Buhajenko O. Diffuse radiation in nebular environments

The dissertation is devoted to the developing and further approbation of new approach to detailed method of diffuse ionizing radiation calculation while photoionization modelling of nebular environments of different types. An approach is based on moving procedure of diffuse radiation integration outside photoionization’s code core, with further iterative process. The code, developed for solving radiation transfer equation along any direction during further integration over 3D volume is introduced. Code algorithm as well as numerical methods, used in code for integration implementation are described. An approach was approbated on photoionization models of "simple" objects with homogeneous density distribution and spherical-symmetry assumption: Meudon and standard planetary nebulae as well as HII regions with grains and without them. Photoionization models were calculated using Outward Only approximation as well as using detailed method for diffuse radiation calculation. Based on results, an analisys of impact of selected approach to diffuse ionizing radiation treatment on ionization structure and output emission lines spectra was performed. Important conclusions regarding efficiency of approximal methods for diffuse ionizing radiation (DIR) calculation in case of homogeneous models were done. Also, obtained emission lines spectra were compared to the ones, obtained by different photoionization codes. The same analysis of impact of selected method of DIR calculation on photoionization modelling results was performed for models of planetary nebulae with inhomogeneous structure (namely, using Golovatiy – Malkov density distribution). As result, electron density and temperature distributions as well as output emission line spectra were obtained. Based on results, conclusions about necessity of detailed approach for DIR calculation in case of objects with inhomogeneous density distribution were done. Detailed method of diffuse ionizing radiation calculation was also used for PhM of optimal models of symbiotic novae shells. It is shown that Outward Only approximation can be used in case of such compact objects in spite of inhomogenity of radial density distribution. Also, a new approach to investigation of dwarf galaxies with active star formation was introduced. An approach is based on calculation of net of multicomponent photoionization models (MPhM) using results of chemodynamical simulations as input parameters for determination of electron density and temperature distributions in super wind region as well chemical abundance distribution. As result of MPhM calculation using detailed method of DIR calculation spatial maps of emissivities and opacities were obtained. These maps were used to obtain synthetic emission lines spectra for different aperture positions. Obtained spectra were analysed and compared to corresponding observation results. Also, in order to test diagnostic methods, the last ones were applied to optical emission lines spectra. As result, oxygen abundances for different aperture positions at different ages were obtained, and compared to corresponding values, received from averaging chemodynamical simulations results. It was shown that in most cases diagnostic methods can’t be applied for correct determination of physical parameters in case of inhomogeneous environments.