Publication Abstracts

Blitz 1978

Blitz, L., 1978: A Study of the Molecular Complexes Accompanying Mon OB1, Mon OB2 and CMa OB1. Ph.D. thesis. Columbia University.

The molecular complexes which accompany the Mon OB1, Mon OB2 and CMa OB1 associations have been fully mapped using the J = 1→0 transition of CO at the 1.2m Columbia Telescope. All three complexes are shown to be extended along the galactic plane with a longest extent which ranges fom 88 pc for the Mon OB1 complex to 99 pc for the Mon OB2 complex. The complexes all appear to have well defined boundaries; extrapolation of the data to zero intensity indicates that the projected area of each complex is probably no more than ~ 40%-50% larger than what is observed. The H2 mass of each complex was estimated by extrapolation from the 13CO tracer method and found to be 1.8-3.6×105 M for the Mon OB1 complex, 2.1-4.2×105 M for the Mon OB2 complex, and 1.8-3.7×105 M for the CMa OB1 complex. The inferred average volume density of each complex is found to be ~ 50-150 for each complex, but is very uncertain.

Mon OB1 and CMa OB1 are seen to consist of two large clouds of comparable size and mass which are similar to the two large clouds related to Ori OB1. One of the clouds in Mon OB1 and the entire Mon OB2 complex have large scale velocity gradients, which if interpreted as rotation imply periods of ~ 4×107 y and a sense of rotation opposite to that of the galaxy. All of the complexes show intricate structure on many scales. In the Mon OB2 complex, the interaction between the Rosette Nebula and the molecular complex is particularly striking. The CO related to the infrared source GL-961 in the Mon OB2 complex is seen to possess unusual CO self-reversal.

The three OB complexes are compared to observations of other OB complexes, and it is shown that the size and mass of all of the complexes mapped to date are quite similar. The parameters for a typical giant molecular complex are derived to be the following: mass = 2×105 M, largest dimension = 90 pc, projected surface area = 2.1×103 pc, mean molecular density = 46 cm-3. The observations of all the molecular complexes mapped to date used to calculate the number of OB associations in the Galaxy (4000). It is argued that the OD moleculcar complexes are the nucleation sites for nearly all of the massive star formation in teh Galaxy, and that the number of giant molecular complexes does not greatly exceed the number of OB associations. The statistics on supernovae and supernova remnants are used to place limits in the importance of supernova induced star formation. It is shown that the rate at which a molecular complex is expected to accrete matter by collisions with typical interstellar clouds is roughly equal to the rate at which a complex converts molecular material into stars.

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BibTeX Citation

  author={Blitz, L.},
  title={A Study of the Molecular Complexes Accompanying Mon OB1, Mon OB2 and CMa OB1},
  school={Columbia University},
  address={New York, N.Y.},

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RIS Citation

ID  - bl09000a
AU  - Blitz, L.
PY  - 1978
BT  - A Study of the Molecular Complexes Accompanying Mon OB1, Mon OB2 and CMa OB1
PB  - Columbia University
CY  - New York, N.Y.
ER  -

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