We perform an extensive test of theoretical stellar models for main-sequence (MS) stars in ugriz, using cluster fiducial sequences obtained in the previous paper of this series. We generate a set of isochrones using the Yale Rotating Evolutionary Code with updated input physics, and derive magnitudes and colors in ugriz from MARCS model atmospheres. Thesemodelsmatch clusterMSs over a wide range of metallicity within the errors of the adopted cluster parameters. However, we find a large discrepancy ofmodel colors at the lowerMS (Teff ≲ 4500 K) for clusters at and above solarmetallicity.We also reach similar conclusions using the theoretical isochrones of Girardi et al. and Dotter et al., but our new models are generally in better agreement with the data. Using our theoretical isochrones, we also derive MS-fitting distances and turnoff ages for five key globular clusters, and demonstrate the ability to derive these quantities from photometric data in the Sloan Digital Sky Survey. In particular, we exploit multiple color indices (g - r, g - i, and g - z) in the parameter estimation, which allows us to evaluate internal systematic errors. Our distance estimates, with an error of σ(m-M) = 0.03-0.11 mag for individual clusters, are consistent with Hipparcos-based subdwarf-fitting distances derived in the Johnson-Cousins or Stromgren photometric systems.
- Globular clusters
- Hertzsprung-russell (hr) diagram
- Individual (m3
- Individual (m67
- Ngc 6791)
- Open clusters and associations