Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-09-21
Astronomy and Astrophysics
Astrophysics
Accepted for publication as a Letter in Astronomy & Astrophysics. Latex with postscript figures. Online-only tables and figure
Scientific paper
10.1051/0004-6361:20066151
Context. Statistical properties of HII region populations in disk galaxies yield important clues to the physics of massive star formation. Aims. We present a set of HII region catalogues and luminosity functions for a sample of 56 spiral galaxies in order to derive the most general form of their luminosity function. Methods. HII region luminosity functions are derived for individual galaxies which, after photometric calibration, are summed to form a total luminosity function comprising 17,797 HII regions from 53 galaxies. Results. The total luminosity function, above its lower limit of completeness, is clearly best fitted by a double power law with a significantly steeper slope for the high luminosity portion of the function. This change of slope has been reported in the literature for individual galaxies, and occurs at a luminosity of log L = 38.6\pm0.1 (L in erg/s) which has been termed the Stromgren luminosity. A steep fall off in the luminosity function above log L = 40 is also noted, and is related to an upper limit to the luminosities of underlying massive stellar clusters. Detailed data are presented for the individual sample galaxies. Conclusions. The luminosity functions of HII regions in spiral galaxies show a two slope power law behaviour, with a significantly steeper slope for the high luminosity branch. This can be modelled by assuming that the high luminosity regions are density bounded, though the scenario is complicated by the inhomogeneity of the ionized interstellar medium. The break, irrespective of its origin, is of potential use as a distance indicator for disc galaxies.
Beckman John E.
Bradley T. R.
Folkes Stuart L.
Knapen Johan H.
No associations
LandOfFree
A composite HII region luminosity function in H alpha of unprecedented statistical weight does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A composite HII region luminosity function in H alpha of unprecedented statistical weight, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A composite HII region luminosity function in H alpha of unprecedented statistical weight will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-134605