GASP XXXVII: The Most Extreme Jellyfish Galaxies Compared with Other Disk Galaxies in Clusters, an H I Study

We present the results of a Very Large Array H I imaging survey aimed at understanding why some galaxies develop long extraplanar Hα tails, becoming extreme jellyfish galaxies. The observations are centered on five extreme jellyfish galaxies optically selected from the WINGS and OMEGAWINGS surveys and confirmed to have long Hα tails through MUSE observations. Each galaxy is located in a different cluster. In the observations, there are in total 88 other spiral galaxies within the field of view (40' × 40') and observed bandwidth (6500 km s^-1). We detect 13 of these 88 spirals, plus one uncataloged spiral, with H I masses ranging from 1 to 7 × 10⁹ M _⊙. Many of these detections have extended H I disks, two show direct evidence for ram pressure stripping, and others are possibly affected by tidal forces and/or ram pressure stripping. We stack the 75 nondetected spiral galaxies and find an average H I mass of 1.9 × 10⁸ M _⊙, which, given their average stellar mass, implies that they are very H I deficient. Comparing the extreme jellyfish galaxies to the other disk galaxies, we find that they are at smaller projected distance from the cluster center, and have a higher stellar mass and higher relative velocity than all other H I detections and most nondetections. We conclude that the high stellar mass allows extreme jellyfish galaxies to fall deeply into the cluster before being stripped, and the surrounding ICM pressure gives rise to their spectacular star-forming tails.