A search for distant radio galaxies from SUMSS and NVSS – III. Radio spectral energy distributions and the z–α correlation
A search for distant radio galaxies from SUMSS and NVSS – III. Radio spectral energy distributions and the z–α correlation
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从 SUMSS 和 NVSS 寻找遥远的射电星系 – III。
DOI：
10.1111/j.1365-2966.2006.10714.x
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发表时间：
2006
影响因子：
4.8
通讯作者：
C. Breuck
中科院分区：
文献类型：
--
作者：
I. Klamer;I. Klamer;R. Ekers;Julia J. Bryant;R. Hunstead;E. Sadler;C. Breuck
这是一系列论文中的第三篇，这些论文介绍了76个超陡谱射电源的观测和结果，这些射电源旨在寻找高红移星系。在这里，我们提出了多频无线电观测，从澳大利亚望远镜紧凑阵列，从样本的一个子集的37个星系。在2.3，4.8和6.2 GHz的匹配分辨率观测所有星系，与z < 2星系另外观察到8.6和18 GHz。新的角度大小的限制，报告19个来源的基础上高分辨率4.8和6.2 GHz的观测。函数形式的休息帧的光谱能量分布的推导：89%的样本是很好的特点是由一个单一的幂律，而其余的11%显示一些平坦化向更高的频率：没有一个来源显示任何证据的高频陡峭。我们讨论了这一结果的影响，在光的红移和光谱指数之间的经验相关性，在流量有限的样本射电星系。最后，一个新的物理机制来解释红移光谱指数相关性的假设：极端陡峭的光谱射电星系在本地宇宙通常居住在中心的丰富的星系团。我们认为，如果较高比例的射电星系，作为红移的函数，位于密度类似于附近的丰富的集群的环境中，那么这可能是一个自然的相关性的解释。我们简要地概述了我们的计划，以追求这一调查路线。
This is the third in a series of papers that present observations and results for a sample of 76 ultrasteep-spectrum radio sources designed to find galaxies at high redshift. Here we present multifrequency radio observations, from the Australia Telescope Compact Array, for a subset of 37 galaxies from the sample. Matched resolution observations at 2.3, 4.8 and 6.2 GHz are presented for all galaxies, with the z < 2 galaxies additionally observed at 8.6 and 18 GHz. New angular size constraints are reported for 19 sources based on high-resolution 4.8- and 6.2-GHz observations. Functional forms for the rest-frame spectral energy distributions are derived: 89 per cent of the sample is well characterized by a single power law, whilst the remaining 11 per cent show some flattening towards higher frequencies: not one source shows any evidence for high-frequency steepening. We discuss the implications of this result in light of the empirical correlation between redshift and spectral index seen in flux-limited samples of radio galaxies. Finally, a new physical mechanism to explain the redshift - spectral index correlation is posited: extremely steep-spectrum radio galaxies in the local universe usually reside at the centres of rich galaxy clusters. We argue that if a higher fractions of radio galaxies, as a function of redshift, are located in environments with densities similar to nearby rich clusters, then this could be a natural interpretation for the correlation. We briefly outline our plans to pursue this line of investigation.