A blazar in the epoch of reionization

TL;DR

This paper reports the discovery of a high-redshift blazar at z=7, providing insights into early Universe black hole growth, jet activity, and their role in galaxy evolution during reionization.

Contribution

It presents the first detailed multi-wavelength characterization of a z=7 blazar, revealing implications for early black hole growth and the population of jetted sources in the early Universe.

Findings

Discovery of a z=7 blazar with a ~7x10^8 Msun black hole.

Implications for the prevalence of jetted quasars at high redshift.

Support for jet-enhanced or obscured super-Eddington accretion in early black hole growth.

Abstract

Relativistic jets are thought to play a crucial role in the formation and evolution of massive galaxies and supermassive black holes. Blazars, which are quasars with jets aligned along our line of sight, provide insights into the jetted population and have been observed up to redshifts of z=6.1. Here, we report the discovery and multi-wavelength characterization of the blazar VLASS J041009.05-013919.88 at z=7 (Universe's age ~750 Myr), powered by a ~7x10^8 Msun black hole. The presence of this high-redshift blazar implies a large population of similar but unaligned jetted sources in the early Universe. Our findings suggest two possible scenarios: in one, the jet in J0410-0139 is intrinsically low-power but appears highly luminous due to relativistic beaming, suggesting that most UV-bright quasars at this redshift host jets. Alternatively, if J0410-0139 represents an intrinsically powerful radio source, there should be hundreds to thousands of radio-quiet quasars at z~7 with properties similar to J0410-0139, a prediction in tension with observed quasar densities based on their UV luminosity function. These results support the hypothesis that rapid black hole growth in the early Universe may be driven by jet-enhanced or obscured super-Eddington accretion, potentially playing a key role in forming massive black holes during the epoch of reionization.