Tidal stability of giant molecular clouds in the Large Magellanic Cloud
  Star formation does not occur until the onset of gravitational collapse
inside giant molecular clouds. However, the conditions that initiate cloud
collapse and regulate the star formation process remain poorly understood.
Local processes such as turbulence and magnetic fields can act to promote or
prevent collapse. On larger scales, the galactic potential can also influence
cloud stability and is traditionally assessed by the tidal and shear effects.
In this paper, we examine the stability of giant molecular clouds (GMCs) in the
Large Magellanic Cloud (LMC) against shear and the galactic tide using CO data
from the Magellanic Mopra Assessment (MAGMA) and rotation curve data from the
literature. We calculate the tidal acceleration experienced by individual GMCs
and determine the minimum cloud mass required for tidal stability. We also
calculate the shear parameter, which is a measure of a clouds susceptibility to
disruption via shearing forces in the galactic disk. We examine whether there
are correlations between the properties and star forming activity of GMCs and
their stability against shear and tidal disruption. We find that the GMCs are
in approximate tidal balance in the LMC, and that shear is unlikely to affect
their further evolution. GMCs with masses close to the minimal stable mass
against tidal disruption are not unusual in terms of their mass, location, or
CO brightness, but we note that GMCs with large velocity dispersion tend to be
more sensitive to tidal instability. We also note that GMCs with smaller radii,
which represent the majority of our sample, tend to more strongly resist tidal
and shear disruption. Our results demonstrate that star formation in the LMC is
not inhibited by to tidal or shear instability.
