We used the new and homogeneous metallicity scale, derived by CG97 from updated model atmospheres and direct detailed abundance analysis of high resolution spectra of globular cluster giants, to calibrate the traditional RGB photometric indicators in terms of the [Fe/H] ratio.
Especially in the plane, the relations found provide very good relative determinations of [Fe/H] with an uncertainty on a single measurement of 0.08 dex on average, and as low as 0.04 dex. This goes towards lessening the disagreement existing in the past between photometric and spectroscopic determination of the metal abundance in globular clusters.
© European Southern Observatory (ESO) 1998
Online publication: December 16, 1997