[C/Fe] versus the bolometric luminosity of the target stars (black asterisks). Both the classical definition for carbon-rich ([C/Fe]  > 1, horizontal dotted line) and the definition from Aoki et al. (2007) taking into account mixing on the RGB (dashed line) are indicated. One Sculptor star from Tafelmeyer et al. (2010) is shown as a large black open triangle. The upper limit for the Sculptor star of Frebel et al. (2010a) is shown as a black arrow and upper limits for Carina stars from (Venn et al. 2012) are shown as gray arrows. Stars from other dwarf galaxies are shown as open gray circles (Fulbright et al. 2004; Cohen & Huang 2009; Tafelmeyer et al. 2010; Norris et al. 2010b,a; Honda et al. 2011; Lai et al. 2011).