# Interacting galaxy NGC4656 and its unusual dwarf companion

## TL;DR

This study investigates the properties and dynamics of the galaxy NGC4656 and its dwarf companion NGC4656UV, revealing it as a dark-matter dominated, low surface brightness galaxy with signs of metal-poor gas accretion.

## Contribution

It provides detailed kinematic and metallicity analysis of NGC4656UV, establishing it as a distinct galaxy rather than a tidal dwarf, and highlights evidence of gas accretion processes.

## Key findings

- NGC4656UV is a dark-matter dominated LSB dwarf galaxy.
- Evidence of metal-poor gas accretion onto both galaxies.
- NGC4656UV is a separate galaxy, not a tidal dwarf.

## Abstract

We studied the nearby edge-on galaxy NGC4656 and its dwarf low surface brightness companion with the enhanced UV brightness, NGC4656UV, belonging to the interacting system NGC4631/56. Regular photometric structure and relatively big size of NGC4656UV allows to consider this dwarf galaxy as a separate group member rather than a tidal dwarf. Spectral long-slit observations were used to obtain the kinematical parameters and gas-phase metallicity of NGC4656UV and NGC4656. Our rough estimate of the total dynamical mass of NGC4656UV allowed us to conclude that this galaxy is the dark-matter dominated LSB dwarf or ultra diffuse galaxy. Young stellar population of NGC4656UV, as well as strong local non-circular gas motions in NGC4656 and the low oxygen gas abundance in the region of this galaxy adjacent to its dwarf companion, give evidence in favour of the accretion of metal-poor gas onto the discs of both galaxies.