ALMA CO Clouds and Young Star Complexes in the Interacting Galaxies IC
  2163 and NGC 2207
  ALMA observations of CO(1-0) emission in the interacting galaxies IC 2163 and
NGC 2207 are used to determine the properties of molecular clouds and their
association with star-forming regions observed with the Hubble Space Telescope.
Half of the CO mass is in 249 clouds each more massive than 4.0x10^5Mo. The
mass distribution functions for the CO clouds and star complexes in a
galactic-scale shock front in IC 2163 both have a slope on a log-log plot of
-0.7, similar to what is observed in Milky Way clouds. The molecular cloud mass
function is steeper in NGC 2207. The CO distribution in NGC 2207 also includes
a nuclear ring, a mini-bar, and a mini-starburst region that dominates the
24micron, radio, and Halpha emission in both galaxies. The ratio of the sum of
the masses of star complexes younger than 30 Myr to the associated molecular
cloud masses is ~4%. The maximum age of star complexes in the galactic-scale
shock front in IC 2163 is about 200 Myr, the same as the interaction time of
the two galaxies, suggesting the destruction of older complexes in the eyelids.
