The Metallicity Distribution Function of Red Giants in the LMC

Abstract

We report new metallicity determinations for 39 red giants in a 220 square arcminute region, 1.8 degrees southwest of the bar of the Large Magellanic Cloud. These abundance measurements are based on spectroscopy of the Ca II infrared triplet. The metallicity distribution function (MDF) shows a strong peak at [Fe/H] = -0.57 +/- 0.04. Half the red giants in our field fall within the range -0.83 < [Fe/H] < -0.41. We find a striking contrast in the shape of the MDF below [Fe/H] < -1 between our inner disk field and the distant outer field studied by Olszewski (1993). Our field-star MDF seems similar to that of the intermediate-age (1-3 Gyr) star clusters. We have also obtained abundance estimates using Stromgren photometry for ~1000 red giants in the same field. The Stromgren measurements, which are sensitive to a combination of cyanogen and iron lines, correlate well with the Ca II measurements, but a metallicity-dependent offset is found (abridged).