A sample of mJy radio sources at 1.4 GHz in the Lynx and Hercules fields - II. Cosmic evolution of the space density of FR I radio sources
A sample of mJy radio sources at 1.4 GHz in the Lynx and Hercules fields - II. Cosmic evolution of the space density of FR I radio sources
复制标题
Lynx 和 Hercules 场中 1.4 GHz 的 mJy 无线电源样本 - II。
DOI：
10.1111/j.1365-2966.2008.12839.x
复制
发表时间：
2007
影响因子：
4.8
通讯作者：
I. Snellen
中科院分区：
文献类型：
--
作者：
E. Rigby;E. Rigby;P. Best;I. Snellen
本文研究了Fanaroff-Riley I类（FR I）射电源空间密度的宇宙演化，直到z ≥ 1，以了解这些射电源与更强大的FR II射电源之间差异的起源。高分辨率的射电图像的最佳高红移FR I候选星系，从莱顿伯克利深调查的两个领域，以前定义的里格比，斯内伦和最好的文件1。连同较低分辨率的无线电观测（以前发表在论文1中，对于一个子集的来源，也在这里），这些被用来形态分类的样本。明确解决的来源是单独的形态分类，而几乎没有或未解决的来源进行分类，使用相结合的形态和通量密度损失的更高分辨率的数据，表示已解决的扩展发射。空间密度的FR的是，然后计算作为一个函数的红移，并比较测量的本地值和更强大的FR II的行为。对于亮度（1.4GHz）> 1025 WHz-1的FR I射电源，空间密度被z 1增强了5-9倍，这意味着这一星群的演化相当强烈，这一增强与相同亮度下FR II演化的模型一致。也有迹象表明，演化是光度依赖的，与较低的功率源演化不太强烈。
In this paper the cosmic evolution of the space density of Fanaroff-Riley Class I (FR I) radio sources is investigated out to z ∼ 1, in order to understand the origin of the differences between these and the more powerful FR IIs. High-resolution radio images are presented of the best high-redshift FR I candidate galaxies, drawn from two fields of the Leiden-Berkeley Deep Survey, and previously defined by Rigby, Snellen & Best in Paper 1. Together with lower resolution radio observations (both previously published in Paper 1 and, for a subset of sources, also presented here) these are used to morphologically classify the sample. Sources which are clearly resolved are classified by morphology alone, whereas barely or unresolved sources were classified using a combination of morphology and flux density loss in the higher resolution data, indicative of resolved-out extended emission. The space densities of the FR Is are then calculated as a function of redshift, and compared to both measurements of the local value and the behaviour of the more powerful FR IIs. The space density of FR I radio sources with luminosities (at 1.4 GHz) > 10 25 W Hz -1 is enhanced by a factor of 5-9 by z ∼ 1, implying moderately strong evolution of this population; this enhancement is in good agreement with models of FR II evolution at the same luminosity. There are also indications that the evolution is luminosity dependent, with the lower powered sources evolving less strongly.