J/ApJ/582/756ivo://CDS.VizieR/J/ApJ/582/756doi:10.26093/cds/vizier.15820756CDSKolpak M.A.Jackson J.M.Bania T.M.Clemens D.P.Dickey J.M.2006-07-25T16:01:49Z2006-07-25T15:58:43ZCDS support team

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

cds-question@unistra.frh-ii-regionsradial-velocityradio-astronomyKinematic distance determinations in the inner Galaxy are hampered by the near-far kinematic distance ambiguity. Here we resolve the ambiguity for 49 HII region complexes with known recombination-line velocities in the first Galactic quadrant. We measured the 21cm HI absorption spectrum toward each source with the Very Large Array in the C array. The maximum velocity of HI absorption was used to discriminate between the near and far kinematic distances. The number ratio of far to near sources, ~3, can be entirely explained as a geometrical effect. The kinematic distances that we derive are compared with previous determinations for the same sources. Although our distance determinations are largely in agreement with previous measurements, there are 22 discrepancies that we discuss. Using our distance determinations, we create a face-on Galactic map of the HII region complexes and compare it with a kinematically derived profile of the distribution of CO-traced molecular hydrogen. The HII region complexes delineate the large-scale features seen in the molecular gas. The 5kpc molecular ring and the Sagittarius spiral arm are clearly evident, and a few HII region complexes lie in the Perseus arm.2003ApJ...582..756Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/582/756CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/50 : CO Radial Velocities Toward Galactic H II Regions (Blitz+ 1982)J/A+A/397/213 : Galactic HII regions (Paladini+, 2003)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/582/756https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/582/756http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/582/756https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/582/756https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/582/756http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/582/756GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/582/756/table1 (HII region complexes)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/582/756/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/582/756/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/582/756/table1?GETtext/xml+votable180.050000true276.255-13.2580280.0055555555555555566/29505 29510 29511 29529 29533 29535 30219 30244 30258 30259 30262 30263 30269 30315 30318 30319 30405 30417 30420 30605 30616 30618 30622 30644 30694 30695https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/582/756?format=asciiOpticalRadiodefaultJ/ApJ/582/756/table1HII region complexesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordint[KJB2003]Source name based on Galactic coordinates (1)meta.id;meta.maincharn_[KJB2003][a] a: sources form the initial target listmeta.notecharRAJ2000Right ascension (J2000.0)pos.eq.ra;meta.mainDEJ2000Declination (J2000.0)pos.eq.dec;meta.mainRVHII region complex recombination-line velocitykm/sspect.dopplerVeloc;obs.field;pos.heliocentricfloatVtangHII region complex tangential-point velocitykm/sphys.veloc.transverseintVabsMaximum velocity of HI absorptionkm/sspect.dopplerVeloc;em.line.HI;stat.maxintKDA[NFT?] Kinematic Distance Ambiguity resolution (2)meta.codecharq_KDA[AB] Quality assignment for our resolution of the KDAmeta.code.qualcharDist? Distancekpcpos.distance;pos.heliocentricfloatnullablee_Dist? rms uncertainty on Distkpcstat.errorfloatnullable