The role of galactic dynamics in shaping the physical properties of
  giant molecular clouds in Milky Way-like galaxies
  We examine the role of the large-scale galactic-dynamical environment in
setting the properties of giant molecular clouds in Milky Way-like galaxies. We
perform three high-resolution simulations of Milky Way-like discs with the
moving-mesh hydrodynamics code Arepo, yielding a statistical sample of $\sim
80,000$ giant molecular clouds and $\sim 55,000$ HI clouds. We account for the
self-gravity of the gas, momentum and thermal energy injection from supernovae
and HII regions, mass injection from stellar winds, and the non-equilibrium
chemistry of hydrogen, carbon and oxygen. By varying the external gravitational
potential, we probe galactic-dynamical environments spanning an order of
magnitude in the orbital angular velocity, gravitational stability, mid-plane
pressure and the gradient of the galactic rotation curve. The simulated
molecular clouds are highly overdense ($\sim 100\times$) and over-pressured
($\sim 25\times$) relative to the ambient interstellar medium. Their
gravo-turbulent and star-forming properties are decoupled from the dynamics of
the galactic mid-plane, so that the kpc-scale star formation rate surface
density is related only to the number of molecular clouds per unit area of the
galactic mid-plane. Despite this, the clouds display clear,
statistically-significant correlations of their rotational properties with the
rates of galactic shearing and gravitational free-fall. We find that galactic
rotation and gravitational instability can influence their elongation, angular
momenta, and tangential velocity dispersions. The lower pressures and densities
of the HI clouds allow for a greater range of significant dynamical
correlations, mirroring the rotational properties of the molecular clouds,
while also displaying a coupling of their gravitational and turbulent
properties to the galactic-dynamical environment.
