CCS OBSERVATIONS OF THE PROTOSTELLAR ENVELOPE OF B335

摘要

We present single-dish and interferometric spectral line observations of CCS at 22 GHz toward the core of B335, a classical example of a young protostellar region. We combined the VLA and DSN 70 m observations to produce high-resolution (6″ and 12″) channel maps at 0.04 km s~(-1) velocity intervals. These maps image for the first time the collapsing envelope around the protostar. These show that CCS emission arises primarily from the outer parts of the collapsing envelope down to half the infall radius and that CCS is clumpy throughout the core. LVG excitation analysis indicates that X(CCS) is ～3 X 10~(-9) in the outer envelope and less than 5 X 10~(-11) in the center of the infall region. The absence of CCS in the interior could be due to time-dependent chemical evolution. The velocity structure supports the evidence for inside-out collapse and the high-velocity features are consistent with accretion onto a rotating central disk. The asymmetric clumpy distribution of CCS emission implies that the physical conditions are not spherically symmetric, and that the gas falling onto the circumstellar disk may be episodic.