A study of three molecular structures at high galactic latitude
Chastain, Raymond Joseph
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A systematic examination of three low-extinction, interstellar, molecular structures is presented in this thesis. Two of the clouds are high-latitude clouds: MBM03 and MBM40. For MBM03, a fully sampled map covering the main portion of the cloud was completed in both the 12CO and 13CO J=1-0 rotational transitions. In addition, CH spectral data of the ground states, hyperfine, main line transition at 3335 MHz were taken along 21 lines of sight through the central region of the cloud. Previously published 12CO and 13CO maps of MBM40 were recalibrated and re-registered and CH observations were made of 164 points which systematically cover the ridge of strongest CO emission and adequately cover the secondary ridge. For both clouds, the CH emission was found to be offset spatially from the peak CO emission and did not trace components of the molecular gas of the cloud that were detected by 12CO. Due to the low signal-to-noise ratio of the CH data, it is not certain whether the lack of congruency between the CO and CH data is due to the astrochemistry of these two objects or an observational threshold for detectable CH 3335 MHz emission. The mass of each cloud is estimated to be 50 M for MBM03 and 25 M for MBM40. External pressure acting on both MBM03 and MBM40 is found to dominate the dynamics of each cloud. This is supported by the likelihood that both clouds have more than one velocity component, requiring small scale ordering within the clouds which is consistent with shear flow-driven dynamics. In addition to the two molecular clouds, previously undetected molecular gas in the Pisces-Pegasus region at high galactic latitude was observed in the J=1-0 and J=2-1 rotational transitions of 12CO. The likelihood that the emission is part of a high-latitude molecular shell is investigated. The most likely scenario is that a portion of the detected emission has formed on the edge of an expanding bubble located within a filament of atomic hydrogen.