The galactic abundance gradient

Abstract

Radio and optical spectroscopy have been combined to measure chemical abundances in a large and representative sample of galactic H II regions covering a wide range in galactocentric radius RG. Radio recombination lines have been used to determine accurate electron temperatures in 67 H II regions spanning the range 3.5 < RG < 13.7 kpc and these temperatures have been applied to optical spectra of 33 of the same H II regions to determine the abundances of O, N, S, Ne and Ar in addition to He+.