J/A+A/552/A40ivo://CDS.VizieR/J/A+A/552/A40doi:10.26093/cds/vizier.35520040CDSChira R.-A.Beuther H.Linz H.Walmsley C. M.MentenK.M.Bonfman L.2017-06-22T14:28:46Z2013-03-20T12:14:46ZCDS support team

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

cds-question@unistra.frgalaxy-planesmilky-way-galaxyinterstellar-mediumradial-velocityradio-spectroscopychemical-abundancessurveysDespite increasing research in massive star formation, little is known about its earliest stages. Infrared Dark Clouds (IRDCs) are cold, dense and massive enough to harbour the sites of future high-mass star formation. But up to now, mainly small samples have been observed and analysed. To understand the physical conditions during the early stages of high-mass star formation, it is necessary to learn more about the physical conditions and stability in relatively unevolved IRDCs. Thus, for characterising IRDCs studies of large samples are needed. We investigate a complete sample of 220 northern hemisphere high-contrast IRDCs using the ammonia (1,1)- and (2,2)-inversion transitions. We detected ammonia (1,1)-inversion transition lines in 109 of our IRDC candidates. Using the data we were able to study the physical conditions within the star-forming regions statistically. We compared them with the conditions in more evolved regions which have been observed in the same fashion as our sample sources. Our results show that IRDCs have, on average, rotation temperatures of 15K, are turbulent (with line width FWHMs around 2km/s), have ammonia column densities on the order of 10^14^cm^-2^ and molecular hydrogen column densities on the order of 10^22^cm^-2^. Their virial masses are between 100 and a few 1000M_{sun}_. The comparison of bulk kinetic and potential energies indicate that the sources are close to virial equilibrium. IRDCs are on average cooler and less turbulent than a comparison sample of high-mass protostellar objects, and have lower ammonia column densities. Virial parameters indicate that the majority of IRDCs are currently stable, but are expected to collapse in the future.2013A&A...552A..40Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/552/A40CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/639/227 : MSX IRDC candidate catalog (Simon+, 2006)J/A+A/540/A113 : Starless clumps in ATLASGAL (Tackenberg+, 2012)J/A+A/544/A146 : ATLASGAL cold high-mass clumps with NH_3_ (Wienen+, 2012)J/MNRAS/431/1752 : ATLASGAL 6.7GHz methanol masers (Urquhart+, 2013)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/552/A40https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/552/A40http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/552/A40https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/552/A40https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/552/A40http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/552/A40GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/552/A40/NH3data (Source position, NH_3_(1,1) line parameters and NH_3_(2,2) line brightness temperature, line width and optical depth, parameters obtained from NH_3_ lines and note about Spitzer association)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/552/A40/NH3data?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/552/A40/NH3data?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/552/A40/NH3data?GETtext/xml+votable180.050000true273.4709-16.63720.005555555555555556Cone search capability for table J/A+A/552/A40/tablec4 (List of sources without detected ammonia (1,1) inversion lines)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/552/A40/tablec4?