重子箍缩导致星系团暗物质轮廓的中等陡化
Moderate Steepening of Galaxy Cluster Dark Matter Profiles by Baryonic Pinching
摘要：
为了评估重子“箍缩”对星系团暗物质晕的影响，用TreeSPH宇宙学方法模拟了两个星系团的形成和演化过程.重子的模拟调用恒星形成，化学演化与非瞬时再循环，金属依赖的辐射冷却，强烈的恒星爆发，驱动银河系的超级风和元银河系紫外线场的影响，包括简化的辐射转移。这两个星系团的T_X分别为3和6 keV，在z~0处，都有一个突出的中央cD星系。比较有和没有重子的模拟，发现后者的内部DM密度分布（r<50-100 kpc）明显变陡：Delta（alpha）~0.5-0.6，其中-alpha是DM密度梯度的对数。这主要是由于中央恒星的cDs变得非常巨大，这是后期冷却流和相关恒星形成的结果。一旦这些虚假的冷却流被修正，并且星系团引力势被动态调整，就会发现小得多的箍缩效应：Δ（α）~0.1。包括重子箍缩的影响，在两个星系团中发现DM的α ~1.0和1.2的中心斜率，有趣的是接近最近的观测结果。对于重子的模拟，发现DM+ICM组合气体的内部密度分布仅比DM的内部密度分布略微陡峭，Delta（alpha）<0.05。然而，总物质的内部密度分布被发现是三角洲（α）~0.5陡峭的内部配置文件中的暗物质只有模拟。
英文摘要：
To assess the effect of baryonic ``pinching'' of galaxy cluster dark matter (DM) haloes, cosmological (LCDM) TreeSPH simulations of the formation and evolution of two galaxy clusters have been performed, with and without baryons included. The simulations with baryons invoke star formation, chemical evolution with non-instantaneous recycling, metallicity dependent radiative cooling, strong star-burst, driven galactic super-winds and the effects of a meta-galactic UV field, including simplified radiative transfer. The two clusters have T_X~3 and 6 keV, respectively, and, at z~0, both host a prominent, central cD galaxy. Comparing the simulations without and with baryons, it is found for the latter that the inner DM density profiles, r<50-100 kpc, steepen considerably: Delta(alpha)~0.5-0.6, where -alpha is the logarithmic DM density gradient. This is mainly due to the central stellar cDs becoming very massive, as a consequence of the onset of late time cooling flows and related star formation. Once these spurious cooling flows have been corrected for, and the cluster gravitational potentials dynamically adjusted, much smaller pinching effects are found: Delta(alpha)~0.1. Including the effects of baryonic pinching, central slopes of alpha~1.0 and 1.2 are found for the DM in the two clusters, interestingly close to recent observational findings. For the simulations with baryons, the inner density profile of DM+ICM gas combined is found to be only very marginally steeper than that of the DM, Delta(alpha)<0.05. However, the total matter inner density profiles are found to be Delta(alpha)~0.5 steeper than the inner profiles in the dark matter only simulations.
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