Presentation #316.08 in the session AGN and Quasars V.
Distinguishing dual quasars from lensed quasars at high redshift is challenging using only optical imaging and spectroscopic techniques, because both sources have similar spectral properties. We present a comprehensive multi-wavelength analysis of a 0.5 arcsec dual quasar system, which was selected using a new “Varstrometry” technique, at z=2.166. The Hubble Space Telescope (HST) optical spectra and the Gemini near infrared (NIR) spectra confirm that both sources are quasars. The HST and Keck adaptive-optics NIR images reveal the non-detection of the lens galaxy and the faint tidal features. The flux ratios between two sources in the X-ray and radio images are significantly different than those in the optical images. These results suggest that the system is a dual quasar, instead of a lensed quasar. We find that this system is a dual quasar with the smallest projected separation (~3.8kpc) of any known dual quasars at z>1. This discovery demonstrates the effectiveness of the “Varstrometry” technique for systematically detecting kpc off-nucleus and dual quasars at cosmic noon.