Chemical evolution in the Milky Way Disk

Classical models of galactic evolution predict a smooth rise in heavy‐element abundance (metallicity) with time. We test this prediction with a new, large and unbiased sample of long‐lived stars in the solar neighbourhood and find that several of the key tests fail to support the classical predictions. In agreement with earlier studies, our observed metallicity distribution function is deficient in low‐mass metal‐poor stars from the generation that produced the heavy elements seen in the Sun and younger stars. In contrast to some earlier studies, we find no clear rise in overall metallicity with time in the Solar neighbourhood; we also find that the galactic disk has experienced kinematic heating throughout its life, and identify groups of stars that may be traces of dwarf galaxies that have merged with the Milky Way.