Resolving Giant Molecular Clouds in NGC 300: A First Look with the
  Submillimeter Array
  We present the first high angular resolution study of giant molecular clouds
(GMCs) in the nearby spiral galaxy NGC 300, based on observations from the
Submillimeter Array (SMA). We target eleven 500 pc-sized regions of active star
formation within the galaxy in the CO(J=2-1) line at 40 pc spatial and 1 km/s
spectral resolution and identify 45 individual GMCs. We characterize the
physical properties of these GMCs, and find that they are similar to GMCs in
the disks of the Milky Way and other nearby spiral galaxies. For example, the
GMC mass spectrum in our sample has a slope of 1.80+/-0.07. Twelve clouds are
spatially resolved by our observations, of which ten have virial mass estimates
that agree to within a factor of two with mass estimates derived directly from
CO integrated intensity, suggesting that the majority of these GMCs are bound.
The resolved clouds show consistency with Larson's fundamental relations
between size, linewidth, and mass observed in the Milky Way. We find that the
linewidth scales with the size as DeltaV ~ R^(0.52+/-0.20), and the median
surface density in the subsample is 54 Msun/pc^(-2). We detect 13CO in four
GMCs and find a mean 12CO/13CO flux ratio of 6.2. Our interferometric
observations recover between 30% and 100% of the integrated intensity from the
APEX single dish CO observations of Faesi et al. 2014, suggesting the presence
of low-mass GMCs and/or diffuse gas below our sensitivity limit. The fraction
of APEX emission recovered increases with the SMA total intensity as well as
with the star formation rate.
