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arXiv 1003.2835astro-ph.CO
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邻近射电星系（II）中的大尺度HI：经典低功率射电源的性质

Large-scale HI in nearby radio galaxies (II): the nature of classical low-power radio sources

B. H. C. Emonts, R. Morganti, C. Struve, T. A. Oosterloo, G. van Moorsel, C. N. Tadhunter, J. M. van der Hulst, E. Brogt, J. Holt, N. Mirabal

备注：
Accepted for publication in MNRAS; 22 pages, 6 figures. A full resolution version of this paper is available at http://www.atnf.csiro.au/people/emo004/Papers/Emonts_MNRAS_HIradiogal.pdf
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摘要：

解决长期存在的问题的一个重要方面是什么触发了各种类型的活动星系核，这涉及到对其宿主星系的整体性质和形成历史的透彻理解。这是一系列论文中的第二篇，系统地研究了附近射电星系中冷中性氢（HI）气体的大尺度性质。主要目标是研究富气星系合并的重要性和射电活动星系核之间的相互作用。在本文中，我们提出了一个完整的样本的经典低功率射电星系的结果。我们发现扩展的Fanaroff & Riley I型射电源通常与富含气体的星系合并或持续的剧烈相互作用无关，但发生在没有大量（> 10^8 M_sun）扩展中性氢气的早期类型星系中。相比之下，在我们的样本中，在相当一部分致密射电源的宿主星系周围检测到了巨大的HI气体盘/环（大小高达190 kpc，质量高达2 x 10^10 M_sun）。HI质量与射电源大小的这种分离可能表明，这些紧凑的射电源要么被大量的气体限制在中心区域，要么它们的燃料供给效率低下，与经典的FR-I射电源的燃料供给过程不同。一阶，我们的完整样本的整体HI属性（检测率，质量和形态）出现类似的无线电安静的早期型星系。如果得到更好的统计数据的证实，这将意味着低功率射电活动星系核活动可能是一个短暂的周期性阶段，发生在许多早期类型星系生命周期的某个时刻。

英文摘要：

An important aspect of solving the long-standing question as to what triggers various types of Active Galactic Nuclei involves a thorough understanding of the overall properties and formation history of their host galaxies. This is the second in a series of papers that systematically study the large-scale properties of cold neutral hydrogen (HI) gas in nearby radio galaxies. The main goal is to investigate the importance of gas-rich galaxy mergers and interactions among radio-loud AGN. In this paper we present results of a complete sample of classical low-power radio galaxies. We find that extended Fanaroff & Riley type-I radio sources are generally not associated with gas-rich galaxy mergers or ongoing violent interactions, but occur in early-type galaxies without large (> 10^8 M_sun) amounts of extended neutral hydrogen gas. In contrast, enormous discs/rings of HI gas (with sizes up to 190 kpc and masses up to 2 x 10^10 M_sun) are detected around the host galaxies of a significant fraction of the compact radio sources in our sample. This segregation in HI mass with radio source size likely indicates that these compact radio sources are either confined by large amounts of gas in the central region, or that their fuelling is inefficient and different from the fuelling process of classical FR-I radio sources. To first order, the overall HI properties of our complete sample (detection rate, mass and morphology) appear similar to those of radio-quiet early-type galaxies. If confirmed by better statistics, this would imply that low-power radio-AGN activity may be a short and recurrent phase that occurs at some point during the lifetime of many early-type galaxies.

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