Redshift, Time, Spectrum - the most distant radio quasars with VLBI

TL;DR

This paper reviews VLBI observations of the most distant radio quasars, revealing their compact structures and suggesting they are young active galactic nuclei, providing insights into early supermassive black hole growth.

Contribution

It presents the first high-resolution VLBI imaging results of the most distant radio quasars, highlighting their young active nuclei and advancing understanding of early universe black hole activity.

Findings

Detection of compact radio structures in distant quasars

Evidence of young active galactic nuclei at high redshift

First VLBI imaging of several of the most distant quasars

Abstract

The highest-redshift quasars are still rare and valuable objects for observational astrophysics and cosmology. They provide important constraints on the growth of the earliest supermassive black holes in the Universe, and information on the physical conditions in their environment. Among the nearly 60 quasars currently known at redshifts z>5.7, only a handful are "strong" emitters in radio continuum. These can be targets of sensitive high-resolution Very Long Baseline Interferometry (VLBI) observations to reveal their innermost structure, down to ~10 pc linear scales. We review the results of our earlier European VLBI Network (EVN) experiments on three of the most distant radio quasars known to date, and give a preliminary report on the EVN detection of a fourth one. The results obtained so far suggest that we see really young active galactic nuclei - not just in a cosmological sense but also in terms of their active life in radio.