Ionization, shocks and evolution of the emission‐line gas of distant 3CR radio galaxies
Ionization, shocks and evolution of the emission‐line gas of distant 3CR radio galaxies
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遥远 3CR 射电星系发射线气体的电离、激波和演化
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发表时间：
1999
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影响因子：
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通讯作者：
M. Longair
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作者：
P. Best;H. Röttgering;M. Longair
本文分析了14个红移为z_0 ~ 1的3CR射电星系的发射线气体的运动学和电离态。用于这些研究的数据，来自威廉赫歇尔望远镜的深长缝光谱曝光，在一份附带的论文中提出。结果表明，小线径射电源（150 kpc）比大线径射电源具有更低的电离态、更高的发射线通量和更宽的谱线宽度。对Baum等人的低红移样本的分析表明，从小到大的射电源，低红移的射电星系在速度结构和发射线比方面表现出相似的演化。
小射电源的发射线比与理论激波电离预言一致，其速度剖面是扭曲的。与其他发射线性质一起，这表明与射电源相关的冲击在射电源通过星际介质膨胀期间主导了发射线气体的运动学和电离。气体云被激波加速，产生了观察到的不规则速度结构，而发射线气体云的激波压缩和与激波相关的电离光子的存在结合联合收割机降低了发射线气体的电离状态。相比之下，在较大的射电源中，激波锋面已经远远超过发射线区域;这些较大射电源的发射线气体具有更稳定的运动学性质，表明旋转，并且发射线比率与电离光子的主要来源是活动星系核一致。
这种强烈的演变与强大的射电星系的发射线气体属性的无线电尺寸的反射镜的无线电尺寸的演变中看到的这些源的光-紫外连续辐射的性质，这意味着连续排列效应很可能是与相同的无线电源冲击。
An analysis of the kinematics and ionization state of the emission-line gas of a sample of 14 3CR radio galaxies with redshifts z∼1 is carried out. The data used for these studies, deep long-slit spectroscopic exposures from the William Herschel Telescope, are presented in an accompanying paper. It is found that radio sources with small linear sizes (≲150 kpc) have lower ionization states, higher emission-line fluxes and broader line widths than larger radio sources. An analysis of the low-redshift sample of Baum et al. demonstrates that radio galaxies at low redshift show similar evolution in their velocity structures and emission-line ratios from small to large radio sources.
The emission-line ratios of small radio sources are in agreement with theoretical shock ionization predictions, and their velocity profiles are distorted. Together with the other emission-line properties, this indicates that shocks associated with the radio source dominate the kinematics and ionization of the emission-line gas during the period that the radio source is expanding through the interstellar medium. Gas clouds are accelerated by the shocks, giving rise to the irregular velocity structures observed, whilst shock compression of emission-line gas clouds and the presence of the ionizing photons associated with the shocks combine to lower the ionization state of the emission-line gas. By contrast, in larger sources the shock fronts have passed well beyond the emission-line regions; the emission-line gas of these larger radio sources has much more settled kinematical properties, indicative of rotation, and emission-line ratios consistent with the dominant source of ionizing photons being the active galactic nucleus.
This strong evolution with radio size of the emission-line gas properties of powerful radio galaxies mirrors the radio size evolution seen in the nature of the optical–ultraviolet continuum emission of these sources, implying that the continuum alignment effect is likely to be related to the same radio source shocks.