z > 0.4 X射线亮星系团中熵和压力分布的演化
On the evolution of the entropy and pressure profiles in X-ray luminous galaxy clusters at z > 0.4
摘要：
星系团是宇宙学尺度上等级吸积的最新产物。从宇宙场吸积的气体在星系团晕内热化。气体熵和压力具有自相似性，其径向分布分别遵循幂律和广义Navarro-Frenk-White分布。这在许多不同的流体动力学模拟中也得到了证明。我们推导了Chandra观测到的47个X射线星系团在红移0.4 < z < 1.2范围内的空间分辨光谱性质，这是迄今为止在这个红移范围内用X射线光谱学研究的最大样本，特别注意重建气体熵和压力径向分布。我们寻找偏离自相似行为，并寻找可能的红移演化。熵和压力分布非常接近重力结构形成的基线预测。我们发现，这些配置文件偏离基线预测的红移的函数，特别是在z > 0.75，其中，在中心区域，我们观察到较高的熵值（由一个因素的2.2）和系统较低的估计（由一个因素的2.5）的压力。有效多变指数保留了气体热分布的信息，它与红移和暗物质分布的浓度呈轻微的线性正演化。正如我们在高红移观测到的那样，非冷核、受扰系统的普遍存在可以解释这种行为。
英文摘要：
Galaxy clusters are the most recent products of hierarchical accretion over cosmological scales. The gas accreted from the cosmic field is thermalized inside the cluster halo. Gas entropy and pressure are expected to have a self-similar behaviour with their radial distribution following a power law and a generalized Navarro-Frenk-White profile, respectively. This has been shown also in many different hydrodynamical simulations. We derive the spatially-resolved thermodynamical properties of 47 X-ray galaxy clusters observed with Chandra in the redshift range 0.4 < z < 1.2, the largest sample investigated so far in this redshift range with X-rays spectroscopy, with a particular care in reconstructing the gas entropy and pressure radial profiles. We search for deviation from the self-similar behaviour and look for possible evolution with redshift. The entropy and pressure profiles lie very close to the baseline prediction from gravitational structure formation. We show that these profiles deviate from the baseline prediction as function of redshift, in particular at z > 0.75, where, in the central regions, we observe higher values of the entropy (by a factor of 2.2) and systematically lower estimates (by a factor of 2.5) of the pressure. The effective polytropic index, which retains informations about the thermal distribution of the gas, shows a slight linear positive evolution with the redshift and the concentration of the dark matter distribution. A prevalence of non-cool-core, disturbed systems, as we observe at higher redshifts, can explain such behaviours.
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