Toward Better Age Estimates for Stellar Populations: The Y2 Isochrones for Solar Mixture

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