천문학회보 (The Bulletin of The Korean Astronomical Society)
- 제35권2호
- /
- Pages.81.2-81.2
- /
- 2010
- /
- 1226-2692(pISSN)
The Effect of Horizontal Branch Stars on the Age-Dating of Simple Stellar Populations
- Chung, Chul (Department of Astronomy, Yonsei University) ;
- Lee, Young-Wook (Department of Astronomy, Yonsei University) ;
- Yoon, Suk-Jin (Department of Astronomy, Yonsei University)
- 발행 : 2010.10.06
초록
Based on Yonsei Evolutionary Population Synthesis (YEPS), we have investigated the effect of horizontal branch stars (HBs) on the age-dating of simple stellar populations (SSPs). A detailed comparison of YEPS SSP with H_beta of M31 globular clusters (GCs) reveals (1) that the age dating without HB prescription gives ~5 Gyr younger ages for metal-poor M31 GCs, and (2) the age dating with HB prescription does not need any age gap between metal-poor and metal-rich GCs. This result is parallel to the well-known discrepancy in ages derived from integrated Balmer strengths and isochrone fittings of Milky Way GCs (MWGCs). Without a synthetic blue HB model, we cannot explain strong Balmer indices of metal-poor and old MWGCs. Our results suggest that the SSP model with well calibrated HBs should be used for the age-dating of SSPs to avoid a serious underestimation of ages due to the strong Balmer indices.
키워드