NCSA Astronomy Digital Image Library
Project Abstract and Description

Observations of the Clumpy Shell of the L1551 Bipolar Outflow

R.L. Plambeck and R.L. Snell

Contact: Dick Plambeck
Email: plambeck@fringe.berkeley.edu

Number of images in project: 2

References: 1995ApJ...446..234P

Abstract

We have studied two regions along the edges of the L1551-IRS5 bipolar outflow where unusually bright "high velocity" CS emission is seen. These regions are 4' west and 2' east of IRS5; a line drawn through them passes directly through IRS5, along the axis of the highly collimated ionized jets from the star.

We mapped the J=2--1 CS emission from these two spots with 7" angular resolution, and obtained single dish spectra of 12 molecular transitions toward both regions. The maps show that the high velocity gas is an integral part of a clumpy shell of molecular gas along the periphery of the bipolar lobes. Typical clumps have CS brightness temperatures of 5--7 K, linewidths of approximately 0.8 km/s, and diameters down to our resolution limit of approximately 1000 AU. One of the CS clumps in the L1551-2E field is coincident with IRAS source L1551NE. The clumps are estimated to have kinetic temperatures of 20--30 K and densities of approximately 4 x 10^5 per cubic cm. The total mass of high velocity gas toward each region is roughly 0.02 solar masses; individual clumps have masses as small as 0.001 solar masses. The chemical abundances of SO, CS, and NH3 may be unusually large in these regions.

The data suggest that low velocity (V < 15 km/s) shocks propagate into the swept-up molecular shell at these locations. Apparently the collimated high velocity jets from IRS5 are degraded into a broader, lower velocity wind before impacting these regions.

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