A new search for distant radio galaxies in the Southern hemisphere - III. Optical spectroscopy and analysis of the MRCR-SUMSS sample
A new search for distant radio galaxies in the Southern hemisphere - III. Optical spectroscopy and analysis of the MRCR-SUMSS sample
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对南半球遥远射电星系的新搜索 - III。
DOI：
10.1111/j.1365-2966.2009.14607.x
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发表时间：
2009
影响因子：
4.8
通讯作者：
B. Gaensler
中科院分区：
文献类型：
--
作者：
J. Bryant;H. Johnston;J. Broderick;R. Hunstead;C. Breuck;B. Gaensler;B. Gaensler
为了寻找高红移射电星系，我们收集了234个超陡谱（USS）选择射电源的样本。样本在南方天空40度2.我们分析了K{z分布，并比较了文献中几次观测中4arcsec孔径星等与64 kpc孔径星等的差异，发现MRCR{SUMSS样本与10 11 {10 12 M星系的模型一致。K{z}图中关于ts的色散支持了射电星系宿主自z > 3以来的被动演化。通过对文献中USS选择的样品的比较，我们发现所示样品的中位红移不依赖于每个样品的ux密度分布或选择频率。此外，我们的发现，大多数的无线电频谱能量分布保持直线在一个很宽的频率范围内表明，k-校正是不负责的USS选择在识别高红移射电星系的成功，因此陡峭的无线电频谱可能是固有的源或环境的产物。有两个星系被发现在Ly线上同时具有紧凑的射电结构和强烈的自吸收，这表明它们被致密介质包围。对于大部分的来源，光谱线比表明，光电离是主要的激发过程。
We have compiled a sample of 234 ultra-steep-spectrum(USS)-selected radio sources in order to nd high-redshift radio galaxies (HzRGs). The sample is in the southern sky at 40 2. We analyse the K{z distribution and compare 4arcsec-aperture magnitudes with 64-kpc aperture magnitudes in several surveys from the literature; the MRCR{SUMSS sample is found to be consistent with models for 10 11 {10 12 M galaxies. Dispersions about the ts in the K{z plot support passive evolution of radio galaxy hosts since z > 3. By comparing USS-selected samples in the literature, we nd that the resultant median redshift of the samples shown is not dependent on the ux density distribution or selection frequency of each sample. In addition, our nding that the majority of the radio spectral energy distributions remain straight over a wide frequency range suggests that a k-correction is not responsible for the success of USS-selection in identifying high redshift radio galaxies and therefore the steep radio spectra may be intrinsic to the source or a product of the environment. Two galaxies have been found to have both compact radio structures and strong self-absorption in the Ly line, suggesting they are surrounded by a dense medium. For the bulk of the sources, spectral line ratios show that photoionisation is the primary excitation process.