CS MULTITRANSITIONAL STUDIES OF DENSITY DISTRIBUTION IN STAR-FORMING REGIONS .1. THE NGC-2071 REGION

The NGC 2071 molecular cloud was observed in the J = 2 --> 1, 5 --> 4, 6 --> 5, and 7 --> 6 transitions of the CS molecule with resolutions of 11"-24". The emission in all transitions peaks strongly at the IRS 1 position. The data are best described by a spherically symmetric gas distribution centered on IRS 1 with a density of 3.0 x 10(6)(r/0.01 pc)-1.3 cm-3 surrounding a central cavity 0.01 pc in radius. In addition, high-velocity (approximately 10 km s-1) wing emission is seen in both the J = 2 --> 1 and 7 --> 6 lines, which had better signal-to-noise ratios than the other two lines. The bipolar morphology is clearly seen in the CS J = 2 --> 1 high-velocity emission, but the CS 7 --> 6 high-velocity emission is unresolved. Both appear to come from dense gas (n > 10(5) cm-3) in the molecular outflow. The morphology of the CS emission is in good agreement with dust continuum emission but is strikingly different from the pattern of NH3 emission. Chemical differentiation of the two molecules must be present in the source. The agreement between CS and dust emission suggests that CS is a better tracer of gas near young stellar objects than NH3.