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OMEGA – OSIRIS mapping of emission-line galaxies in A901/2 – V. The rich population of jellyfish galaxies in the multi-cluster system Abell 901/2

Roman-Oliveira, Fernanda V.; Chies-Santos, Ana L.; Rodr�guez Del Pino, Bruno; Arag�n-Salamanca, A.; Gray, Meghan E.; Bamford, Steven P.

OMEGA – OSIRIS mapping of emission-line galaxies in A901/2 – V. The rich population of jellyfish galaxies in the multi-cluster system Abell 901/2 Thumbnail


Fernanda V. Roman-Oliveira

Ana L. Chies-Santos

Bruno Rodr�guez Del Pino

Professor of Astronomy


We present the results of a systematic search and characterisation of galaxies with morphological signatures of ram-pressure stripping, known as jellyfish galaxies, in the multi-cluster system A901/2, at z ∼ 0.165, as part of the OMEGA survey. By visual inspecting ACS/HST F606W images looking for morphological signatures of ram-pressure stripping events in Hα-emitting galaxies, we identify a total of 70 jellyfish candidates. Out of these, 53 are clearly star-forming galaxies and 5 are highly probable AGN hosts, the classification of the remaining galaxies is more uncertain. They have late-type and irregular morphologies and most of them are part of the blue cloud with only 4 being previously classified as dusty reds. The AGN activity is not prominent in the sample and, of the few cases of galaxies hosting AGN, such activity does not seem to be correlated to the gas stripping phenomenon. Our jellyfish galaxy candidates do not have a preferential pattern of motion within the multi-cluster system, although the most compelling cases appear to inhabit the inner regions of the most massive sub-cluster centres. The specific star-formation rate of these galaxies indicates that their star formation activity is enhanced, in contrast with what is observed for the rest of the star-forming galaxy population in the system. Half of the sample is forming stars at a higher rate than the main-sequence for field galaxies and this behaviour is more evident for the most compelling candidates. For some galaxies, the spatially resolved Hα emission appears to be as disturbed and extended as their continuum counterparts. Our findings point towards a scenario where the ram pressure stripping is triggering a period of intense and extended star formation throughout the galaxy while it is also disturbing the morphology. This is the largest sample of jellyfish galaxy candidates found in a single system suggesting that cluster mergers might be the ideal environment for studying ram pressure stripping effects.

Journal Article Type Article
Acceptance Date Dec 10, 2018
Online Publication Date Jan 5, 2019
Publication Date 2019-03
Deposit Date Dec 18, 2018
Publicly Available Date Dec 18, 2018
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 484
Issue 1
Pages 892–905
Keywords galaxies: evolution; galaxies: clusters: general; galaxies: clusters: intra- cluster medium; galaxies: star formation
Public URL
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Additional Information This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record [insert complete citation information here] is available online at:


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