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arXiv 0712.0824astro-ph
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团簇内介质的热平衡：AGN反馈是否必要？

Thermal Balance in the Intracluster Medium: Is AGN Feedback Necessary?

Charlie Conroy, Jeremiah P. Ostriker

备注：
16 pages, 8 figures. ApJ in press
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摘要：

各种物理加热机制相结合的辐射冷却探索，通过一维流体动力学模拟，预期的热性能的簇内介质（ICM）的背景下的冷却流问题。能量注入Ia型超新星，热传导，和动力学摩擦（DF）从轨道卫星星系被认为是。这项工作的新颖之处在于探索了每个加热过程的各种效率。虽然后两者可以提供大量的能量，但单独运行的机制都不能在宇宙学时间尺度上产生或维持ICM的热平衡，这与观测形成鲜明对比。对于具有初始等温温度分布的模拟团簇，这两种机制的共同作用导致了ICM温度范围和中心电子密度小于n_e~0.02 cm^-3时的长期热平衡;在更大的密度下，灾难性的冷却总是发生。此外，这些加热机制既不能产生也不能维持在中心区域具有下降温度分布的簇，这意味着所观察到的具有这种下降温度分布的“冷却核”簇不能单独用这些机制来维持。因此，虽然似乎有充足的能量供应能够加热团簇中的ICM，但要使ICM在宇宙学时间尺度上保持热平衡，能量沉积是极其困难的。这些结果强烈地表明，一个更动态的加热过程，如从中央黑洞的反馈，需要产生所观察到的集群内介质的属性。（简略）

英文摘要：

A variety of physical heating mechanisms are combined with radiative cooling to explore, via one dimensional hydrodynamic simulations, the expected thermal properties of the intracluster medium (ICM) in the context of the cooling flow problem. Energy injection from type Ia supernovae, thermal conduction, and dynamical friction (DF) from orbiting satellite galaxies are considered. The novel feature of this work is the exploration of a wide range of efficiencies of each heating process. While the latter two can provide a substantial amount of energy, neither mechanism operating alone can produce nor maintain an ICM in thermal balance over cosmological timescales, in stark contrast with observations. For simulated clusters with initially isothermal temperature profiles, both mechanisms acting in combination result in long-term thermal balance for a range of ICM temperatures and for central electron densities less than n_e~0.02 cm^-3; at greater densities catastrophic cooling invariably occurs. Furthermore, these heating mechanisms can neither produce nor maintain clusters with a declining temperature profile in the central regions, implying that the observed "cooling-core'' clusters, which have such declining temperature profiles, cannot be maintained with these mechanisms alone. Thus, while there appears to be an abundant supply of energy capable of heating the ICM in clusters, it is extremely difficult for the energy deposition to occur in such a way that the ICM remains in thermal balance over cosmological time-scales. These results strongly suggest that a more dynamic heating process such as feedback from a central black hole is required to generate the properties of observed intracluster media. (ABRIDGED)

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