Structure in Small Molecular Clouds: Pedestals and Clumping
NAVAL RESEARCH LAB WASHINGTON DC
Pagination or Media Count:
Observations of wings or pedestals from three regions in high-latitude molecular clouds are presented in order to determine the morphology and physical conditions of the gas responsible for this phenomenon. High-sensitivity spectra along 10-25 lines of sight in each region show extended emission in addition to the typical narrow Gaussian emission from cold clumps. The pedestal profiles resemble the wings seen in CO and other molecules in low-luminosity molecular outflow regions such as B335. In the case of the bipolar outflows, the energy required to drive the outflow comes from a young stellar object in contrast, it is virtually certain that the small molecular clouds studied in this paper do not contain any low-mass star formation sites. The data indicate that the pedestal emission is optically thick. Large velocity gradient and LTE analyses data indicate that the narrow-line emission is produced by cold clumps of size 0.2 pc and density several times, while the pedestal emission is produced by gas with perhaps an order of magnitude less density. Adjacent spectra often reveal a pedestal which increases in antenna temperature until it resembles a narrow Gaussian line typical of clump emission. This change in spectral shape occurs over length scales of a few hundredths of a parsec and may represent the transition region between a dense clump and its less dense outer region.