The Old Halo metallicity gradient:
the trace of a self-enrichment process
Figure 1.
he whole galactic Halo exhibits no clear-cut
dependence of the metallicity on the galactocentric distance.
It includes different subpopulations,
such as the Old Halo and the Younger Halo.
For the meaning of the different symbols, see
Sect. 4.1.
Data are based on Harris 1996