Ages of Dwarfs in the Solar Neighborhood: Considering C and O Enhancements

Precise stellar ages of stars are necessary to study the evolution of the Milky Way. The age determination is significantly affected by C and O abundances of stars due to their contribution to the overall metallicity and opacity. On the basis of C and O abundances derived from high-resolution observations, we determine the ages of 148 FGK-type dwarfs in the solar neighborhood by considering C and O enhancements individually. Our results show that using C and O enhancements individually could affect the age determination of the high-alpha population, especially for stars with [O/alpha] > 0.2 dex, making them about 1 Gyr younger compared to the results using traditional a-enhanced models. This results in a steeper slope in the age-[alpha/Fe] relation for the high-alpha population (changes from 0.0339 +/- 0.0075 to 0.0436 +/- 0.0086), indicating a higher formation rate. We find no tight relation between age and [alpha/Fe] or [O/Fe] in the high-alpha populations. The distribution of space velocity for young a-rich stars shows that they are more likely characterized to the low-a populations.