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/552/A40/tablec4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/552/A40/tablec4?GETtext/xml+votable180.050000true273.7494-15.49650.0055555555555555565/7377 7561 7578-7579 6/14692 28830 29113-29114 29118 29457 29506 29512 29523 29526-29527 29529 29532-29533 29535 30216 30218-30219 30222-30223 30241 30256-30258 30260 30262-30263 30268-30269 30306 30330 30341 30405 30416-30417 30419-30421 30423 30429 30595 30601 30605 30689 30692 30694https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/552/A40?format=asciiOpticalRadiodefaultJ/A+A/552/A40/NH3dataSource position, NH_3_(1,1) line parameters and NH_3_(2,2) line brightness temperature, line width and optical depth, parameters obtained from NH_3_ lines and note about Spitzer associationrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameMSX-IRDC source name (GLLL.ll+BB.bbA)meta.id;meta.maincharprimaryn_NameSimbad column added by the CDSmeta.ref.urlcharGLONGalactic Longitudedegpos.galactic.lonGLATGalactic Latitudedegpos.galactic.latTmb(1,1)NH_3_(1,1) main beam brightness temperatureKphys.temperature;meta.mainfloate_Tmb(1,1)rms uncertainty on Tmb(1,1)Kstat.errorfloatTmb(2,2)NH_3_(2,2) main beam brightness temperatureKphys.temperature;meta.mainfloate_Tmb(2,2)rms uncertainty on Tmb(2,2)Kstat.errorfloatdv(1,1)NH_3_(1,1) line width FWHMkm/sspect.line.widthfloatdv(2,2)NH_3_(2,2) line width FWHMkm/sspect.line.widthfloatvlsr(1,1)LSR velocity of NH_3_(1,1) inversion linekm/sphys.veloc;pos.lsrfloattau(1,1)Optical depth {tau} of NH_3_(1,1) linephys.absorption.opticalDepthfloate_tau(1,1)rms uncertainty on tau(1,1)stat.errorfloattau(2,2)Optical depth of {tau} NH_3_(2,2) linephys.absorption.opticalDepthfloate_tau(2,2)rms uncertainty on tau(2,2)stat.errorfloatTrotRotation Temperature between NH_3_(1,1) and (2,2) inversion lineKspect.line.intensity;spect.linefloate_Trotrms uncertainty on TrotKstat.errorfloatTkinKinetic TemperatureKphys.temperaturefloatNNH3NH_3_ column density1e+15cm**-2phys.columnDensityfloatDist(near) kinematic distancekpcpos.distance;pos.heliocentricfloate_Distrms uncertainty on distkpcstat.errorfloatMvir-1virial mass by assuming a r-1 density profilesolMassphys.massinte_Mvir-1rms uncertainty on Mvir-1solMassstat.errorintMvir-2virial mass by assuming a r-2 density profilesolMassphys.massinte_Mvir-2rms uncertainty on Mvir-2solMassstat.errorintSpitzer[yes/no ] note whether source has a Spitzer 24um counterpart ("yes") or not ("no")meta.codecharMSXDCDetails from Simon's MSXDC catalog (2006, Cat. J/ApJ/639/227)meta.ref.urlchar_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/A+A/552/A40/tablec3Parameters obtained with 870 micron dust continuum, in combination with NH_3_ datarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameMSX-IRDC source name (GLLL.ll+BB.bbA)meta.id;meta.maincharF19870 micron dust continuum flux density integrated over 19"Jyphot.flux.density;em.mm.200-400GHzfloatF40870 micron dust continuum flux density integrated over 40"Jyphot.flux.density;em.mm.200-400GHzfloatNH2+19H_2_ column density averaged on 19" beam1e+22cm**-2phys.columnDensity;instr.beamfloatNH2+40H_2_ column density averaged on 40" beam1e+22cm**-2phys.columnDensity;instr.beamfloatchiNH3NH_3_ abundance ({kappa}=1.85cm^2^/g)phys.abundfloatM.OHgas mass M_gas_ using {kappa}=1.85cm^2^/g (1)solMassphys.massinte_M.OHrms uncertainty on MOHsolMassstat.errorintM.MRNgas mass M_gas_ using {kappa}=0.6cm^2^/g (1)solMassphys.massinte_M.MRNrms uncertainty on MMRNsolMassstat.errorintal.OHvirial parameter {alpha} using {kappa}=1.85cm^2^/g (1)phys.mass;arith.ratiofloate_al.OHrms uncertainty on al.OHstat.errorfloatal.MRNvirial parameter {alpha} using {kappa}=0.6cm^2^/g (1)phys.mass;arith.ratiofloate_al.MRNrms uncertainty on al.MRNstat.errorfloatJ/A+A/552/A40/tablec4List of sources without detected ammonia (1,1) inversion linesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameMSX-IRDC source name (GLLL.ll+BB.bbA)meta.id;meta.maincharGLONGalactic Longitudedegpos.galactic.lonGLATGalactic Latitudedegpos.galactic.latMSXDCDetails from Simon's MSXDC catalog (2006, Cat. J/ApJ/639/227)meta.ref.urlchar_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