年轻射电星系的发射线气体电离
Emission line gas ionisation in young radio galaxies
摘要：
本文是第二次在一系列中，我们提出了一个完整的样本的14个紧凑的射电源的中分辨率光谱，采取的目的是调查的影响，核活动的cirumnuclear星际介质（ISM）在射电源演化的早期阶段。在第一篇论文中，我们提出了运动学的结果，从线模型和报告的快速外流的环核气体。在这里，我们使用线通量调查的物理条件和主导的电离机制的发射线气体。我们发现大的电子密度和高的核区域，特别是在更广泛的，蓝移组件的红化的证据。这些结果是一致的想法，年轻的，最近触发的无线电源仍然驻留在密集和尘埃茧沉积最近的活动触发事件。此外，我们发现，静止的核和扩展窄的组件是一致的活动星系核的光电离。对于核更广泛和移动的组件，结果不太清楚。虽然有建议，更广泛的组件可能更接近冲击加前兆模型的诊断图（高电子温度和密度），我们无法明确区分的主要电离机制使用的光发射线比。这是令人惊讶的，因为有强有力的证据表明喷流-云相互作用（宽发射线，大流出速度和强烈的无线电光学对准），这有利于这样的想法，即温暖的气体已经在冲击中加速，这些冲击是由无线电波瓣通过触发事件期间沉积的致密气体茧膨胀驱动的。
英文摘要：
This paper is the second in a series in which we present intermediate-resolution spectra for a complete sample of 14 compact radio sources, taken with the aim of investigating the impact of the nuclear activity on the cirumnuclear interstellar medium (ISM) in the early stages of radio source evolution. In the first paper we presented the kinematic results from the line modelling and reported fast outflows in the circumnuclear gas. Here, we use the line fluxes to investigate the physical conditions and dominant ionisation mechanisms of the emission line gas. We find evidence for large electron densities and high reddening in the nuclear regions, particularly in the broader, blueshifted components. These results are consistent with the idea that the young, recently triggered radio sources still reside in dense and dusty cocoons deposited by the recent activity triggering event. In addition, we find that the quiescent nuclear and extended narrow components are consistent with AGN photoionisation. For the nuclear broader and shifted components the results are less clear. Whilst there are suggestions that the broader components may be closer to shock plus precursor models on the diagnostic diagrams (with high electron temperatures and densities), we are unable to unambiguously distinguish the dominant ionisation mechanism using the optical emission line ratios. This is surprising given the strong evidence for jet-cloud interactions (broad emission lines, large outflow velocities and strong radio-optical alignments), which favours the idea that the warm gas has been accelerated in shocks driven by the radio lobes expanding through a dense cocoon of gas deposited during the triggering event.
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