Abundances and kinematics for ten anticentre open clusters
  Open clusters are distributed all across the disk and are convenient tracers
of its properties. In particular, outer disk clusters bear a key role for the
investigation of the chemical evolution of the Galactic disk. The goal of this
study is to derive homogeneous elemental abundances for a sample of ten outer
disk OCs, and investigate possible links with disk structures such as the
Galactic Anticenter Stellar Structure. We analyse high-resolution spectra of
red giants, obtained from the HIRES@Keck and UVES@VLT archives. We derive
elemental abundances and stellar atmosphere parameters by means of the
classical equivalent width method. We also performed orbit integrations using
proper motions. The Fe abundances we derive trace a shallow negative radial
metallicity gradient of slope -0.027+/-0.007 dex.kpc-1 in the outer 12 kpc of
the disk. The [alpha/Fe] gradient appears flat, with a slope of 0.006+/-0.007
dex.kpc-1 . The two outermost clusters (Be 29 and Sau 1) appear to follow
elliptical orbits. Be 20 also exhibits a peculiar orbit with a large excursion
above the plane. The irregular orbits of the three most metal-poor clusters (of
which two are located at the edge of the Galactic disk), if confirmed by more
robust astrometric measurements such as those of the Gaia mission, are
compatible with an inside-out formation scenario for the Milky Way, in which
extragalactic material is accreted onto the outer disk. We cannot determine if
Be 20, Be 29,and Sau 1 are of extragalactic origin, as they may be old genuine
Galactic clusters whose orbits were perturbed by accretion events or minor
mergers in the past 5 Gyr, or they may be representants of the thick disk
population. The nature of these objects is intriguing and deserves further
investigations in the near future.
