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UBC Theses and Dissertations

The preparation of a telescope for operation at millimeter wavelengths, and observations of carbon monoxide and in the galactic dust cloud lynds 134 Mahoney, Michael Joseph

Abstract

This dissertation is written in two parts. The first part discusses the development of a millimeter wave telescope at the University of British Columbia, and presents details on a very versatile yet cost effective computer control system which has been developed for this facility. Also included is a comprehensive theoretical and practical treatment of the problem of aligning an equatorially mounted telescope. The second part, on the other hand, presents the results of observations of the J = 1 - 0 transitions of ¹²C¹⁶O, ¹³C¹⁶O and ¹²C¹⁸O in the dark dust cloud Lynds 134. Analysis indicates that L134 is in fact comprised of four molecular clouds with nominal radial velocities of 0.1, 0.7, 2.7,and 4.0 km s⁻¹ with respect to the local standard of rest, and it is suggested that these clouds might be the result of fragmentation. The clouds at 0.7 and 2.7 km s⁻¹ are approximately isothermal (with an excitation temperature of ~12 K) and are shown to coincide with known HI absorption features, while the clouds at 2.7 and 4.0 km s⁻¹ coincide with regions of maximum visible extinction, and are also the most massive of the four clouds. Ac comparison of velocities and line widths for nine molecular species at the position of the 2.7 km s⁻¹ cloud suggests strongly that the atomic hydrogen coexists with the molecules, and does not form a shell as previously thought. It is estimated that in this cloud the H/H₂ abundance ratio is ≥7.7 x 10⁻³ and that the number density of atomic hydrogen is ~11 cm⁻³. In the region of maximum visible extinction on this cloud, the ¹³C¹⁶O/¹²C¹⁸O abundance ratio is 6.5 ± 0.9, but it appears to be significantly larger where the visible extinction is less, perhaps due to excitation effects. Finally, an analysis of the spatial dependence of the line widths indicates a collapse or expansion with a radial velocity dependence v ∝ r[sup -1/2] ; on the basis of some higher resolution CO results, and previous OH results, it is suggested, that it may be possible to distinguish between collapse or expansion, although better sensitivity is needed.

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