On the properties of dust grains in H II regions
Abstract
Infrared and radio data from H II regions are analyzed with the aid of theoretical models. It is found that: (1) dust absorbs a substantial fraction of Lyman continuum radiation; (2) in the ionized region the dust opacity, and hence the dust abundance relative to the gas, is not the same for all sources; (3) the differences in dust abundance from region to region can easily be explained by the presence of large amounts of a dust component with low melting temperature in addition to other components that are much more resistant; and (4) a wavelength-dependent dust absorption cross section is sufficient to explain the observed decrease in He ionization with increasing values of the ratio of IR to Ly-alpha luminosity.
- Publication:
-
Memorie della Societa Astronomica Italiana
- Pub Date:
- March 1978
- Bibcode:
- 1978MmSAI..49..213P
- Keywords:
-
- Cosmic Dust;
- H Ii Regions;
- Infrared Absorption;
- Photoabsorption;
- Plasma Clouds;
- Radio Attenuation;
- Abundance;
- Astronomical Models;
- Granular Materials;
- Hydrogen Ions;
- Interstellar Extinction;
- Lyman Alpha Radiation;
- Astrophysics