Schematic representation of the new parameters introduced in this paper, namely [α/Fe]_o and [Fe/H]_o. These represent the average [α/Fe] and [Fe/H] of stars older than 9.5 Gyr on a per galaxy basis. The upper panel shows a schematic star formation history, which separates into these two stellar populations. The lower panels depicts on the standard [α/Fe] vs. [Fe/H] diagram familiar for the Milky Way what is expected for the old and intermediate age stars respectively.