Off-campus UMass Amherst users: To download dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.

Non-UMass Amherst users, please click the view more button below to purchase a copy of this dissertation from Proquest.

(Some titles may also be available free of charge in our Open Access Dissertation Collection, so please check there first.)

Anatomy of the Gem OB1 molecular cloud complex

John Michael Carpenter, University of Massachusetts Amherst


I have conducted an extensive study of the Gem OB1 molecular cloud complex in order to determine the global morphology of the molecular gas and how the morphology is correlated with the distribution of embedded star forming regions. The distribution and properties of the molecular gas were determined through molecular line surveys in $\sp{12}$CO(J = 1-0), $\sp{13}$CO(J = 1-0), and CS(J = 2-1), and the embedded stellar content was traced using the IRAS point source catalog and a J, H, and K band imaging survey of a portion of the cloud complex. The global morphology of the cloud complex is dominated by a series of arc and ring shaped structures found on nearly all resolved spatial scales from ${\sim}1$ pc to possibly even 100 pc. Several of these arc-shaped structures are found on the periphery of optical H II regions and the physical properties of these features are consistent with being swept up molecular material. Other arc-shaped features are found without associated optical counterparts, but possess morphological and kinematic evidence that suggests that these structures also represent swept up regions of molecular gas. The large scale CS mapping found 13 cores of dense molecular gas with masses ranging from 40 M$\sb\odot$ to 2600 M$\sb\odot$. These cores are preferentially found within the arcs of molecular gas found in the $\sp{12}$CO and $\sp{13}$CO surveys, which suggests that the cores formed as this molecular gas was swept up. Twelve of the 13 cores are associated with a IRAS point source or a cluster of stars. This indicates that star formation must proceed rapidly after the formation of dense cores that have masses exceeding at least ${\sim}50$ M., and that dense cores must be continually formed throughout the lifetime of the Gem OB1 cloud complex if massive star formation is to continue. These observations suggest that once massive stars form, the evolution of cloud complexes and the subsequent formation of massive stars and embedded stellar clusters is dominated by the interactions of massive stars with the ambient molecular material.

Subject Area


Recommended Citation

Carpenter, John Michael, "Anatomy of the Gem OB1 molecular cloud complex" (1994). Doctoral Dissertations Available from Proquest. AAI9434463.