Physics
Scientific paper
Dec 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997phdt........14h&link_type=abstract
Thesis (PHD). UNIVERSITY OF CALIFORNIA, SANTA CRUZ , Source DAI-B 58/06, p. 3090, Dec 1997, 120 pages.
Physics
Scientific paper
Candidates for the physical factor which could determine the star formation efficiency in molecular clouds are the magnetic field, the radiation field, the composition, the clumpiness of the cloud and the turbulence. However it is not clear, either from theory or observations, how any of these factors influence the star formation efficiency. I chose to observe two star formation regions at near-infrared wavelengths to attempt to establish a relationship between the composition of molecular species and the star formation efficiency in high mass star formation regions. The two regions chosen for study are Orion BN, a cluster formation region, and GL 2136, an isolated mode formation region. Focusing on the water ice absorption feature at 3.08 μm, direct images of Orion BN and GL 2136 were taken at 2.2, 3.08, and 3.45 μm. From these observations, I constructed two-dimensional water optical depth maps for each region from which the column density of H2O molecules in icy grain mantles is calculated. I made an M2.2-M3.45 color map for each region through which I discovered a bipolar reflection nebula around BN. The presence of infrared reflection nebulae in both regions was critical to my calculation of the column density of H nuclei and the abundance of water. I was also able to calculate a dust photospheric temperature for each protostellar object and isolate the size distribution of the grains in the reflection nebula. I found that the water abundance was greater by a factor of 1.3 in reflection nebula of the individual mode formation region than in the corresponding parts of the cluster formation region, and the water abundance was less by a factor of 2 towards the protostellar object and in the circumstellar material of the individual mode formation region than of the cluster formation region. When I take a large aperture average of both regions, I find that the water abundance is greater by a factor of 1.2 towards the individual mode star formation region. The water abundances towards equivalent low mass star formation regions show an increased abundance towards the individual mode star formation region, the same trend I measure towards the reflection nebulae of the objects in this study.
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