A High-Resolution Study of the Hydra A Cluster with Chandra: Comparison of the Core Mass Distribution with Theoretical Predictions and Evidence for Feedback in the Cooling Flow
A High-Resolution Study of the Hydra A Cluster with Chandra: Comparison of the Core Mass Distribution with Theoretical Predictions and Evidence for Feedback in the Cooling Flow
复制标题
钱德拉对 Hydra A 星团的高分辨率研究：核心质量分布与理论预测的比较以及冷却流反馈的证据
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
M. Wise
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作者：
L. David;P. Nulsen;B. McNamara;B. McNamara;W. Forman;C. Jones;T. Ponman;B. Robertson;M. Wise
冷却流团Hydra A是在钱德拉天文台的轨道激活和校准阶段观测到的。虽然星系团的X射线图像在中心区域显示出复杂的结构，如McNamara等人所报道的那样，大尺度的X射线形态的集群是相当平滑的。光谱分析的ACIS数据表明，在长蛇座A的气体温度增加向外，达到最高温度4千电子伏在200千秒差距，然后略有下降，在更大的半径。重元素的分布是不均匀的，在中心100千秒差距内的Fe和Si丰度增加了2倍。超过中央100千秒差距的Si-Fe丰度比是太阳的两倍，而中央过剩的Si-Fe比与太阳值一致。其中一个更令人惊讶的结果是缺乏光谱证据的多相气体内的大部分冷却流。超过中央30千秒差距，ACIS光谱充分拟合与一个单一的温度模型。添加冷却流组件不会显著改善配合。只有在中央30千秒差距（冷却时间小于1 Gyr）内，才有多相气体的光谱证据。然而，光谱质量沉积率是一个多的因素比形态学推导的质量吸积率在30千秒差距小于10。我们建议，冷却流区域是对流不稳定的，由于加热的中心射电源，这显着降低了净吸积率。此外，我们发现，在中央30-200 kpc区域内的质量分布的比例为ρd ε r-1.3，中间的NFW和摩尔配置文件，但与最佳拟合NFW浓度参数（cNFW = 12）约3倍以上的数值模拟中发现的。然而，考虑到有限的光子统计，我们不能排除存在一个平坦密度的核心半径小于30千秒差距的核心。
The cooling flow cluster Hydra A was observed during the orbital activation and calibration phase of the Chandra Observatory. While the X-ray image of the cluster exhibits complex structure in the central region as reported in McNamara et al., the large-scale X-ray morphology of the cluster is fairly smooth. A spectroscopic analysis of the ACIS data shows that the gas temperature in Hydra A increases outward, reaches a maximum temperature of 4 keV at 200 kpc, and then decreases slightly at larger radii. The distribution of heavy elements is nonuniform, with a factor of 2 increase in the Fe and Si abundances within the central 100 kpc. Beyond the central 100 kpc the Si-to-Fe abundance ratio is twice solar, while the Si-to-Fe ratio of the central excess is consistent with the solar value. One of the more surprising results is the lack of spectroscopic evidence for multiphase gas within the bulk of the cooling flow. Beyond the central 30 kpc, the ACIS spectra are adequately fitted with a single-temperature model. The addition of a cooling flow component does not significantly improve the fit. Only within the central 30 kpc (where the cooling time is less than 1 Gyr) is there spectroscopic evidence for multiphase gas. However, the spectroscopic mass deposition rate is more than a factor of 10 less than the morphologically derived mass accretion rate at 30 kpc. We propose that the cooling flow region is convectively unstable owing to heating by the central radio source, which significantly reduces the net accretion rate. In addition, we show that the mass distribution within the central 30-200 kpc region scales as ρd ∝ r-1.3, intermediate between an NFW and a Moore profile, but with a best-fit NFW concentration parameter (cNFW = 12) approximately 3 times greater than that found in numerical simulations. However, given the limited photon statistics, we cannot rule out the presence of a flat-density core with a core radius less than 30 kpc.