Left: spatial distribution (bottom), CMD (top-right), and radial velocity distribution of the RAVE stars in a 20 degree field centered on NGC 1851. The crosses (red in the online version) show the RAVE stars whereas the triangles (blue in the online version) show the NGC 1851 stars from Milone et al. (2009) and Carretta et al. (2011). The circled RAVE stars are those for which a chemical analysis could be carried out. In the bottom panel we also show the expected angular distribution of tidal debris stars (black dots) as predicted by an N-body simulation of the cluster orbiting the MW for one Gyr on the most likely orbit (see Sect. 3.2 for details). Right: [ Fe / H ], [ Si / Fe ] and [ Mg / Fe ] ratio of a subsample of these same stars for which abundances could be determined. The triangles (green in the online version) are the parameters of the NGC 1851 red giant stars obtained from intermediate-resolution spectra by Carretta et al. (2011, 2012).