型拟合:在碰撞电离平衡(CIE)中的双温度等离子体模型,温度为7.9 keV和>34 keV,或者CIE+幂律模型,温度为9.4 keV,光子指数为1.1。两组分模型能较好地描述Fe XXVI Ly α/Fe XXV He α谱线的强度比。另一方面,在外部区域(r> 300“)中的光谱可以通过具有5-8 keV温度的单个CIE等离子体模型来解释。根据NEI等离子体的光谱特征及其环形结构,我们认为NEI等离子体是沿视线方向合并产生的。

英文摘要:

Results of the spectral analysis for the galaxy cluster IGR J17448-3232 are presented. The intracluster medium (ICM) in the central region (r<300", 320 kpc) has a high electron temperature plasma of kTe~13-15 keV and an ionization temperature estimated from an intensity ratio of Fe XXVI Ly alpha/Fe XXV He alpha lines is lower than the electron temperature, which suggests that the ICM is in the non-ionization equilibrium (NEI) state. The spectrum in the central region can be also fitted with a two-component model: a two-temperature plasma model in a collisional ionization equilibrium (CIE) with temperatures of 7.9 keV and >34 keV or a CIE+power law model with a temperature of 9.4 keV and a photon index of 1.1. The two component models can represent the intensity ratio of Fe XXVI Ly alpha/Fe XXV He alpha lines. On the other hand, the spectrum in the outer region (r>300'') can be explained by a single CIE plasma model with a temperature of 5-8 keV. Based on the spectral feature and its circular structure, we propose that the NEI plasma was produced by merging along the line-of-sight direction.

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