COMMENTS ON THE DDO CALIBRATION AND THE DEMISE OF THE METAL-POOR DISK

The spectroscopic abundances of Ryan & Lambert [AJ, 109, 2068 (1995)] are reanalyzed and shown to be consistent with the general and detaile d conclusions of Twarog & Anthony-Twarog [AJ, 107, 1371 (1994)] regard ing the DDO calibration and the metal-weak thick disk. The metal-rich red giants form a natural extension of the trend found among stars wit h [Fe/H](SPEC)<-1.1, without any evidence for a significant break near [Fe/H](SPEC)= - 1.2. Using an expanded sample comprised of only high dispersion spectroscopic abundances, it is demonstrated that the origi nal DDO isometallicity relations based upon globular cluster giants di ffer in both slope and zero-point from the relations defined by the fi eld giants. The globular cluster calibrators at intermediate metallici ty exhibit systematically higher CN strength than the field stars at t he same [Fe/H]. At the metal-rich end, the 47 Tuc isometallicity relat ion reveals a dope which differs from the field stars in the same mann er as found for the intermediate-metallicity clusters. The hotter fiel d stars with [Fe/H](SPEC) between -0.35 and -0.55 occupy the same regi on of the C-0(3845)- C-0(4548) diagram as 47 Tuc. The possibility of p roblems with the zero points of the cluster and field star photometry is also noted. (C) 1996 American Astronomical Society.