Astronomy and Astrophysics, volume 430, 911-926 (2005/2-2)
Expansive components in HII regions.
RELANO M. and BECKMAN J.E.
Abstract (from CDS):
We study the presence of low intensity high velocity components, which we have termed wing features in the integrated Hα emission line profiles of the HII region populations of the spiral barred galaxies NGC 1530, NGC 3359 and NGC 6951. We find that more than a third of the HII region line profiles in each galaxy show these components. The highest fraction is obtained in the galaxy whose line profiles show the best S:N, which suggests that wing features of this type may well exist in most, if not all, HII region line profiles. Applying selection criteria to the wing features, we obtain a sample of HII regions with clearly defined high velocity components in their profiles. Deconvolution of a representative sample of the line profiles eliminates any doubt that the wing features could possibly be due to instrumental effects. We present an analysis of the high velocity low intensity features fitting them with Gaussian functions; the emission measures, central velocities and velocity dispersions for the red and blue features take similar values. We interpret the features as signatures of expanding shells inside the HII regions. Up to a shell radius of Rshell∼0.2Rreg, the stellar winds from the central ionizing stars appear to satisfy the energy and momentum requirements for the formation and driving the shell. Several examples of the most luminous HII regions show that the shells appear to have larger radii; in these cases additional mechanisms may well be needed to explain the kinetic energies and momenta of the shells.
ISM: H II regions - ISM: kinematics and dynamics - galaxies: individual: NGC 1530 - galaxies: individual: NGC 6951 - galaxies: individual: NGC 3359 - galaxies: ISM
VizieR on-line data:
<Available at CDS (J/A+A/430/911): tables.dat notes.dat>
Table 1: [RBZ2005] NGC 1530 NNN N=18 among 119. Table 2: [RBZ2005] NGC 6951 NN N=17 among 91. Table 3: [RBZ2005] NGC 3359 NNN N=21 among 202.
Status at CDS:
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