MODELING THE CONTINUUM AND LINE SPECTRA OF THE SEYFERT 2 GALAXY NGC 5252

The SO galaxy NGC 5252 is one of the best examples of the anisotropic radiation theories believed to govern the physics of active galactic n uclei. Considerable amounts of observational data, from the radio to t he hard X-ray domain, have been accumulated from the central nuclear r egion of this galaxy. This work makes use of all the available observa tional information in an attempt to model in a self-consistent manner the continuum and line emission spectra of the nuclear region and the extended emission-line region. It is suggested that both the nuclear c ontinuum and the nuclear line emission originate in gaseous clouds tha t are exposed to the nuclear ionizing radiation and subjected to shock s. The best fit to the data in the nuclear region is obtained with a w eighted-average model that includes radiation-dominated clouds with lo w velocities (similar or equal to 100 km s(-1)), producing most of the emission lines and the low-frequency continuum, and high-velocity (si milar to 400 mm s(-1)) shock-dominated clouds, where the soft X-ray co ntinuum originates. The far-infrared emission is due to dust heated by both the nuclear radiation and shocks. Modeling of the extended emiss ion-line region was performed on the basis of the derived nuclear mode l. That region was found to be characterized by densities of a few cm( -3) and a cloud size of about 100 pc. Excitation via shocks is found n egligible, whereas photoionization by the central power source widely accounts for the observed line spectrum.