Tidal origin of NGC 1427A in the Fornax cluster

TL;DR

This study uses new HI and optical data to reveal that NGC 1427A's disturbed appearance is due to tidal interactions and merging, rather than ram pressure effects, providing insights into its recent dynamical history.

Contribution

It demonstrates that NGC 1427A's features are primarily caused by tidal interactions and merging, challenging previous ram pressure hypotheses.

Findings

Discovery of a star-less HI tail containing ~10% of the galaxy's atomic gas.

Evidence of extended stellar emission indicating recent tidal disturbance.

NGC 1427A is likely two objects in advanced merging stages.

Abstract

We present new HI observations from the Australia Telescope Compact Array and deep optical imaging from OmegaCam on the VLT Survey Telescope of NGC 1427A, an arrow-shaped dwarf irregular galaxy located in the Fornax cluster. The data reveal a star-less HI tail that contains ~10% of the atomic gas of NGC 1427A as well as extended stellar emission that shed new light on the recent history of this galaxy. Rather than being the result of ram pressure induced star-formation, as previously suggested in the literature, the disturbed optical appearance of NGC 1427A has tidal origins. The galaxy itself likely consists of two individual objects in an advanced stage of merging. The HI tail may be made of gas expelled to large radii during the same tidal interaction. It is possible that some of this gas is subject to ram pressure, which would be considered a secondary effect and imply a northwest trajectory of NGC 1427A within the Fornax cluster.