X-ray spectral analysis of elliptical galaxies from ASCA: the Fe abundance in a multiphase medium
X-ray spectral analysis of elliptical galaxies from ASCA: the Fe abundance in a multiphase medium
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DOI：
10.1046/j.1365-8711.1998.01478.x
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发表时间：
1997-07
影响因子：
4.8
通讯作者：
D. Buote;A. Fabian
中科院分区：
文献类型：
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作者：
D. Buote;A. Fabian
我们给出了17个椭圆形星系和3个透镜状星系的ASCA数据的光谱分析，这些星系大多具有高LX/Lb。单温模型(梅卡尔和雷蒙德-史密斯)给出了令人无法接受的拟合(χ2red>；1.5在大多数情况下，并且与以前的研究一致，给出了非常接近太阳的丰度，<Z>=0.19±0.12Z⊙(梅卡尔))。冷却流动模型对大约一半样品的光谱进行了更好的拟合，在三种情况下给出了更好的拟合。从冷流模型得到的丰度也要大得多，<Z>=0.6±0.5Z⊙。我们在铁L地区对等离子体代码的可靠性进行了经验测试，没有发现与所确定的温度和丰度存在严重问题的证据。双温模型提供了形式上可接受的更好的拟合(χ2red∼1.0)，但在少数情况下除外。信噪比最高的星系(也有最高的lx/lb)对这两个组分的温度均为<；2keV，且每个组分都是不同的热气相。信噪比最低的星系(也具有最低的Lx/Lb)通常有一个温度为Th≳5keV的热分量，这与离散源的辐射是一致的。(我们从LX−Lb和LX/Lb的分析来讨论这两个组分的来源。)这两个温度模型的丰度近似为太阳，<Z>=0.9±0.7Z⊙(Mekal)，与最近提出的椭圆形热气体演化的多相模型一致。最后，对于几个星系，我们找到了吸收超过银河系价值的证据，并讨论了它的含义。
We present spectral analysis of ASCA data of 17 elliptical and three lenticular galaxies most of which have high Lx/LB. Single-temperature models ( mekal and Raymond–Smith) give unacceptable fits (χ2red > 1.5 in most cases and, in agreement with previous studies, give very subsolar abundances, 〈 Z〉 = 0.19 ± 0.12 Z⊙ ( mekal). The spectra for approximately half the sample are fitted better by a cooling-flow model, which in three cases gives a substantially better fit. The abundances derived from the cooling-flow model are also significantly larger, 〈Z〉 = 0.6 ± 0.5 Z⊙. We empirically tested the reliability of the plasma codes in the Fe L region and found no evidence for serious problems with the determined temperatures and abundances. Two-temperature models give substantially better fits that are formally acceptable (χ2red ∼ 1.0) in all but a few cases. The highest signal-to-noise ratio galaxies (which also have highest Lx/LB) have fitted temperatures < 2 keV for both components consistent with each being distinct phases of hot gas. The lowest signal-to-noise ratio galaxies (which also have lowest Lx/LB) generally have a hot component with temperature, TH ≳ 5 keV, which is consistent with emission from discrete sources. (We discuss the origin of these two components from analysis of Lx − LB and Lx/LB.) The abundances of these two-temperature models are approximately solar, 〈Z〉 = 0.9 ± 0.7 Z⊙ ( mekal), consistent with a recent multiphase model for the evolution of hot gas in ellipticals. Finally, for several galaxies we find evidence for absorption in excess of the Galactic value and discuss its implications.