1999A&A...351.1075R

An analysis of CCD spectra in the range λλ4200-8775, obtained at several positions of seven bright Galactic HII regions, with galactocentric distances in the range 6-10kpc, is presented. Temperatures, densities and ionic abundances are calculated for all the positions, and the relative trends followed by these parameters are established. It is shown that all these HII regions share the same abundances of O, S, Cl, N, Ar and He, within their expected uncertainties, a result which is consistent with a flat or small abundance gradient in the Galactic disc within ±2kpc from the Sun, as suggested by some studies of the abundances in HII regions and B-type stars. The same set of homogeneously derived ionic abundances is also used to test the accuracy of the fractional ionization predicted by available grids of models for photoionized nebulae.