Kinematic and Dynamics of the Galaxy ESO 358-60

Abstract We investigate the velocity field derived from H I measurements of the irregular galaxy ESO 358-60 using the velocity ring model (VRM) method. This technique, which assumes a coplanar disk, allows us to reconstruct coarse-grained maps of both radial and tangential velocity components from the observed line-of-sight velocity field. Such maps reveal that tangential motions dominate the inner regions, while radial motions become increasingly significant toward the outskirts. This kinematic behavior contrasts with that inferred from the tilted ring model (TRM), which suggests that radial motions are more prominent in the intermediate disk and negligible in the outskirts and detects a pronounced warp of approximately 20°, with the inner disk nearly edge on and the outer regions inclined by approximately 60°. In contrast, the VRM analysis finds that the disk exhibits a bar-like structure in its central regions. This interpretation is further supported by the intensity and velocity dispersion maps. To test the origin of the TRM-derived warp, we construct a toy model based on the TRM results and analyze it with the VRM technique, finding evidence that the warp is likely an artifact arising from the TRM’s assumptions. Finally, we estimate the galaxy’s mass using both the standard dark matter halo model and a dark matter disk (DMD) model, where all mass lies in the disk plane. The DMD yields a total mass approximately three times lower and provides a slightly better fit to the rotation curve.