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arXiv:astro-ph/0011139 (astro-ph)
[Submitted on 7 Nov 2000]

Title:47 Tuc: The Spectroscopic Versus CMD Age Discrepancy

Authors:Alexandre Vazdekis, Maurizio Salaris, Nobuo Arimoto, James A. Rose
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Abstract: We investigate current problems in obtaining reliable ages for old stellar systems based on stellar population synthesis modelling of their integrated spectra. In particular, we address the large ages derived for the globular cluster 47 Tuc, which is at odds with its Color-Magnitude-Diagram (CMD) age. Using a new age indicator, Hgamma_sigma<130, which is particularly effective at breaking the degeneracy between age and metallicity, we confirm the discrepancy between the spectroscopic age and the CMD age of 47 Tuc, in that the spectroscopic age is much older. Nebular emission appears unlikely to be a source for weakening the observed Balmer lines. We then explore a number of key parameters affecting the temperature of Turn-Off stars, which are the main contributors to the Balmer lines for old metal-rich stellar populations. We find that alpha-enhanced isochrones with atomic diffusion included not only provides a good fit to the CMD of 47 Tuc, but also leads to a spectroscopic age in better agreement with the CMD age.
Comments: 7 pages, 5 figures. Accepted for publication in The Astrophysical Journal, vol. 549, Mar 1, 2001 issue
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:astro-ph/0011139
  (or arXiv:astro-ph/0011139v1 for this version)
  https://doi.org/10.48550/arXiv.astro-ph/0011139

Submission history

From: Alexandre Vazdekis [view email]
[v1] Tue, 7 Nov 2000 10:41:23 UTC (230 KB)
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