Radio-loud active galaxy morphology and host-galaxy properties in the LOFAR Two-Metre Sky Survey Data Release 2

Active galactic nuclei (AGN) are compact regions at the centre of some galaxies that emit radiation across the electromagnetic spectrum. AGN that have large regions of radio emission (also known as radio lobes) that can extend well beyond the visible structure of the host galaxy are known as radio-loud AGN (RLAGN) or radio galaxies. These regions are driven by collimated outflows of plasma from the AGN, known as radio jets, at relativistic speeds on pc to Mpc scales [1,2]. Extended RLAGN can exhibit various morphologies but will most commonly consist of one of two categories established by Fanaroff & Riley (FR) [3]: centre-bright type 1 (FRI) or edge-bright type 2 (FRII). The FR classifications were initially found to correlate with radio luminosity. However, recent surveys have demonstrated that radio luminosity alone does not reliably predict radio morphology. We have devised a new-semi automated method involving ridgeline characterisations to compile the largest known classified catalogue of RLAGN to date with data from the second data release of the Low Frequency Array (LOFAR) Two-Metre Sky Survey (LoTSS DR2). In this work we reassess the FR divide and its cause by examining the physical and host galaxy properties of 3590 FRIIs and 2354 FRIs (at redshift, z ≤ 0.8). Overall, we find the cause of different radio morphologies in this sample to be complex. Considering sources near the FR divide with 10²⁵ ≤ L₁₄₄ ≤ 10²⁶ WHz⁻¹, we find evidence to support inner environment having a role in determining jet disruption. The classified catalogue is publicly available at https://lofar-surveys.org/dr2_release.html to be used for future investigations of RLAGN and their impact on their surroundings.