LoTSS中的双活动星系核：增强的可探测性与系统性搜寻前景
LoTSS of dual AGN: enhanced detectability and prospects for a systematic search
- INAF - Istituto di Astrofisica e Planetologia Spaziali（意大利国家天体物理研究所）
- INAF - Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）
- University of Hamburg（汉堡大学）
- INAF - Istituto di Radioastronomia（意大利国家天体物理研究所射电天文台）
- Department of Astronomy, University of Cape Town（开普敦大学天文学系）
- University of Trento（特伦托大学）
- Dipartimento di Fisica e Astronomia, Università di Firenze（佛罗伦萨大学物理与天文学系）
- Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, NCU（尼古拉·哥白尼大学物理、天文与信息学院天体物理研究所）
- Center for Theoretical Physics, Polish Academy of Sciences（波兰科学院理论物理中心）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究利用LoTSS亚角秒成像在144 MHz下探测高红移双活动星系核，发现其探测率（约24%）显著高于单活动星系核，证明低频射电观测是高效且不受尘埃影响的搜寻方法。
AI中文摘要：
背景：双活动星系核（DAGN）——即两个处于千秒差距尺度间距上的吸积超大质量黑洞系统——追踪星系合并过程，并且是脉冲星计时阵列和即将到来的激光干涉空间天线（LISA）所瞄准的引力波源的 progenitors。然而，它们的射电性质仍然受到较差的约束，特别是在高红移处。目标：我们通过LOFAR两米巡天（LoTSS）的亚角秒成像展示了高红移DAGN在144 MHz下的可探测性，并刻画了它们的低频射电性质。方法：我们将92个经光谱证认的DAGN（红移z > 0.3，投影间距r_p < 30 kpc）与LoTSS DR2星表进行交叉匹配，并对其中三个系统（0.59 < z < 2.39）重新处理了国际LOFAR望远镜（ILT）数据，在144 MHz下实现了约0.3角秒的分辨率。我们利用多频率分析和亮温度诊断来研究射电辐射。结果：我们获得了所有三个系统的高质量ILT图像。在其中一个红移z = 1.49的源中，两个活动星系核均以>5σ的显著性被探测到，使其成为红移最高且最暗弱的射电探测DAGN之一。亮温度确认了即使在亚毫央斯基（sub-mJy）源中也存在由活动星系核驱动的辐射。在另外两个系统中，仅探测到一个活动星系核；对于其中一个，新数据约束了一个致密陡谱源的低频谱，表明其形态由喷流-星际介质相互作用驱动，而非伴星系。对于92个源的样本，LoTSS探测率约为24%，显著高于匹配的单个活动星系核（约9-10%），表明DAGN在LoTSS中具有增强的可探测性。结论：低频亚角秒射电观测提供了一种高效、不受尘埃影响的方法来探测和刻画DAGN。这项先导研究为即将到来的全天约0.3角秒分辨率的iLoTSS巡天以及未来的SKA观测建立了基准。
英文摘要：
Context: Dual active galactic nuclei (DAGN) - systems of two accreting supermassive black holes at kpc-scale separations - trace galaxy mergers and are the progenitors of gravitational-wave sources targeted by pulsar timing arrays and the upcoming Laser Interferometer Space Antenna. However, their radio properties remain poorly constrained, particularly at high redshift. Aims: We demonstrate the detectability of high-redshift DAGN at 144 MHz through sub-arcsec imaging of the LOFAR Two-metre Sky Survey (LoTSS) and characterize their low-frequency radio properties. Methods: We cross-matched 92 spectroscopically confirmed DAGN (z > 0.3, projected separation r_p < 30 kpc) with the LoTSS DR2 catalog and reprocessed international LOFAR telescope (ILT) data for three systems (0.59 < z < 2.39), achieving ~0.3 arcsec resolution at 144 MHz. Multi-frequency analysis and brightness-temperature diagnostics were used to investigate the radio emission. Results: We obtained high-quality ILT images for all three systems. In one source at z = 1.49, both AGN are detected at >5 sigma, making it one of the highest-redshift and faintest radio-detected DAGN. Brightness temperatures confirm AGN-powered emission even in sub-mJy sources. In the other two systems only one AGN is detected; for one, the new data constrain the low-frequency spectrum of a compact steep-spectrum source, indicating that its morphology is driven by jet-ISM interaction rather than the companion galaxy. For the 92 objects sample, the LoTSS detection rate is ~24%, significantly higher than for matched single AGN (~9-10%), suggesting an enhanced detectability of DAGN in the LoTSS. Conclusions: Low-frequency sub-arcsec radio observations provide an efficient, dust-unbiased method to detect and characterize DAGN. This pilot study establishes a benchmark for the forthcoming all-sky ~0.3 arcsec iLoTSS survey and future SKA observations.
