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

Abstract

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 rampressure 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.

Diving deeper into jellyfish: The rich population of jellyfish galaxies in Abell 901/2

“…• We also could not find a strong correlation between ram pressure stripping and AGN (Roman-Oliveira et al 2019).…”

“…We present the results of a systematic search and analysis of 73 ram pressure stripping candidates in the Abell 901/2 multi-cluster system (Roman-Oliveira et al 2019). The sample was selected through visual inspection in the Hubble Space Telescope F606W Figure 1.…”

“…The sample was selected through visual inspection in the Hubble Space Telescope F606W Figure 1. Specific star formation rate versus mass plot (adapted from Roman-Oliveira et al 2019). We represent different JClasses by green star markers according to the legend.…”

“…The WHAN diagram for the Abell 901/2 ram pressure stripping candidates in the left panel and for the public GASP sample in the right panel (adapted fromRoman-Oliveira et al 2019). The markers with a black ring are the galaxies present inPoggianti et al (2017b).…”

Galaxy kinematics across different environments in the RXJ1347−1145 cluster complex

“…Recent results by the STAGES collaboration show signs of star formation enhancement in some cases of RPS detected thanks to the analysis of deep HST photometry and narrowband H α imaging in the Abell 901/902 cluster complex at z∼0.16 (Roman-Oliveira et al 2019). In that work the average log (sS FR) value of RPS-galaxies is ∼0.2 dex higher than that measured for their cluster star-forming mother-sample at a fixed M * .…”