Koshmak I. Modelling of the low-metalicity H II regions radiation surrounding starbursts star-forming regions

The dissertation is devoted to the developing of the method for multicomponent photoionization modelling (MPhM) of low-metalicity H II regions surrounding starburst star-forming regions and the application of this method for study of blue compact dwarf galaxies (BCDGs). The complex structure of H II region has been divided into internal and external components. Internal components correspond to the region of free expansion of superwind and the cavity of superwind correspondinly, while the external ones – to a thick layer of gas, compressed by a superwind shock, and hydrodynamically undisturbed outer part of H II region, where the most of observed strong emission lines are formed. The components of the model were calculated in the assumption of spherical symmetry. The gas photoinization was caused by ionizing quanta of both direct and diffuse ionizing radiation. Fluxes of this radiation were calculated during simulation using radiative transfer equations which take into account all important processes in the H II region that are causing this transfer. The diffuse ionizing radiation was calculated in the outward only approach. The total stellar Lyman continuum spectra (Lyc-spectra), the total number of ionizing quanta, the chemical abundance of the elements entering into the surrounding region due to the superwind and supernova explosions, the mass loss rate by starburst region, and mechanical luminosity of superwind in the region of its free expansion have been obtained from the evolutionary-population modelling of the evolution of stars-formation region with taking into account the rotation of the WR-stars. In the region of free expansion of the superwind the chemical abundances were determined using evolutionary population synthesis models of star-formation region. The chemical abundances of rarefied gas in the cavity of the superwind were determined by averaging over mass of the values of the abundances in the star-formation region and in the external components correspondingly, due to gas evaporation from the external components into the cavity. The decrement of the chemical abundance values for the elements O, Ne, S, Ar, Fe was taken from the analysis of the chemical abundances of H II regions in the BCDG obtained by Izotov et al. 1994–2005, the dependence of N/H – O/H was also taken into account. The models of Chevalier and Clegg (for the description of superwind free expansion) and Weaver et al. (for the description of gas in hot cavity) were used for the determination of radial distributions of the gas density, the expansion velocity as well as the temperature of gas within internal components of superwind. The distribution of the electron temperature and density in the external components was obtained during the calculation of their radiation as solution of the energy balance equation. It was adopted the stop criterion for evolutionary modelling corresponding to the condition of equilibrium of pressure on the boundary between third and fourth components. The evolutionary grid of multicomponent low-metalicity models of H II regions was calculated. It was shown that internal structure of H II region at some conditions can cause the formation of a lack of quanta in the spectrum of ionizing radiation. There were detected four types of impact estimation on the shape of Lyc-spectrum of ionizing radiation during its transfer through superwind components. Also, it was demonstrated the possibility of [Ne V] and He II lines formation within range of relative intensities that contains their observed values for BCDG was demonstrated. An analysis of the influence of the presence of dust grains on the distribution of physical parameters and important diagnostic relations in the H II region was carried out. The comparison of modelling spectra with observed ones was done using intensities of strong emission lines. Only models reproducing intensities of these lines within observed ranges were used for the following work. The ionic abundances of models, averaged over volume, and chemical ones adopted in the models were used to derive the new expressions for ionization-correction factors (ICFs). These ICFs were used to redetermine the chemical abundances of 83 H II regions in BCDGs, on the base of ionic abundances obtained by Izotov et al. (2007). As a result, the value of the primordial helium abundance and its enrichment during the stellar chemical evolution of matter in the Universe more precisely. The obtained value of the primordial helium abundance within the errors coincides with one obtained by Izotov and et al. (2007). The oxygen abundance coincides at low metalicity with one from Izotov et al.(2007) and decreases in comparison with these data with increasing metalicity. The value of helium enrichment during stellar chemical evolution of matter was obtained slighthly higher than one from Izotov et al. (2007).