Detailed representation of the [O/Fe] abundance ratio. Left panel: Zoom into the [O/Fe] vs. [Fe/H] plot of Fig. 6 with upper limits (solid triangles). Right panel: [O/Fe] vs. [P/Fe] to illustrate the correlation between P and O. Solid circles correspond to real measurements in both O and in P, empty circles to upper limits in P, solid triangles to upper limits in O, and empty triangles denote upper limits in O and P. Error bars are defined to reflect the typical standard deviation given in Table D.2