Bibcode
Relaño, M.; Beckman, J. E.
Bibliographical reference
Astronomy and Astrophysics, v.430, p.911-926 (2005)
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2
2005
Journal
Citations
35
Refereed citations
28
Description
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 H II region populations of the spiral barred galaxies
NGC 1530, NGC 3359 and NGC 6951. We find that more than a third of the H
II 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, H II region line profiles. Applying selection
criteria to the wing features, we obtain a sample of H II 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 H II regions. Up to a shell radius of
Rshell˜ 0.2 Rreg, 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 H II 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.