Properties of thick discs formed in clumpy galaxies
  We examine a possible formation scenario of galactic thick discs with
numerical simulations. Thick discs have previously been argued to form in
clumpy disc phase in the high-redshift Universe, which host giant clumps of
<10^9 M_sun in their highly gas-rich discs. We performed SPH simulations using
isolated galaxy models for the purpose of verifying whether dynamical and
chemical properties of the thick discs formed in such clumpy galaxies are
compatible with observations. The results of our simulations seem nearly
consistent with observations in dynamical properties such as radial and
vertical density profiles, significant rotation velocity lag with height and
distributions of orbital eccentricities. In addition, the thick discs in our
simulations indicate nearly exponential dependence of azimuthal and vertical
velocity dispersions with radius, nearly isothermal kinematics in vertical
direction and negligible metallicity gradients in radial and vertical
directions. However, our simulations cannot reproduce altitudinal dependence of
eccentricities, metallicity relations with eccentricities or rotation
velocities, which shows striking discrepancy from recent observations of the
Galactic thick disc. From this result, we infer that the clumpy disc scenario
for thick-disc formation would not be suitable at least for the Milky Way. Our
study, however, cannot reject this scenario for external galaxies if not all
galaxies form their thick discs by the same process. In addition, we found that
a large fraction of thick-disc stars forms in giant clumps.
