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CO in the Magellanic type irregular galaxy NGC 4214

Becker, R., Henkel C., Bomans D.J., Wilson T.L.
GKSS Forschungszentrum, Institut für Physik, Maz-Plank-Strasse, D-21502 Geestacht, Germany
Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
Sternwarte der Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany
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 Mpc) toward 20 positions. At eight positions, emission was detected from a molecular cloud complex with a size of 1000 pc 700 pc (at the 0.7 K kms contour) and a mass of a few . The 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 a conversion factor, which is a few times the standard Galactic value of (cm K kms ). 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 kms , demonstrate that the E--W velocity change across the central bar is not smooth on linear scales <1 kpc. A prominent loop of H emission (diameter : pc) is found at the interface between the western and eastern complex. A narrow linewidth and a lack of associated H 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 emission and must form massive stars.
Accepted by Astronomy and Astrophysics

Robert Lucas
Thu Mar 9 12:42:24 MET 1995