The circumstellar environment of IRAS 05338-0624
Millimeter continuum and spectral line observations with 10", 30", and 60" resolution are used to characterize the structure and chemistry of the gas around the young, embedded star, IRAS 05338-0624. On arcminute scales, emission from dense gas tracers outline an isolated condensation centered on the IRAS source position. The condensation is characterized by a size of ~60", a density of 2 x 10^5 cm^(-3), and a virial mass of 40 M_☉. Interferometric CS J = 2-1 observations show two peaks, one toward the continuum peak and the other toward a position 14" west and 8" south. Single-dish maps of SO, CH_3OH, and SiO show pronounced wing emission to the west of the IRAS source, which interferometer observations reveal to be a compact region of outflow activity. CS emission at redshifted and blueshifted velocities reveals a bipolar outflow oriented with a position angle of 45°, while SiO emission appears to be tracing a fast shock interaction region at the CS red-lobe peak, 14" west and 8" south of the IRAS source. Finally, H^(13)CO^+ emission traces clumps of quiescent gas toward the IRAS source and adjacent to the blue lobe of the outflow. Column densities and molecular fractional abundances are derived to explore the interaction between the surrounding condensation and the young stellar object. We find evidence for gas phase depletions within the overall condensation in several gas tracers (CO, CS, HCN, SO) but not in the region immediately around the young stellar object. Enhanced abundances of SO, CH_3OH, and SiO (by factors of 4, > 100, > 1000, respectively) are observed in the shocked gas; these enhancements may be explained in terms of a nondissociative shock liberating mantle materials that contain some amount of refractory materials, a moderate velocity dissociative shock in which only minor sputtering of Si occurs, or a shock that impacts surrounding material with a range of speeds.
© 1994 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1994 March 25; accepted 1994 June 16. We would like to thank Jocelyn Keene, Tamara Helfer, and John Howe for help with observations. We thank Phil Jewell and the telescope operators of the NRAO 12 meter for their kind assistance as well as Rick Forster, Lanie Dickel and the BIMA observers. We are grateful to our anonymous referee, Gary Fuller, and Ken Tatematsu for helpful comments on this work. This work was sponsored by National Science Foundation grant AST 9314847 and by NASA grant NAGW-3066. G. A. B. acknowledges support from the David & Lucille Packard and Alfred P. Sloan Foundations, and NASA grant NAGW-2297.
Published - 1994ApJ___437__305M.pdf