GASP. XXI. Star Formation Rates in the Tails of Galaxies Undergoing Ram Pressure Stripping

Using MUSE observations from the GASP survey, we study 54 galaxies undergoing ram pressure stripping (RPS) and spanning a wide range in galaxy mass and host cluster mass. We use this rich sample to study how the star formation rate (SFR) in the tails of stripped gas depends on the properties of the galaxy and its host cluster. We show that the interplay between all the parameters involved is complex and that there is not a single, dominant one in shaping the observed amount of SFR. Hence, we develop a simple analytical approach to describe the mass fraction of stripped gas and the SFR in the tail, as a function of the cluster velocity dispersion, galaxy stellar mass, clustercentric distance, and speed in the intracluster medium. Our model provides a good description of the observed gas truncation radius and of the fraction of SFR observed in the stripped tails, once we take into account the fact that the star formation efficiency in the tails is a factor of ∼5 lower than in the galaxy disk, in agreement with GASP ongoing H i and CO observations. Finally, we estimate the contribution of RPS to the intracluster light (ICL) and find that the average SFR in the tails of ram pressure stripped gas is ∼ 0.22 ,M⊙ yr-1 per cluster. By extrapolating this result to evaluate the contribution to the ICL at different epochs, we compute an integrated average value per cluster of ∼4 × 109 M of stars formed in the tails of RPS galaxies since z ∼ 1.