Physical Properties of Molecular Cloud Cores in L1630 and Implications for Star Formation

Abstract

We present the results of a multitransition, CS study of massive dense cores in the L1630 molecular cloud with spatial resolutions ranging from 11A to 64A. The primary goal of this investigation is to deter- mine whether the physical properties of massive cores are related to their star formation efficiency (SFE) and, in particular, their ability to form rich embedded clusters. The spatial and density structure of four massive cores and two low-mass cores in this cloud were examined. Densities for each core were deter- mined through an large velocity gradient analysis. We -nd that all the massive cores contain regions with densities of at least 105 cm~3. In general, cores with rich embedded clusters, and consequently with high SFE, tend to be larger (i.e., to have larger areas of detectable CS J 5 ) 4 emission) than those without clusters and low SFE. In addition, the region emitting CS J 5 ) 4 emission has a lower volume -lling factor of gas denser than 105 cm~3 in high SFE cores than in low SFE cores. These di†erences suggest that regions forming rich embedded clusters have larger amounts of dense gas and that they are more fragmented. Subject headings: ISM: individual (L1630) E ISM: molecules E radio lines: ISM E stars: formation