Re-analysis of the Radio Luminosity Function of Galactic H II Regions
Abstract
We have re-analyzed continuum and recombination lines radio data available in the literature in order to derive the luminosity function (LF) of Galactic H II regions. The study is performed by considering the first and fourth Galactic quadrants independently. We estimate the completeness level of the sample in the fourth quadrant at 5 Jy, and the one in the first quadrant at 2 Jy. We show that the two samples (fourth or first quadrant) include, as well as giant and supergiant H II regions, a significant number of subgiant sources. The LF is obtained, in each Galactic quadrant, with a generalized Schmidt's estimator using an effective volume derived from the observed spatial distribution of the considered H II regions. The re-analysis also takes advantage of recently published ancillary absorption data allowing to solve the distance ambiguity for several objects. A single power-law fit to the LFs retrieves a slope equal to -2.23 ± 0.07 (fourth quadrant) and to -1.85 ± 0.11 (first quadrant). We also find marginal evidence of a luminosity break at L knee = 1023.45 erg s-1 Hz-1 for the LF in the fourth quadrant. We convert radio luminosities into equivalent Hα and Lyman continuum luminosities to facilitate comparisons with extragalactic studies. We obtain an average total H II regions Lyman continuum luminosity of 0.89 ± 0.23 × 1053 s-1, corresponding to 30% of the total ionizing luminosity of the Galaxy.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2009
- DOI:
- 10.1088/0004-637X/702/2/1036
- arXiv:
- arXiv:0907.2216
- Bibcode:
- 2009ApJ...702.1036P
- Keywords:
-
- Galaxy: general;
- H II regions;
- radio continuum: stars;
- stars: luminosity function;
- mass function;
- Astrophysics - Galaxy Astrophysics
- E-Print:
- accepted for publication in ApJ