DIFFERENCES IN C O DISTRIBUTIONS OF CARBON STARS AS AN INDICATOR OF THE INHOMOGENEITY OF CHEMICAL-COMPOSITION IN THE GALAXY/

The C/O ratio in the atmospheres of N carbon stars in the Perseus and Orion arms of the Galaxy have been obtained using moderate-dispersion spectrograms. The resulting C/O distributions for these arms are diffe rent. Theoretical C/O distributions are determined using synthetic pop ulation calculations for asymptotic giant branch carbon stars. The fol lowing three ways in which heavy-element abundances influence C/O dist ributions are considered: the rate of increase of C/O during each burn ing flare of the helium shell source, the mass-loss rate, and the mini mum mass of a star at which the ''third dredge-up'' is possible. All t hree factors influence the results in the same way: the number of carb on stars with high C/O ratios and the dispersion of the C/O ratio abou t the value C/O = 1 both decrease with increase in the heavy-element a bundance. Comparison of the calculations with the observational result s indicates that the Perseus arm has a higher heavy-element abundance than the Orion arm.