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