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We report the H13CO+(1-0) survey observations toward embedded clustersobtained using the Nobeyama 45m telescope, which were performed to follow upour previous study in the C18O survey with a dense gas tracer. Our aim is toaddress the evolution of cluster-forming clumps. We observed the same 14clusters in C18O, which are located at distances from 0.3-2.1kpc with 27"resolution in H13CO+. We detected the 13 clumps in H13CO+ line emission andobtained the physical parameters of the clumps with radii of 0.24-0.75pc,masses of 100-1400Msun, and velocity widths in FWHM of 1.5-4.0kms^-1. The meandensity is 3.9x10^4cm^-3 and the equivalent Jeans length is 0.13pc at 20K. Weclassified the H13CO+ clumps into three types, Type A, B, and C according tothe relative locations of the H13CO+ clumps and the clusters. Ourclassification represents an evolutionary trend of cluster-forming clumpsbecause dense clumps are expected to be converted into stellar constituents, ordispersed by stellar activities. We found a similar but clearer trend than ourprevious results for derived star formation efficiencies to increase from TypeA to C in the H13CO+ data, and for the dense gas regions within the clumpstraced by H13CO+ to be sensitive to the physical evolution of clump-clustersystems. In addition, we found that four out of 13 H13CO+ clumps which we namedDVSOs(Distinct Velocity Structure Objects) have distinct velocity gradients atthe central parts of them. Assuming that the velocity gradients represent therigid-like rotation of the clumps, we calculated the virial parameter of theH13CO+ clumps by taking into account the contribution of rotation, and foundthat the DVSOs tend to be gravitationally unbound. In order to explain theabove physical properties for DVSOs, we propose a clump-clump collision modelas a possible mechanism for triggering formation of clusters.

A Mapping Survey of Dense Clumps Associated with Embedded Clusters II : Can Clump-Clump Collisions Induce Stellar Clusters?