Chandra Observation of the Cluster of Galaxies MS 0839.9+2938 at z = 0.194: The Central Excess Iron and Type Ia Supernova Enrichment
Chandra Observation of the Cluster of Galaxies MS 0839.9+2938 at z = 0.194: The Central Excess Iron and Type Ia Supernova Enrichment
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DOI：
10.1086/432369
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发表时间：
2005-06
期刊：
影响因子：
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通讯作者：
Yu Wang;Haiguang Xu;Zhongli Zhang;Yueheng Xu;Xiang-Ping Wu;S. Xue;Zong-wei Li
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文献类型：
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作者：
Yu Wang;Haiguang Xu;Zhongli Zhang;Yueheng Xu;Xiang-Ping Wu;S. Xue;Zong-wei Li
我们介绍了对MS 0839.9+2938星系团的中间红移(z=0.194)的钱德拉研究。通过进行投影和反投影光谱分析，我们发现气体温度在130-444hKPC内近似恒定在4keV左右。在内区，气体温度向中心方向下降，在37hkpc中心达到≲3keV。这意味着在74hKPC内，质量沉积速率的下限和上限分别为9-34M☉yr-1和96-126M kpc yr-1，此时气体明显较冷。随着温度的下降，我们检测到向内的铁丰度显著增加，从外区的0.4Z☉增加到中央37hKPC内的≃1Z☉。因此，MS 0839.9+2938是在z≳0.2时显示最显著中心铁过剩的星系团。我们认为，大部分过剩的铁应该是由SNE Ia贡献的。根据观测到的Sn Ia率和恒星质量损失率，我们估计用过剩的铁丰富中心区域所需的时间为6.4-7.9Gyr，这与发现的附近星团的时间相似。与CD星系的光学延伸相吻合(高达30hkpc)，观测到的X射线表面亮度轮廓显示出超出β模型或纳瓦罗-弗伦克-怀特模型预期的分布，并且可以很好地与经验的双β模型很好地拟合，从而在最里面的区域产生相对平坦的质量轮廓。
We present the Chandra study of the intermediate-redshift (z = 0.194) cluster of galaxies MS 0839.9+2938. By performing both projected and deprojected spectral analyses, we find that the gas temperature is approximately constant at about 4 keV within 130-444 h kpc. In the inner regions, the gas temperature decreases toward the center, reaching ≲3 keV in the central 37 h kpc. This implies that the lower and upper limits of the mass deposit rate are 9-34 and 96-126 M☉ yr-1, respectively, within 74 h kpc, where the gas is significantly colder. Along with the temperature drop, we detect a significant inward iron abundance increase from about 0.4 Z☉ in the outer regions to ≃1 Z☉ within the central 37 h kpc. Thus, MS 0839.9+2938 is the cluster showing the most significant central iron excess at z ≳ 0.2. We argue that most of the excess iron should have been contributed by SNe Ia. Using the observed SN Ia rate and stellar mass loss rate, we estimate that the time needed to enrich the central region with excess iron is 6.4-7.9 Gyr, which is similar to those found for nearby clusters. Coinciding with the optical extension of the cD galaxy (up to about 30 h kpc), the observed X-ray surface brightness profile exhibits an excess beyond the distribution expected by either the β model or the Navarro-Frenk-White (NFW) model and can be well fitted with an empirical two-β model that leads to a relatively flatter mass profile in the innermost region.