A Mapping Survey of Dense Clumps Associated with Embedded Clusters :
  Evolutionary Stages of Cluster-Forming Clumps
  We have carried out a survey of the dense clumps associated with 14 embedded
clusters in the C^18O (J=1-0) line emission with the Nobeyama 45m telescope in
order to understand the formation and evolution of stellar clusters in dense
clumps of molecular clouds. We have selected these clusters at distances from
0.3 to 2.1kpc and have mapped about 6' X 6' to 10' X 10'regions (corresponding
to 3.8pc X 3.8pc at 2.1kpc) for all the clumps with 22" resolution
(corresponding to Jeans length at 2.1kpc). We have obtained dense clumps with
radii of 0.40-1.6pc, masses of 150-4600M_sun, and velocity widths in FWHM of
1.4-3.3kms^-1. Most of the clumps are found to be approximately in virial
equilibrium, which implies that C^18O gas represents parental dense clumps for
cluster formation. From the spatial relation between the distributions of
clumps and clusters, we classified C^18O clumps into three types (Type A, B,
and C). The C^18O clumps as classified into Type A have emission distributions
with a single peak at the stellar clusters and higher brightness contrast than
that of other target sources. Type B clumps have double or triple peaks which
are associated with the cluster and moderately high brightness contrast
structure. Type C clumps have also multiple peaks although they are not
associated with the cluster and low brightness contrast structure. We suggest
that our classification represents an evolutionary trend of cluster-forming
dense clumps because dense gas in molecular clouds is expected to be converted
into stellar constituents, or to be dispersed by stellar activities. Moreover,
although there is a scatter, we found a tendency that the SFEs of the dense
clumps increase from Type A to Type C, which also supports our scenario.
