VLA OBSERVATIONS OF 43-GHZ CONTINUUM AND CS J=1-0 EMISSION FROM ORION-IRC2 AND THE HOT CORE

We have used the VLA to image at 2-arcsec resolution the Orion-IRc2 re gion in 43-GHz continuum and CS(1-0) emission. In the continuum, radio sources I and B are detected together with an extended emission compo nent which peaks at source I. Comparison of this extended component wi th lower frequency data suggests that it is free-free emission from a dusty H II region ionized by source I. The compact CS(1-0) emission or iginates from the hot core, the compact ridge and the western clump. T he hot core component has a line brightness temperature of similar to 150 K, and is optically thick. We derive an abundance for the CS relat ive to H-2 in the hot core of 1.2 x 10(-8), considerably higher than t he previous upper limit based on a single-dish spectral line survey. T he difference can be explained as being due to beam dilution of the ho t core component in the earlier, low-resolution study, and the confusi on of the hot core with emission from the extended ridge. A similar re sult is also suggested for the sulphur-bearing molecules SO and SO2, a nd existing models of sulphur chemistry are unable to reproduce these new abundance estimates. We conclude that models extending to higher t emperatures and densities are required to explain these data.