X-ray haloes and star formation in early-type galaxies
  High resolution 2D hydrodynamical simulations describing the evolution of the
hot ISM in axisymmetric two-component models of early-type galaxies well
reproduced the observed trends of the X-ray luminosity ($L_\mathrm{x}$) and
temperature ($T_\mathrm{x}$) with galaxy shape and rotation, however they also
revealed the formation of an exceedingly massive cooled gas disc in rotating
systems. In a follow-up of this study, here we investigate the effects of star
formation in the disc, including the consequent injection of mass, momentum and
energy in the pre-existing interstellar medium. It is found that subsequent
generations of stars originate one after the other in the equatorial region;
the mean age of the new stars is $> 5$ Gyr, and the adopted recipe for star
formation can reproduce the empirical Kennicutt-Schmidt relation. The results
of the previous investigation without star formation, concerning $L_\mathrm{x}$
and $T_\mathrm{x}$ of the hot gas, and their trends with galactic shape and
rotation, are confirmed. At the same time, the consumption of most of the cold
gas disc into new stars leads to more realistic final systems, whose cold gas
mass and star formation rate agree well with those observed in the local
universe. In particular, our models could explain the observation of
kinematically aligned gas in massive, fast-rotating early-type galaxies.
