paper

A Neighboring Dwarf Irregular Galaxy Hidden by the Milky Way

arXiv:astro-ph/0308080 · doi:10.1086/378908

Abstract

We have obtained VLA and optical follow-up observations of the low-velocity H I source HIZSS 3 discovered by Henning et al. (2000) and Rivers (2000) in a survey for nearby galaxies hidden by the disk of the Milky Way. Its radio characteristics are consistent with this being a nearby (~1.8 Mpc) low-mass dwarf irregular galaxy (dIm). Our optical imaging failed to reveal a resolved stellar population, but did detect an extended H-alpha emission region. The location of the H-alpha source is coincident with a partially-resolved H I cloud in the 21-cm map. Spectroscopy confirms that the H source has a similar radial velocity to that of the H I emission at this location, and thus we have identified an optical counterpart. The H emission (100 pc in diameter and with a luminosity of ergs s) is characteristic of a single H II region containing a modest population of OB stars. The galaxy's radial velocity and distance from the solar apex suggests that it is not a Local Group member, although a more accurate distance is needed to be certain. The properties of HIZSS 3 are comparable to those of GR 8, a nearby dIm with a modest amount of current star formation. Further observations are needed to characterize its stellar population, determine the chemical abundances, and obtain a more reliable distance estimate.

Scheduled for the November 2003 issue of the Astronomical Journal

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