ИСТИНА

Sources of ionization of diffuse ionized gas at various heights in 436 edge-on disk galaxies are explored in dependence of their stellar mass, Hα luminosity, and specific star formation rate. The MaNGA (Mapping Nearby Galaxies at Apache Point Observatory) spectroscopic survey data from DR17 (Data Release) of SDSS-IV (Sloan Digital Sky Survey) project together with photoionization and shock ionization theoretical models from the 3MdB (Mexican Million Models database) are used. We reach very high galactic altitudes with the help of spectra stacking. It is demonstrated that models of the gas photoionization in a combination of young OB-stars and hot low-mass evolved stars adequately describe the gas ionization state in the galaxies of all types. Moreover, the fraction of the ionizing flux from OB-stars and the ionization parameter decrease with the altitude, while the role of the ionization by the hot low-mass evolved stars increases. The difference in the contribution from these types of ionizing sources correlates with the specific star formation rate and with stellar masses of galaxies. The hot low-mass evolved stars are the principal gas ionization sources in massive galaxies with low specific star formation rate, while OB-stars dominate the gas ionization in low-mass galaxies with high specific star formation rate. Nevertheless, the shock waves may contribute to the gas ionization in massive galaxies with low specific star formation rates. In addition to our work, recent works on the DIG of other groups of scientists are discussed.