Astronomy and Astrophysics, volume 294, 835-854 (1995/2-3)
Physical properties of the OMC-2 and OMC-3 cores from CS and C18O observations.
CASTETS A. and LANGER W.D.
Abstract (from CDS):
We have investigated the properties of the OMC-2 and OMC-3 cores in the Orion giant molecular cloud using high spatial and spectral resolution observations of several transitions of the 13CO, C18O, C32S and C34S molecules taken with the SEST telescope. The OMC-2 core consists of one clump (22M☉) with a radius of 0.11pc surrounded by a cluster of 11 discrete infrared sources. The H2 column density and volume density in the center of this clump are 2x1022cm–2 and 9x105cm–3 respectively. From a comparison between physical parameters derived from C18O and C32S observations we conclude that the molecular envelope around the core has been completely removed by these sources and that only the very dense gas is left. OMC-3 shows a more complex elongated structure in C18O and CS than OMC-2. The C32S and C34S maps show that the denser region can be separated into at least three sub-cores of roughly equal sizes (radius≃0.13pc), with n(H2)=6x105cm–3, and a mass of 10M☉(from C32S). The very different masses obtained for the central core from C18O and C32S (55 and 12M☉respectively) indicate that a massive envelope is still present around the very dense sub-cores. We report the first detection of several molecular outflows in OMC-3. The presence of an IRAS source and the first detection of these outflows confirm that star formation is going on in OMC-3. Based on the different physical properties of these regions compared with OMC-1, OMC-2 appears to be in an intermediate evolutionary stage between OMC-1 and OMC-3.