Publication Abstracts

Chin 1978

Chin, G., 1978: Observations of CO and 13CO Emission from the Molecular Complex in Orion. Ph.D. thesis. Columbia University.

Microwave emission from the J = 1→0 transition of 12C16O and 13C16O has been observed over an area of 28 square degrees in the Orion region. The observations reveal the existence of two giant molecular complexes, a northern and a southern cloud, which are roughly aligned with the dust clouds in which Ori A and Ori B are embedded. The northern cloud extends from Ori B towards the reflection nebula M 78; the southern cloud is aligned along an axis defined by Ori A and NGC 1999. Peaks in both CO and 13CO emission can be identified with regions of prominent emission and reflection nebulae.

Observable CO emission from the northern cloud covers about 750 pc2 while emission from the southern cloud covers about 1500 pc2. Observable 13CO emission is seen only in the inner 33% core area in both the northern and southern clouds in which CO emission is found.

The total mass of the molecular complexes, derived from the LTE 13CO column density related to molecular hydrogen column density, is > 7×104 M, implying that a sizable fraction of matter in the Orion region is in the form of molecular hydrogen.

Although the northern and southern complexes are in the same region in the sky and at the same distance, the two clouds appear to be separate entities. The CO and 13CO emission is localized around the emission and reflection nebulae in the northern clouds while emission in the southern cloud is concentrated in a ridge which extends along the length of the cloud. The emission in the northern cloud has no systematic velocity structure while the CO emission in the southern cloud has a velocity gradient which is indicative of rotation. Hence the morphology and kinematics of these neighboring complexes are clearly different.

Early-type objects and OB stars in the solar neighborhood are members of Gould's Belt, and the Orion molecular complexes are outstanding examples of this association. Of particular interest is the relationship between the Ori OB1 association and the southern molecular cloud. The OB association forms a sequence of subgroups of descending ages which terminate at M42, site of the latest episode of star formation in the southern cloud.

This thesis also gives a general description of the Columbia 4-foot millimeter telescope with which the observations were made. Detailed descriptions of the telescope computer operating system and line calibration techniques are given in the Appendices.

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BibTeX Citation

@phdthesis{ch00900o,
  author={Chin, G.},
  title={Observations of CO and 13CO Emission from the Molecular Complex in Orion},
  year={1978},
  school={Columbia University},
  address={New York, N.Y.},
}

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RIS Citation

TY  - THES
ID  - ch00900o
AU  - Chin, G.
PY  - 1978
BT  - Observations of CO and 13CO Emission from the Molecular Complex in Orion
PB  - Columbia University
CY  - New York, N.Y.
ER  -

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