Six more quasars at redshift 6 discovered by the Canada-France High-z Quasar Survey

TL;DR

This paper reports the discovery of six new quasars at redshift around 6, expanding the known population with lower luminosities, and demonstrates the effectiveness of optical selection methods for high-redshift quasar detection.

Contribution

The study introduces six newly discovered quasars at z>5.9 with lower luminosities, highlighting the survey's ability to probe fainter quasar populations at high redshift.

Findings

Discovered six quasars at z>5.9 with lower luminosities.

Optical selection remains effective for high-redshift quasar detection.

The least luminous quasar has M_1450=-22.21, below the luminosity function break.

Abstract

We present imaging and spectroscopic observations for six quasars at z>5.9 discovered by the Canada-France High-z Quasar Survey (CFHQS). The CFHQS contains sub-surveys with a range of flux and area combinations to sample a wide range of quasar luminosities at z~6. The new quasars have luminosities 10 to 75 times lower than the most luminous SDSS quasars at this redshift. The least luminous quasar, CFHQS J0216-0455 at z=6.01, has absolute magnitude M_1450=-22.21, well below the likely break in the luminosity function. This quasar is not detected in a deep XMM-Newton survey showing that optical selection is still a very efficient tool for finding high redshift quasars.