Finding binary active galactic nuclei by the centroid shift in imaging surveys

TL;DR

This paper proposes a novel method to identify binary active galactic nuclei by detecting centroid shifts in imaging surveys caused by non-synchronous variability, enabling large-scale detection in future surveys.

Contribution

It introduces a new technique leveraging centroid shifts for binary AGN detection, suitable for large-scale surveys like LSST.

Findings

Simulations show hundreds of observations needed for detection.

Method is promising for future large-scale surveys.

Potential to identify a large sample of binary AGNs.

Abstract

The census of binary active galactic nuclei (AGNs) is important in order to understand the merging history of galaxies and the triggering of AGNs. However, there is still no efficient method for selecting the candidates of binary AGNs. The non-synchronous variations of the two AGNs in one binary system will induce the shift of the image centroid. Since the astrometric error is normally much smaller than the angular resolution of telescopes, it is possible to detect such shifts even in the unresolved system via multi-epoch observations. We perform some simulations and find that hundreds of observations are required to discover compact binary AGNs. This method is suitable for the future large-scale surveys, e.g., the Large Synoptic Survey Telescope, and it might lead to a large sample of binary AGNs with a 1-2 yr survey.