Line formation in H II regions during the champagne phase
H. W. Yorke, G. Tenorio-Tagle, P. Bodenheimer;
AaA, 1984, 138, 325
ABSTRACT:Line transfer calculations are presented for interpreting complex velocity fields
in H II regions detected by radio telescopes.
Consideration is focused
on hydrogen and forbidden oxygen lines which exhibit an emissivity
proportional to the square of the electron density inside the H II region and zero
outside.
Account is taken of factors such as the ionization rate, recombination,
absorption by dust, opacity and the extinction coefficient.
Spectral intensity
arrays are generated for specific view angles of the champagne
phase.
Doppler shifts are obtained for intensities in various positions around the
central star of the H II region.
Typical features of a champagne flow are
concluded to be a Doppler shift of no more than 5 km/sec for the ionized gas relative
to the outer surface of the ionized cloud, ionized matter flowing away
from the molecular cloud, velocity differences of up to 4 km/sec of various
components of the nebula, and greater complexity occurring mostly in the low
density-bounded periphery of the H II regions.
KEYWORDS: astronomical spectroscopy, h ii regions, h lines, line shape, doppler effect, electron density (concentration), forbidden transitions, frequency shift, ion production rates, molecular clouds, radio astronomy
PERSOKEY:region hii, ,
CODE: yorke84