Circumnuclear obscuration of the Circinus galaxy by a starburst-radiation supported wall

We consider the radiation-hydrodynamical formation of a dusty wall in the c ircumnuclear regions of the Circinus Seyfert 2 galaxy. We focus on the radi ative flux force due to the circumnuclear starburst, the nuclear starburst and the active galactic nucleus (AGN), and analyze the equilibrium configur ation and stability of the dusty gas in the circumnuclear regions. The mass distributions used to model the gravitational fields are determined by the observed rotation velocities of the stars and of the gas. Moreover, by usi ng the simple stellar evolution in the circumnuclear starburst, the bolomet ric luminosity of the starburst is estimated as a function of time. As a re sult, it is shown that the radiation force by the circumnuclear starburst d oes play an important role to build up a radiatively-supported dusty wall o f less than or similar to 100 pc, which obscures the circumnuclear regions with AV of a few magnitudes. It is also found that the age of a circumnucle ar starburst when the circumnuclear regions are enshrouded by the dusty wal l is constrained to be less than or similar to 10(8) yr, which is consisten t with the age observationally inferred for the starburst, 4 10(7) yr-1.5 1 0(8) yr.