All cosmological models of structure formation predict the existence of a widespread population of dual supermassive black holes in-spiralling inside their common host galaxy, eventually merging and giving rise to intense gravitational waves. These systems can be identified as dual active galactic nuclei (AGNs) at kiloparsec separations, but only very few have been confirmed at z > 0.5. The appearance of multiple AGNs at small angular separations can also be due to gravitational lensing of single AGNs, which are themselves very important systems for many astrophysical topics. Here we present a novel technique, dubbed the Gaia multipeak method, to obtain large and reliable samples of dual/lensed AGN candidates with sub-arcsec separations by looking for AGNs showing multiple peaks in the light profiles observed by the Gaia satellite. All of the Gaia multipeak method-selected sources with high-resolution images (26 from the Hubble Space Telescope archive and 5 from dedicated adaptive-optics-assisted imaging at the Large Binocular Telescope) show multiple components with sub-arcsec separation pointing toward a very high reliability of the method. By sampling separations down to ~2 kpc at z > 1, this method allows us to probe the physical processes that drive the in-spiralling of a pair of supermassive black holes inside a single galaxy.

所有结构形成的宇宙学模型都预测，在它们共同的宿主星系内部存在着大量的双超大质量黑洞螺旋，最终合并并产生强烈的引力波。这些系统可以在千秒差距处被识别为双活动星系核 (AGN)，但在z处只有极少数得到证实 > 0.5。多个活动星系核以小角度间隔出现也可能是由于单个活动星系核的引力透镜效应，这些活动星系核本身对于许多天体物理学主题来说都是非常重要的系统。在这里，我们提出了一种新技术，称为 Gaia 多峰方法，通过在 Gaia 卫星观测到的光剖面中寻找显示多个峰值的 AGN，获得具有亚弧秒间隔的双/透镜 AGN 候选的大量可靠样本。所有盖亚多峰方法选择的高分辨率图像源（26 个来自哈勃太空望远镜档案，5 个来自大型双筒望远镜的专用自适应光学辅助成像）显示多个分量的亚弧秒间隔指向一个非常方法可靠性高。通过在z处采样低至 ~2 kpc 的分离 > 1，这种方法使我们能够探测驱动单个星系内一对超大质量黑洞螺旋化的物理过程。