The Cloud Factory I: Generating resolved filamentary molecular clouds
  from galactic-scale forces
  We introduce a new suite of simulations, "The Cloud Factory", which
self-consistently forms molecular cloud complexes at high enough resolution to
resolve internal substructure (up to 0.25 Msol in mass) all while including
galactic-scale forces. We use a version of the Arepo code modified to include a
detailed treatment of the physics of the cold molecular ISM, and an analytical
galactic gravitational potential for computational efficiency. The simulations
have nested levels of resolution, with the lowest layer tied to tracer
particles injected into individual cloud complexes. These tracer refinement
regions are embedded in the larger simulation so continue to experience forces
from outside the cloud. This allows the simulations to act as a laboratory for
testing the effect of galactic environment on star formation. Here we introduce
our method and investigate the effect of galactic environment on filamentary
clouds. We find that cloud complexes formed after a clustered burst of
feedback, have shorter lengths and are less likely to fragment compared to
quiescent clouds (e.g. the Musca filament) or those dominated by the galactic
potential (e.g. Nessie). Spiral arms and differential rotation preferentially
align filaments, but strong feedback randomises them. Long filaments formed
within the cloud complexes are necessarily coherent with low internal velocity
gradients, which has implications for the formation of filamentary
star-clusters. Cloud complexes formed in regions dominated by supernova
feedback have fewer star-forming cores, and these are more widely distributed.
These differences show galactic-scale forces can have a significant impact on
star formation within molecular clouds.
