The origin of molecular hydrogen emission in cooling‐flow filaments★
The origin of molecular hydrogen emission in cooling‐flow filaments★
复制标题
冷却流丝中氢分子发射的起源★
DOI：
10.1111/j.1745-3933.2008.00463.x
复制
发表时间：
2008
影响因子：
4.8
通讯作者：
R. Williams
中科院分区：
文献类型：
--
作者：
G. Ferland;G. Ferland;A. Fabian;N. Hatch;R. Johnstone;R. Porter;R. Porter;P. V. Hoof;R. Williams
在许多星系团的冷却流中发现的光学细丝是由低密度（约10 3 cm −3）冷（约10 3 K）气体组成，周围有大量的宇宙射线和磁场能量。与暴露于电离辐射的银河系分子云（如猎户座复合体）相比，它们的光谱显示出非常强的低电离和分子发射线。以前的研究表明，光谱不能产生O-星光电离。在这里，我们计算的物理条件，以及屏蔽电离光子的外部来源，并通过宇宙射线或耗散磁流体动力学波的尘埃气体。强分子氢线，与观察到的类似的相对强度，产生。由微观物理学引入的选择效应产生了H2线上能级能量和粒子数温度之间的相关性。这些选择效应允许纯碰撞气体产生H2辐射，其伪装成星光泵浦的H2，但强度要强得多。这种物理学可以应用于气体密度或加热速率范围很广的任何环境。
The optical filaments found in many cooling flows in galaxy clusters consist of low-density (∼10 3 cm −3 ) cool (∼10 3 K) gas surrounded by significant amounts of cosmic-ray and magnetic field energy. Their spectra show anomalously strong low-ionization and molecular emission lines when compared with Galactic molecular clouds exposed to ionizing radiation such as the Orion complex. Previous studies have shown that the spectra cannot be produced by O-star photoionization. Here, we calculate the physical conditions in dusty gas that is well shielded from external sources of ionizing photons and is energized either by cosmic rays or dissipative magnetohydrodynamics waves. Strong molecular hydrogen lines, with relative intensities similar to those observed, are produced. Selection effects introduced by the microphysics produce a correlation between the H2 line upper level energy and the population temperature. These selection effects allow a purely collisional gas to produce H2 emission that masquerades as starlight-pumped H2 but with intensities that are far stronger. This physics may find application to any environment where a broad range of gas densities or heating rates occur.