The MeerKAT Fornax Survey V. H i kinematics and Fornax cluster membership of the dwarf galaxy ESO 358-60 (2503.05262v1)

Abstract: The MeerKAT Fornax Survey (MFS) is a large survey project mapping the HI in the Fornax cluster. Most of the cluster members detected in HI show significant signs of interaction with the intra-cluster medium or other galaxies. The galaxy ESO 358-60 however stands out as its large HI disk appears regular and undisturbed. A possible explanation for this undisturbed disk is that the galaxy is not in Fornax. We analyze the HI distribution within and around ESO 358-60 based on the MFS observations. We visually inspect the low resolution data in order to study the HI disk from the center to its outskirts and look for low column density gas that could reveal recent interactions. We then construct a detailed parameterization of the HI disk by fitting a tilted ring model to the high resolution data cube. We use the fitted rotational velocity to place the galaxy on the baryonic Tully-Fisher relationship. By equating the galaxy's HI and 3.6 $\mu$m fluxes to the thus retrieved baryonic mass, we obtain a redshift independent distance. Our modeling confirms the regularity of the HI disk in ESO 358-60 but also shows that the galaxy contains a significant line of sight warp and contains radial motions, of the order of 10 km s$^{-1}$, that cover the extent of the optical disk. From the modeling we obtain a velocity V${\rm flat} = $48.1 $\pm$ 1.4 km s$^{-1}$ for the best fit rotation curve. This leads to a distance from the baryonic Tully-Fisher relation of 9.4 $\pm$ 2.5 Mpc,$\sim$ 10 Mpc less than the distance to the Fornax cluster. This distance not only fits better with V${\rm flat}$ but also with the overall HI distribution of low mass galaxies and the fact that the galaxy appears undisturbed and reasonably symmetric. At 9.4 Mpc ESO 358-60 cannot be a member of the Fornax cluster but is a foreground field galaxy.