Discovery of a Radio-Selected z ~ 6 Quasar

TL;DR

This paper reports the discovery of a rare radio-selected quasar at redshift approximately 6, highlighting the importance of radio surveys in identifying high-redshift quasars that optical surveys may miss.

Contribution

It presents the second known radio-selected z ~ 6 quasar, demonstrating the effectiveness of combining optical and radio data for high-redshift quasar detection.

Findings

The quasar is optically faint but radio-bright with high radio-loudness.

It was identified through matching SDSS optical data with VLA radio data.

The quasar's optical colors fall outside existing survey selection criteria.

Abstract

We present the discovery of only the second radio-selected, z ~ 6 quasar. We identified SDSS J222843.54+011032.2 (z=5.95) by matching the optical detections of the deep Sloan Digital Sky Survey (SDSS) Stripe 82 with their radio counterparts in the Stripe82 VLA Survey. We also matched the Canadian-France-Hawaiian Telescope Legacy Survey Wide (CFHTLS Wide) with the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey but have yet to find any z ~ 6 quasars in this survey area. The discovered quasar is optically-faint, z = 22.3 and M_{1450} ~ -24.5, but radio-bright, with a flux density of f$_{1.4GHz, peak}$ = 0.31mJy and a radio-loudness of R ~ 1100 (where R = f_{5GHz}/f_{2500}). The i-z color of the discovered quasar places it outside the color selection criteria for existing optical surveys. We conclude by discussing the need for deeper wide-area radio surveys in the context of high-redshift quasars.