FCC046: a candidate gaseous polar ring dwarf elliptical galaxy in the Fornax Cluster

TL;DR

FCC046, a dwarf elliptical galaxy in the Fornax Cluster, hosts a decoupled gaseous ring evidenced by 21cm observations, revealing unique kinematic features and a significant gas reservoir that explains its optical properties.

Contribution

This study reports the first discovery of a gaseous ring with minor-axis rotation around a dwarf galaxy, based on 21cm observations of FCC046.

Findings

Discovery of a ~10^7 solar mass HI cloud around FCC046.

Detection of a gaseous ring with decoupled kinematics from stellar motion.

Explanation of optical properties through the gas reservoir.

Abstract

FCC046 is a Fornax Cluster dwarf elliptical galaxy. Optical observations have shown that this galaxy, besides an old and metal-poor stellar population, also contains a very young centrally concentrated population and is actively forming stars, albeit at a very low level. Here, we report on 21cm observations of FCC046 with the Australia Telescope Compact Array (ATCA) which we conducted in the course of a small survey of Fornax Cluster early-type dwarf galaxies. We have discovered a ~10^7 Mo HI cloud surrounding FCC046. We show that the presence of this significant gas reservoir offers a concise explanation for this galaxy's optical morphological and kinematical properties. Surprisingly, the HI gas, as evidenced by its morphology and its rotational motion around the galaxy's optical major axis, is kinematically decoupled from the galaxy's stellar body. This is the first time such a ring of gaseous material in minor-axis rotation is discovered around a dwarf galaxy.