Optical BVI imaging and H i synthesis observations of the dwarf irregular Galaxy ESO 364-G029

Abstract

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 I 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 I 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 I flux FH 1 = 23.1 ± 1.2 Jy km s-1, yielding a total H I mass MH I = (6.4 ± 1.7) × 108 M⊙ (for a distance D = 10.8 ± 1.4 Mpc) and a total H I mass-to-blue-luminosity ratio MH I/L B = (0.96 ± 0.14) M⊙/LB,⊙0 (distance independent). The Hi data suggest a very complex small-scale H I 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 I bears little resemblance to the optical. © ESO 2007.