The internal dynamical equilibrium of H II regions: A statistical study

Relaño, M.; Beckman, J. E.; Zurita, A.; Rozas, M.; Giammanco, C.
Bibliographical reference

Astronomy and Astrophysics, v.431, p.235-251 (2005)

Advertised on:
2
2005
Number of authors
5
IAC number of authors
4
Citations
41
Refereed citations
36
Description
We present an analysis of the integrated Hα emission line profiles for the H SHAPE Ii 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 (log LHα) and non-thermal line width (log σnt) for the H SHAPE Ii regions of the three galaxies are studied and compared with the relation found taken all the H SHAPE Ii regions of the three galaxies as a single distribution. In all of these distributions we find a lower envelope in log σnt. A clearer envelope in σnt is found when only those H SHAPE Ii regions with σnt >σs(13 km s-1) 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 H SHAPE Ii region catalogue. When the Hα luminosity used instead is that fraction of the H SHAPE Ii region luminosity, corresponding to the principal velocity component, i.e. to the turbulent non-expanding contribution, the linear fit is log LHα=(36.8±0.6)+(2.0±0.5) log σnt, i.e. unchanged but slightly tighter. The masses of the H SHAPE Ii regions on the envelope using the virial theorem and the mass estimates from the Hα luminosity are comparable, which offers evidence that the H SHAPE Ii regions on the envelope are virialized systems, while the remaining regions, the majority, are not in virial equilibrium.