The Chemical-Composition of Distant Globular-Clusters - Are There Any Metal-Poor Clusters

The authors report echelle spectroscopy of giants in the distant globular clusters N4147, M53, N5466, and N6229. Abundances are determined from model atmosphere analyses of the equivalent widths of the metal lines. The analyses yield [Fe/H] values in the range of -1.3 to -1.9. These values are moderately high for clusters at these galactocentric distances (R ≡ 20 kpc). The data argue against the existence of a strong metallicity gradient in the halo. They may also suggest that the cluster system of the Galaxy predates the formation of the bulge and halo system