A sample of 6C radio sources designed to find objects at redshift z > 4 - II. Spectrophotometry and emission-line properties
A sample of 6C radio sources designed to find objects at redshift z > 4 - II. Spectrophotometry and emission-line properties
复制标题
设计用于寻找红移 z > 4 - II 物体的 6C 射电源样本。
DOI：
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发表时间：
2001
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通讯作者：
Chris J.Willott
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作者：
Matt J.Jarvis;S. Rawlings;M. Lacy;Katherine M.Blundell;Andrew J.Bunker;S. Eales;R. Saunders;H. Spinrad;D. Stern;Chris J.Willott
这是一系列三篇论文中的第二篇，这些论文介绍并解释了6C* 151-MHz射电样本的基本观测数据：一个低频选择样本，利用基于射电特性（陡峭的光谱指数和小角度大小）的过滤标准，在0.133-sr的天空中的红移内联图像上找到射电源。我们目前的结果的一个方案的光谱学，产生了红移的范围内的图像中的29个来源的样品，但其中六个是安全的。我们发现，用于6C* 的过滤标准是非常有效的，在排除低红移，低光度的射电源：6C* 的中值红移是内联图像相比，内联图像为一个完整的样本匹配在151 MHz的通量密度。通过将6C* 射电源的发射线数据集与3CRR、6CE和7 CRS样本的发射线数据集相结合，我们确定了顺列影像射电星系遵循Lyα和151-MHz光度之间的大致比例关系，这与在低红移射电源样本中看到的类似相关性相似，表明光致电离光子源（很可能是隐藏的类星体核）的能量与射电喷流携带的能量之间存在主要联系。我们认为，无线电源修改他们的环境，看到的发射线属性的范围是由源年龄的范围比在周围环境中的范围。如果发光高红移陡谱射电源的尺寸分布反映了一个范围较窄的宽范围（102 dex）源年龄，那么最小的顺列像射电星系具有所有预期的性质（1）相对低光度的高电离线，如Lyα，（2）增强的低电离线，如C Ⅱ];（3）空间紧凑的发射线区;（4）H_i吸收的Lyα分布。这与所有高红移、高光度的射电源都是在类似的环境中触发的想法是雅阁的，可能是最近坍塌的大质量结构。
This is the second in a series of three papers that present and interpret basic observational data on the 6C* 151-MHz radio sample: a low-frequency selected sample that exploits filtering criteria based on radio properties (steep spectral index and small angular size) to find radio sources at redshift inline image within a 0.133-sr patch of sky. We present results of a programme of optical spectroscopy that has yielded redshifts in the range inline image for the 29 sources in the sample, all but six of which are secure. We find that the filtering criteria used for 6C* are very effective in excluding the low-redshift, low-luminosity radio sources: the median redshift of 6C* is inline image compared with inline image for a complete sample matched in 151-MHz flux density. By combining the emission-line data set for the 6C* radio sources with those for the 3CRR, 6CE and 7CRS samples we establish that inline image radio galaxies follow a rough proportionality between Lyα and 151-MHz luminosity, which, like similar correlations seen in samples of lower redshift radio sources, is indicative of a primary link between the power in the source of the photoionizing photons (most likely a hidden quasar nucleus) and the power carried by the radio jets. We argue that radio sources modify their environments and that the range of emission-line properties seen is determined more by the range of source age than by the range in ambient environment. The smallest inline image radio galaxies have all the properties expected if the size distribution of luminous high-redshift steep-spectrum radio sources reflects a broad range (∼2 dex) of source ages with a narrower range (≲ 1.5 dex) of environmental densities, namely: (1) high-ionization lines, e.g. Lyα, of relatively low luminosity; (2) boosted low-ionization lines, e.g. C ii]; (3) spatially compact emission-line regions; and (4) H i-absorbed Lyα profiles. This is in accord with the idea that all high-redshift, high-luminosity radio sources are triggered in similar environments, presumably recently collapsed massive structures.