SIMBAD references

We obtained high S/N, high resolution spectra of 16 B-type main sequence stars in young open clusters and in HII regions with galactocentric distances between 7 and 16 kpc. Chemical abundances for this sample were derived using line-blanketed LTE model atmospheres and line formation in LTE. Our analyses together with published data from similar analyses of B-type stars result in flat gradients or even no gradients at all for oxygen and nitrogen in the outer part of the galactic disk. It is conjectured that the larger metallicity gradients cited for HII regions are essentially due to a steepening within the inner 6 kpc towards the galactic center.