Environments of Star Formation - Relationship Between Molecular Clouds Dense Cores and Young Stars

In this chapter, the star-forming properties of three molecular cloud complexes, Taurus-Auriga, Ophiuchus and Orion, are discussed. In particular, recent observational knowledge of the distribution and properties of dense molecular gas and young stellar objects within each complex is reviewed. Studies of the two nearest molecular cloud complexes, Taurus and Ophiuchus, have shown that at least two modes or environments of star formation exist: isolated and clustered. Studies of the nearest giant molecular clouds in the Orion complex also show evidence for both modes. However, the recent and extensive census for dense cores and young stellar objects in the L1630 (Orion B) cloud has clearly shown that the clustered mode of star formation is dominant in this region. Existing observations of the L1641 GMC (Orion A) suggest that the clustered mode of star formation may also dominate in this cloud. If star formation in L1630 is representative of star formation in other giant molecular clouds, then the clustered mode of star formation may be the dominant mode of star formation in our Galaxy.