{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/19063"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/19063","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Neutral gas and the magnetic field in the Galactic Center","abstract":"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.","abstract_html":"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<span class=\"etd-inline-math\">&sigma;</span> upper limit of 2 mG for $B\\sb\\Vert$ in the neutral hydrogen within the circumnuclear disk of M82.","abstract_has_math":true,"creators":["Plante, Raymond Louis"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Astronomy","degree_department":null,"school":null,"contributors":["Lo, K.Y."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T11:55:50Z","date_published":"2011-05-07T11:55:50Z","updated_at":"2026-07-22T22:25:12Z","subjects":["Physics, Astronomy and Astrophysics"],"languages":["eng"],"rights":["Copyright 1995 Plante, Raymond Louis"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9522160","(UMI)AAI9522160"],"render_values":[{"text":"AAI9522160","href":null,"code":true},{"text":"(UMI)AAI9522160","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/19063","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Lo, K.Y."]},{"key":"dc:creator","label":"Author","values":["Plante, Raymond Louis"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T11:55:50Z","10000-01-01","1995"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Astronomy"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Physics, Astronomy and Astrophysics"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1995 Plante, Raymond Louis"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9522160","(UMI)AAI9522160","http://hdl.handle.net/2142/19063"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["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"]},{"key":"dc:title","label":"Title","values":["Neutral gas and the magnetic field in the Galactic Center"]}]}],"canonical_facts":{"dc:contributor":["Lo, K.Y."],"dc:creator":["Plante, Raymond Louis"],"dc:date":["2011-05-07T11:55:50Z","10000-01-01","1995"],"dc:description":["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"],"dc:identifier":["AAI9522160","(UMI)AAI9522160","http://hdl.handle.net/2142/19063"],"dc:language":["eng"],"dc:rights":["Copyright 1995 Plante, Raymond Louis"],"dc:subject":["Physics, Astronomy and Astrophysics"],"dc:title":["Neutral gas and the magnetic field in the Galactic Center"],"dc:type":["text"],"thesis:degree_discipline":["Astronomy"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:12Z"}