# Discovery of a dual active galactic nucleus with ~ 8 kpc separation

## TL;DR

This study reports the discovery of a dual active galactic nucleus separated by approximately 8 kpc, identified through combined mid-infrared, optical, and X-ray observations, demonstrating an effective multi-wavelength approach for such detections.

## Contribution

The paper introduces a novel multi-wavelength method combining mid-IR, optical, and X-ray diagnostics to identify dual AGN in galaxy mergers, improving detection strategies.

## Key findings

- Confirmed dual AGN with Chandra X-ray observations
- Dual AGN separated by 8.3 kpc
- Lower neutral hydrogen absorption than expected

## Abstract

Targeted searches for dual active galactic nuclei (AGN), with separations 1 -- 10 kpc, have yielded relatively few successes. A recent pilot survey by Satyapal et al. has demonstrated that mid-infrared (mid-IR) pre-selection has the potential to significantly improve the success rate for dual AGN confirmation in late stage galaxy mergers. In this paper, we combine mid-IR selection with spatially resolved optical AGN diagnostics from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey to identify a candidate dual AGN in the late stage major galaxy merger SDSS J140737.17+442856.2 at z=0.143. The nature of the dual AGN is confirmed with Chandra X-ray observations that identify two hard X-ray point sources with intrinsic (corrected for absorption) 2-10 keV luminosities of 4*10^41 and 3.5*10^43 erg/s separated by 8.3 kpc. The neutral hydrogen absorption (~10^22 cm^-2) towards the two AGN is lower than in duals selected solely on their mid-IR colours, indicating that strategies that combine optical and mid-IR diagnostics may complement techniques that identify the highly obscured dual phase, such as at high X-ray energies or mid-IR only.