We present a novel algorithm to detect double nuclei galaxies (DNG) called GOTHIC (Graph BOosted iterated HIll Climbing) - that detects whether a given image of a galaxy has two or more closely separated nuclei. Our aim is to detect samples of dual or multiple active galactic nuclei (AGN) in galaxies. Although galaxy mergers are common, the detection of dual AGN is rare. Their detection is very important as they help us understand the formation of supermassive black hole (SMBH) binaries, SMBH growth and AGN feedback effects in multiple nuclei systems. There is thus a need for an algorithm to do a systematic survey of existing imaging data for the discovery of DNGs and dual AGN. We have tested GOTHIC on a known sample of DNGs and subsequently applied it to a sample of a million SDSS DR16 galaxies lying in the redshift range of 0 to 0.75 approximately, and have available spectroscopic data. We have detected 159 dual AGN in this sample, of which 2 are triple AGN systems. Our results show that dual AGN are not common, and triple AGN even rarer. The color (u-r) magnitude plots of the DNGs indicate that star formation is quenched as the nuclei come closer and as the AGN fraction increases. The quenching is especially prominent for dual/triple AGN galaxies that lie in the extreme end of the red sequence.

翻译：本文提出了一种名为GOTHIC（图增强迭代爬山法）的新型算法，用于检测双核星系（DNG），即判断给定星系图像是否包含两个或更多紧密分离的核。我们的目标是探测星系中成对或多重活动星系核（AGN）的样本。尽管星系合并现象普遍存在，但双AGN的探测却十分罕见。它们的探测至关重要，有助于我们理解超大质量黑洞（SMBH）双星系统的形成、SMBH增长以及在多核系统中的AGN反馈效应。因此，需要一种算法来系统性地梳理现有成像数据，以发现DNGs和双AGN。我们在已知的DNG样本上测试了GOTHIC，随后将其应用于约一百万颗SDSS DR16星系样本（红移范围大致为0至0.75，且具备可用光谱数据）中。在该样本中，我们检测到159个双AGN，其中包含2个三重AGN系统。结果表明，双AGN并不常见，而三重AGN则更为稀有。DNGs的（u-r）色星等图显示，随着核间距减小及AGN比例增加，恒星形成活动受到抑制。这种抑制效应在位于红序极端的双/三重AGN星系中尤为显著。