Astronomy and Astrophysics, volume 431, 235-251 (2005/2-3)
The internal dynamical equilibrium of H II regions: A statistical study.
RELANO M., BECKMAN J.E., ZURITA A., ROZAS M. and GIAMMANCO C.
Abstract (from CDS):
We present an analysis of the integrated Hα emission line profiles for the HII region population of the spiral galaxies NGC 1530, NGC 6951 and NGC 3359. We show that ∼70% of the line profiles show two or three Gaussian components. The relations between the luminosity (logLHα) and non-thermal line width (logσnt) for the HII regions of the three galaxies are studied and compared with the relation found taken all the HII regions of the three galaxies as a single distribution. In all of these distributions we find a lower envelope in logσnt. A clearer envelope in σnt is found when only those HII regions with σnt>σs(13km/s) are considered, where σs is a canonical estimate of the sound speed in the interestellar medium. The linear fit for the envelope is log LHα=(36.8±0.7)+(2.0±0.5) log σnt where the Hα luminosity of the region is taken directly from a photometric HII region catalogue. When the Hα luminosity used instead is that fraction of the HII region luminosity, corresponding to the principal velocity component, i.e. to the turbulent non-expanding contribution, the linear fit is logLHα=(36.8±0.6)+(2.0±0.5)logσnt, i.e. unchanged but slightly tighter. The masses of the HII regions on the envelope using the virial theorem and the mass estimates from the Hα luminosity are comparable, which offers evidence that the HII regions on the envelope are virialized systems, while the remaining regions, the majority, are not in virial equilibrium.
ISM: H II regions - ISM: kinematics and dynamics - galaxies: individual: NGC 1530, NGC 6951, NGC 3359 - galaxies: ISM
Tables 2, 9 ,10: [RBZ2005] NGC 1530 NNN N=15 added, [RBZ2005] NGC 6951 NN N=5 added, [RBZ2005] NGC 3359 NNN N=13 added.
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