Abundance of the α elements Ca, Mg, Si, Ti ii and combined α relative to iron (Fe i) as a function of [Fe i/H]. The sample is split into stars that have spatial and kinematic properties compatible with membership to the Sag stream (green) and those unlikely to be compatible (purple). The other symbols indicate the chemical abundances for samples of stars in MW satellites, as described in the legend (Fnx = Fornax, Scl = Sculptor).