Wave focusing model for starbursts

A model for starbursts is considered in which spiral density waves provide the primary triggering mechanisms, by achieving largest amplitude within about 1 kpc of a galactic center, a process referred to as wave focusing. Radio observations of molecular gas are suggested to test the model. First, simple linear, WKB, steady state density waves are considered. Wave focusing occurs when the disk's effective velocity dispersion does not increase rapidly near the galactic center. This condition can be achieved by either having a fairly low stellar velocity dispersion in the central region (Q=1) or by having a significant (about 10 percent by mass) low-velocity dispersion gaseous component in the central region. To consider nonlinear effects, a marginally applicable formalism is used in the context of planetary rings. The model indicates that wave nonlinearities enhance wave focusing, when it is predicted by linear theory. 37 references