A monolithic collapse origin for the thin/thick disc structure of ESO
  243-49
  ESO 243-49 is a high-mass (circular velocity $v_{\rm c}\approx200\,{\rm
km\,s^{-1}}$) edge-on S0 galaxy in the Abell 2877 cluster at a distance of
$\sim95\,{\rm Mpc}$. To elucidate the origin of its thick disc, we use MUSE
science verification data to study its kinematics and stellar populations. The
thick disc emits $\sim80\%$ of the light at heights in excess of
$3.5^{\prime\prime}$ ($1.6\,{\rm kpc}$). The rotation velocities of its stars
lag by $30-40\,{\rm km\,s^{-1}}$ compared to those in the thin disc, which is
compatible with the asymmetric drift. The thick disc is found to be more
metal-poor than the thin disc, but both discs have old ages. We suggest an
internal origin for the thick disc stars in high-mass galaxies. We propose that
the thick disc formed either ${\rm a)}$ first in a turbulent phase with a high
star formation rate and that a thin disc formed shortly afterwards, or ${\rm
b)}$ because of the dynamical heating of a thin pre-existing component. Either
way, the star formation in ESO 243-49 was quenched just a few Gyrs after the
galaxy was born and the formation of a thin and a thick disc must have occurred
before the galaxy stopped forming stars. The formation of the discs was so fast
that it could be described as a monolithic collapse where several generations
of stars formed in a rapid succession.
