CHEMICAL CARTOGRAPHY WITH APOGEE: LARGE-SCALE MEAN METALLICITY MAPS OF THE MILKY WAY DISK

摘要

We present Galactic mean metallicity maps derived from the first year of the SDSS-III APOGEE experiment.Mean abundances in different zones of projected Galactocentric radius (0 6 kpc, the gradient flattens as one moves off the plane, and is flatter at all heights for high-α/M stars than for low-α/M stars. Alternatively, these gradients can be described as vertical gradients that flatten at larger Galactocentric radius; these vertical gradients are similar for both low- and high-α/M populations. Stars with higher α/M appear to have a flatter radial gradient than stars with lower α/M. This could suggest that the metallicity gradient has grown steeper with time or, alternatively, that gradients are washed out over time by migration of stars.