Vovk K. Effects of the massive stars evolution in spectra of starburst galaxies

The thesis presents the study of the impact of the massive stars evolution on the interstellar medium in star-forming galaxies, selected from the Data Release 7 of the Sloan Digital Sky Survey. The comparison of the observed massive stars (Wolf-Rayet (WR) and O-types) statistics in the WR-galaxies with the population synthesis models has shown, that the number ratio of WR-stars to all massive stars decreases with the metallicity of the galaxy and the available models describe well the observations with the bursting star formation scenario, excluding the galaxies with the smallest metallicities, if possible variations of the initial mass function slope are assumed. The implementation of the new stellar evolution models with account for the proper stellar rotation to the evolutionary code Starburst99 is described; the manifestations of massive stars rotation in the integrated properties of the single star population are also investigated. Based on the sample of 79 galaxies with the nebular emission line of ionized helium we show that the doubly ionized helium in the interstellar medium is formed by the radiation of not only massive stars, but also shocks. The chemical composition of the both above mentioned samples is determined. The abundance ratios Ne/O, S/O, Cl/O and Ar/O in these samples do not depend on the metallicity. On the other hand, the abundance ratio N/O increases at the metallicities 12+logO/H>8.0. It is found that the WR stars contribute 20% of nitrogen to the enrichment of the interstellar medium. The dependence of the abundance ratio N/O on the starburst age also strengthens the importance of the WR stars in the enrichment of the interstellar medium by nitrogen. The spectrum of the blue compact galaxy IC 4662 is investigated. One of the two galaxy's star-forming regions is more metal-rich and contains 29 of total 33 WR stars. The distribution of the radial velocities in galaxy did not show any noticeable its rotation.