Chemical Evolution in the Milky Way: Rotation-based Ages for APOGEE-Kepler Cool Dwarf Stars

• Published in: The Astrophysical journal Vol. 888; no. 1; pp. 43 - 59
• Main Authors: Claytor, Zachary R., Saders, Jennifer L. van, Santos, Ângela R. G., García, Rafael A., Mathur, Savita, Tayar, Jamie, Pinsonneault, Marc H., Shetrone, Matthew
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01-01-2020; IOP Publishing
• Subjects: Abundance; Age; Analogs; Angular momentum; Astronomical models; Astrophysics; Chemical evolution; Dwarf stars; Galactic rotation; Galaxy chemical evolution; Main sequence stars; Massive stars; Milky Way; Organic chemistry; Stellar age; Stellar ages; Stellar evolution; Stellar models; Stellar rotation
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab5c24

We use models of stellar angular momentum evolution to determine ages for ∼500 stars in the APOGEE-Kepler Cool Dwarfs sample. We focus on lower-main-sequence stars, where other age-dating tools become ineffective. Our age distributions are compared to those derived from asteroseismic and giant samples and solar analogs. We are able to recover gyrochronological ages for old, lower-main-sequence stars, a remarkable improvement over prior work in hotter stars. Under our model assumptions, our ages have a median relative uncertainty of 14%, comparable to the age precision inferred for more massive stars using traditional methods. We investigate trends of Galactic -enhancement with age, finding evidence of a detection threshold between the age of the oldest -poor stars and that of the bulk -rich population. We argue that gyrochronology is an effective tool reaching ages of 10-12 Gyr in K and early M dwarfs. Finally, we present the first effort to quantify the impact of detailed abundance patterns on rotational evolution. We estimate a ∼15% bias in age for cool, -enhanced (+0.4 dex) stars when standard solar-abundance-pattern rotational models are used for age inference, rather than models that appropriately account for -enrichment.