Abstract
High angular resolution CO(2-1) and (1-0) observations are reported from the central region of the Magellanic-type irregular galaxy NGC 4214. CO(2-1) spectra were obtained with a beam size of 13'' (340 pc at D=5.4 Mpc) toward 20 positions. At eight positions, emission was detected from a molecular cloud complex with a size of 1000 pc x 700 pc (at the 0.7 K km s(-1) contour) and a mass of a few similar to 10(7) M.. The I-CO(2-1)/I-CO(1-0) line intensity ratio is 0.4, indicating emission from optically thick subthermally excited lines. Comparing virial masses with masses deduced from the integrated CO intensities yields an NH2/I-CO conversion factor, which is a few times the standard Galactic value of 2.3 10(20) (cm(2) K km s(-1))(-1). On the basis of radial velocity, the huge CO complex is resolved into a western, a central, and an eastern component. The radial velocities, 298, 308, and 305 km s(-1), demonstrate that the E-W velocity change across the central bar is not smooth on linear scales <1 kpc. A prominent loop of H alpha emission (diameter: similar to 250 pc) is found at the interface between the western and eastern complex. A narrow linewidth and a lack of associated H alpha emission indicates that the western CO complex is in a quiescent state. The eastern region, being located close to the starburst knot at the optical center of the galaxy, exhibits broader CO lines and intense H alpha emission and must form massive stars.