Candidate ram-pressure stripped galaxies in six low-redshift clusters revealed from ultraviolet imaging

TL;DR

This study uses ultraviolet imaging to identify and analyze galaxies undergoing ram-pressure stripping in six low-redshift clusters, revealing new candidates and insights into galaxy infall and evolution within clusters.

Contribution

It presents the first UV-based identification of ram-pressure stripped galaxy candidates in multiple clusters, expanding the known sample and providing new insights into their orientations and infall processes.

Findings

Identified 54 ram-pressure stripping candidates, including 47 new ones.

Confirmed that tail orientations tend to point away from cluster centers.

Spectroscopic data suggest some candidates are in structures along the line of sight.

Abstract

The assembly of galaxy clusters is understood to be a hierarchical process with a continuous accretion of galaxies over time, which increases the cluster size and mass. Late-type galaxies that fall into clusters can undergo ram-pressure stripping, forming extended gas tails within which star formation can happen. The number, location, and tail orientations of such galaxies provide clues about the galaxy infall process, the assembly of the cluster over time, and the consequences of infall for galaxy evolution. Here, we utilise the $\sim$ 0.5 degree diameter circular field of the Ultraviolet Imaging Telescope to image six galaxy clusters at z < 0.06 that are known to contain jellyfish galaxies. We searched for stripping candidates in the ultraviolet images of these clusters, which revealed 54 candidates showing signs of unilateral extra-planar emission, due to ram-pressure stripping. Seven candidates had already been identified as likely stripping based on optical B-band imaging. We identified 47 new candidates through UV imaging. Spectroscopic redshift information is available for 39 of these candidate galaxies, of which 19 are associated with six clusters. The galaxies with spectroscopic redshifts that are not part of the clusters appear to be within structures at different redshifts identified as additional peaks in the redshift distribution of galaxies, indicating that they might be ram-pressure stripped or disturbed galaxies in other structures along the line of sight. We examine the orbital history of these galaxies based on their location in the position-velocity phase-space diagram and explore a possible connection to the orientation of the tail direction among cluster member candidates. The tails of confirmed cluster member galaxies are found to be oriented away from the cluster centre.