垂直于射流轴线加热簇内介质
Heating the intra-cluster medium perpendicular to the jets axis
摘要：
利用PLUTO流体动力学程序对冷却流场中的射流膨胀气泡进行了数值模拟，结果表明，高熵冲击射流中的物质与团簇内介质的混合是垂直于射流轴线的主要加热过程。前向激波的加热并不显著。混合在所有方向上加热ICM是非常有效的，达到~ 10 kpc和更远的距离。尽管喷流的活跃时间只有2000万年，但在喷流消失后，赤道面附近以及沿对称轴的混合和加热仍在持续超过10^8年的时间来对抗辐射冷却。我们讨论了一些可能的影响的结果。(i)强烈的混合预期纠缠磁场线，从而抑制任何全球性的热传导在ICM中心附近。(ii)剧烈的混合在星系团内部区域形成多相ICM，在那里最冷的气体包最终会首先冷却，向内流动，并为活动星系核提供能量，以形成下一个喷流活动事件。这进一步支持冷反馈机制。(iii)在r~ 10 kpc区域外的介质密度不如星系群和星系团的情况下，例如在星系形成的过程中，前向激波和激波喷流物质的高压可能会将气体排出系统。
英文摘要：
By simulating jet-inflated bubbles in cooling flows with the PLUTO hydrodynamic code we show that mixing of high entropy shocked jet's material with the intra-cluster medium (ICM) is the major heating process perpendicular to the jets' axis. Heating by the forward shock is not significant. The mixing is very efficient in heating the ICM in all directions, to distances of ~10kpc and more. Although the jets are active for a time period of only 20 Myr, the mixing and heating near the equatorial plane, as well as along the symmetry axis, continues to counter radiative cooling for times of >10^8 yr after the jets have ceased to exist. We discuss some possible implications of the results. (i) The vigorous mixing is expected to entangle magnetic field lines, hence to suppress any global heat conduction in the ICM near the center. (ii) The vigorous mixing forms multi-phase ICM in the inner cluster regions, where the coolest parcels of gas will eventually cool first, flow inward, and feed the active galactic nucleus to set the next jet-activity episode. This further supports the cold feedback mechanism. (iii) In cases where the medium outside the region of r~10kpc is not as dense as in groups and clusters of galaxies, like during the process of galaxy formation, the forward shock and the high pressure of the shocked jets' material might expel gas from the system.
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