2025A&A...699A.338H

The LOw Frequency ARray Two-metre Sky Survey second data release (LoTSS DR2) covers 27% of the northern sky and contains around four million radio sources. The development of this catalogue involved a large citizen science project (Radio Galaxy Zoo: LOFAR), and more than 116 000 resolved sources went through visual inspection. We took a subset of sources with a flux density above 75 mJy and an angular size of 90″ or greater, yielding a total of 9985 sources, or ∼10% of the visually inspected sources. We classified these by visual inspection in terms of broad source type (e.g. Fanaroff-Riley class I or II, narrow or wide-angle tail, relaxed double), noticeable features (wings, visible jets, banding, filaments), environmental features (cluster environment, merger, diffuse emission). Our specific aim was to search for features linked to jet precession, such as a misaligned jet axis, curvature, and multiple hotspots. This combination of features and morphology allowed us to detect increasingly fine-grained sub-populations of interesting or unusual sources. We find that 28% of sources show evidence of one or more precession indicators, which could make them candidates for hosting close binary supermassive black holes. Potential precession signatures occur in sources of all sizes and luminosities in our sample but appear to favour more massive host galaxies. Our work greatly expands the sample size and parameter space of searches for precession signatures in powerful jetted sources. This work also showcases the diversity of large bright radio sources in the LOFAR surveys, whether or not precession indicators are present.