Dense Cores in the Orion Molecular Cloud

We have used the Heinrich Hertz submillimeter telescope to measure the J = 3-2 and J = 2-1 lines of 12C16O and 12C18O, and the J = 3-2 line of 13C16O toward 125 high-density cores in the prominent S-shaped feature in L1640. We have also measured the (J,K) = (1,1) and (2,2) inversion transitions of NH3 from these sources. These results have been used to determine kinetic temperatures, H2 densities, and column densities. Estimates of the stability of these cores are made. Comparisons are also made with other nearby star formation regions such as the Taurus clouds. Sources in the northern part of the region surveyed have larger line widths, kinetic temperatures, Tk, and higher ratios of the J = 3-2 to J = 2-1 lines of C18O. It is likely that these sources are heated externally. Except for cores in the southern part of this cloud, Tk exceeds 10 K, the value found for dark dust clouds. The average density for all cores is ~3 × 104 cm-3. Orion KL is an extraordinary source, with much larger Tk, local density, and column density than any other source in our sample.