发表机构
Max-Planck-Institut für Astronomie; INAF-Osservatorio di Astrofisica e Scienza dello Spazio; NSF NOIRLab, Gemini Observatory; ASTRON, The Netherlands Institute for Radio Astronomy; Leiden Observatory, Leiden University; National Radio Astronomy Observatory; Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales; Department of Astronomy Astrophysics and Space Engineering, Indian Institute of Technology Indore（马克斯·普朗克天文学研究所; 意大利国家天体物理研究所空间科学观测站; 美国国家光学红外天文研究实验室双子座天文台; 荷兰射电天文研究所; 莱顿大学莱顿天文台; 国家射电天文台; 迭戈·波特莱斯大学工程与科学学院天体物理研究所; 印度印多尔理工学院天文、天体物理与空间工程系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过多波段射电观测发现最遥远耀变体VLASS J0410-0139存在快速射电变化，推断其具有紧密对准的相对论性喷流，并指示宇宙黎明时期存在大量未被探测的弱射电喷流群体。
AI 中文摘要
多普勒增亮使得耀变体能够在高红移处被探测到，使其成为通过21厘米森林研究星系际介质的有前景的探针。我们报告了对已知最遥远耀变体 VLASS J041009.05$-$013919.88（红移 $z\sim7$）在0.144$-$11 GHz频段的观测，这些观测使用升级后的巨米波射电望远镜（uGMRT）、低频阵列（LOFAR）和甚大阵列（VLA）获得。第一个uGMRT观测时段（300$-$820 MHz，2023年4月）揭示了倒转的射电谱，结合早期（2021$-$2022年）的VLA数据（1.5$-$11 GHz），揭示了一个双峰谱，可能表明多历元喷流活动。第二次uGMRT观测活动（2023年8月）与新的VLA观测（1.5$-$11 GHz）同时进行，反而揭示了平坦的低频谱和峰值的高频谱，排除了这一解释。尽管受限于两个uGMRT观测时段，变异性分析倾向于内在喷流过程，表明存在一个高度相对论性、紧密对准的喷流（$\theta<3$度，$\delta>19.3$，$\Gamma>9.7$）。均分磁场（$>1$ mG）超过了红移 $z\sim7$ 处等效宇宙微波背景场（0.2 mG），表明同步辐射损失占主导。推断的多普勒增亮（$\delta>19.3$）意味着J0410$-$0139本质上是射电弱的。作为一个耀变体，它追踪了红移 $z\sim7$ 处更大的射电类星体母体群，这些类星体只能通过深度（$\leq \mu$Jy）的下一代射电观测才能探测到。LOFAR 144 MHz观测（2024年4月和7月）产生了约2 mJy的通量，远低于从uGMRT观测时段预测的约8 mJy，证实了静止系约1 GHz处的强烈变异性。低频监测对于识别适合未来21厘米森林研究的高射电强度状态至关重要。
英文摘要
Doppler boosting allows blazars to be detected out to high-$z$, making them promising probes of the intergalactic medium through the 21 cm forest. We report 0.144$-$11 GHz observations of the most distant known blazar, VLASS J041009.05$-$013919.88 at z$\sim$7, obtained with the upgraded Giant Metrewave Radio Telescope (uGMRT), the LOw Frequency ARray (LOFAR) and the Very Large Array (VLA). The first uGMRT epoch (300$-$820 MHz, April 2023) revealed an inverted radio spectrum which, combined with earlier (2021$-$2022) VLA data (1.5$-$11 GHz), unveiled a double-peaked spectrum potentially indicative of multi-epoch jet activity. A second uGMRT campaign (August 2023), simultaneous with new VLA observations (1.5$-$11 GHz), instead revealed a flat low-frequency and a peaked high-frequency spectrum, ruling out this interpretation. While limited by the two uGMRT epochs, variability analysis favors intrinsic jet processes, indicating a highly relativistic, closely aligned jet ($θ<3$ deg, $δ>19.3$, $Γ>9.7$). The equipartition magnetic field ($> 1$ mG) exceeds the equivalent Cosmic Microwave Background field at $z\sim7$ (0.2 mG), indicating synchrotron losses dominate. The inferred Doppler boosting ($δ>19.3$) implies that J0410$-$0139 is intrinsically radio-weak. As a blazar, it traces a much larger parent population of radio quasars at $z\sim7$, detectable only with deep ($\leq μ$Jy) next-generation radio observations. LOFAR 144 MHz observations (April and July 2024) yielded $\sim$2 mJy, well below the $\sim$8 mJy predicted from uGMRT epochs, confirming strong variability at rest-frame $\sim$1 GHz. Low-frequency monitoring will be crucial for identifying high radio intensity states suitable for future 21 cm forest studies.
Comments16 pages, 3 figures, 3 tables, Accepted for publication in ApJ
