GASP - XVII. Hi imaging of the jellyfish galaxy JO206: gas stripping and enhanced star formation

We present VLA Hi observations of JO206, a prototypical ram-pressure-stripped galaxy in the GASP sample. This massive galaxy (M-*= 8.5x10(10) M-circle dot) is located at a redshift of z= 0.0513, near the centre of the low-mass galaxy cluster, IIZw108 (sigma similar to 575kms(-1)). JO206 is characterized by a long tail (>= 90kpc) of ionized gas stripped away by ram pressure. We find a similarly long Hi tail in the same direction as the ionized gas tail and measure a total Hi mass of 3.2x10(9) M-circle dot. This is about half the expected Hi mass given the stellar mass and surface density of JO206. A total of 1.8x10(9) M-circle dot (60percent) of the detected Hi is in the gas-stripped tail. An analysis of the star formation rate shows that the galaxy is forming more stars compared to galaxies with the same stellar and Hi mass. On average we find an Hi gas depletion time of similar to 0.5Gyr which is about four times shorter than that of normal' spiral galaxies. We performed a spatially resolved analysis of the relation between star formation rate density and gas density in the disc and tail of the galaxy at the resolution of our Hi data. The star formation efficiency of the disc is about 10times higher than that of the tail at fixed Hi surface densities. Both the inner and outer parts of JO206 show an enhanced star formation compared to regions of similar Hi surface density in field galaxies. The enhanced star formation is due to ram-pressure stripping during the galaxy's first infall into the cluster.