J/ApJ/817/128ivo://CDS.VizieR/J/ApJ/817/128doi:10.26093/cds/vizier.18170128CDSGao F.Braatz J.A.Reid M.J.Lo K.Y.Condon J.J.Henkel C.Kuo C.Y.,Impellizzeri C.M.V.Pesce D.W.Zhao W.2017-01-23T22:00:00Z2016-05-17T14:37:38ZCDS support team

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

cds-question@unistra.frgalaxiesinterferometryastrophysical-masersradio-astronomyastronomical-modelsAs part of the Megamaser Cosmology Project, here we present a new geometric distance measurement to the megamaser galaxy NGC 5765b. Through a series of very long baseline interferometry observations, we have confirmed the water masers trace a thin, sub-parsec Keplerian disk around the nucleus, implying an enclosed mass of 4.55+/-0.40x10^7^M_{sun}_. Meanwhile, from single-dish monitoring of the maser spectra over two years, we measured the secular drifts of maser features near the systemic velocity of the galaxy with rates between 0.5 and 1.2km/s/yr. Fitting a warped, thin-disk model to these measurements, we determine a Hubble Constant H_0_ of 66.0+/-6.0km/s/Mpc with an angular-diameter distance to NGC 5765b of 126.3+/-11.6Mpc. Apart from the distance measurement, we also investigate some physical properties related to the maser disk in NGC 5765b. The high-velocity features are spatially distributed into several clumps, which may indicate the existence of a spiral density wave associated with the accretion disk. For the redshifted features, the envelope defined by the peak maser intensities increases with radius. The profile of the systemic masers in NGC 5765b is smooth and shows almost no structural changes over the two years of monitoring time, which differs from the more variable case of NGC 4258.2016ApJ...817..128Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/817/128CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJS/218/10 : HET Massive Galaxy Survey (HETMGS) (van den Bosch+, 2015)J/MNRAS/412/1419 : Nearby supernova rates (Leaman+, 2011)J/ApJ/727/20 : The Megamaser Cosmology Project (MCP). III. (Kuo+, 2011)J/ApJ/659/1040 : VLBI monitoring of NGC 4258 (Argon+, 2007)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/817/128https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/817/128http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/817/128https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/817/128https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/817/128http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/817/128GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapRadiodefaultJ/ApJ/817/128/table6Input data for the disk fitting programrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintVel[7537.5/9081.3] Maser Recession Velocitykm/sphys.veloc;pos.heliocentricfloatX[-0.7/1.2] Black Hole Position, Xmaspos.cartesian.xfloate_X[0.0007/0.03] Uncertainty in Xmasstat.error;pos.cartesian.xfloatY[-1.58/0.92] Black Hole Position, Ymaspos.cartesian.yfloate_Y[0.001/0.07] Uncertainty in Ymasstat.error;pos.cartesian.yfloatA[-0.6/1.3] Accelerationkm.s**-1.yr**-1phys.accelerationfloate_A[0.01/0.9] Uncertainty in Akm.s**-1.yr**-1stat.errorfloat