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dc.contributor.authorGreenhill, Lincoln Jared
dc.contributor.authorKondratko, Paul T.
dc.contributor.authorMoran, James M.
dc.contributor.authorTilak, Avanti
dc.date.accessioned2016-04-12T15:59:57Z
dc.date.issued2009
dc.identifier.citationGreenhill, Lincoln J., Paul T. Kondratko, James M. Moran, and Avanti Tilak. 2009. “Discovery of Candidate H2O Disk Masers in Active Galactic Nuclei and Estimations of Centripetal Accelerations.” The Astrophysical Journal 707 (1) (November 25): 787–799. doi:10.1088/0004-637x/707/1/787.en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://nrs.harvard.edu/urn-3:HUL.InstRepos:26519245
dc.description.abstractBased on spectroscopic signatures, about one-third of known H2O maser sources in active galactic nuclei (AGNs) are believed to arise in highly inclined accretion disks around central engines. These “disk maser candidates” are of interest primarily because angular structure and rotation curves can be resolved with interferometers, enabling dynamical study. We identify five new disk maser candidates in studies with the Green Bank Telescope, bringing the total number published to 30. We discovered two (NGC 1320, NGC 17) in a survey of 40 inclined active galaxies (vsys < 20,000 km s−1). The remaining three disk maser candidates were identified in monitoring of known sources: NGC 449, NGC 2979, and NGC 3735. We also confirm a previously marginal case in UGC 4203. For the disk maser candidates reported here, inferred rotation speeds are 130–500 km s−1. Monitoring of three more rapidly rotating candidate disks (CG 211, NGC 6264, VV 340A) has enabled measurement of likely orbital centripetal acceleration, and estimation of central masses ((2–7) ×107 M) and mean disk radii (0.2–0.4 pc). Accelerations may ultimately permit estimation of distances when combined with interferometer data. This is notable because the three AGNs are relatively distant (10,000 km s−1 < vsys < 15,000 km s−1), and fractional error in a derived Hubble constant, due to peculiar motion of the galaxies, would be small. As signposts of highly inclined geometries at galactocentric radii of ∼0.1–1 pc, disk masers also provide robust orientation references that allow analysis of (mis)alignment between AGNs and surrounding galactic stellar disks, even without extensive interferometric mapping. We find no preference among published disk maser candidates to lie in high-inclination galaxies. This provides independent support for conclusions that in late-type galaxies, central engine accretion disks and galactic plane orientations are not correlated.en_US
dc.description.sponsorshipAstronomyen_US
dc.language.isoen_USen_US
dc.publisherIOP Publishingen_US
dc.relation.isversionofdoi::10.1088/0004-637X/707/1/787en_US
dc.relation.hasversionhttp://arxiv.org/pdf/0911.0382.pdfen_US
dash.licenseLAA
dc.subjectgalaxies: activeen_US
dc.subjectgalaxies: Seyferten_US
dc.subjectISM: moleculesen_US
dc.subjectmasersen_US
dc.titleDiscovery of Candidate H2O Disk Masers in Active Galactic Nuclei and Estimations of Centripetal Accelerationsen_US
dc.typeJournal Articleen_US
dc.description.versionVersion of Recorden_US
dc.relation.journalApJen_US
dash.depositing.authorMoran, James M.
dc.date.available2016-04-12T15:59:57Z
dc.identifier.doi10.1088/0004-637X/707/1/787*
dash.contributor.affiliatedTilak, Avanti
dash.contributor.affiliatedGreenhill, Lincoln
dash.contributor.affiliatedMoran, James


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