LoTSS/HETDEX: Optical quasars I. Low-frequency radio properties of optically selected quasars
LoTSS/HETDEX: Optical quasars I. Low-frequency radio properties of optically selected quasars
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LoTSS/HETDEX：光学类星体 I. 光学选择类星体的低频射电特性
DOI：
10.1051/0004-6361/201833892
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发表时间：
2019
影响因子：
6.5
通讯作者：
Gürkan G
中科院分区：
文献类型：
--
作者：
Gürkan G
类星体中的射电大声/射电安静（RL/RQ）二分法仍然是一个悬而未决的问题。尽管人们认为类星体宿主星系中心超大质量黑洞的吸积造成了一些射电连续谱发射，但对于恒星形成还是活动星系核（AGN）活动主导射电连续谱光度仍然存在争议。迄今为止，类星体的射电发射几乎完全使用高频观测进行研究，其中多普勒增强可能对测量的射电光度产生重要影响，而在低射电频率下最好观测到的扩展结构不受多普勒增强的影响。作为 LOFAR 两米巡天 (LoTSS) 的一部分，我们使用根据光谱选择的类星体样本，结合低频阵列 (LOFAR) 提供的敏感且高分辨率的低频射电数据，利用射电响度参数 ( ) 研究其射电特性。对类星体射电连续谱发射和 RL/RQ 二分法的检查表明，类星体表现出广泛的射电特性连续谱（即 ℛ 的分布没有明显的双峰性）。低光度类星体的低频射电连续谱发射与恒星形成的主导一致。我们发现 ℛ 对源核参数有显着但微弱的依赖性。我们第一次能够解析大量类星体的射电形态。所有这些重要结果都凸显了深度和高分辨率低频射电勘测的影响，这预示着平方公里阵列（SKA）令人信服的科学案例。
The radio-loud/radio-quiet (RL/RQ) dichotomy in quasars is still an open question. Although it is thought that accretion onto supermassive black holes in the centre the host galaxies of quasars is responsible for some radio continuum emission, there is still a debate as to whether star formation or active galactic nuclei (AGN) activity dominate the radio continuum luminosity. To date, radio emission in quasars has been investigated almost exclusively using high-frequency observations in which the Doppler boosting might have an important effect on the measured radio luminosity, whereas extended structures, best observed at low radio frequencies, are not affected by the Doppler enhancement. We used a sample of quasars selected by their optical spectra in conjunction with sensitive and high-resolution low-frequency radio data provided by the LOw Frequency ARray (LOFAR) as part of the LOFAR Two-Metre Sky Survey (LoTSS) to investigate their radio properties using the radio loudness parameter ( ). The examination of the radio continuum emission and RL/RQ dichotomy in quasars exhibits that quasars show a wide continuum of radio properties (i.e. no clear bimodality in the distribution of ℛ). Radio continuum emission at low frequencies in low-luminosity quasars is consistent with being dominated by star formation. We see a significant albeit weak dependency of ℛ on the source nuclear parameters. For the first time, we are able to resolve radio morphologies of a considerable number of quasars. All these crucial results highlight the impact of the deep and high-resolution low-frequency radio surveys that foreshadow the compelling science cases for the Square Kilometre Array (SKA).