用于核外和亚千秒级双活动星系核的变星测量法（VODKA）：甚长基线阵搜索双或核外类星体及小尺度喷流
Varstrometry for Off-nucleus and Dual Sub-kpc AGN (VODKA): Very Long Baseline Array Searches for Dual or Off-nucleus Quasars and Small-scale Jets
AI总结：
本研究利用甚长基线阵对23个经变星测量法筛选的射电明亮候选体开展系统性观测，识别出潜在秒差距尺度双类星体等目标，验证了该方法在发现相关候选体方面的潜力。
摘要：
在等级结构形成范式中，双活动超大质量黑洞和核外活动超大质量黑洞预计较为常见，但由于对角分辨率的严格要求，在秒差距尺度上识别它们仍是一项挑战。我们利用甚长基线阵（VLBA）开展了一项系统性研究，对23个射电明亮的双类星体及核外类星体候选体进行了检测。这些目标是通过一种来自Gaia的新型天体测量技术（“varstrometry（变星测量法）”）筛选出来的，旨在识别（亚）千秒差距尺度上的双类星体或核外类星体。在这些类星体中，有8个要么表现出多个射电成分，要么在VLBA位置与Gaia位置之间存在显著（>3σ）的位置偏移。根据其形态，表现出多个射电成分的3个候选体的射电辐射很可能源自小尺度喷流。在其余5个存在显著VLBA-Gaia偏移的候选体中，3个被确定为秒差距尺度上的潜在双类星体，1个可能归因于小尺度喷流，最后1个候选体的起源仍不明确。我们探究了观测到的VLBA-Gaia偏移的其他可能解释。我们没有发现千秒差距尺度上光学喷流的证据，也没有发现宿主星系对Gaia天体测量噪声存在任何污染的迹象；坐标系不对齐也不太可能是造成我们观测到的偏移的原因。我们的研究凸显了变星测量法在发现双类星体或核外类星体候选体方面的潜力，并强调需要进一步的确认和研究，以验证并了解这些引人关注的候选体。
英文摘要：
Dual and off-nucleus active supermassive black holes are expected to be common in the hierarchical structure formation paradigm, but their identification at parsec scales remains a challenge due to strict angular resolution requirements. We conduct a systematic study using the Very Long Baseline Array (VLBA) to examine 23 radio-bright candidate dual and off-nucleus quasars. The targets are selected by a novel astrometric technique ("varstrometry") from Gaia, aiming to identify dual or off-nucleus quasars at (sub)kilo-parsec scales. Among these quasars, 8 exhibit either multiple radio components or significant (>3$σ$) positional offsets between the VLBA and Gaia positions. The radio emission from the three candidates which exhibit multiple radio components is likely to originate from small-scale jets based on their morphology. Among the remaining five candidates with significant VLBA-Gaia offsets, three are identified as potential dual quasars at parsec scales, one is likely attributed to small-scale jets, and the origin of the last candidate remains unclear. We explore alternative explanations for the observed VLBA-Gaia offsets. We find no evidence for optical jets at kilo-parsec scales, nor any contamination to Gaia astrometric noise from the host galaxy; misaligned coordinate systems are unlikely to account for our offsets. Our study highlights the promise of the varstrometry technique in discovering candidate dual or off-nucleus quasars and emphasizes the need for further confirmation and investigation to validate and understand these intriguing candidates.
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