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arXiv 2109.07523astro-ph.HEastro-ph.GA
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射电发光类星体比例与红移的关系及其理论意义

The dependence of the fraction of radio luminous quasars on redshift and its theoretical implications

Katarzyna Rusinek-Abarca, Marek Sikora

摘要:

虽然类星体中的射电辐射可以由各种过程(包括恒星形成区、吸积盘日冕和风和喷流)贡献,但射电最强的类星体的动力必须涉及非常强的喷流,推测是由结合磁制动盘(MAD)的布兰德福德-兹纳杰克机制发射的。我们专注于后者,并调查其分数的红移的依赖性。我们还研究了射电大声部分(RLF)对BH质量($M_{\rm BH}$)和爱丁顿比($λ_{\rm Edd}$)的依赖性,同时通过缩小其范围来排除红移偏差。在这两项研究中,我们消除了与以下方面相关的偏差:(1)通过构建两个定义明确的均匀类星体样本(第一个在$0.7 \leq z < 1.9$内,第二个在$0.5 \leq z < 0.7$内)来选择源的多样性;(2)通过选择BH质量大于$10^{8.5} M_{\odot}$的类星体,使BH质量较小的类星体的RLF大幅下降。我们证实了以前的一些结果,表明无线电响亮的类星体的比例与宇宙时间的增加,这种趋势可以更陡峭,如果我们考虑到的RLF对BH质量的依赖而引入的偏差的RLF对爱丁顿比的依赖被证明是可以忽略不计的偏差。假设类星体活动是由星系合并引发的,我们认为这种增加可能是由于混合合并比湿合并的宇宙时间下降得更慢。

英文摘要:

While radio emission in quasars can be contributed to by a variety of processes (involving star forming regions, accretion disk coronas and winds, and jets), the powering of the radio loudest quasars must involve very strong jets, presumably launched by the Blandford-Znajek mechanism incorporating the magnetically arrested disk (MAD) scenario. We focus on the latter and investigate the dependence of their fraction on redshift. We also examine the dependence of the radio-loud fraction (RLF) on BH mass ($M_{\rm BH}$) and Eddington ratio ($λ_{\rm Edd}$) while excluding the redshift bias by narrowing its range. In both these investigations we remove the bias associated with: (1) the diversity of source selection by constructing two well-defined, homogeneous samples of quasars (first within $0.7 \leq z < 1.9$, second within $0.5 \leq z < 0.7$); (2) a strong drop in the RLF of quasars at smaller BH masses by choosing those with BH masses larger than $10^{8.5} M_{\odot}$. We confirm some previous results showing the increase in the fraction of radio-loud quasars with cosmic time and that this trend can be even steeper if we account for the bias introduced by the dependence of the RLF on BH mass whereas the bias introduced by the dependence of the RLF on Eddington ratio is shown to be negligible. Assuming that quasar activities are triggered by galaxy mergers we argue that such an increase can result from the slower drop with cosmic time of mixed mergers than of wet mergers.

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