J/ApJ/659/1040ivo://CDS.VizieR/J/ApJ/659/1040doi:10.26093/cds/vizier.16591040CDSArgon A.L.Greenhill L.J.Reid M.J.Moran J.M.Humphreys E.M.L.2018-01-30T07:18:24Z2009-04-01T15:46:31ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.fractive-galactic-nucleivery-long-baseline-interferometryastrophysical-masersradio-astronomyradio-sourcesWe report a 3yr, 18 epoch, VLBI monitoring study of H_2_O masers in the subparsec, warped, accretion disk within the NGC 4258 AGN. Our immediate goals are to trace the geometry of the underlying disk, track rotation via measurement of proper motion, and ascertain the radii of masers for which centripetal acceleration may be measured separately. The monitoring includes 4 times as many epochs, 3 times denser sampling, and tighter control over sources of systematic error than earlier VLBI investigations. Coverage of a 2400km/s bandwidth has also enabled mapping of molecular material 30% closer to the black hole than accomplished previously, which will strengthen geometric and dynamical disk models. Through repeated observation we have also measured for the first time a 5uas (1sigma) thickness of the maser medium.2007ApJ...659.1040Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/659/1040CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/268/419 : HII Regions in NGC 4258 (Courtes+ 1993)J/ApJ/652/1133 : BVI photometry of NGC 4258 Cepheids (Macri+, 2006)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/659/1040https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/659/1040http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/659/1040https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/659/1040https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/659/1040http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/659/1040GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapRadiodefaultJ/ApJ/659/1040/table1The observationsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsObservation codemeta.code;obscharprimarySpPlot of line profilemeta.ref.urlcharExpCodeExperiment codemeta.code;obscharObsDateObservation datetime.epoch;obsnullableObsYear? Observation date in decimal yearyrtime.epoch;obsfloatnullableAntAntennas used for the observation (1)meta.id;instrcharBeam1? Size beam, average restoring beam full-width half-powermasphys.angSize;instr.beamfloatnullableBeam2? Size beam, average restoring beam full-width half-powermasphys.angSize;instr.beamfloatnullablePA[-32/39]? Beam position angle, measured east of northdegpos.posAng;instr.beamfloatnullableSen? Sensivity (2)mJyinstr.sensitivityfloatnullableCL[x-] Coverage in velocity range L = low-velocity emissionmeta.codecharCR[x-] Coverage in velocity range R = redshift emissionmeta.codecharCB[x-] Coverage in velocity range B = blue-shifted emissionmeta.codecharComCommentsmeta.codecharJ/ApJ/659/1040/table5Channel data for 18 epochs of observationChanChannel numbermeta.id;instrintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsObservation code, as defined in table1.datmeta.code;obscharczNonrelativistic LSR velocity (1)km/sspect.dopplerVeloc;pos.lsrdoubleRelVelRelativistic LSR velocity (1)km/sphys.velocdoubleFluxFlux density (2)Jyphot.flux.density;em.radiofloate_FluxThe rms error in FluxmJystat.error;phot.fluxdoubleEWoffEast-West offset (3)maspos.angDistance;arith.difffloate_EWoffError (fitted random) in EWoffmasstat.errorfloatNSoffNorth-South offset (3)maspos.angDistance;arith.difffloate_NSoffError (fitted random) in NSoffmasstat.errorfloatMajaxisMajor axis of spotmasphys.angSizefloate_MajaxisError in Majaxismasstat.errorfloatMinaxisMinor axis of spotmasphys.angSize;srcfloate_MinaxisError in Minaxismasstat.errorfloatPAPosition angle of spot (3)degpos.posAnginte_PAError in PAdegstat.errorintRefVelBand identifier for reference velocity (4)km/sphys.velocdouble