More pieces of the puzzle: Chemistry and substructures in the Galactic
  thick disk
  We present a study of the chemical abundances of Solar neighbourhood stars
associated to dynamical structures in the Milky Way's (thick) disk. These stars
were identified as overdensity in the eccentricity range 0.3< ecc < 0.5 in the
Copenhagen-Geneva Survey by Helmi et al. (2006). We find that the stars with
these dynamical characteristics do not constitute a homogeneous population. A
relatively sharp transition in dynamical and chemical properties appears to
occur at a metallicity of [Fe/H] ~ -0.4. Stars with [Fe/H] > -0.4 have mostly
lower eccentricities, smaller vertical velocity dispersions, are alpha-enhanced
and define a rather narrow sequence in [alpha/Fe] vs [Fe/H], clearly distinct
from that of the thin disk. Stars with [Fe/H] < -0.4 have a range of
eccentricities, are hotter vertically, and depict a larger spread in
[alpha/Fe]. We have also found tentative evidence of substructure possibly
associated to the disruption of a metal-rich star cluster. The differences
between these populations of stars is also present in e.g. [Zn/Fe], [Ni/Fe] and
[SmII/Fe], suggesting a real physical distinction.
