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Fig. 3


Upper panels: Yonsei-Yale isochrones for 1 Gyr (dashed lines), 5 Gyr (dotted lines), and 12 Gyr (full lines) for one particular metallicity. For [Fe/H]  =  −3 and [Fe/H]  =  −2, [α/Fe]  = 0.4, for [Fe/H]  = 0.0, [α/Fe]  = 0.0 and for [Fe/H]  =  −1 both alpha enhancements are given ([α/Fe]  = 0.0 in gray). All values for which the synthetic spectra are calculated are covered with a gray dot. Overplotted are regions where the giants above the HB (green), (sub)giants below the HB (blue) and main-sequence (red) branches would lie in Teff − log (g) space, if the temperature restrictions from photometry are taken into account (vertical dotted lines). Lower panels: EWs for the two strongest CaT line versus the MgI 8806.8 line for models that fall within the boxes of the panel above. Giants above the HB are shown as green triangles, (sub)giants below the HB as blue diamonds and dwarfs as red asterisks. Overplotted is a distinction line for dwarfs and giants (except for the extremely low-metallicity case), and is the same in all panels.

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