Shocking Tails in the Major Merger Abell 2744

TL;DR

This paper reports the discovery of rare jellyfish galaxies in Abell 2744, showing that the high-pressure environment of a major cluster merger can rapidly transform galaxies and induce star formation in stripped gas tails.

Contribution

It provides observational evidence linking galaxy transformation and star formation to the dynamic environment of a major cluster merger, supported by multi-wavelength data.

Findings

Identification of four jellyfish galaxies with star-forming tails

Evidence of galaxy transformation linked to merger shock fronts

Starburst and AGN features indicating rapid galaxy evolution

Abstract

We identify four rare "jellyfish" galaxies in Hubble Space Telescope imagery of the major merger cluster Abell 2744. These galaxies harbor trails of star-forming knots and filaments which have formed in-situ in gas tails stripped from the parent galaxies, indicating they are in the process of being transformed by the environment. Further evidence for rapid transformation in these galaxies comes from their optical spectra, which reveal starburst, poststarburst and AGN features. Most intriguingly, three of the jellyfish galaxies lie near ICM features associated with a merging "Bullet-like" subcluster and its shock front detected in Chandra X-ray images. We suggest that the high pressure merger environment may be responsible for the star formation in the gaseous tails. This provides observational evidence for the rapid transformation of galaxies during the violent core passage phase of a major cluster merger.