Parsec-scale properties of the peculiar gigahertz-peaked spectrum quasar 0858-279

TL;DR

This study uses multi-frequency VLBI observations to analyze the parsec-scale structure, magnetic fields, and shock formation in the peculiar gigahertz-peaked spectrum quasar 0858-279, revealing detailed jet and core properties.

Contribution

It provides the first detailed VLBI analysis of the high-redshift quasar 0858-279, including core-jet structure, magnetic field estimates, and evidence of shock formation, advancing understanding of such sources.

Findings

Resolved core-jet structure and located a compact core.

Estimated magnetic field strength of about 1 G in the jet.

Detected high Faraday rotation measures over 6000 rad/m^2.

Abstract

We performed multi-frequency studies on the gigahertz-peaked spectrum high-redshift quasar 0858-279. Initially, the source presented itself in the early VLBI images as a very peculiar resolved blob. We observed the quasar with the VLBA at 1.4-24 GHz in a dual-polarization mode. The high spatial resolution and the spectral index maps enabled us to resolve the core-jet structure and locate a weak and compact core by its inverted spectrum. The dominant jet component 20 parsecs away from the core was optically thin above 10 GHz and opaque below it. We also estimated an uncommonly strong magnetic field in the bright jet feature, which turned out to be around 1 G. The Faraday rotation measure maps revealed high RM values over 6000 rad/m^2. Additionally, these maps allowed us to follow the magnetic field direction in the bright jet feature being perpendicular to the propagation direction of the jet. All the results strongly indicated the formation of a shock wave in the dominant component arising from an interaction with the surrounding matter. Using the proposed hypothesis and the core shift approach, we discovered that the magnetic field in the core region is of the order of 0.1 G.