SIMBAD references

As a continuation of our previous work on the abundance gradient in the outer part of the galactic disc, this paper presents results on the metallicicty distribution over galactocentric distances up to 15kpc. The outer disc is clearly separated from the middle part by the existence of a step in the metallicity distribution at about 10kpc. Taking the region of galactocentric distances from 10kpc to 15kpc, one can derive an iron gradient -0.03±0.01dex/kpc (25 stars). The existence of a discontinuity can be caused by the effective suppression of mixing processes near the corotation circle where the radial component of the gas velocity should be very small.