Parsec-scale Jet in the Distant Gigahertz-Peaked Spectrum Quasar PKS 0858-279

TL;DR

This study investigates the parsec-scale jet structure of the distant GPS quasar PKS 0858-279, revealing a core-jet morphology, high Doppler boosting, and synchrotron self-absorption effects through multi-frequency VLBA and RATAN-600 observations.

Contribution

It provides detailed VLBA imaging and analysis of the jet structure and magnetic field in a high-redshift GPS quasar, highlighting its unusual variability and morphology.

Findings

Detected high-amplitude, short-term radio variability.

Revealed a core-jet structure with high Doppler factor.

Confirmed synchrotron self-absorption dominates at low frequencies.

Abstract

The high redshift GPS quasar PKS 0858-279 exhibits the following properties which make the source unusual. Our RATAN-600 monitoring of 1-22 GHz spectrum has detected broad-band radio variability with high amplitude and relatively short time scale. In the same time, the milliarcsecond scale structure observed in a snapshot VLBA survey turned out to be very resolved which is not expected from the fast flux density variations. We performed 1.4-22 GHz VLBA observations of this quasar in 2005-2007. It has revealed a core-jet morphology. A high Doppler factor delta is suggested for the jet, its nature is discussed in this report on the basis of the multi-frequency VLBA and RATAN data collected. Synchrotron self-absorption was confirmed to be dominating at low frequencies, the magnetic field strength of the dominating jet feature is estimated of an order of 0.1*delta mG.