Spatial Distribution of Embedded Clusters in the Rosette Molecular Cloud: Implications for Cluster Formation

Abstract

We have imaged a D0.7 deg2 region of the Rosette Molecular Cloud (RMC) using the simultaneous quad infrared imaging device on the Kitt Peak National Observatory 1.3 m telescope. The region observed covers most of the 13CO emission detected by Blitz & Stark, as well as the majority of the IRAS point sources listed by Cox, Deharveng, & Leene and Williams, Blitz, & Stark. In this paper, we report the detection of seven young embedded clusters in the RMC, Ðve of which were previously unknown. All seven clusters are associated with IRAS sources and with molecular (13CO) clumps (Williams et al.), although not all IRAS sources or molecular clumps are associated with clusters. The molecular clumps that contain clusters are among the most massive clumps in the cloud, indicating that high-mass regions are required for the formation of clusters. However, the majority of massive 13CO clumps in the RMC are not associated with embedded clusters, suggesting that conditions other than high mass, such as high density, are needed for cluster formation. The spatial location of most of the clusters suggests that cluster formation may be triggered by the ionization fronts from the nearby H II region associated with NGC 2244. However, triggered star forma-tion cannot explain the presence of all of the clusters, suggesting that more than one mechanism may be at work forming clusters in this cloud. Subject headings : ISM : clouds È ISM : individual (Rosette) È ISM : molecules È open clusters and associations : general È stars : formation