Field Stars, Open Clusters, and the Galactic Abundance Gradient

Abstract

The effects of the orbital diffusion of stars and clusters on the galactic abundance gradient have been modelled. For a single generation of field stars, the results confirm previous analyses based upon the assumption of a linear gradient with galactocentric distance. Though the dispersion in metallicity at a given radius grows with time, the underlying slope across the disk remains unchanged. For a disk dominated by a discontinuity in [Fe/H] beyond the solar circle, but no gradient within the inner or outer disk, a gradient is derived for any sample whose galactocentric baseline overlaps the discontinuity. The consequence of orbital diffusion is to shift the observable edge of the transition in [Fe/H] to smaller galactocentric distance. In contrast, star clusters of a single generation evaporate so quickly that the small surviving sample of the oldest clusters is statistically insufficient to define any but a linear gradient. Inclusion of multiple generations of stars and clusters with a plausible age-metallicity relation enhances these patterns by expanding the metallicity range at a given galactocentric distance through the inclusion of stars with a wide range in both age and galactocentric origin. For field stars, the metallicity distribution of stars in the solar neighborhood is virtually indistinguishable for the two cases modelled. Because ages, abundances, and distances can be reliably determined for clusters and any sample of clusters is invariably dominated by clusters formed over the last 2 Gyrs, the cluster population offers a means for finding detailed structure within the recent galactic abundance gradient. Using clusters to extend the galactocentric baseline would supply an additional critical test of the discontinuity.

16 pages, 8 postscript figures, to be published in Astronomical Journal, August 2001

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Cited by in corpus (15)

• On the Galactic Disk Metallicity Distribution from Open Clusters I. New Catalogues and Abundance Gradient
• On the metallicity of open clusters. III. Homogenised sample
• The evolution of the Galactic metallicity gradient from high-resolution spectroscopy of open clusters
• The Bologna Open Cluster Chemical Evolution (BOCCE) Project: midterm results from the photometric sample
• The Open Cluster Chemical Analysis and Mapping Survey: Local Galactic Metallicity Gradient with APOGEE using SDSS DR10
• Open clusters as key tracers of Galactic chemical evolution. III. Element abundances in Berkeley 20, Berkeley 29, Collinder 261, and Melotte 66
• High Spatial Resolution Galactic 3D Extinction Mapping with IPHAS
• The Structure of the Outer Galactic Disc as revealed by IPHAS early A Stars
• vbyCaHbeta CCD Photometry of Clusters. VI. The Metal-Deficient Open Cluster NGC 2420
• uvbyHbeta CCD Photometry of Clusters. IV. Solving the Riddle of NGC 3680
• uvbyCaHbeta CCD Photometry of Clusters. V. The Metal-Deficient Open Cluster NGC 2243
• Berkeley 22, an old and distant open cluster towards the Galactic anticentre
• uvbyCa H beta CCD Photometry of Clusters. VII. The Intermediate-Age Anticenter Cluster Melotte 71
• Observational properties of the open cluster system of the Milky Way and what they tell us about our Galaxy
• Old open clusters as key tracers of Galactic chemical evolution. I. Fe abundances in NGC 2660, NGC 3960, and Berkeley 32