Toward better age estimates for stellar populations

The Y2 isochrones for solar mixture

Sukyoung Yi, Pierre Demarque, Yong Cheol Kim, Young-Wook Lee, Chang H. Ree, Thibault Lejeune, Sydney Barnes

Research output: Contribution to journalArticle

596 Citations (Scopus)

Abstract

We have constructed a new set of isochrones, called the Y2 Isochrones, that represent an update of the Revised Yale Isochrones (RYI), using improved opacities and equations of state. Helium diffusion and convective core overshoot have also been taken into consideration. This first set of isochrones is for the scaled solar mixture. A subsequent paper will consider the effects of α-element enhancement, believed to be relevant in many stellar systems. Two additionally significant features of these isochrones are that (1) the stellar models start their evolution from the pre - main-sequence birthline instead of from the zero-age main sequence and (2) the color transformation has been performed using both the latest table of Lejeune et al., and the older, but now modified, Green et al. table. The isochrones have performed well under the tests conducted thus far. The reduction in the age of the Galactic globular clusters caused by this update in stellar models alone is approximately 15% relative to RYI-based studies. When the suggested modification for the α-element enhancement is made as well, the total age reduction becomes approximately 20%. When post-RGB evolutionary stages are included, we find that the ages of globular clusters derived from integrated colors are consistent with the isochrone fitting ages.

Original languageEnglish
Pages (from-to)417-437
Number of pages21
JournalAstrophysical Journal, Supplement Series
Volume136
Issue number2
DOIs
Publication statusPublished - 2001 Oct 1

Fingerprint

stellar models
globular clusters
color
stellar systems
augmentation
estimates
opacity
equations of state
helium
equation of state

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Yi, Sukyoung ; Demarque, Pierre ; Kim, Yong Cheol ; Lee, Young-Wook ; Ree, Chang H. ; Lejeune, Thibault ; Barnes, Sydney. / Toward better age estimates for stellar populations : The Y2 isochrones for solar mixture. In: Astrophysical Journal, Supplement Series. 2001 ; Vol. 136, No. 2. pp. 417-437.
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Toward better age estimates for stellar populations : The Y2 isochrones for solar mixture. / Yi, Sukyoung; Demarque, Pierre; Kim, Yong Cheol; Lee, Young-Wook; Ree, Chang H.; Lejeune, Thibault; Barnes, Sydney.

In: Astrophysical Journal, Supplement Series, Vol. 136, No. 2, 01.10.2001, p. 417-437.

Research output: Contribution to journalArticle

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