Radio continuum observations of the Leo Triplet at 2.64 GHz

TL;DR

This study used radio continuum observations at 2.64 GHz to investigate magnetic fields in the Leo Triplet, finding weak magnetic fields and identifying a tidal dwarf galaxy candidate with a detectable magnetic component.

Contribution

First radio continuum mapping of the Leo Triplet at 2.64 GHz, providing magnetic field estimates and identifying a tidal dwarf galaxy candidate with magnetic properties.

Findings

Magnetic field strength in the Triplet does not exceed 2.8 μG.

Extended emission is below the detection limit, indicating very weak or absent large-scale magnetic fields.

A tidal dwarf galaxy candidate hosts a detectable magnetic field with a non-zero ordered component.

Abstract

Aims. The magnetic fields of the member galaxies NGC 3628 and NGC 3627 show morphological peculiarities, suggesting that interactions within the group may be caused by stripping of the magnetic field. This process could supply the intergalactic space with magnetised material, a scenario considered as a possible source of intergalactic magnetic fields (as seen eg. in the Taffy pairs of galaxies). Additionally, the plumes are likely to be the tidal dwarf galaxy candidates. Methods. We performed radio continuum mapping observations at 2.64 GHz using the 100-m Effelsberg radio telescope. We obtained total power and polarised intensity maps of the Triplet. These maps were analysed together with the archive data, and the magnetic field strength (as well as the magnetic energy density) was estimated. Results. Extended emission was not detected either in the total power or the polarised intensity maps. We obtained upper limits of the magnetic field strength and the energy density of the magnetic field in the Triplet. We detected emission from the easternmost clump and determined the strength of its magnetic field. In addition, we measured integrated fluxes of the member galaxies at 2.64 GHz and estimated their total magnetic field strengths. Conclusions. We found that the tidal tail hosts a tidal dwarf galaxy candidate that possesses a detectable magnetic field with a non-zero ordered component. Extended radio continuum emission, if present, is weaker than the reached confusion limit. The total magnetic field strength does not exceed 2.8 {\mu}G and the ordered component is lower than 1.6 {\mu}G.