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Jellyfish galaxies, characterized by long filaments of stripped interstellarmedium extending from their disks, are the prime laboratories to study theoutcomes of ram pressure stripping. At radio wavelengths, they often showunilateral emission extending beyond the stellar disk, and an excess of radioluminosity with respect to that expected from their current star formationrate. We present new 144 MHz images provided by the LOFAR Two-metre Sky Surveyfor a sample of six galaxies from the GASP survey. These galaxies arecharacterized by a high global luminosity at 144 MHz ($6-27\times10^{22}$ WHz$^{-1}$), in excess compared to their ongoing star formation rate. Thecomparison of radio and H$\alpha$ images smoothed with a Gaussian beamcorresponding to $\sim$10 kpc reveals a sub-linear spatial correlation betweenthe two emissions with an average slope $k=0.50$. In their stellar disk wemeasure $k=0.77$, which is close to the radio-to-star formation linearrelation. We speculate that, as a consequence of the ram pressure, in thesejellyfish galaxies the cosmic rays transport is more efficient than in normalgalaxies. Radio tails typically have higher radio-to-H$\alpha$ ratios than thedisks, thus we suggest that the radio emission is boosted by the electronsstripped from the disks. In all galaxies, the star formation rate has decreasedby a factor $\leq10$ within the last $\sim10^8$ yr. The observed radio emissionis consistent with the past star formation, so we propose that this recentdecline may be the cause of their radio luminosity-to-star formation rateexcess.

Walk on the Low Side: LOFAR explores the low-frequency radio emission of GASP jellyfish galaxies