A VLBA-resolved Jet Associated with Super-Eddington Accretion in a Radio-loud Quasar at $z=3.4$

TL;DR

This study presents the first resolved parsec-scale jet in a high-redshift super-Eddington quasar, revealing relativistic jet properties and implications for early galaxy evolution.

Contribution

It provides the first VLBA-resolved jet in a super-Eddington quasar at z=3.4, demonstrating sustained large-scale collimation during super-Eddington accretion.

Findings

Resolved a 745 pc jet in a high-z super-Eddington quasar.

Detected relativistic jet speed of at least 0.19c.

Indicates jets can be sustained over 10^3-10^4 years in super-Eddington phase.

Abstract

We report the detailed jet properties of eROSITA Final Equatorial Depth Survey (eFEDS) J084222.9+001000 (hereafter ID830), a radio-loud super-Eddington quasar at $z=3.4351$, revealed by Very Long Baseline Array (VLBA) observations at 1.6 GHz, 4.9 GHz, and 8.2 GHz. Thanks to the high spatial resolution of the VLBA, we successfully resolve a parsec-scale core-jet structure of ID830, and find a well-collimated jet extending over $\approx 745$ pc, making it the most distant and one of the very few currently known radio-loud quasars with a resolved jet associated with super-Eddington accretion. The physical scale and evolutionary track of ID830 differs markedly from the low-$z$ analogues, such as nearby radio-luminous high-Eddington narrow-line Seyfert 1 galaxies, suggesting that this source represents a distinct high-$z$ population compared to previously known samples, with important implications for AGN feedback in early galaxy evolution. We also find that the jet has a relativistic speed of $v \gtrsim 0.19c$ and a modest viewing angle of $\phi \lesssim 79^\circ$ to the line of sight, although its emission is not significantly Doppler-boosted ($\delta \sim 1$). This provides the first evidence that such a relativistic and collimated jet can be produced over several hundred parsecs in the super-Eddington phase, lasting for at least $10^{3\text{-}4}$ yr. Our results call for further theoretical and numerical studies to understand the physical processes required to sustain such large-scale collimation in super-Eddington accretion, which remains a missing piece.