The radio spectral turnover of radio-loud quasars at z > 5
The radio spectral turnover of radio-loud quasars at z > 5
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z > 5 处射电响类星体的射电频谱周转
DOI：
10.1051/0004-6361/202142489
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发表时间：
2022
影响因子：
6.5
通讯作者：
Brunthaler, Andreas
中科院分区：
文献类型：
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作者：
Shao, Yali;Wagg, Jeff;Wang, Ran;Momjian, Emmanuel;Carilli, Chris L.;Walter, Fabian;Riechers, Dominik A.;Intema, Huib T.;Weiss, Axel;Brunthaler, Andreas
我们介绍卡尔G。Jansky甚大阵列S-（2-4 GHz），C-（4-8 GHz），和X-波段（8-12 GHz）连续观测到七个射电大声类星体atz> 5。 该样品先前已被发现在高于101 GHz的双标架频率处表现出光谱峰值。我们还介绍了升级后的巨米波射电望远镜（uGMRT）波段-2（200 MHz），波段-3（400 MHz）和波段-4（650 MHz）射电连续观测到八个射电大声类星体atz> 5，从我们以前的GMRT调查中选择，以采样其低频同步辐射。 结合档案无线电连续观测，所有十个目标都显示出频谱周转的证据。在静止帧中，转换频率为101 -50 GHz，使这些目标成为千兆赫兹峰值频谱或高频峰值候选者。对于九个约束良好的目标与观测的光谱营业额的两侧，我们适合整个无线电频谱与同步自吸收和自由-自由吸收（FFA）相关的吸收模型。我们的研究结果表明，FFA在外部非均匀介质中可以准确地描述所观察到的光谱的所有9个目标，这可能表明FFA起源的无线电频谱营业额在我们的样本。对于J114657.79+403708.6 atz= 5.00的具有两个光谱峰的复杂光谱，它可能是由多个组分引起的（即， 核心射流）和FFA的高密度介质在核区。然而，我们不能排除光谱周转的变异性起源。基于我们的无线电频谱模型，我们计算出我们的样本的无线电频率R2500，范围从12到674。
We presentKarl G. JanskyVery Large ArrayS- (2–4 GHz),C- (4–8 GHz), andX-band (8–12 GHz) continuum observations toward seven radio-loud quasars atz> 5. This sample has previously been found to exhibit spectral peaks at observed-frame frequencies above ∼1 GHz. We also present upgraded Giant Metrewave Radio Telescope (uGMRT) band-2 (200 MHz), band-3 (400 MHz), and band-4 (650 MHz) radio continuum observations toward eight radio-loud quasars atz> 5, selected from our previous GMRT survey, in order to sample their low-frequency synchrotron emission. Combined with archival radio continuum observations, all ten targets show evidence for spectral turnover. The turnover frequencies are ∼1–50 GHz in the rest frame, making these targets gigahertz-peaked-spectrum or high-frequency-peaker candidates. For the nine well-constrained targets with observations on both sides of the spectral turnover, we fit the entire radio spectrum with absorption models associated with synchrotron self-absorption and free-free absorption (FFA). Our results show that FFA in an external inhomogeneous medium can accurately describe the observed spectra for all nine targets, which may indicate an FFA origin for the radio spectral turnover in our sample. As for the complex spectrum of J114657.79+403708.6 atz= 5.00 with two spectral peaks, it may be caused by multiple components (i.e., core-jet) and FFA by the high-density medium in the nuclear region. However, we cannot rule out the spectral turnover origin of variability. Based on our radio spectral modeling, we calculate the radio loudnessR2500 Åfor our sample, which ranges from 12 to 674 .
CAPTURE：用于根据 GMRT 数据创建图像的干涉测量管道
DOI：
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发表时间：
2020
期刊：
影响因子：
--
作者：
R. Kale;C. Ishwara
通讯作者：
C. Ishwara