As part of a series of papers aimed at understanding the evolution of the Milky Way ’ s Central Molecular Zone ( CMZ ) , we present hydrodynamical simulations of turbulent molecular clouds orbiting in an accurate model of the gravitational potential extant there .
We consider two sets of model clouds differing in the energy content of their velocity fields .
In the first , self–virialised set , the turbulent kinetic energies are chosen to be close in magnitude to the clouds ’ self–gravitational potential energies .
Comparison with isolated clouds evolving without an external potential shows that the self–virialised clouds are unable to withstand the compressive tidal field of the CMZ and rapidly collapse , forming stars much faster and reaching gas exhaustion after a small fraction of a Galactocentric orbit .
In the second , tidally–virialised , set of simulations , the clouds ’ turbulent kinetic energies are in equilibrium with the external tidal field .
These models are better supported against the field and the stronger turbulence suppresses star formation .
Our results strongly support the inference that anomalously low star formation rates in the CMZ are due primarily to high velocity dispersions in the molecular gas .
The clouds follow open , eccentric orbits oscillating in all three spatial coordinates .
We examine the consequences of the orbital dynamics , particularly pericentre passage , by performing companion simulations of clouds on circular orbits .
The increased tidal forces at pericentre produce transient accelerations in star formation rates of at most a factor of 2.7 .
Our results demonstrate that modelling star formation in galactic centres requires the inclusion of tidal forces .