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The Detailed Chemical Properties of M31 Star Clusters. I. Fe, Alpha and Light Elements

Colucci, Janet E. and Bernstein, Rebecca A. and Cohen, Judith G. (2014) The Detailed Chemical Properties of M31 Star Clusters. I. Fe, Alpha and Light Elements. Astrophysical Journal, 797 (2). Art. No. 116. ISSN 0004-637X.

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We present ages, Fe/H] and abundances of the a elements Ca I, Si I, Ti I, Ti II, and light elements Mg I, Na I, and Al I for 31 globular clusters (GCs) in M31, which were obtained from high-resolution, high signal-to-noise ratio > 60 echelle spectra of their integrated light (IL). All abundances and ages are obtained using our original technique for high-resolution IL abundance analysis of GCs. This sample provides a never before seen picture of the chemical history of M31. The GCs are dispersed throughout the inner and outer halo, from 2.5 kpc < R_(M31) < 117 kpc. We find a range of Fe/H] within 20 kpc of the center of M31, and a constant Fe/H] ~-1.6 for the outer halo clusters. We find evidence for at least one massive GC in M31 with an age between 1 and 5 Gyr. The ɑ-element ratios are generally similar to the Milky Way GC and field star ratios. We also find chemical evidence for a late-time accretion origin for at least one cluster, which has a different abundance pattern than other clusters at similar metallicity. We find evidence for star-to-star abundance variations in Mg, Na, and Al in the GCs in our sample, and find correlations of Ca, Mg, Na, and possibly Al abundance ratios with cluster luminosity and velocity dispersion, which can potentially be used to constrain GC self-enrichment scenarios. Data presented here were obtained with the HIRES echelle spectrograph on the Keck I telescope.

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Cohen, Judith G.0000-0002-8039-4673
Additional Information:© 2014 American Astronomical Society. Received 2014 July 18; accepted 2014 October 29; published 2014 December 5. The authors thank the anonymous referee for a thoughtful report, which improved the clarity of the paper. J.E.C. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1302710. J.G.C. thanks NSF grant AST-0908139 for partial support. J.E.C. and R.A.B. thank NSF grant AST-0507350 for partial support. Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The Second Palomar Observatory Sky Survey (POSS-II) was made by the California Institute of Technology with funds from the National Science Foundation, the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman Kodak Corporation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Funding AgencyGrant Number
National Geographic SocietyUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Samuel Oschin Foundation UNSPECIFIED
Eastman Kodak Corporation UNSPECIFIED
Subject Keywords:galaxies: halos; galaxies: individual (M31); galaxies: star clusters: general; Local Group; stars: abundances
Record Number:CaltechAUTHORS:20150115-104353320
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Official Citation:The Detailed Chemical Properties of M31 Star Clusters. I. Fe, Alpha and Light Elements Janet E. Colucci et al. 2014 ApJ 797 116
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53778
Deposited By: Ruth Sustaita
Deposited On:15 Jan 2015 19:56
Last Modified:21 Nov 2017 22:23

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