{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/30862"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/30862","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Astrophysical maser radiation from Keplerian disks near active galactic nuclei","abstract":"Calculations are performed that are relevant for understanding maser radiation emerging from gaseous disks at the nuclei of active galaxies. In at least one galaxy (NGC 4258), such maser radiation is observed and arises from a disk around a presumed massive black hole. The heating, cooling, and excitation mechanisms necessary for creating the physical conditions and pumping for the masing are investigated. The emergent spectra are first calculated for a smooth, Keplerian disk including the effects of radiative saturation. To understand the irregularities in space and frequency in the observations of NGC 4258, calculations are then performed with idealized turbulent velocities superimposed on the Keplerian velocity of the disk. These turbulent velocities are created by statistical sampling from a Kolmogorov-like distribution. In addition to rays of radiation parallel to the plane of the disk, rays inclined at a 7° angle (that indicated for NGC 4258) to the plane of the disk are considered. Within the context of this turbulent disk model, calculations for the time dependence of the low- and high-velocity masing features are performed and compared with observed variations from NGC 4258.","abstract_html":"Calculations are performed that are relevant for understanding maser radiation emerging from gaseous disks at the nuclei of active galaxies. In at least one galaxy (NGC 4258), such maser radiation is observed and arises from a disk around a presumed massive black hole. The heating, cooling, and excitation mechanisms necessary for creating the physical conditions and pumping for the masing are investigated. The emergent spectra are first calculated for a smooth, Keplerian disk including the effects of radiative saturation. To understand the irregularities in space and frequency in the observations of NGC 4258, calculations are then performed with idealized turbulent velocities superimposed on the Keplerian velocity of the disk. These turbulent velocities are created by statistical sampling from a Kolmogorov-like distribution. In addition to rays of radiation parallel to the plane of the disk, rays inclined at a 7° angle (that indicated for NGC 4258) to the plane of the disk are considered. Within the context of this turbulent disk model, calculations for the time dependence of the low- and high-velocity masing features are performed and compared with observed variations from NGC 4258.","abstract_has_math":false,"creators":["Wallin, Bradley Karl"],"institution":null,"degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":["Watson, W.D."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2012,"date_issued":"2012-05-18T15:50:20Z","date_published":"2012-05-18T15:50:20Z","updated_at":"2026-07-22T22:25:29Z","subjects":["maser radiation","NGC 4258"],"languages":["en"],"rights":["©1997 Bradley Karl Wallin"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["4120436"],"render_values":[{"text":"4120436","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/30862","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Watson, W.D."]},{"key":"dc:creator","label":"Author","values":["Wallin, Bradley Karl"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2012-05-18T15:50:20Z","10000-01-01","1997"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation / Thesis","text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Physics"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["maser radiation","NGC 4258"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["©1997 Bradley Karl Wallin"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/30862","4120436"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Calculations are performed that are relevant for understanding maser radiation emerging from gaseous disks at the nuclei of active galaxies. In at least one galaxy (NGC 4258), such maser radiation is observed and arises from a disk around a presumed massive black hole. The heating, cooling, and excitation mechanisms necessary for creating the physical conditions and pumping for the masing are investigated. The emergent spectra are first calculated for a smooth, Keplerian disk including the effects of radiative saturation. To understand the irregularities in space and frequency in the observations of NGC 4258, calculations are then performed with idealized turbulent velocities superimposed on the Keplerian velocity of the disk. These turbulent velocities are created by statistical sampling from a Kolmogorov-like distribution. In addition to rays of radiation parallel to the plane of the disk, rays inclined at a 7° angle (that indicated for NGC 4258) to the plane of the disk are considered. Within the context of this turbulent disk model, calculations for the time dependence of the low- and high-velocity masing features are performed and compared with observed variations from NGC 4258.","Submitted by Elizabeth Kent (eckent2@illinois.edu) on 2012-05-18T15:50:20Z No. of bitstreams: 1 1997_wallin.pdf: 4875840 bytes, checksum: 3954d04c859d46c1873e8e9436168f99 (MD5)","Made available in DSpace on 2012-05-18T15:50:20Z (GMT). No. of bitstreams: 1 1997_wallin.pdf: 4875840 bytes, checksum: 3954d04c859d46c1873e8e9436168f99 (MD5) Previous issue date: 1997","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Elizabeth Kent (eckent2@illinois.edu) on 2012-05-18T15:50:20Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:33:26-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: thesis","thesis","U of I Only"]},{"key":"dc:title","label":"Title","values":["Astrophysical maser radiation from Keplerian disks near active galactic nuclei"]}]}],"canonical_facts":{"dc:contributor":["Watson, W.D."],"dc:creator":["Wallin, Bradley Karl"],"dc:date":["2012-05-18T15:50:20Z","10000-01-01","1997"],"dc:description":["Calculations are performed that are relevant for understanding maser radiation emerging from gaseous disks at the nuclei of active galaxies. In at least one galaxy (NGC 4258), such maser radiation is observed and arises from a disk around a presumed massive black hole. The heating, cooling, and excitation mechanisms necessary for creating the physical conditions and pumping for the masing are investigated. The emergent spectra are first calculated for a smooth, Keplerian disk including the effects of radiative saturation. To understand the irregularities in space and frequency in the observations of NGC 4258, calculations are then performed with idealized turbulent velocities superimposed on the Keplerian velocity of the disk. These turbulent velocities are created by statistical sampling from a Kolmogorov-like distribution. In addition to rays of radiation parallel to the plane of the disk, rays inclined at a 7° angle (that indicated for NGC 4258) to the plane of the disk are considered. Within the context of this turbulent disk model, calculations for the time dependence of the low- and high-velocity masing features are performed and compared with observed variations from NGC 4258.","Submitted by Elizabeth Kent (eckent2@illinois.edu) on 2012-05-18T15:50:20Z No. of bitstreams: 1 1997_wallin.pdf: 4875840 bytes, checksum: 3954d04c859d46c1873e8e9436168f99 (MD5)","Made available in DSpace on 2012-05-18T15:50:20Z (GMT). No. of bitstreams: 1 1997_wallin.pdf: 4875840 bytes, checksum: 3954d04c859d46c1873e8e9436168f99 (MD5) Previous issue date: 1997","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Elizabeth Kent (eckent2@illinois.edu) on 2012-05-18T15:50:20Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:33:26-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: thesis","thesis","U of I Only"],"dc:identifier":["http://hdl.handle.net/2142/30862","4120436"],"dc:language":["en"],"dc:rights":["©1997 Bradley Karl Wallin"],"dc:subject":["maser radiation","NGC 4258"],"dc:title":["Astrophysical maser radiation from Keplerian disks near active galactic nuclei"],"dc:type":["Dissertation / Thesis","text"],"thesis:degree_discipline":["Physics"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."]},"updated_at":"2026-07-22T22:25:29Z"}