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Lo, K.Y. Plante, Raymond Louis 2011-05-07T11:55:50Z 2011-05-07T11:55:50Z 10000-01-01 1995 There is substantial evidence that the Galactic Center harbors some of the strongest observable magnetic fields in the Galaxy, which are expected to have a major role in the astrophysical processes there. In this thesis, I present results from an experiment to measure the line-of-sight component of the magnetic field, $B\sb\Vert$, via Zeeman splitting of the 21-cm line of neutral hydrogen. In addition, I report a 3$\sigma$ upper limit of 2 mG for $B\sb\Vert$ in the neutral hydrogen within the circumnuclear disk of M82. Milligauss fields were detected with the highest confidence from three regions within the northern portion of the circumnuclear gas approximately 2 pc from the Galactic Center. The measurement of $B\sb\Vert$ with the highest signal-to-noise ratio (S/N) was $-3.0\pm0.6$ mG which comes from the highest velocity component within the region. Marginal detections were made elsewhere in the circumnuclear gas; 3$\sigma$ upper-limits call for $\vert B\sb\Vert\vert\ <$ 2.5 mG for the circumnuclear gas and $\vert B\sb\Vert\vert\ <$ 0.9 mG for the giant molecular clouds associated with the Sgr A East shell. The distribution and kinematics of the H I gas were also studied. The signature of a rotating gas ring can be seen in the H I approximately 1 pc south of the inner edge of the molecular ring; considered in conjunction with results from dense gas observations, the ring implies an increasing rotation velocity for the disk for R = 2-3 pc. No clear indication of disk rotation can be seen in the H I gas north of the Sgr A*. Some of the gas displays streamer-like structures in position-velocity space. This may be indicative of tidal stretching of clouds in the differentially rotating disk or, alternatively, of gas infall along a highly eccentric orbit similar to the orbit inferred previously for the ionized gas streamer known as the northern arm. A model is suggested in which the H I gas north of Sgr A* is part of a massive infalling cloud, and evidence which supports this picture is discussed. Such a model implies that the infall would have as large an effect on the structural evolution of the large-scale poloidal magnetic field as the rotating circumnuclear disk. The observations confirm the presence of gas associated with M-0.02-0.07 in front of the Sgr A East shell: the previously observed blue shifted gas and both components of the red shifted gas are seen. The H I gas is found to be quite clumpy and demonstrates small-scale variations in bulk velocity over large scale gradients. In general, the H I distribution is consistent with the picture suggested by Serabyn et al. (1992, Astrophys. J., 395, 166) based on observations of the dense gas in which Sgr A East shell is expanding into the neighboring molecular cloud. Made available in DSpace on 2011-05-07T11:55:50Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9522160.pdf: 9222277 bytes, checksum: 1446f5b08e443986be3c4ce4a5402c1d (MD5) Previous issue date: 1995 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:34:24Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:13:07-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9522160 (UMI)AAI9522160 http://hdl.handle.net/2142/19063 eng Copyright 1995 Plante, Raymond Louis Physics, Astronomy and Astrophysics Neutral gas and the magnetic field in the Galactic Center text Astronomy Astronomy University of Illinois at Urbana-Champaign Dissertation Ph.D.