Re-analysis of the radio luminosity function of Galactic HII regions
  We have re-analyzed continuum and recombination lines radio data available in
the literature in order to derive the luminosity function (LF) of Galactic HII
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
super-giant HII regions, a significant number of sub-giant 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 HII 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 = 10^23.45 erg s^(-1)
Hz^(-1) for the LF in the fourth quadrant. We convert radio luminosities into
equivalent H_alpha and Lyman continuum luminosities to facilitate comparisons
with extra-galactic studies. We obtain an average total HII regions Lyman
continuum luminosity of 0.89 +/- 0.23 * 10^(53) sec^(-1), corresponding to 30%
of the total ionizing luminosity of the Galaxy.
