Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) XXII. Chandra observations of narrow-line quasar candidates at z>6

Understand

We report on Chandra X-ray observations of four narrow-line quasar candidates at z~6, selected from the SHELLQs project, based on the Subaru Hyper Suprime-Cam survey.

• These objects are characterised by narrow (FWHM<310 km/s), luminous (>1e44 erg/s) Lya and faint UV continuum (M_1450 = -22 - -21), prompting us to examine whether they are obscured luminous AGN at the epoch of reionization.
• However, none of these objects were detected by Chandra, giving an upper limit to their rest-frame 2-10 keV luminosity (Lx) of 2e44 erg/s (2 sigma), assuming a spectral slope Gamma=2.
• Subsequent rest-frame optical spectroscopy of these objects by the JWST-NIRSpec, presented in a companion paper, show weak broad Balmer emission at the base of narrow cores.