An Out-of-Plane CO (J = 21) Survey of the Milky Way. Ⅱ. Physical Conditions of Molecular Gas

摘要

The HRG and VHRG are found predominantly along the Sagittarius and Scutum arms, probably in their downstream. This fact and the deficiency of atomic gas compared with molecular gas in the inner Galaxy indicate that physical conditions of interstellar gas are affected by grand-design, nonlinear pro- cesses, such as compression by spiral density waves followed by gravitational collapse, and not by disso- ciation of low-density molecular gas by young stars.