Metal content of K giants in the nuclear bulge of the galaxy

Whitford, A.E. & Rich, R.M. 1983. Ap. J. 274, 723.

The metallicity of 21 K giants in Baade's (1963) window has been determined by comparison of the strengths of strong iron lines and the Mg b feature with those in 22 calibration stars having high-resolution abundance analyses. The (J-K) colors were used to separate the effects of temperature and metallicity on line strengths. The majority of the stars are super-metal-rich with a mean aggregate forbidden Fe/forbidden H = 0.29 or 0.44 and an upper extreme forbidden Fe/forbidden H = 0.7 or 1.0, depending on the method of extrapolation for stars more metal-rich than any solar neighborhood calibration stars. These values for individual stars support the super-metal-rich explanation of very strong lines in the spectra of unresolved external galaxies. The minority fraction of metal-poor stars, for which aggregate forbidden Fe/forbidden H is about -1.0, includes the progenitors of Baade's RR Lyrae variables. The small-number statistics of the present sample leave the relative proportion of the metal-poor stars and their possible status as a separate group uncertain.