Journal Article

The SLUGGS survey: calcium triplet-based spectroscopic metallicities for over 900 globular clusters

Christopher Usher, Duncan A. Forbes, Jean P. Brodie, Caroline Foster, Lee R. Spitler, Jacob A. Arnold, Aaron J. Romanowsky, Jay Strader and Vincenzo Pota

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 426, issue 2, pages 1475-1495
Published in print October 2012 | ISSN: 0035-8711
Published online October 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21801.x
The SLUGGS survey: calcium triplet-based spectroscopic metallicities for over 900 globular clusters

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Although the colour distribution of globular clusters in massive galaxies is well known to be bimodal, the spectroscopic metallicity distribution has been measured in only a few galaxies. After redefining the calcium triplet index–metallicity relation, we use our relation to derive the metallicity of 903 globular clusters in 11 early-type galaxies. This is the largest sample of spectroscopic globular cluster metallicities yet assembled. We compare these metallicities with those derived from Lick indices finding good agreement. In six of the eight galaxies with sufficient numbers of high-quality spectra we find bimodality in the spectroscopic metallicity distribution. Our results imply that most massive early-type galaxies have bimodal metallicity as well as colour distributions. This bimodality suggests that most massive early-type galaxies experienced two periods of star formation.

Keywords: globular clusters: general; galaxies: abundances; galaxies: star clusters: general; galaxies: stellar content

Journal Article.  12891 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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