  We study the physical properties of giant molecular cloud associations (GMAs)
in M100 (NGC 4321) using the ALMA Science Verification feathered (12-m+ACA)
data in 12CO (1-0). To examine the environmental dependence of GMA properties,
GMAs are classified based on their locations in the various environments as
circumnuclear ring (CNR), bar, spiral, and inter-arm GMAs. The CNR GMAs are
massive and compact, while the inter-arm GMAs are diffuse with low surface
density. GMA mass and size are strongly correlated, as suggested by Larson
(1981). However, the diverse power-law index of the relation implies that the
GMA properties are not uniform among the environments. The CNR and bar GMAs
show higher velocity dispersion than those in other environments. We find
little evidence for a correlation between GMA velocity dispersion and size,
which indicates that the GMAs are in diverse dynamical states. Indeed, the
virial parameter of GMAs spans nearly two orders of magnitude. Only the spiral
GMAs are in general self-gravitating. Star formation activity of the GMAs
decreases in order over the CNR, spiral, bar, and the inter-arm GMAs. The
diverse GMA and star formation properties in different environments lead to
variations in the Kennicutt-Schmidt relation. A combination of multiple
mechanisms or gas phase change is necessary to explain the observed slopes.
Comparisons of GMA properties acquired with the use of the 12-m-array
observations with those from the feathered data are also presented. The results
show that the missing flux and extended emission cannot be neglected for the
study of environmental dependence.
