Limitations of the 'standard test model'

The 'standard' model used so far has been useful in the study of the observability of such objects but suffers from numerous simplifications when used to attempt to model a real cloud. Some of the changes that might be needed to model a real cloud are

• A more realistic density profile for the disk. This would probably mean making the disk considerably denser than the surrounding material.

• A different disk shape. The disk has been considered as the volume of revolution of a rectangle. In reality it is much more likely to be an oblate ellipsoid.

• A different velocity profile in the disk. The disk used here is simultaneously collapsing and rotating. It may be better to stop the collapse at the edge of the disk and then allow only rotation in the disk. The rotation should possibly not have a sharp outer velocity edge in the manner that the model used here has had. It is however, not entirely clear from theoretical work how the infall is accreted onto a disk.

• Some small rotation in the envelope might be necessary since the angular momentum in the disk must come from somewhere originally. It may be that this initial rotation is so small that it is unimportant though.