aDepartment of Geophysics, Beijing University, China
b1. Physikalisches Institut, Universität zn Köln, China
Abstract:
We observed the molecular cloud NGC 2023 in the NH3 rotation-inversion lines NH3(1.1) and NH3(2.2). The hyperfine structures shown in these lines can be advantageously used to derive the physical parameters of the cloud. We re-confirm that the star HD 37903 is the unique exciting source of the cloud and heated dust is the exciting medium. Analysis leads to the conclusion that the star is located on the periphery of the cloud, as in Zuckerman's “blister” model. If HD 37003 originated in NGC 2023, then the star will have existed long enough to blow away the molecular cloud to a distance of 0.1 pc. There may exist clumps of relatively high density in the cloud.