LoTSS jellyfish galaxies: I. Radio tails in low redshift clusters

Context. The cluster environment has a strong impact on galaxy star formation, as seen by the fact that clusters host proportionally more red, passive galaxies relative to the field. Ram pressure stripping may drive this environmental quenching by directly stripping cold gas from galactic disks. In some cases, ram pressure stripping gives rise to 'jellyfish galaxies', observed with clear 'tentacles' of stripped gas extending beyond the optical extent of the galaxy.Aims. In this paper we present a large sample of jellyfish galaxies in low redshift clusters (z<0.05), identified through 120-168 MHz radio continuum from the LOFAR Two-metre Sky Survey (LoTSS).Methods. From a parent sample of 29 X-ray-detected SDSS galaxy clusters and their spectroscopic members, we visually identify 95 star-forming, LoTSS jellyfish galaxies with 144 MHz radio tails. Star formation rates (SFRs) and stellar masses are obtained for all galaxies from SED fits. For each jellyfish galaxy we determine the tail orientation with respect to the cluster centre and quantify the prominence of the radio tails with the 144 MHz shape asymmetry.Results. After carefully accounting for redshift-dependent selection effects, we find that the frequency of jellyfish galaxies is relatively constant from cluster to cluster. LoTSS jellyfish galaxies are preferentially found at small clustercentric radius and large velocity offsets within their host clusters and have radio tails that are oriented away from the cluster centre. These galaxies also show enhanced star formation, relative to both 'normal' cluster galaxies and isolated field galaxies, but generally fall within the scatter of the L-144 MHz-SFR relation.Conclusions. The properties of the LoTSS jellyfish galaxies identified in this work are fully consistent with expectations from ram pressure stripping. This large sample of jellyfish galaxies will be valuable for further constraining ram pressure stripping and star formation quenching in nearby galaxy clusters. We show that LOFAR is a powerful instrument for identifying ram pressure stripped galaxies across extremely wide fields. Moving forward, we will push the search for jellyfish galaxies beyond this initial cluster sample, including a comprehensive survey of the galaxy group regime.

Automated summary

The cluster environment has a significant impact on galaxy star formation, with clusters hosting more red, passive galaxies compared to the field. Ram pressure stripping is believed to drive this environmental quenching by stripping cold gas directly from galactic disks, leading to the formation of 'jellyfish galaxies' with stripped gas extending beyond the galaxy's optical extent. The study identifies a large sample of jellyfish galaxies with enhanced star formation in low redshift clusters through the LOFAR Two-metre Sky Survey (LoTSS), providing valuable insights into ram pressure stripping and star formation quenching in nearby galaxy clusters.