Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21732804c&link_type=abstract
American Astronomical Society, AAS Meeting #217, #328.04; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astronomy
Scientific paper
We present detailed chemical abundances of 21 elements in 8 clusters in the Large Magellanic Cloud (LMC). These abundances were obtained from individual absorption lines using our new method of analyzing high resolution (R 25,000) integrated-light spectra of globular clusters. We have previously used old (>10 Gyr) Milky Way clusters to demonstrate that we obtain accuracies comparable to those obtained from analysis of individual RGB stars. Here we use the LMC, which contains the necessary sample of clusters over a wide age range, to demonstrate for the first time that this abundance analysis method can be successfully applied to clusters of any age (50 Myrs to 13 Gyrs). Uniformly obtaining chemical abundances of clusters over a wide range in age allows us to investigate the chemical evolution history of the LMC in great detail. We find a spread in [α/Fe] at constant [Fe/H], as well as evolution of [α/Fe] with [Fe/H] and age. In older clusters, the light elements Na, Al, and Mg appear to be strongly affected by inter-cluster abundance variations; intermediate age and young clusters have light element abundances that are more consistent with LMC field stars. The heavy elements Ba, La, Nd, Sm, and Eu are enhanced in the youngest clusters. The heavy to light s-process ratio is elevated, ([Ba/Y] >+0.5), and increases with decreasing age, indicating a strong contribution of low-metallicity AGB star ejecta throughout the later history of the LMC. These results are consistent with prolonged, low-efficiency star formation between short bursts of more rapid star formation that resulted in massive, surviving clusters. Detailed chemical abundances measured using our new method can be obtained for galaxies within 4 Mpc using current telescopes. These abundances can be used to constrain the star formation history of galaxies in and beyond the Local Group in unprecedented detail.
Bernstein Rebecca A.
Colucci Janet E.
McWilliam Andrew
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