Enhanced Star Formation Activity of Extreme Jellyfish Galaxies in Massive Clusters and the Role of Ram Pressure Stripping

Jellyfish galaxies are an excellent tool to investigate the short-term effects of ram pressure stripping (RPS) on star formation in cluster environments. It has been thought that the star formation activity of jellyfish galaxies may depend on the host-cluster properties, but previous studies have not yet found a clear correlation. In this study, we estimate the Hα-based star formation rates (SFRs) of five jellyfish galaxies in massive clusters (σv,cl ≳ 1000 km s−1) at z ∼ 0.3−0.4 using Gemini GMOS/IFU observations to explore the relationship. Combining our results with those in the literature, we find that the star formation activity of jellyfish galaxies shows a positive correlation with their host-cluster velocity dispersion as a proxy of cluster mass and dynamical states. We divide the jellyfish galaxy sample into two groups with strong and weak RPS signatures using a morphological class. In the phase-space diagram, the jellyfish galaxies with strong RPS features show a higher SFR and a stronger central concentration than those with weak RPS features. We estimate their SFR excess relative to the star formation main sequence (starburstiness; RSB = SFR/SFRMS(z)) and the density of the surrounding intracluster medium (ICM) using scaling relations with the cluster velocity dispersion. As a result, the starburstiness of jellyfish galaxies with strong RPS signatures clearly exhibits positive correlations with cluster velocity dispersion, ICM density, and strength of ram pressure. This shows that the relation between RPS and star formation activity of jellyfish galaxies depends on the host-cluster properties and strength of the ram pressure.