Chandra Observations of a 1.9 kpc Separation Double X-ray Source in a Candidate Dual AGN Galaxy at z=0.16

TL;DR

This study presents Chandra X-ray observations of a galaxy with a 1.9 kpc separation double X-ray source, supporting the identification of a dual AGN system initially suggested by optical spectral features.

Contribution

It introduces a new systematic method combining optical spectroscopy and X-ray imaging to identify promising dual AGN candidates.

Findings

Detection of two X-ray sources with matching spatial and orientation offsets.

Evidence suggesting the galaxy hosts a Compton-thick dual AGN.

Potential alternative explanation involving AGN jets.

Abstract

We report Chandra observations of a double X-ray source in the z=0.1569 galaxy SDSS J171544.05+600835.7. The galaxy was initially identified as a dual AGN candidate based on the double-peaked [O III] emission lines, with a line-of-sight velocity separation of 350 km/s, in its Sloan Digital Sky Survey spectrum. We used the Kast Spectrograph at Lick Observatory to obtain two longslit spectra of the galaxy at two different position angles, which reveal that the two AGN emission components have not only a velocity offset, but also a projected spatial offset of 1.9 kpc/h70 on the sky. Chandra/ACIS observations of two X-ray sources with the same spatial offset and orientation as the optical emission suggest the galaxy most likely contains Compton-thick dual AGN, although the observations could also be explained by AGN jets. Deeper X-ray observations that reveal Fe K lines, if present, would distinguish between the two scenarios. The observations of a double X-ray source in SDSS J171544.05+600835.7 are a proof of concept for a new, systematic detection method that selects promising dual AGN candidates from ground-based spectroscopy that exhibits both velocity and spatial offsets in the AGN emission features.