Through thick and thin: Structure of the Galactic thick disc from
  extragalactic surveys
  We aim to understand the accretion history of the Milky Way by exploring the
vertical and radial properties of the Galactic thick disc.
  We study the chemical and kinematic properties of roughly a thousand spectra
of faint magnitude foreground Galactic stars observed serendipitously during
extra-galactic surveys in four lines-of-sight: three in the southern Galactic
hemisphere (surveys of the Carina, Fornax and Sculptor dwarf spheroidal
galaxies) and one in the northern Galactic hemisphere (a survey of the Sextans
dwarf spheroidal galaxy). The foreground stars span distances up to 3kpc from
the Galactic plane and Galactocentric radii up to 11kpc.
  Only three lines-of-sight have a sufficient number of foreground stars for a
robust analysis. Towards Sextans in the Northern Galactic hemisphere and
Sculptor in the South, we measure a consistent decrease in mean metallicity
with height from the Galactic plane, suggesting a chemically symmetric thick
disc. This decrease can either be due to an intrinsic thick disc metallicity
gradient, or simply due to a change in the thin disc/thick disc population
ratio and no intrinsic metallicity gradients for the thick disc. We favour the
latter explanation. In contrast, we find evidence of an unpredicted metal-poor
population in the direction of Carina. This population was earlier detected by
Wyse et al. (2006), but our more detailed analysis provides robust estimates of
its location (|Z|<1kpc), metallicity (-2<[M/H]<-1 dex) and azimuthal orbital
velocity (V_phi ~120 km/s).
  Given the chemo-dynamical properties of the over-density towards the Carina
line-of-sight, we suggest that it represents the metal-poor tail of the
canonical thick disc. In spite of the small number of stars available, we
suggest that this metal-weak thick disc follows the often suggested thick disc
velocity-metallicity correlation of dV_phi/d[M/H]~40-50km/s/dex.
