Bibcode
Rozas, M.; Sabalisck, N.; Beckman, J. E.
Bibliographical reference
Astrophysics and Space Science, v. 276, Issue 2/4, p. 413-419 (2001).
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3
2001
Journal
Citations
1
Refereed citations
1
Description
We analyse spectral images across the full emission line in H_α of
the discs of M100 and M101, extracting for each HII region its spectrum,
and for the more luminous and extended, spectra over a range of circular
apertures. The principal components of these spectra are presented in
log-log plots of luminosity vs. turbulent line-width. These plots are
apparently scatter diagrams, with no convincing linear fits, e.g. with
slope ~ 4 as predicted for a population of virialized systems. Both
plots do show, however, clean linear lower envelopes in turbulent width.
We interpret these as the loci of HII regions in virial equilibrium. The
emissions with greater widths (the great majority), show the effects of
not yet fully damped kinematic inputs from stellar winds and supernovae.
As expected, a greater fraction of the most luminous regions, which are
the most massive, lie on or near the virial envelopes. The slopes of
these envelopes are in fact 2.6, not 4, which is explicable if the most
luminous regions are density bounded, so that a fraction of their
ionizing luminosity, (increasing with luminosity above a critical value)
is not registered in H_α. The regions on the envelopes are also
those of greatest surface brightness, as predicted for density bounded
regions. The masses of the regions on the envelopes, computed via the
virial expression, agree well with masses estimated via their emission
measures and assuming density bounding.