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dc.contributor.authorGallimore, J.F.
dc.contributor.authorBaum, S.A.
dc.contributor.authorO'Dea, C.P.
dc.contributor.authorBrinks, E.
dc.contributor.authorPedlar, A.
dc.identifier.citationGallimore , J F , Baum , S A , O'Dea , C P , Brinks , E & Pedlar , A 1996 , ' H 2O and OH Masers as Probes of the Obscuring Torus in NGC 1068 ' , The Astrophysical Journal , vol. 462 , pp. 740-745 .
dc.identifier.otherPURE: 168888
dc.identifier.otherPURE UUID: cfa5453d-2185-404c-8946-55c206dc187e
dc.identifier.otherdspace: 2299/2780
dc.identifier.otherScopus: 21344460573
dc.identifier.otherORCID: /0000-0002-7758-9699/work/30407936
dc.descriptionOriginal article can be found at: Copyright American Astronomical Society. DOI: 10.1086/177187 [Full text of this article is not available in the UHRA]
dc.description.abstractWe report the discovery of OH masers and positionally resolved H_2_O maser emission in the nucleus of NGC 1068. The brightest H_2_O masers are associated with the radio continuum component that is probably the location of the central engine (Gallimore, Muxlow, and coworkers). These masers trace a ~50 mas (~5 pc) roughly linear velocity gradient along P.A 94^deg^ +/- 4^deg^, which is almost at right angles to the local radio jet axis. The kinematics of the masers are well described as an edge-on Keplerian disk surrounding a large central mass concentration (black hole?). The inner radius of the maser disk is ~> 1.3 pc, and the outer radius is ~2.5 pc, assuming a distance of 22 Mpc. The mass within the inner radius, normalized to the best-fit disk parameters, is 4.4 x 10^7^ M_sun_ x (r_in_/1.3 pc) (ν_max_/378 km s^-1^)^2^. These masers might occur in the parsec-scale torus thought to obscure the central engine. Radio continuum emission fills the region interior to the H_2_O masers, in agreement with the prediction that the continuum emission is thermal free-free radiation from the inner face of the molecular torus (Gallimore and coworkers). The location of-the OH masers and nuclear H I absorption (Gallimore and coworkers), measured with ~1" angular resolution, is consistent with the location of the H_2_O masers associated with the central engine. The H I absorption profile is also consistent with the Keplerian model for the H_2_O maser disk kinematics, and the velocity range of the OH masers is similar to that spanned by both the H I and H_2_O spectral features. It therefore seems likely that the OH masers and H I absorption also originate in the obscuring material surrounding the central engine. The OH masers indicate the presence of a more tenuous molecular medium in the torus, in addition to the denser material traced by the H_2_O maser emission. We have also discovered fainter H_2_O masers located 0.3" (~30 pc) downstream along the radio jet. These masers are too distant from the central engine to arise in a parsec-scale torus. They may instead occur at the shock interface between the radio jet and an intervening molecular cloud. The implication is that H_2_O magamaser emission may probe both circumnuclear disks and shock fronts in other active galactic nuclei.en
dc.relation.ispartofThe Astrophysical Journal
dc.titleH 2O and OH Masers as Probes of the Obscuring Torus in NGC 1068en
dc.contributor.institutionSchool of Physics, Astronomy and Mathematics
dc.contributor.institutionSchool of Physics, Engineering & Computer Science
dc.contributor.institutionDepartment of Physics, Astronomy and Mathematics
dc.contributor.institutionCentre for Astrophysics Research
dc.description.statusPeer reviewed
rioxxterms.typeJournal Article/Review

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