Shapley Supercluster Survey: ram-pressure stripping versus tidal interactions in the Shapley supercluster

We present two new examples of galaxies undergoing transformation in the Shapley supercluster core. These low-mass galaxies are members of the two clusters SC 1329-313 and SC 1327-312 z similar to 0.049). Integral-field spectroscopy complemented by imaging in the bands and in H alpha narrow band is used to disentangle the effects of tidal interaction (TI) and ram-pressure stripping (RPS). In both galaxies, SOS 61086 and SOS 90630, we observe one-sided extraplanar ionized gas extending respectively similar to 30 and similar to 41 kpc in projection from their discs. The galaxies' gaseous discs are truncated, and the kinematics of the stellar and gas components are decoupled, supporting the RPS scenario. The emission of the ionized gas extends in the direction of a possible companion for both galaxies suggesting a TI. The overall gas velocity field of SOS 61086 is reproduced by ad hoc N-body/hydrodynamical simulations of RPS acting almost face-on and starting similar to 250 Myr ago, consistent with the age of the young stellar populations. A link between the observed gas stripping and the cluster-cluster interaction experienced by SC 1329-313 and A3562 is suggested. Simulations of ram pressure acting almost edge-on are able to fully reproduce the gas velocity field of SOS 90630, but cannot at the same time reproduce the extended tail of outflowing gas. This suggests that an additional disturbance from a TI is required. This study adds a piece of evidence that RPS may take place in different environments with different impacts and witnesses the possible effect of cluster-cluster merger on RPS.