O. Fuentes-masip et al., On the size and luminosity versus velocity dispersion correlations from the giant HII regions in the irregular galaxy NGC 4449, ASTRONOM J, 120(2), 2000, pp. 752-762
Here we present the size and luminosity versus velocity dispersion empirica
l correlations for the giant H II regions in the large irregular galaxy NGC
4449. We show that correlations only hold for nebulae with a surface brigh
tness higher than 2 x 10(35) ergs s(-1) pc(-2) in H alpha and with a supers
onic single-line Gaussian profile. The exponents of the fits are consistent
with virial mechanisms. A comparison with the results from other studies t
hat have only used first-ranked giant H II regions from a variety of star-f
orming galaxies is also given.