Determining Ages of APOGEE Giants with Known Distances Diane Feuillet New Mexico State University Jon Holtzman, Jo Bovy, Leo Girardi The APOGEE Team

Thick disk: Old Kinematically hot Metal poor Alpha rich Thin disk: Younger Kinematically cold Metal rich Alpha poor Metallicity gradients Age-metallicity relation Nidever Galactic Chemical Evolution Frinchaboy+ 2013

Apache Point Observatory Galactic Evolution Experiment Explore Galactic evolution through detailed chemical abundances R~23,000, μ spectrograph 130,000 red giants, ~400,000 in APOGEE-2

Abundances Across the Disk Hayden+ 2015

Abundances Across the Disk Hayden Direct comparisons of different radial bins is difficult SFR, inflow, mixing, etc

Absolute Ages of Stars Not Easy! Empirical o Gyrochronology o Chromospheric activity Model-dependent o Isochrone model matching o Asteroseismology Recently, CN abundances Age adds important third dimension to traditional [Fe/H] vs [α/Fe] space

Ages and Abundances Haywood Age adds crucial evolutionary information and population identification

Ages and Abundances ? ? ? Haywood+ 2013

Ages of Red Giants Age can be determined from mass Seismic masses are good, uncertainty ~15% CN masses L, T eff, log g mass Uncertainty depends on log g, ~0.11 dex or 30% PARSEC Bressan Feuillet dex uncertainty in age

Ages of Red Giants Use Bayesian isochrone matching with all parameters M V adds age resolution to giant branch PARSEC Feuillet+ 2016

Test Sample Isochrone points with APOGEE-like uncertainties imposed Bayesian Assume flat SFH in age Chabrier IMF Take mean of age PDF [Fe/H], T eff, M V, log g σ = Feuillet+ 2016

Local Sample 700 local giants within 400 pc Observed with 1m+APOGEE Reduced and analyzed with APOGEE software Hipparcos distances Apache Point Observatory Feuillet+ 2016

Local Sample 324 RC stars identified Feuillet+ 2016

Local Sample Reasonable age distribution Suggests age-alpha relation Observed Expected Feuillet+ 2016

Hierarchical Modeling Find a more informed prior for the SFH Use the full age PDF to constrain a model SFH α-dependent Gaussian SFH Feuillet+ 2016

Hierarchical Modeling Feuillet+ 2016

Age Trends Strong relation between α abundance and mean age of Gaussian model Age-metallicity relation consistent with other work Velocity dispersion consistent with GCS Feuillet+ 2016

Age Trends Strong relation between α abundance and mean age of Gaussian model Age-metallicity relation consistent with other work Velocity dispersion consistent with GCS Feuillet+ 2016

Age Trends Strong relation between α abundance and mean age of Gaussian model Age-metallicity relation consistent with other work Velocity dispersion consistent with GCS Feuillet+ 2016

Age Trends Strong relation between α abundance and mean age of Gaussian model Age-metallicity relation consistent with other work Velocity dispersion consistent with GCS Power law indices UVWTotal Feuillet GCS (Holmberg+ 2009) Feuillet+ 2016

Future Work Need large samples with distance measurements Apply to APOGEE RC sample Test monoabundance subsamples Expand hierarchical modeling method With Gaia distances APOGEE APOGEE-2 GALAH Gaia-ESO

Future Work Need large samples with distance measurements Apply to APOGEE RC sample Test monoabundance subsamples Expand hierarchical modeling method With Gaia distances APOGEE APOGEE-2 GALAH Gaia-ESO QUESTIONS?