GASP XXXVII: The Most Extreme Jellyfish Galaxies Compared to Other Disk Galaxies in Clusters, an HI Study

TL;DR

This study uses VLA HI imaging to compare extreme jellyfish galaxies with other disk galaxies in clusters, revealing that jellyfish galaxies have higher stellar mass, are closer to cluster centers, and exhibit signs of ram pressure stripping, explaining their unique tails.

Contribution

First HI imaging survey focusing on extreme jellyfish galaxies, linking their properties to cluster environment and stripping processes, with new insights into their mass and location.

Findings

Jellyfish galaxies have higher stellar mass than most disk galaxies.

They are located closer to cluster centers and have higher velocities.

Evidence of ram pressure stripping and extended HI disks was observed.

Abstract

We present the results of a VLA HI imaging survey aimed at understanding why some galaxies develop long extraplanar H$\alpha$ 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 H$\alpha$ 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'x40') and observed bandwidth (6500 km s$^{-1}$). We detect 13 of these 88 spirals, plus one uncatalogued spiral, with HI masses ranging from 1 to 7 $\times$ 10${^9}$ M$_{\odot}$. Many of these detections have extended HI disks, two show direct evidence for ram pressure stripping, while others are possibly affected by tidal forces and/or ram-pressure stripping. We stack the 75 non-detected spiral galaxies and find an average HI mass of 1.9 $\times$ 10$^{8}$ M$_{\odot}$, which given their average stellar mass, implies they are very HI deficient. Comparing the extreme jellyfish galaxies to the other disk galaxies, we find that they have a larger stellar mass than almost all disk galaxies and than all HI detected galaxies, they are at smaller projected distance from the cluster center and at higher relative velocity to the cluster mean than all HI detections and most non-detections. 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.