Studies of Star-forming Complexes in the Galaxies NGC 628, NGC 2976, and NGC 3351

Abstract

The parameters of the radiation of interstellar matter in star-forming complexes in the high-metallicity galaxies NGC 628, NGC 2976, and NGC 3351, which have different morphological types, are analyzed. The relationship between the emission in Hα and in lines of CO and HI is considered, as well as the relationship between Hα and the emission of dust in the infrared range (IR). The fluxes and surface brightnesses in the UV and IR correlate well with the Hα emission. The HI emission also correlates well with Hα, while the correlation between the CO and Hα emission is much weaker. The ratio of the fluxes at 8 and 24 µm decreases with increasing Hα flux. This may be due to changes in the properties of the dust ensemble (a decrease in the mass fraction of polycyclic aromatic hydrocarbons) or to changing excitation conditions. Analysis of the kinematics of the CO lines shows that the CO flux grows with increasing velocity scatter ΔV when ΔV ≾ 70 km/s. Preliminary evidence for the existence of star-forming complexes with higher values of ΔV is provided, when the increase in the velocity scatter is accompanied by a decrease in the CO luminosity of the complex. © 2019, Pleiades Publishing, Ltd.