PKS 0745-191星系团核心的反馈、散射和结构
Feedback, scatter and structure in the core of the PKS 0745-191 galaxy cluster
摘要：
我们介绍钱德拉X射线天文台观测的核心的星系团PKS 0745-191。它的中心显示了由活动星系核反馈和冷锋引起的X射线空洞，并有相关的螺旋结构。空腔能量学意味着它们足够强大以补偿冷却。尽管有活动星系核反馈的证据，钱德拉和XMM-RGS的X射线光谱与每年几百个太阳质量的X射线阶段冷却一致，足以为发射线星云提供动力。最冷的X射线发射气体和最亮的星云发射与射电和X射线核的距离约为5千秒差距。虽然星团有着规则的外观，但其核心在内部100 kpc上显示出密度，温度和压力的偏差，可能与冷锋有关。修正椭圆率和投影效应后，我们估计密度波动的~ 4%，而温度，压力和熵的变化为10- 12%.We描述了一个新的代码，MBPROJ，能够准确地获得crackical集群配置文件，假设流体静力平衡和球对称。前向拟合代码使用马尔可夫链蒙特卡罗将模型与观察到的配置文件进行比较，并适用于在1000或更少计数上操作的调查。在PKS 0745中，在离地核40 kpc半径范围内的重力加速度最好非常低，这表明缺乏流体静力平衡，偏离了球对称或非热源压力。
英文摘要：
We present Chandra X-ray Observatory observations of the core of the galaxy cluster PKS 0745-191. Its centre shows X-ray cavities caused by AGN feedback and cold fronts with an associated spiral structure. The cavity energetics imply they are powerful enough to compensate for cooling. Despite the evidence for AGN feedback, the Chandra and XMM-RGS X-ray spectra are consistent with a few hundred solar masses per year cooling out of the X-ray phase, sufficient to power the emission line nebula. The coolest X-ray emitting gas and brightest nebula emission is offset by around 5 kpc from the radio and X-ray nucleus. Although the cluster has a regular appearance, its core shows density, temperature and pressure deviations over the inner 100 kpc, likely associated with the cold fronts. After correcting for ellipticity and projection effects, we estimate density fluctuations of ~4 per cent, while temperature, pressure and entropy have variations of 10-12 per cent. We describe a new code, MBPROJ, able to accurately obtain thermodynamical cluster profiles, under the assumptions of hydrostatic equilibrium and spherical symmetry. The forward-fitting code compares model to observed profiles using Markov Chain Monte Carlo and is applicable to surveys, operating on 1000 or fewer counts. In PKS0745 a very low gravitational acceleration is preferred within 40 kpc radius from the core, indicating a lack of hydrostatic equilibrium, deviations from spherical symmetry or non-thermal sources of pressure.
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