H i and CO in Blue Compact Dwarf Galaxies: Haro 2 and Haro 4

Abstract

We present Very Large Array H I imaging of two blue compact dwarf galaxies, Haro 2 and Haro 4, and of the spiral galaxy Haro 26, which is projected some 22' southwest of Haro 4. We also show a map of the CO(1-0) distribution of Haro 2 obtained with the Owens Valley Radio Observatory Millimeter Array, as well as derive an upper limit for CO(2-1) emission from Haro 4 obtained with the Caltech Submillimeter Observatory. The H I data of Haro 2 reveal that the kinematical major axis lies perpendicular to the photometric major axis, indicating that the atomic hydrogen rotates about the major axis of the galaxy. This confirms earlier indications based on CCD photometry that Haro 2 is a dust-lane dE rather than a dIrr. We propose that the present neutral and molecular ISM configuration is due to recent gas accretion or a merger. The H I distribution and dynamics of Haro 4 and the neighboring spiral Haro 26 suggest that they are currently undergoing a tidal interaction, reinforcing the notion that interactions play an important role in triggering the star formation witnessed in blue compact galaxies.