J/ApJ/764/102ivo://CDS.VizieR/J/ApJ/764/102doi:10.26093/cds/vizier.17640102CDSFinn S.C.Jackson J.M.Rathborne J.M.Chambers E.T.Simon R.2014-12-06T08:51:02Z2014-11-19T14:21:31ZCDS support team

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

cds-question@unistra.frmolecular-cloudsradio-astronomyinfrared-sourcesmilky-way-galaxyInfrared dark clouds (IRDCs) are believed to host the earliest stages of high-mass star and cluster formation. Because O stars typically travel short distances over their lifetimes, if IRDCs host the earliest stages of high-mass star formation then these cold, dense molecular clouds should be located in or near the spiral arms in the Galaxy. The Galactic distribution of a large sample of IRDCs should therefore provide information on Galactic structure. Moreover, determination of distances enables mass and luminosity calculations. We have observed a large sample of IRDC candidates in the first Galactic quadrant in the dense gas tracer CS(2-1) using the Mopra telescope in order to determine kinematic distances from the molecular line velocities. We find that the IRDCs are concentrated around a Galactocentric distance of ~4.5kpc, agreeing with the results of Simon et al. (2006, J/ApJ/653/1325). This distribution is consistent with the location of the Scutum-Centaurus spiral arm. The group of IRDCs near the Sun in the first quadrant detected in ^13^CO(1-0) in Simon et al. is not detected in the CS data. This discrepancy arises from the differences in the critical densities between the ^13^CO(1-0) and CS(2-1) lines. We determine that the Midcourse Space Experiment selected IRDCs are not a homogeneous population, and ^13^CO(1-0) traces a population of IRDCs with lower column densities and lower 1.1 mm flux densities in addition to more dense IRDCs detected in CS. Masses of the first quadrant IRDCs are calculated from ^13^CO(1-0) maps. We find a strong peak in the Galactocentric IRDC mass surface density distribution at R_Gal_~4.5kpc.2013ApJ...764..102Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/764/102CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)J/A+A/559/A79 : IRDC APEX/SABOCA observations (Ragan+, 2013)J/ApJ/754/62 : HRDS III. HII region kinematic distances (Anderson+, 2012)J/ApJ/721/137 : The Bolocam Galactic Plane Survey (BGPS) (Bally+, 2010)J/MNRAS/399/1506 : IRDC cores in SCUBA Legacy Catalogue (Parsons+, 2009)J/A+A/505/405 : A catalogue of Spitzer dark clouds (Peretto+, 2009)J/A+A/499/149 : 1.2mm maps of southern Infrared Dark Clouds (Vasyunina+, 2009)J/ApJ/686/384 : ^12^CO, ^13^CO, C^18^O survey of IRDCs (Du+, 2008)J/ApJ/680/349 : Galactic distribution of IRDCs (Jackson+, 2008)J/ApJ/653/1325 : Galactic distribution of infrared dark clouds (Simon+, 2006)J/ApJ/641/389 : Millimetric observations of IRDC cores (Rathborne+, 2006)J/ApJ/639/227 : MSX IRDC candidate catalog (Simon+, 2006)J/ApJ/566/945 : Massive star forming regions at 1.2mm (Beuther+, 2002)J/A+A/358/257 : Molecular clouds SO and CS obs. II. (Nilsson+, 2000)J/A+A/291/943 : Protostellar cores (Ossenkopf+, 1994)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/764/102https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/764/102http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/764/102https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/764/102https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/764/102http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/764/102GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/764/102/table1 (First quadrant IRDCs detected in CS(2-1) (97.98GHz))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/764/102/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/764/102/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/764/102/table1?GETtext/xml+votable180.050000true273.7109-16.19320.005555555555555556Cone search capability for table J/ApJ/764/102/table2 (^13^CO(1-0) clouds not detected in CS(2-1))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/764/102/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/764/102/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/764/102/table2?GETtext/xml+votable180.050000true274.4782-15.9440.0055555555555555565/7377 7383 7561 7564 7579 7605 6/29115 29118 29119 29461 29504 29505 29506 29522 29523 29526 29528 29529 30216 30218 30219 30222 30223 30240 30241 30260 30262 30263 30268 30269 30306 30312 30314 30315 30330 30405 30416 30417 30419 30429 30601 30605 30607 30622 30644 30689 30692 30694 30695 30712 30716https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/764/102?format=asciiInfraredRadiodefaultJ/ApJ/764/102/table1First quadrant IRDCs detected in CS(2-1) (97.98GHz)m_MSXDCCloud componentsmeta.code.multipcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMSXDCMSXDC designation (GLLL.ll+BB.bb)meta.id;meta.maincharGLONGalactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latT*A[0.06/2.1] Antenna peak temperatureKphot.antennaTemp;stat.maxfloatV(CS)[9.2/113] CS velocitykm/sspect.dopplerVelocfloatFWHM[0.5/16] CS line FWHMkm/sspect.line.width;spect.linefloatInt[0.1/13.2] Integrated intensityK.km/sphot.flux.density;em.radiofloatRgal[3.5/8] Galactocentric radiuskpcpos.distance;pos.galactocentricfloatDnear[0.8/8] Kinematic distance (D_near_)kpcpos.distance;pos.heliocentricfloatMass[20/57970] LTE mass from ^13^CO(1-0) mapssolMassphys.massintNv[1/3] Number of velocity components in the spectrum for the sourcemeta.numberintV(CO)? ^13^CO velocity (1)km/sspect.dopplerVelocfloatnullablef_V(CO)[*] Mismatch in CO and CS velocities (1)meta.codecharNH2[2.4/37] Peak H_2_ column density (2)1e+21cm**-2phys.columnDensity;stat.maxfloat_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data)degpos.eq.decnullableindexedJ/ApJ/764/102/table2^13^CO(1-0) clouds not detected in CS(2-1)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMSXDCMSXDC designation (GLLL.ll+BB.bba)meta.id;meta.maincharm_MSXDCCloud componentsmeta.code.multipcharGLONGalactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latrms[0.07/0.3] rms noise of T*AKstat.stdev;instr.det.noisefloatNH2[0.1/17] Peak H_2_ column density (1)1e+21cm**-2phys.columnDensity;stat.maxfloat_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data)degpos.eq.decnullableindexed