标题： 热传导对室女座星系团的影响 显示英文标题

标题： The Effect of Thermal Conduction on the Virgo Cluster

摘要： 热传导被建议作为一种可能的机制，通过该机制向星系团中心区域提供足够的能量以平衡辐射冷却效应。 在这里，我们展示了针对不同热导率值（1、1/10、1/100、0倍全Spitzer值）的模拟高分辨率三维室女座星系团的结果。 从初始的等温星团大气开始，我们允许星团在大约$ 1.3-4.7 \times 10^{9} $年的时间尺度上自由演化。 我们的结果显示，热导率为Spitzer值时可使中央ICM辐射冷却时间增加约3.6倍。 此外，对于较大的热导率值，模拟得到的温度和密度分布与观测数据匹配得更好，而较低的热导率值则较差。 然而，没有任何物理上有意义的热导率值能够推迟冷却灾难（以中央密度迅速增加为特征）超过哈勃时间的几分之一，也无法解释为何室女座星系团今天没有强烈的冷却流。 我们还计算了星团气体的有效绝热指数，并将模拟和观测数据的值与理论预期进行了比较。 使用这种方法可以看出，室女座星系团的中心正在通过一种非热传导的机制加热。 基于此以及我们的模拟结果，热导率很可能被抑制至少10倍，甚至更多。 因此，我们认为如果热传导确实存在的话，它会通过辐射冷却减缓ICM的演化速度，但仅限于几倍的因子范围内。 显示英文摘要

摘要： Thermal conduction has been suggested as a possible mechanism by which sufficient energy is supplied to the central regions of galaxy clusters to balance the effect of radiative cooling. Here we present the results of a simulated, high-resolution, 3-d Virgo cluster for different values of thermal conductivity (1, 1/10, 1/100, 0 times the full Spitzer value). Starting from an initially isothermal cluster atmosphere we allow the cluster to evolve freely over timescales of roughly $ 1.3-4.7 \times 10^{9} $ yrs. Our results show that thermal conductivity at the Spitzer value can increase the central ICM radiative cooling time by a factor of roughly 3.6. In addition, for larger values of thermal conductvity the simulated temperature and density profiles match the observations significantly better than for the lower values. However, no physically meaningful value of thermal conductivity was able to postpone the cooling catastrophe (characterised by a rapid increase in the central density) for longer than a fraction of the Hubble time nor explain the absence of a strong cooling flow in the Virgo cluster today. We also calculate the effective adiabatic index of the cluster gas for both simulation and observational data and compare the values with theoretical expectations. Using this method it appears that the Virgo cluster is being heated in the cluster centre by a mechanism other than thermal conductivity. Based on this and our simulations it is also likely that the thermal conductvity is suppressed by a factor of at least 10 and probably more. Thus, we suggest that thermal conductvity, if present at all, has the effect of slowing down the evolution of the ICM, by radiative cooling, but only by a factor of a few.