Radio galaxies with a ‘double-double’ morphology – II. The evolution of double-double radio galaxies and implications for the alignment effect in FRII sources
Radio galaxies with a ‘double-double’ morphology – II. The evolution of double-double radio galaxies and implications for the alignment effect in FRII sources
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DOI：
10.1046/j.1365-8711.2000.03431.x
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发表时间：
1999-12
影响因子：
4.8
通讯作者：
C. Kaiser;A. Schoenmakers;Hans-Walter Rix University of Oxford;D. Physics;M. F. Astrophysik
中科院分区：
文献类型：
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作者：
C. Kaiser;A. Schoenmakers;Hans-Walter Rix University of Oxford;D. Physics;M. F. Astrophysik
双双射电星系（DDRG）被定义为由一对具有共同中心的双射电源组成。本文提出了一个解析模型，其中DDRGs的特殊无线电结构是由AGN中心的射流中断引起的。从重新启动的AGN中出现的新喷流在旧的外部茧区域内产生了内部源结构。FRII源演化的标准模型预测了旧茧区域内的气体密度，这不足以解释观测到的内部源结构的特性。因此，额外的物质必须从源的环境通过围绕外部源结构的弓形激波进入茧。我们认为这种物质是嵌入在热IGM中的暖云（~ 104k）气体，这些气体最终由于茧材料通过引起的表面不稳定性而分散在茧体上。这些云的体积填充因子的下限与光学观测的结果很一致。云色散的长时间尺度（~ 10.7年）与在大型（≥700kpc）射电源中明显只出现DDRG现象一致，也与观测到的z ~1 FRII源的光学/紫外对准效应强度与它们的线性尺寸的相关性一致。
A double-double radio galaxy (DDRG) is defined as consisting of a pair of double radio sources with a common centre. In this paper we present an analytical model in which the peculiar radio structure of DDRGs is caused by an interruption of the jet flow in the central AGN. The new jets emerging from the restarted AGN give rise to an inner source structure within the region of the old, outer cocoon. Standard models of the evolution of FRII sources predict gas densities within the region of the old cocoon that are insufficient to explain the observed properties of the inner source structure. Therefore additional material must have passed from the environment of the source through the bow shock surrounding the outer source structure into the cocoon. We propose that this material is warm clouds (~10 4 K) of gas embedded in the hot IGM which are eventually dispersed over the cocoon volume by surface instabilities induced by the passage of cocoon material. The derived lower limits for the volume filling factors of these clouds are in good agreement with results obtained from optical observations. The long time-scales for the dispersion of the clouds (~10 7 yr) are consistent with the apparently exclusive occurrence of the DDRG phenomenon in large (≥700 kpc) radio sources, and with the observed correlation of the strength of the optical/UV alignment effect in z ~1 FRII sources with their linear size.