Optical BVI Imaging and H Synthesis Observations of the Dwarf Irregular Galaxy ESO 364 - G 029

As part of an effort to enlarge the number of well-studied Magellanic-type galaxies, we obtained broadband optical imaging and neutral hydrogen radio synthesis observations of the dwarf irregular galaxy ESO 364-G029. The optical morphology characteristically shows a bar-like main body with a one-sided spiral arm, an approximately exponential light distribution, and offset photometric and kinematic centers. The H  distribution is mildly asymmetric and, although slightly offset from the photometric center, roughly follows the optical brightness distribution, extending to over 1.2 Holmberg radii (where μB = 26.5 mag arcsec−2). In particular, the highest H  column densities closely follow the bar, one-arm spiral, and a third optical extension. The rotation is solid-body in the inner parts but flattens outside of the optical extent. The total H  flux FH i = 23.1 ± 1.2 Jy km s−1, yielding a total H  mass MH i = (6.4 ± 1.7) × 108 M⊙ (for a distance D = 10.8 ± 1.4 Mpc) and a total H  mass-to-blue-luminosity ratio MH i/LB = (0.96 ± 0.14) M⊙/LB,⊙ (distance independent). The H  data suggest a very complex small-scale H  structure, with evidence of large shells and/or holes, but deeper observations are required for a detailed study. Follow-up observations are also desirable for a proper comparison with the Large Magellanic Cloud, where despite an optical morphology very similar to ESO 364-G029 the H  bears little resemblance to the optical.