Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1989
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989jkas...22..127h&link_type=abstract
Journal of the Korean Astronomical Society, vol. 22, no. 2, p. 127-140
Astronomy and Astrophysics
Astronomy
1
Scientific paper
Problems of the diffuse radiation(DFR) transfer is solved exactly for pure hydrogen nebulae of uniform density, and accuracies of on-the-spot(OTS) approximation are critically examined. For different values of density and spectral types of the central star, we have calculated the degree of ionization and the kinematic temperature of electrons as functions of distance from the central star, and compared them with the corresponding results of the OTS approximation. At most locations inside an HII region, the DFR ionizes considerable amount of hydrogen; therefore, the OTS approximation under-estimates the size of ionized regions. The exact treatment of the DFR transfer results in an about 10 to 20 percent increase in the classical Stroemgren radius. The OTS approximation over-estimates the local heating rate by raising the density of neutral hydrogens. Consequently, it predicts higher values for the local electron temperature. The OTS approximation also exaggerates the dependence of electron temperature on density. When hydrogen density is changed from 10/cm3 to 1000/cm3 with an O6.5 V star, the OTS approximation shows an about 3000K difference in the electron temperature, while the exact treatment of the DFR-transfer reduces the difference to about 1000K. The OTS approximation fails to demonstrate the brightening of the electron temperature close to the ionization boundary.
Hong Seung Sae
Sung Hyun-Il
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