Thomas A. Pauls

Small Scale Clumping in the Orion Molecular Cloud

The results of new maps of the Orion Molecular Cloud in lines of NH3 and H2CO are presented. The angular resolution of these maps varies from 1’ (for the 211 – 212 line of H2CO at 14.5 GHz, using the 100-m telescope) to 2.2” x 1.6” (for the (3,3) line of NH3, using the VLA). There are two quiescent molecular clouds NE and south of the BN/KL region. The contours of vibrationally excited H2 (H2*) straddle the position of these clouds; we conclude that the physical confinement of the H2* between these clouds explains the observed distribution of the H2*contours. The quiescent clouds themselves have H2 densities of ≥106 cm-3 and masses close to the Jeans masses. From our VLA data, the kinetic temperature of the 5.5 km s-1 (so called “Hot Core”) feature is ∼200 K, the size of the main peak is ∼3”, and the maximum is centered on IRc4. We believe that this gas is heated by IRc4. An analysis of 100-m spectra for six metastable lines gives roughly consistent, but considerably more uncertain values of temperature and size. Our VLA data show that the Plateau feature (△V½ ≥30 km s-1) has a main beam brightness temperature of 70 K, about twice the estimate from 100-m data. This discrepancy could be caused by a core-halo structure. The Plateau emission consists of two peaks; these are not centered on any single compact IR source.