Considerations on the physical parameters, evolution and ionization structure of H II regions
Abstract
Some aspects of H II regions, which may have an important influence on the conditions in the interstellar medium are discussed. The discussion covers four classes of H II regions: (1) the classical small condensed H II regions ionized by the UV flux of hot stars, (2) diffuse ionized regions observed in the nucleus of some galaxies, exhibiting violent motions and anomalous line intensity ratios, (3) faint diffuse ionized gas confined to the arms of spiral galaxies, particularly Sc and Sd galaxies, and (4) very faint diffuse fully ionized gas that forms a disk around the nucleus of Sc and Sd galaxies. The range of parameters which define these classes of H II regions is examined.
- Publication:
-
Memorie della Societa Astronomica Italiana
- Pub Date:
- May 1974
- Bibcode:
- 1974MmSAI..45..259C
- Keywords:
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- Galactic Structure;
- Gas Ionization;
- H Ii Regions;
- Interstellar Gas;
- Electron Density (Concentration);
- Electron Energy;
- Galactic Radiation;
- Hydrogen Ions;
- Main Sequence Stars;
- O Stars;
- Pulsars;
- Recombination Reactions;
- Supernovae;
- Astrophysics