A luminous quasar at a redshift of z = 7.085

TL;DR

This paper reports the discovery of a luminous quasar at redshift 7.085, providing new insights into the state of the intergalactic medium less than a billion years after the Big Bang.

Contribution

It presents the first detailed observation of a quasar at redshift 7.085, extending the observational frontier beyond previous limits and probing the early universe's reionization.

Findings

Quasar at z=7.085 with luminosity 6.3x10^13 L_Sun

Black hole mass of 2x10^9 M_Sun

Smaller ionized near zone indicating higher neutral hydrogen fraction

Abstract

The intergalactic medium was not completely reionized until approximately a billion years after the Big Bang, as revealed by observations of quasars with redshifts of less than 6.5. It has been difficult to probe to higher redshifts, however, because quasars have historically been identified in optical surveys, which are insensitive to sources at redshifts exceeding 6.5. Here we report observations of a quasar (ULAS J112001.48+064124.3) at a redshift of 7.085, which is 0.77 billion years after the Big Bang. ULAS J1120+0461 had a luminosity of 6.3x10^13 L_Sun and hosted a black hole with a mass of 2x10^9 M_Sun (where L_Sun and M_Sun are the luminosity and mass of the Sun). The measured radius of the ionized near zone around ULAS J1120+0641 is 1.9 megaparsecs, a factor of three smaller than typical for quasars at redshifts between 6.0 and 6.4. The near zone transmission profile is consistent with a Ly alpha damping wing, suggesting that the neutral fraction of the intergalactic medium in front of ULAS J1120+0641 exceeded 0.1.