Space densities and unified models of AGN

Using combined information from both FIRST and NVSS radio surveys at 1.4GHz, a sample of 282 sources with Slim = 1.3Jy was constructed. Radio morphological type were determined for each sources, and redshift information was found for 94% of the sample members, from databases such as SIMBAD and SDSS. A source count at 1.4 GHz was constructed from results in the literature. Space-density models using the Wall, Pearson & Longair (1980) technique were then applied using the sample and the source count; parameters for these models were optimized for the entire sample, as well as for the sample of extended sources only. In both cases, it was found that an exponential evolution with Pt = alog(z) + b gave the best fit. In the case of the entire sample, the V/Vmax statistics was computed, where = 0.6113 with σ = 0.0174. This project was mainly a pilot study to determine if the modeling of the luminosity function and epoch dependence of radio AGN was possible, primarily using the FIRST and NVSS samples in a complementary manner. This is a further way in which these huge radio surveys may be exploited for cosmological purposes and physical understanding of AGN. Since this study was successful, future work will involve using samples from FIRST and NVSS at different flux limits and applying this and much more sophisticated modeling techniques to determine the evolutions of the FRI and FRII populations separately. Ultimately, the goal of such a project would be to compare these evolutions and to use them as bases to derive new versions of the dual-population unified model described by Wall & Jackson (1997). This unified model has been successful until now but these new data should provide a comprehensive test--which may reject the formulation; or may suggest modifications that further our physical insight into the hosting/beaming paradigm of powerful radio AGN.Science, Faculty ofPhysics and Astronomy, Department ofGraduat