Work

The diverse morphologies and evolution of low-luminosity edge-brightened radio galaxies

Year: 2026

Type: article

Abstract: ABSTRACT Fanaroff–Riley class I (FRI) radio galaxies show centre-brightened emission from disrupted lower power jets, while traditionally more luminous class II (FRIIs), are edge-brightened, with relativistic jets terminating in hotspots. Population studies of radio-loud AGN (RLAGN) with low frequency, deep, wide-field surveys have revealed FRII-like radio structures at lower luminosities. We present the first high-resolution morphological investigation of a representative LOw Frequency ARray (LOFAR)-selected sample of low-luminosity FRIIs, to determine whether this new population is physically distinct from traditional high-luminosity FRIIs. Using new 1.5-GHz Jansky Very Large Array observations for a sample of 19 low-luminosity FRIIs, from the LOFAR Two Metre Sky Survey Data Release 1, with luminosities up to three orders of magnitude lower than the typical FR break ($L_{150} = 10^{26}$ W Hz$^{-1}$). We examine the compact features and perform spectral index analysis to identify hotspots, cores, and signatures of restarting or remnant activity. We find a higher prevalence of cores and a comparable number of hotspots in the low-luminosity FRII sample compared to a randomly selected sample of luminous ($L_{150}\gt 10^{26}$ W Hz$^{-1}$) FRIIs selected from the same parent LOFAR sample. Approximately 32 per cent of low-luminosity FRIIs show restarting or remnant behaviour, while ${\sim} 32$ per cent are active FRIIs with compact hotspots. Our results show that FRII source dynamics occur at low-radio luminosities, but reinforce earlier conclusions that the population of low-luminosity edge-brightened RLAGN is highly diverse. Binary morphological classifications should be used cautiously as a first step towards more nuanced investigations of the complexity of jet life cycles and evolution.

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/stag894

Authors: B Barkus, J H Croston, B Mingo, M J Hardcastle, G Gürkan, V H Mahatma

Institutions: University of Hertfordshire, The Open University, Commonwealth Scientific and Industrial Research Organisation, University of Cambridge

Language: English

Topic: Galaxies: Formation, Evolution, Phenomena

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,046