DES J0454-4448: Discovery of the First Luminous z > 6 Quasar from the Dark Energy Survey

TL;DR

This paper reports the discovery and spectroscopic confirmation of the first luminous quasar at redshift greater than 6 from the Dark Energy Survey, demonstrating the survey's potential to find high-redshift quasars for studying the early universe.

Contribution

It introduces a new method for identifying high-redshift quasars using DES multi-colour photometry and reports the discovery of a luminous z=6.10 quasar, expanding the sample for early universe studies.

Findings

Discovered and confirmed a luminous z=6.10 quasar from DES data.

The quasar's properties are consistent with existing luminosity functions at z~6.

The survey is expected to find over 50 new quasars at z>6 in future observations.

Abstract

We present the first results of a survey for high redshift, z $\ge$ 6, quasars using izY multi-colour photometric observations from the Dark Energy Survey (DES). Here we report the discovery and spectroscopic confirmation of the $\rm z_{AB}, Y_{AB}$ = 20.2, 20.2 (M$_{1450}$ = $-$26.5) quasar DES J0454$-$4448 with an emission line redshift of z = 6.10$\pm$0.03 and a HI near zone size of 4.6 $\pm$ 1.7 Mpc.The quasar was selected as an i-band drop out with i$-$z = 2.46 and z$_{AB} < 21.5$ from an area of $\rm \sim$300 deg$^2$. It is the brightest of our 43 candidates and was identified for follow-up spectroscopically solely based on the DES i$-$z and z$-$Y colours. The quasar is detected by WISE and has $W1_{AB} = 19.68$. The discovery of one spectroscopically confirmed quasar with 5.7 $<$ z $<$ 6.5 and z$_{AB} \leq$ 20.2 is consistent with recent determinations of the luminosity function at z $\sim$ 6. DES when completed will have imaged $\rm \sim$5000 deg$^2$ to $Y_{AB}$ = 23.0 ($5\sigma$ point source) and we expect to discover $>$ 50-100 new quasars with z $>$ 6 including 3-10 with z $>$ 7 dramatically increasing the numbers of quasars currently known that are suitable for detailed studies including determination of the neutral HI fraction of the intergalactic medium (IGM) during the epoch of Hydrogen reionization.