The bases of extragalactic radio jets

Abstract

Using deep transverse resolved radio and multi-waveband observations, I investigate the dynamics and energetics of the inner jets of selected 3CRR radio galaxies. High dynamic range (DR ≳ 10⁴:1) LOFAR HBA total intensity and spectral images allow a deep look at the oldest radio plasma in the sources. The anomalous tail to the east and a tight loop to the west of 3C 83.1B are revealed, and we show for the first time the counterjet in the BL Lac object 3C 371. We also report for the first time the detection of a compact component at the bend in the main jet at about 12 kpc from the radio core in 3C 264 and interpret this as evidence of transverse stratification with a fast inner jet (spine) embedded in a slower outer flow (layer). The inner jets in our sample are well resolved and there is good correspondence between features of the jet observed at all frequencies. Our estimate of τ_syn = 4.2×10⁷ yrs, for synchrotron lifetime in 3C 83.1B suggest that relativistic electrons created in and around the central engine could travel the entire ∼ 25 kpc length of the inner jets within their lifetime for bulk velocities of v_bulk > 0.05c if there is no reacceleration or adiabatic losses. We measure an intrinsic speed of 0.42c (Γ_jet = 1.1) for 3C 264 which constrains the jet viewing angle θ to assume relatively large values (52^o ≲ θ ≲ 74^o), and when compared with the higher initial VLBI jet velocities of ∼ 0.99c (Γ = 7) for the inner 300–400 pc, a deceleration of the order of a factor 2 from the initial parsec-scale jet can be inferred. Our observations reveal double asymmetric radio knots in the inner jets of 3C 371 and the values we find for the radiative lifetime (a few 10⁵ yrs) suggests that the jets in 3C 371 are relatively young compared with the other sources studied here. Future work suggested on this sample is described in Chapter 8.

Date of Award	27 Sept 2022
Original language	English
Awarding Institution	University of Bristol
Supervisor	Mark Birkinshaw (Supervisor) & Martin J. Hardcastle (Supervisor)