The Nature of Nearby Counterparts to Intermediate-Redshift Luminous Compact Blue Galaxies. I. Optical/H I Properties and Dynamical Masses

We present single-dish H I spectra obtained with the Green Bank Telescope, along with optical photometric properties from the Sloan Digital Sky Survey, of 20 nearby (D ≲ 70 Mpc) luminous compact blue galaxies (LCBGs). These ~L*, blue, high surface brightness, starbursting galaxies were selected using the same criteria as were used to define LCBGs at higher redshifts. We find that these galaxies are gas-rich, with M_{H i} ranging from 5 × 10⁸ to 8 × 10⁹ M_☉ and M_{H i}L ranging from 0.2 to 2 M_☉ L, consistent with a variety of morphological types of galaxies. We find that the dynamical masses (measured within R₂₅) span a wide range, from 1 to 1 × 10¹¹ M_☉. However, at least half have dynamical mass-to-light ratios smaller than those of nearby galaxies of all Hubble types, as found for LCBGs at intermediate redshifts. By comparing line widths and effective radii with local galaxy populations, we find that LCBGs are consistent with the dynamical mass properties of Magellanic (low luminosity) spiral galaxies and the more massive irregular and dwarf elliptical galaxies, such as NGC 205.