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Session 20 - Molecular Clouds, Dense Cores, and Protostars.
Display session, Monday, January 15
North Banquet Hall, Convention Center
L1498 is a classical example of a dense quiescent pre-protostellar core We use single dish and interferometric observations of CCS at 22 amp; 93 GHz, interferometric observations of CS(2-1) at 98 GHz and single dish observations of ^12CO, ^13CO amp; C^18O (1-0) to analyse its structure. The high spectral resolution (0.008 km s^-1) CCS maps obtained with the DSN 70 m show an elongated egg shaped structure possibly rotating with axis at 30^\circ position angle. Channel maps at 0.04 to 0.05 km s^-1 separation with angular resolution 12\arcsec are presented for all interferometer observations. In the VLA maps the 22 GHz CCS emission is resolved into arcs to the SE and NW of center. One interpretation of this distribution is that CCS emission originates in a torus around the central NH_3 emitting region. The OVRO maps of the 93 GHz CCS and CS(2-1) emission show small scale condensations located inside the arcs detected by the 22 GHz CCS emission which roughly marks the 10^4 cm^-3 density boundary. The differences in the distribution of the large scale CCS and NH_3 emissions and the small scale structures in the CCS 93 GHz and CS(2-1) emissions may be a result of density and time dependent chemical evolution.
This research was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
