早期星系大气中非热压力的测量：M87和NGC1399中X射线和光学势分布的比较
Measuring the non-thermal pressure in early type galaxy atmospheres: A comparison of X-ray and optical potential profiles in M87 and NGC1399
摘要：
本文比较了椭圆星系NGC 4486（M87）和NGC 1399（天炉座星系团中央星系）的X射线和光学数据的引力势分布。这种比较表明，宇宙射线、磁场和微湍流对压力的综合贡献约为NGC 1399和M87核心气体热压力的10%，尽管我们模型假设的不确定性（例如，球对称）足够大，使得贡献可以与零一致。在没有任何其他形式的非热压力支持的情况下，这些上限转化为磁场的上限约为10-20 μ G，距离NGC 1399和M87中心1“-2”。我们表明，这些结果是一致的，与当前的范例冷集群核心的基础上，假设活动星系核活动调节气体的热状态，通过注入能量到集群内的介质。相对论质子形式的能量密度的~10-20%的限制不仅适用于气体的当前状态，而且基本上适用于团簇内介质的整个历史，前提是宇宙射线质子的演化是连续的，并且它们的空间扩散被抑制。
英文摘要：
We compare the gravitational potential profiles of the elliptical galaxies NGC 4486 (M87) and NGC 1399 (the central galaxy in the Fornax cluster) derived from X-ray and optical data. This comparison suggests that the combined contribution of cosmic rays, magnetic fields and micro-turbulence to the pressure is ~10% of the gas thermal pressure in the cores of NGC 1399 and M87, although the uncertainties in our model assumptions (e.g., spherical symmetry) are sufficiently large that the contribution could be consistent with zero. In the absence of any other form of non-thermal pressure support, these upper bounds translate into upper limits on the magnetic field of ~10-20 muG at a distance of 1'-2' from the centers of NGC1399 and M87. We show that these results are consistent with the current paradigm of cool cluster cores, based on the assumption that AGN activity regulates the thermal state of the gas by injecting energy into the intra-cluster medium. The limit of ~10-20% on the energy density in the form of relativistic protons applies not only to the current state of the gas, but essentially to the entire history of the intra-cluster medium, provided that cosmic ray protons evolve adiabatically and that their spatial diffusion is suppressed.
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