Geometric nature of the SMA3 continuum-emitting structure

Determine whether the 250 GHz continuum emission from S255N SMA3 traces a geometrically thin, circular protostellar disk or a geometrically thick protostellar envelope, thereby establishing whether the inclination inferred from the continuum major-to-minor axis ratio is physically valid.

Background

The paper infers an inclination angle of approximately 42.7 degrees for SMA3 by treating the deconvolved major and minor axes of its 250 GHz continuum emission as the projected axes of a geometrically thin, circular disk. Because SMA3 is expected to be a very young protostellar system, the authors explicitly question whether this geometric assumption is valid.

Resolving whether the continuum emission originates in a thin disk or a geometrically thick envelope is important because the inferred inclination is subsequently used to de-project the jet velocity and length and to estimate its dynamical age. The issue remains unresolved by the observations presented.