CO survey toward starless cores

It is found that the peak intensity and line width of ^13^CO are roughly correlated with those of CS, suggesting that the outer envelope is kinematically related to the inner dense core. Confirming that the ^12^CO lines seldom exhibit deep self-reversal features, whereas this is not unusual for the CS lines, we propose a heuristic model where the outer part is clumpy, but the inner part has a rather smooth density profile, with a uniform temperature and mean density decreasing outward.

We apply three-dimensional radiative transfer calculations to this simple model, demonstrating that the essential observational features of the starless cores are successfully reproduced.