Gas and dust emission from the nuclear region of the Circinus galaxy

Simultaneous modeling of the line and continuum emission from the nuclear r egion of the Circinus galaxy is presented. Composite models that include th e combined effect of shocks and photoionization from the active center and from the circumnuclear star-forming region are considered. The effects of d ust reradiation, bremsstrahlung from the gas, and synchrotron radiation are treated consistently. Models that fit the continuum energy distribution of Circinus are used to constrain all possible models suitable for the line e mission; they are all, together, aimed to converge to a most probable repre sentation of the central emission region of Circinus. The proposed model ac counts for two important observational features. First, the high obscuratio n of Circinus central source is produced by high-velocity and dense clouds with characteristic dust-to-gas ratios above 10(-12). Their large velocitie s, up to 1500 km s(-1), place them very close to the active center. Second, the derived size of the line-emitting region (similar to 13 pc) Is well in agreement with the observed limits for the coronal(<10 pc) and narrow-line regions (similar to 30 pc) of Circinus.