Small-scale structure of the protostellar collapse candidate B335 imaged in CS J=5-4 emission.
WILNER D.J., MYERS P.C., MARDONES D. and TAFALLA M.
Abstract (from CDS):
We present interferometer observations of CS J=5-4 emission in B335, an isolated round globule generally recognized from single-dish spectral line mapping to be the best candidate for a collapsing protostar. The images, with ∼2".5 (0.003 pc) spatial resolution and 0.13 km.s–1 velocity resolution, show complex structure in the purported infall zone. The emission is dominated by a clumpy conical structure oriented in the east-west direction that we identify with a slow, dense component of the bipolar flow visible on larger size scales. Comparison with the detailed predictions of the inside-out collapse model previously derived from single-dish observations show important discrepancies. The high-resolution CS J=5-4 images show no evidence for infalling material at velocities greater than 0.5 km.s–1 coincident with the protostar that corresponds to emission in the wings of the single-dish spectrum. Instead, the emission at velocities expected for collapse is found to be associated with the outflow lobes, offset from the protostar position. Depletion may diminish the signal from infall of the densest gas. Bright clumps at blueshifted velocities within the outflow may contribute to the asymmetric appearance of optically thick lines observed with beam sizes too large to resolve these small-scale structures.