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：我们提出了一种名为GOTHIC（图增强迭代爬山算法）的新算法，用于检测双核星系——该算法能够判断一幅给定的星系图像是否包含两个或更多个紧密靠近的核。我们的目标是发现星系中双核或多核的活动星系核样本。虽然星系并合现象普遍存在，但双活动星系核的探测却十分罕见。这类探测至关重要，因为它们有助于我们理解超大质量黑洞双星的形成、超大质量黑洞的增长以及多核系统中的活动星系核反馈效应。因此，需要一种算法对现有成像数据进行系统性巡天，以发现双核星系和双活动星系核。我们已在已知双核星系样本上测试了GOTHIC，随后将其应用于约一百万颗SDSS DR16星系样本（红移范围约为0至0.75，并具有可用光谱数据）。在此样本中，我们检测到159个双活动星系核，其中包含2个三重活动星系核系统。我们的结果表明，双活动星系核并不普遍，三重活动星系核则更为罕见。双核星系的颜色-星等图（u-r）显示，随着核间距缩小及活动星系核比例增加，恒星形成过程受到抑制，这种抑制在位于红序极端区域的双/三重活动星系核星系中尤为显著。