The nature of nearby counterparts to intermediate-redshift luminous compact blue galaxies. III. Interferometric observations of neutral atomic and molecular gas

We present the results of a Very Large Array (VLA) and Owens Valley Radio Observatory Millimeter Wavelength Array (OVRO MMA) follow-up to our single-dish surveys of the neutral atomic and molecular gas in a sample of nearby luminous compact blue galaxies (LCBGs). These luminous, blue, high surface brightness, starbursting galaxies were selected using criteria similar to those used to define LCBGs at higher redshifts. The surveys were undertaken to study the nature and evolutionary possibilities of LCBGs, using dynamical masses and gas depletion timescales as constraints. Here we present nearly resolved VLA H I maps of four LCBGs, as well as results from the literature for a fifth LCBG. In addition, we present OVRO MMA maps of CO(J = 1-0) in two of these LCBGs. We have used the resolved H I maps to separate the H I emission from target galaxies and their companions to improve the accuracy of our gas and dynamical mass estimates. For this subsample of LCBGs, we find that the dynamical masses measured with the single-dish telescope and interferometer are in agreement. However, we find that we have overestimated the mass of H I in two galaxies by a significant amount, possibly as much as 75%, when compared to the single-dish estimates. These two galaxies have companions within a few arcminutes; we find that our single-dish and interferometric measurements of H I masses are in reasonable agreement for galaxies with more distant companions. Our CO( J = 1-0) maps, despite long integration times, were faint and barely resolved, making analysis difficult, except to verify the central concentration of the molecular gas. The H I velocity fields indicate that all five galaxies are clearly rotating, yet distorted, likely due to recent interactions. Our measurements of the gas and dynamical masses of LCBGs point toward evolution into low-mass galaxies such as dwarf ellipticals, irregulars, and low-mass spirals, consistent with studies of LCBGs at higher redshifts.