Discovery of two bright $z\sim5$ quasars with SkyMapper, Pan-STARRS1 and WISE

TL;DR

This paper reports the discovery of two bright quasars at redshift around 5 using combined data from SkyMapper, Pan-STARRS1, and WISE, demonstrating an effective selection and follow-up method for high-redshift quasars.

Contribution

It introduces a new candidate selection method combining WISE with SkyMapper and Pan-STARRS1 data, leading to the discovery of two new bright $z ilde{5}$ quasars.

Findings

Two new bright $z ilde{5}$ quasars discovered.

Candidates selected effectively using combined WISE and optical data.

Quasars ranked among the brightest known at $z>4.5$.

Abstract

We present a search for bright $z\sim5$ quasars using imaging data from SkyMapper Southern Survey, Pan-STARRS1 and the Wide-field Infrared Survey Explorer (WISE). We select two sets of candidates using WISE with optical bands from SkyMapper and alternatively from Pan-STARRS1, limited to a magnitude of $i<18.2$. We follow up several candidates with spectroscopy and find that the four candidates common to both lists are quasars, while others turned out to be cool stars. Two of the four quasars, SMSS J013539.27-212628.4 at $z=4.86$ and SMSS J093032.58-221207.7 at $z=4.94$, are new discoveries and ranked among the dozen brightest known $z>4.5$ QSOs in the $i$-band.