Kinematic and abundance gradients in the Galactic disk

Abstract

This paper presents photometric observations on 364 G and K stars in the Galactic-center and anticenter directions, made for the purpose of measuring the variation of velocity dispersion with galactocentric distance and with metallicity in the Galactic disk. The abundance gradient for these stars was found to be similar to the gradients found in other studies of mixed-age objects. No significant gradients were seen of the U component of velocity dispersion with metallicity, but the U component was found to vary stongly with galactocentric distance, showing a gradient of d(sigma-U)/dR = -3.8 + or - 0.6 km/s per kpc over a distance range of 14 kpc, and falling off to a value of about 10 km/s at 5 kpc beyond the sun's position. This variation is reminiscent of the observed distribution of molecular gas in the Galactic disk, and suggests that the velocity-dispersion structure in the disk is at least partly due to the interaction of the stars throughout their lifetimes with molecular cloud complexes.