Dual AGNs on 100 kpc Scales from the Million Quasar Catalog

TL;DR

The study leverages the Million Quasar Catalog (MQC) to assemble a low-redshift sample of dual and multiple AGNs with $r_p<100\,h^{-1}_{70}$ kpc and $|\Delta v|<600\,\mathrm{km\,s^{-1}}$, identifying 178 systems (173 dual AGNs, 4 triplets, 1 quadruplet). Visual inspection of DESI-LS images finds tidal features in about 16% of dual AGNs, with NLAGNs dominating the sample (approximately 71% in dual pairs). A large population of wide-separation pairs ($r_p>10\,h^{-1}_{70}$ kpc) is found (165 systems, 25 tidal), while close pairs reveal scarce sub-10 kpc systems due to resolution and fiber limitations. The results illuminate merger-driven SMBH fueling at various scales, but are tempered by MQC’s inhomogeneous composition; future homogeneous surveys are expected to substantially expand the census and enable more precise demographic and evolutionary studies.

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 173 new dual AGNs, 4 AGN triplets, and 1 AGN quadruplet from the Million Quasars Catalog, all with low redshift ($z < 0.5$), a projected distance ($r_p$) of no more than 100 kpc, and a line-of-sight velocity difference ($|Δv|$) 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 $\sim$16\% of pairs exhibit tidal features. Statistical analyses show an increasing number of dual AGNs with decreasing redshift, with velocity difference primarily at $|Δv| < $ 300 km s$^{-1}$, which is likely an artifact of our selection strategy. The tidal sample peaks as having 13 pairs at 5-20$h^{-1}_{70}$ kpc, but drops to 1 pair $> 55\,h^{-1}_{70}$ kpc. Our study also explores thewide separation ($r_p>10$ kpc) dual AGNs, finding 165 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.

Figures (14)

• Figure 1: DESI$-$LS grz(i) images of each tidal system, showing clear tidal features associated with dual AGNs. Red and blue circles mark the locations of the AGNs. North is up and east is to the left. The field of view (FOV) of each image is labeled at the bottom right corner. The redshifts, $r_p$, and angular separation of each pair are also presented. The pinkish appearance in some images is likely due to incomplete band coverage.
• Figure 1: Mosaic of dual AGN systems. Each triplet of images shows the $grz(i)$-band composite, the corresponding model, and the residual map from DESI Legacy Surveys DR10. The pinkish appearance in some images is likely due to incomplete band coverage.
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