Dual Active Galactic Nuclei on 100 kpc Scales from the Million Quasar Catalog

Abstract Research on dual active galactic nuclei (AGNs) is crucial for understanding the coevolution of galaxies and supermassive black holes. However, the current number of dual AGNs remains scarce. In this work, we selected 171 new dual AGNs, four AGN triplets, and one AGN quadruplet from the Million Quasars Catalog, all with low redshift ( z &lt; 0.5), a projected distance ( r p ) of no more than 100 kpc, and a line-of-sight velocity difference (∣Δ v ∣) of less than 600 km s −1 , thus supplementing existing low-redshift dual-AGNs demographics. Visual inspection of the optical images from the Dark Energy Spectroscopic Instrument Legacy Survey was performed for each pair, revealing that ∼16% of pairs exhibit tidal features. Statistical analyses show an increasing number of dual AGNs with decreasing redshift, with a velocity difference primarily at ∣Δ v ∣ &lt; 300 km s −1 , which is likely an artifact of our selection strategy. The tidal sample peaks as having 13 pairs at 5–20 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>h</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>70</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> kpc, but drops to one pair at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>&gt;</mml:mo> <mml:mn>55</mml:mn> <mml:mspace width="0.25em"/> <mml:msubsup> <mml:mrow> <mml:mi>h</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>70</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> kpc. Our study also explores the wide separation ( r p &gt; 10 kpc) dual AGNs, finding 164 such systems, with 25 displaying clear tidal features. Furthermore, some extra galaxies, AGNs, and/or their candidates were found in the same regions of the pairs or multiplets, forming interacting systems with these pairs or multiplets.