Ram-pressure stripped radio tails detected in the dynamically active environment of the Shapley Supercluster

TL;DR

This study detects and analyzes radio tails caused by ram-pressure stripping in galaxies within the Shapley Supercluster, revealing how cluster interactions influence galaxy evolution through magnetic field and gas dynamics.

Contribution

It provides detailed multi-band radio and spectroscopic analysis of ram-pressure stripped tails, linking them to cluster interactions and magnetic field behavior.

Findings

Radio tails are tens of kiloparsecs long and caused by ram pressure.

Radio spectral index analysis supports in situ star formation, electron stripping, or shock excitation as powering mechanisms.

Cluster interactions enhance ram pressure, affecting galaxy and intergalactic medium dynamics.

Abstract

We study the radio continuum emission of four galaxies experiencing ram-pressure stripping in four clusters of the Shapley supercluster at redshift z~0.05. Multi-band (235-1367 MHz) radio data, complemented by integral-field spectroscopy, allow us to detect and analyse in detail the non-thermal component both in the galaxy discs and the radio continuum tails. Three galaxies present radio continuum tails which are tens of kiloparsecs long. By deriving the radio spectral index in the inner and outer tails and comparing our findings with the distribution of the extraplanar ionised gas and the results of N-body/hydrodynamical simulations, we demonstrate that these tails are caused by the ram pressure which, together with the ionised gas, sweeps the magnetic field from the galaxy discs. We suggest that the radio continuum emission in these tails can be differently powered by (i) in situ star formation; (ii) relativistic electrons stripped from the disc; (iii) shock excitation or a combination of them. All the ram-pressure stripped galaxies are found in environments where cluster-cluster interactions occurred and/or are ongoing thus strongly supporting the thesis that cluster and group collisions and mergers may locally increase the ram pressure and trigger hydrodynamical interactions between the intracluster medium and the interstellar medium of galaxies.