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Radio spectra and polarisation properties of a bright sample of Radio-Loud Broad Absorption Line Quasars

机译:光谱样品的无线电光谱和偏振特性   Radio-Loud Broad absorption Line Quasars

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摘要

The origin of broad-absorption-line quasars (BAL QSOs) is still an openissue. Accounting for ~20% of the QSO population, these objects present broadabsorption lines in their optical spectra generated from outflows withvelocities up to 0.2c. In this work we present the results of a multi-frequencystudy of a well-defined radio-loud BAL QSO sample, and a comparison sample ofradio-loud non-BAL QSOs, both selected from the Sloan Digital Sky Survey(SDSS). We aim to test which of the currently-popular models for the BAL phenomenon -`orientation' or 'evolutionary' - best accounts for the radio properties of BALquasars. Observations from 1.4 to 43 GHz have been obtained with the VLA andEffelsberg telescopes, and data from 74 to 408 MHz have been compiled from theliterature. The fractions of candidate GHz-peaked sources are similar in the two samples(36\pm12% vs 23\pm8%), suggesting that BAL QSOs are not generally younger thannon-BAL QSOs. BAL and non-BAL QSOs show a large range of spectral indices,consistent with a broad range of orientations. There is weak evidence (91%confidence) that the spectral indices of the BAL QSOs are steeper than those ofnon-BAL QSOs, mildly favouring edge-on orientations. At a higher level ofsignificance (\geq97%), the spectra of BAL QSOs are not flatter than those ofnon-BAL QSOs, which suggests that a polar orientation is not preferred.
机译:宽吸收线类星体(BAL QSO)的起源仍然是一个未解决的问题。这些物体约占QSO总量的20%,它们在光谱中呈现出的宽吸收线是由流速高达0.2c的流出物产生的。在这项工作中,我们提出了一个明确定义的无线电大声BAL QSO样本的多频研究结果,以及无线电大声非BAL QSO的比较样本,这两个样本均选自斯隆数字天空调查(SDSS)。我们的目的是测试BAL现象目前最流行的模型中的“方向”或“进化”模型,这些模型最能说明BAL类星体的无线电特性。使用VLA和Effelsberg望远镜获得了1.4至43 GHz的观测值,并且从文献中收集了74至408 MHz的数据。在两个样本中,候选GHz峰值源的分数相似(36 \ pm12%对23 \ pm8%),这表明BAL QSO通常不比非BAL QSO年轻。 BAL和非BAL QSO表现出大范围的光谱指数,与广泛的方向一致。很少有证据(91%的置信度)表明BAL QSO的光谱指数比非BAL QSO的光谱指数陡,偏向于边沿取向。在较高的显着性水平(\ geq97%)下,BAL QSO的光谱并不比非BAL QSO的光谱平坦,这表明极性取向不是优选的。

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