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P. Barai (Physics & Astronomy, GSU)
I am developing an essentially analytical model for the cosmological evolution of Fanaroff-Riley Class II Radio Galaxies (RGs) as they age and evolve. RGs have been found to have important impacts on the growth of structure in the universe. The radio lobes occupy a significant volume of the ``relevant universe'', i.e., the filaments which are the sites of galaxy formation, during the quasar era (between redshifts of 1.5 and 3). This implies that RGs have significant effects on: triggering large scale star formation in other galaxies, metal enrichment of the intergalactic medium, and spreading magnetic field over large scales. I am analyzing the robustness of this scenario by examining models that can successfully predict RG evolution.
The predictions of three sophisticated semi-analytical models for the evolution of linear size and lobe power of FR-II RGs, those of Kaiser, Dennett-Thorpe, & Alexander (1997), Blundell, Rawlings & Willott (1999), and Manolakou & Kirk (2002) have been compared with the 3CRR, 6CE and 7CRS observational surveys. I performed multi-dimensional Monte Carlo simulations to create pseudo-surveys, in order to compare each model's predictions for distributions of radio power, size, redshift and spectral index with the observations. I have searched for the best parameters of each model, and have quantified the comparisons using statistical tests. Despite investigating a wide range of parameters, I find that no existing model can give excellent fits to all the data simultaneously, although the Manolakou & Kirk model gives better overall results than do either of the other two.
I am currently improving the models by incorporating conical jet expansion for a significant fraction of a RG's lifetimes in and results of these simulations also will be presented. My goal it to employ the best-fitting model to compute fraction of the relevant volume of the universe filled by the radio lobes.
Support from NSF grant AST-0507529 and GSU's Research Program Enhancement funds is gratefully acknowledged.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.