UV and H$\alpha$ HST observations of 6 GASP jellyfish galaxies

TL;DR

This study uses high-resolution HST UV and Hα observations to analyze star-forming clumps in the tails and disks of six jellyfish galaxies, revealing detailed structures and signs of ram-pressure stripping.

Contribution

First high-resolution, statistical UVIS/HST imaging of star-forming clumps in jellyfish galaxy tails and disks, enabling detailed analysis of their properties and distribution.

Findings

Bright, compact star-forming regions in stripped tails

Signatures of ram-pressure stripping near galactic disks

Limited detection of star-forming clumps outside tails

Abstract

Star-forming, H$\alpha$-emitting clumps are found embedded in the gaseous tails of galaxies undergoing intense ram-pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a unique opportunity to study star formation under extreme conditions, in the absence of an underlying disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination of broad-band filters and a narrow-band H{\alpha} filter. HST observations are needed to study the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will be used to study the clump scaling relations, the universality of the star formation process and verify whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations, data reduction strategy, and some general results based on the preliminary data analysis: the UVIS high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions of the galaxies and of the substructures in the galaxy disks; we found clear signatures of stripping in regions very close in projection to the galactic disk; the star-forming regions in the stripped tails are extremely bright and compact while we did not detect a significant number of star-forming clumps outside those detected by MUSE. The paper finally presents the development plan for the project.