Multiwavelength investigations of PKS 2300-18: S-shaped radio quasar with precessing jets and double-peaked broad emission-line spectrum

TL;DR

This study presents a comprehensive multiwavelength analysis of the S-shaped radio galaxy PKS 2300-18, revealing jet precession, plasma aging, and complex central activity, shedding light on its dynamic evolution and interaction with the environment.

Contribution

It provides the first detailed multiwavelength investigation of PKS 2300-18, combining radio, X-ray, and optical data with models to understand jet precession and central black hole activity.

Findings

Jet precession period of ~12 Myr.

Maximum plasma age of ~40 Myr.

Detection of a Mpc-scale X-ray halo.

Abstract

S-shaped radio galaxy jets are prime sources for investigating the dynamic interplay between the central active galactic nucleus, the jets, and the ambient intergalactic medium. These sources are excellent candidates for studying jet precession, as their S-shaped inversion symmetry strongly indicates underlying precession. We present a multiwavelength analysis of the giant inversion-symmetric S-shaped radio galaxy PKS 2300-18, which spans 0.76 Mpc. The host is a quasar at a redshift of 0.128, displaying disturbed optical morphology due to an ongoing merger with a companion galaxy. We conducted a broadband radio spectral study using multifrequency data ranging from 183 MHz to 6 GHz, incorporating dedicated observations with the uGMRT and JVLA alongside archival radio data. A particle injection model was fitted to the spectra of different regions of the source to perform ageing analysis, which was supplemented with a kinematic jet precession model. The ageing analysis revealed a maximum plasma age of ~ 40 Myr, while the jet precession model indicated a precession period of ~ 12 Myr. ROSAT data revealed an X-ray halo of Mpc size, and from Chandra the AGN X-ray spectrum was modelled using thermal and power-law components. The optical spectrum displaying double-peaked broad emission lines was modelled, indicating complex broad-line region kinematics at the centre with the possibility of a binary SMBH. We present the results of our multiwavelength analysis of the source, spanning scales from a few light-days to a few Mpc, and discuss its potential evolutionary path.