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Outer Versus Inner Halo Globular Clusters: NGC 7492 Abundances

Cohen, Judith G. and Meléndez, Jorge (2005) Outer Versus Inner Halo Globular Clusters: NGC 7492 Abundances. Astronomical Journal, 129 (3). pp. 1607-1615. ISSN 0004-6256. doi:10.1086/427717.

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We have carried out a detailed abundance analysis for 21 elements in a sample of four RGB stars in the outer halo globular cluster NGC 7492 (R_(GC) 25 kpc); we find [Fe/H] = -1.82 dex inferred from Fe Ilines (-1.79 from Fe II) using high-dispersion (R = λ/Δλ = 35,000) spectra obtained with HIRES at the Keck Observatory. Most elements show no sign of star-to-star variation within our limited sample. We have, however, detected an anticorrelation between O and Na abundances similar to that seen in our previous analyses of inner halo GCs as well as in studies of relatively nearby GCs by others. We compare the abundance ratios in NGC 7492 with those we previously determined for the much closer old halo GCs M3 and M13. After making corrections for trends of abundance ratio with metallicity characteristic of halo stars, we find that for these three GCs, for each of the elements in common we deduce identical abundance ratios with respect to Fe to within the probable measurement uncertainties. Thus, the chemical history of the outer halo as exemplified by the metal-poor outer halo globular cluster NGC 7492 is indistinguishable from that of the inner halo, exemplified by M3 and M13, at least through the epoch of formation of these old globular clusters. This applies to the neutron capture processes as well.

Item Type:Article
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URLURL TypeDescription Paper
Cohen, Judith G.0000-0002-8039-4673
Meléndez, Jorge0000-0002-4933-2239
Additional Information:© 2005 The American Astronomical Society. 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. 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 authors wish 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. This publication makes use of data from the Two Micron All-Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, funded by the National Aeronautics and Space Administration and the National Science Foundation. We are grateful to the National Science Foundation for partial support under grant AST 02-05951 to J. G. C.
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
NSFAST 02-05951
Subject Keywords:Galaxy: halo — globular clusters: general — globular clusters: individual (NGC 7492) — stars: abundances
Issue or Number:3
Record Number:CaltechAUTHORS:20190522-081846297
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Official Citation:Judith G. Cohen and Jorge Melendez 2005 AJ 129 1607
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95684
Deposited By: Tony Diaz
Deposited On:22 May 2019 22:39
Last Modified:16 Nov 2021 17:14

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