J2102+6015: an Intriguing Radio-loud Active Galactic Nucleus in the Early Universe

TL;DR

This study investigates the high-redshift quasar J2102+6015, revealing its complex structure, lack of Doppler boosting, and potential quasi-periodic positional variations, providing insights into early universe supermassive black hole activity.

Contribution

The paper presents new high-resolution EVN imaging of J2102+6015 at 5 and 22 GHz, offering detailed insights into its structure and variability, which were previously uncharacterized.

Findings

Complex compact structure observed with VLBI

No evidence of Doppler-boosted jets

Quasi-periodic (~3 yr) positional variation detected

Abstract

The powerful high-redshift quasar J2102+6015 (at z=4.575) may provide useful information for studying supermassive black hole growth, galaxy evolution and feedback in the early Universe. The source has so far been imaged with very long baseline interferometry (VLBI) at 2/8 GHz (S/X) bands only, showing complex compact structure. Its total radio spectrum peaks at ~6 GHz in the rest frame. There is no sign of Doppler-boosted jet emission, and the separation of the two major features in its east-west oriented structure spanning ~10 milliarcsec does not change significantly on a timescale longer than a decade. However, VLBI astrometric monitoring observations suggest quasi-periodic (~3 yr) variation in its absolute position. J2102+6015 is presumably a young radio source with jets misaligned with respect to the line of sight. Here we briefly report on our new high-resolution imaging observations made with the European VLBI Network (EVN) at 5 and 22 GHz frequencies in 2021 June, and give an overview of what is currently known about this peculiar distant jetted active galactic nucleus.