Multifrequency VLBI Observations of the Broad Absorption Line Quasar J1020+4320: Recently Restarted Jet Activity?

TL;DR

This study uses multifrequency VLBI observations to analyze the compact radio morphology and spectrum of the BAL quasar J1020+4320, revealing evidence of recent jet activity and possible recurrent jet episodes within a short timescale.

Contribution

It provides the first detailed VLBI imaging and spectral analysis of J1020+4320, indicating recent restart of jet activity in a BAL quasar, and links spectral features to jet lifecycle.

Findings

Compact radio structure (~10 pc) observed.

Stable convex spectrum with a peak at 3.2 GHz.

Evidence of relic emission indicating past jet activity.

Abstract

This paper reports very-long-baseline interferometry observations of the radio-loud broad absorption line (BAL) quasar J1020+4320 at 1.7, 2.3, 6.7, and 8.4 GHz using the Japanese VLBI network (JVN) and European VLBI network (EVN). The radio morphology is compact with a size of ~10 pc. The convex radio spectrum is stable over the last decade; an observed peak frequency of 3.2 GHz is equivalent to 9.5 GHz in the rest frame, suggesting an age of the order of ~100 years as a radio source, according to an observed correlation between linear size and peak frequency of compact steep spectrum (CSS) and giga-hertz peaked spectrum (GPS) radio sources. A low-frequency radio excess suggests relic of past jet activity. J1020+4320 may be one of the quasars with recurrent and short-lived jet activity during a BAL-outflowing phase.