2001AJ....121..727W

We present the first interferometric study of the molecular gas in the metal-poor dwarf starburst galaxy NGC 4214. Our map of the ¹²CO (1-0) emission, obtained at the Owens Valley Radio Observatory's millimeter array, reveals an unexpected structural wealth. We detected three regions of molecular emission in the northwest, southeast, and center of NGC 4214 that are in very different and distinct evolutionary stages (total molecular mass: ∼5.1x10⁶ M_☉). These differences are apparent most dramatically when the CO morphologies are compared with optical ground-based and Hubble Space Telescope imaging: massive star formation has not started yet in the northwestern region; the well-known starburst in the center is the most evolved, while star formation in the southeastern complex has begun more recently. We derive a star formation efficiency of ∼8% for the southeastern complex. Using high-resolution VLA observations of neutral hydrogen (H I) and our CO data, we generated a total gas column density map for NGC 4214 (H I+H₂). No clear correlation is seen between the peaks of H I, CO, and the sites of ongoing star formation. This emphasizes the irregular nature of dwarf galaxies. The H I and CO velocities agree well, as do the Hα velocities. In total, we cataloged 14 molecular clumps in NGC 4214. Our results from a virial mass analysis are compatible with a Galactic CO-to-H₂ conversion factor for NGC 4214 (lower than what is usually found in metal-poor dwarf galaxies).