Synthetic CO, H2 and HI surveys of the Galactic 2nd Quadrant, and the
  properties of molecular gas
  We present CO, H2, HI and HISA distributions from a set of simulations of
grand design spirals including stellar feedback, self-gravity, heating and
cooling. We replicate the emission of the 2nd Galactic Quadrant by placing the
observer inside the modelled galaxies and post process the simulations using a
radiative transfer code, so as to create synthetic observations. We compare the
synthetic datacubes to observations of the 2nd Quadrant of the Milky Way to
test the ability of the current models to reproduce the basic chemistry of the
Galactic ISM, as well as to test how sensitive such galaxy models are to
different recipes of chemistry and/or feedback. We find that models which
include feedback and self-gravity can reproduce the production of CO with
respect to H2 as observed in our Galaxy, as well as the distribution of the
material perpendicular to the Galactic plane. While changes in the
chemistry/feedback recipes do not have a huge impact on the statistical
properties of the chemistry in the simulated galaxies, we find that the
inclusion of both feedback and self-gravity are crucial ingredients, as our
test without feedback failed to reproduce all of the observables. Finally, even
though the transition from H2 to CO seems to be robust, we find that all models
seem to underproduce molecular gas, and have a lower molecular to atomic gas
fraction than is observed. Nevertheless, our fiducial model with feedback and
self-gravity has shown to be robust in reproducing the statistical properties
of the basic molecular gas components of the ISM in our Galaxy.
