Luminosity-stellar [Fe/H] relation for Local Group dwarf galaxies. Blue stars represent the MW-dSph satellites; red squares are M31-dSph satellites; green diamonds are dIrrs in the LG; the black circle is the position of Aquarius based on the [Fe/H] derived in this work; gray lines are the least-squares linear fit for the dIrrs and MW dSphs and the 0.16 scatter limits. All the values apart from Aquarius were taken from Kirby et al. (2013).