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Palomar 12 as a Part of the Sagittarius Stream: The Evidence from Abundance Ratios

Cohen, Judith G. (2004) Palomar 12 as a Part of the Sagittarius Stream: The Evidence from Abundance Ratios. Astronomical Journal, 127 (3). pp. 1545-1554. ISSN 0004-6256. doi:10.1086/382104.

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We present a detailed abundance analysis for 21 elements based on high-dispersion, high spectral resolution Keck spectra for four members of the outer halo "young" Galactic globular cluster Palomar 12. All four stars show identical abundance distributions with no credible indication of any star-to-star scatter. However, the abundance ratios of the Pal 12 stars are very peculiar. There is no detected enhancement of the α-elements; the mean of [Si/Fe], [Ca/Fe], and [Ti/Fe] is -0.07 ± 0.05 dex, O/Fe is also solar, while Na is very deficient. The distribution among the heavy elements shows anomalies as well. These are inconsistent with those of almost all Galactic globular clusters or of field stars in the Galaxy. The peculiarities shown by the Pal 12 stars are, however, in good general agreement with the trends established by Smecker-Hane & McWilliam and by Bonifacio et al. for stars in the Sagittarius dwarf spheroidal (dSph) galaxy evaluated at the [Fe/H] of Pal 12. This reinforces earlier suggestions that Pal 12 originally was a cluster in the Sgr dSph galaxy that during the process of accretion of this galaxy by our own was tidally stripped from the Sgr galaxy to become part of the extended Sgr stream.

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Cohen, Judith G.0000-0002-8039-4673
Additional Information:© 2004. The American Astronomical Society. Received 2003 November 7; accepted 2003 December 11. Based in part on observations obtained at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. This paper is for Chris Sneden, who at his review talk in 2003 February at the Carnegie symposium on "The Origin and Evolution of the Elements" appealed for someone to take another look at Pal 12. The entire Keck/HIRES user communities owes a huge debt to Jerry Nelson, Gerry Smith, Steve Vogt, and many other people, who have worked to make the Keck Telescope and HIRES a reality and to operate and maintain the Keck Observatory. We are grateful to the W. M. Keck Foundation for the vision to fund the construction of the W. M. Keck Observatory. The author wishes to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, none of the observations presented herein would have been possible. We are grateful to the National Science Foundation for partial support under grant AST 02-05951 to J. G. C. We thank Jason Prochaska and Andy McWilliam for providing their tables of hyperfine structure in digital form, and Andy McWilliam and Tammy Smecker-Hane for providing their Sgr dSph abundances in digital form in advance of publication.
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
NSFAST 02-05951
Subject Keywords:globular clusters: general; globular clusters: individual (Palomar 12) ; galaxies: individual (Sagittarius dSph) ; stars: abundances
Issue or Number:3
Record Number:CaltechAUTHORS:20190604-144843374
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Official Citation:Judith G. Cohen 2004 AJ 127 1545
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96121
Deposited By: George Porter
Deposited On:04 Jun 2019 22:09
Last Modified:16 Nov 2021 17:18

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