X-RAY DIAGNOSTICS OF THERMAL CONDITIONS OF THE HOT PLASMAS IN THE CENTAURUS CLUSTER
X-RAY DIAGNOSTICS OF THERMAL CONDITIONS OF THE HOT PLASMAS IN THE CENTAURUS CLUSTER
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DOI：
10.1088/0004-637x/701/1/377
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发表时间：
2009-07
期刊：
影响因子：
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通讯作者：
I. Takahashi;M. Kawaharada;K. Makishima;K. Matsushita;Y. Fukazawa;Y. Ikebe;T. Kitaguchi;M. Kokubun;K. Nakazawa;S. Okuyama;N. Ota;T. U. O. Tokyo;Riken;Tokyo University of Science;H. University;National Museum of Emerging Science;Innovation;Japan Aerospace Exploration Agency
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文献类型：
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作者：
I. Takahashi;M. Kawaharada;K. Makishima;K. Matsushita;Y. Fukazawa;Y. Ikebe;T. Kitaguchi;M. Kokubun;K. Nakazawa;S. Okuyama;N. Ota;T. U. O. Tokyo;Riken;Tokyo University of Science;H. University;National Museum of Emerging Science;Innovation;Japan Aerospace Exploration Agency
利用xmm -牛顿望远镜对半人马座星团45 k的x射线数据进行了分析。通过单相等离子体发射模型或由ASCA开发的两相模型，可以同样很好地再现来自同心薄壳区的预投影EPIC光谱，两者都包含冷（1.7-2.0 keV）和热（~ 4 keV）等离子体温度。然而，在三维厚壳区积累的统计量较高的EPIC光谱，两相模型比单相模型能更好地再现。因此，热等离子体相和冷等离子体相被推断在~ 70kpc内共存于星团核心区域。等离子体中铁和硅的丰度再次向中心显著增加，而氧的丰度则与径向恒定一致。隐含的非太阳丰度比解释了先前报道的来自中心区域的过量x射线吸收。虽然在中心的~ 20kpc范围内检测到额外的冷（~ 0.7 keV）发射，但RGS数据给出了温度低于~ 0.5 keV的任何发射的严格上限。这些结果被汇编成一个磁层模型，该模型将冷相解释为被限制在固定在cD星系的封闭磁环内。当与适用于太阳日冕的所谓Rosner-Tucker-Vaiana机制相结合时，该模型可以潜在地解释冷却阶段的基本特性，包括温度和热稳定性。
X-ray data of the Centaurus cluster, obtained with XMM-Newton for 45 ks, were analyzed. Deprojected EPIC spectra from concentric thin-shell regions were reproduced equally well by a single-phase plasma emission model, or by a two-phase model developed by ASCA, both incorporating cool (1.7–2.0 keV) and hot (∼ 4 keV) plasma temperatures. However, EPIC spectra with higher statistics, accumulated over three-dimensional thick-shell regions, were reproduced better by the two-phase model than by the singe-phase one. Therefore, hot and cool plasma phases are inferred to co-exist in the cluster core region within ∼ 70 kpc. The iron and silicon abundances of the plasma were reconfirmed to increase significantly toward the center, while that of oxygen was consistent with being radially constant. The implied nonsolar abundance ratios explain away the previously reported excess X-ray absorption from the central region. Although an additional cool (∼ 0.7 keV) emission was detected within ∼ 20 kpc of the center, the RGS data gave tight upper limits on any emission with temperatures below ∼ 0.5 keV. These results are compiled into a magnetosphere model, which interprets the cool phase as confined within closed magnetic loops anchored to the cD galaxy. When combined with the so-called Rosner–Tucker–Vaiana mechanism which applies to solar coronae, this model can potentially explain basic properties of the cool phase, including its temperature and thermal stability.