Shkvarun R. Investigation of radial distributions of heavy elements in disks of spiral galaxies

The thesis is devoted to determination of oxygen abundance in disks of spiral galaxies. Oxygen abundances in Galactic HII regions are determined. The parameters of the radial oxygen abundance distribution in disk of the Galaxy are derived. The obtained oxygen abundance at the solar galactocentric distance is in agreement with the oxygen abundance in the interstellar medium in the solar vicinity derived with high precision from the interstellar absorption lines toward stars. This is evidence in favor of the validity of two-zone model of HII region. The neon and oxygen abundances in HII regions of seven spiral galaxies have been determined through the P-method. The parameters of radial distributions of neon and oxygen abundances in disks of those galaxies obtained. Comparison between the radial distributions of neon and oxygen abundances in galaxies shows that the slopes in these distributions are in agreement. This is evidence in favor of that the neon-to-oxygen abundances ratio is a constant within theuncertainties of the abundance determination.