Blasting away a dwarf galaxy: The "tail" of ESO 324-G024

TL;DR

This study uses radio observations to analyze the dwarf galaxy ESO 324-G024, revealing its disrupted morphology likely caused by ram pressure stripping and determining its position relative to Centaurus A's radio lobe.

Contribution

It provides new insights into the interaction between a dwarf galaxy and a giant radio galaxy, especially regarding the galaxy's morphology and its spatial relation to the radio lobe.

Findings

ESO 324-G024 shows a distorted HI morphology indicating external forces.

Ram pressure stripping is the most probable cause of the HI tail.

ESO 324-G024 is likely located behind the northern radio lobe of Centaurus A.

Abstract

We present Australia Telescope Compact Array radio data of the dwarf irregular galaxy ESO 324-G024 which is seen in projection against the giant, northern lobe of the radio galaxy Centaurus A (Cen A, NGC 5128). The distorted morphology and kinematics of ESO 324-G024, as observed in the 21 cm spectral line emission of neutral hydrogen, indicate disruptions by external forces. We investigate whether tidal interactions and/or ram pressure stripping are responsible for the formation of the HI tail stretching to the northeast of ESO 324-G024 with the latter being most probable. Furthermore, we closely analyze the sub-structure of Cen A's polarized radio lobes to ascertain whether ESO 324-G024 is located in front, within or behind the northern lobe. Our multi-wavelength, multi-component approach allows us to determine that ESO 324-G024 is most likely behind the northern radio lobe of Cen A. This result helps to constrain the orientation of the lobe, which is likely inclined to our line of sight by approximately 60 degrees if NGC 5128 and ESO 324-G024 are at the same distance.