A Radio-Quiet Radio Galaxy at High Redshift

Abstract.

We report on observations of CXO52, a Type 2 quasar at redshift z = 3.288 identified as a hard X-ray source in a deep observation with the Chandra X-ray Observatory. Optical and near-infrared Keck spectroscopy of CXO52 show high-ionization, relatively-narrow emission lines with velocity widths $\sim 1000$ km s^-1 and flux ratios similar to a Seyfert 2 galaxy or radio galaxy. The latter are the only class of high-redshift, Type 2 luminous AGN which have been extensively studied to date. Unlike radio galaxies, however, CXO52 is radio quiet, remaining undetected in deep radio observations, $f_{\rm 4.8GHz} < 40 \mu$Jy. This discovery marks amongst the first high-redshift, radio-quiet Type 2 quasars identified to date. Such systems are expected from unification models of active galaxies and long-thought necessary to explain the X-ray background.