Comparing the Properties of GMCs in M33 from Simulations and
  Observations
  We compare the properties of clouds in simulated M33 galaxies to those
observed in the real M33. We apply a friends of friends algorithm and CPROPS to
identify clouds, as well as a pixel by pixel analysis. We obtain very good
agreement between the number of clouds, and maximum mass of clouds. Both are
lower than occurs for a Milky Way-type galaxy and thus are a function of the
surface density, size and galactic potential of M33. We reproduce the observed
dependence of molecular cloud properties on radius in the simulations, and find
this is due to the variation in gas surface density with radius. The cloud
spectra also show good agreement between the simulations and observations, but
the exact slope and shape of the spectra depends on the algorithm used to find
clouds, and the range of cloud masses included when fitting the slope.
Properties such as cloud angular momentum, velocity dispersions and virial
relation are also in good agreement between the simulations and observations,
but do not necessarily distinguish between simulations of M33 and other galaxy
simulations. Our results are not strongly dependent on the level of feedback
used here (10 and 20%) although they suggest that 15% feedback efficiency may
be optimal. Overall our results suggest that the molecular cloud properties are
primarily dependent on the gas and mass surface density, and less dependent on
the localised physics such as the details of stellar feedback, or the numerical
code used.
