J/A+A/578/A29ivo://CDS.VizieR/J/A+A/578/A29doi:10.26093/cds/vizier.35780029CDSSchneider N.Csengeri T.Klessen R.S.Tremblin P.Ossenkopf V.,Peretto N.Simon R.Bontemps S.Fedrrath C.2016-03-18T12:10:26Z2015-05-27T07:00:47ZCDS support team

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

cds-question@unistra.frmolecular-cloudsinfrared-sourcesWe analyse column density and temperature maps derived from Herschel dust continuum observations of a sample of prominent, massive infrared dark clouds (IRDCs) i.e. G11.11-0.12, G18.82-0.28, G28.37+0.07, and G28.53-0.25. We disentangle the velocity structure of the clouds using ^13^CO 1->0 and ^12^CO 3->2 data, showing that these IRDCs are the densest regions in massive giant molecular clouds (GMCs) and not isolated features. The probability distribution function (PDF) of column densities for all clouds have a power-law distribution over all (high) column densities, regardless of the evolutionary stage of the cloud: G11.11-0.12, G18.82-0.28, and G28.37+0.07 contain (proto)-stars, while G28.53-0.25 shows no signs of star formation. This is in contrast to the purely log-normal PDFs reported for near and/or mid-IR extinction maps. We only find a log-normal distribution for lower column densities, if we perform PDFs of the column density maps of the whole GMC in which the IRDCs are embedded. By comparing the PDF slope and the radial column density profile of three of our clouds, we attribute the power law to the effect of large-scale gravitational collapse and to local free-fall collapse of pre- and protostellar cores for the highest column densities. A significant impact on the cloud properties from radiative feedback is unlikely because the clouds are mostly devoid of star formation. Independent from the PDF analysis, we find infall signatures in the spectral profiles of ^12^CO for G28.37+0.07 and G11.11-0.12, supporting the scenario of gravitational collapse. Our results are in line with earlier interpretations that see massive IRDCs as the densest regions within GMCs, which may be the progenitors of massive stars or clusters. At least some of the IRDCs are probably the same features as ridges (high column density regions with N>10^23^cm^-2^ over small areas), which were defined for nearby IR-bright GMCs. Because IRDCs are only confined to the densest (gravity dominated) cloud regions, the PDF constructed from this kind of a clipped image does not represent the (turbulence dominated) low column density regime of the cloud.2015A&A...578A..29Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/578/A29CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/578/A29https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/578/A29http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/578/A29https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/578/A29https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/578/A29http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/578/A29GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/578/A29/list (List of fits maps)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/578/A29/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/578/A29/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/578/A29/list?GETtext/xml+votable180.050000true272.5770488-19.36387450.0055555555555555566/29097 29508 30256 30258https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/578/A29?format=asciiInfrareddefaultJ/A+A/578/A29/listList of fits mapsGLONGalactic longitudedegpos.galactic.lonrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGLATGalactic latitudedegpos.galactic.latScale[13/14] Scale of the imagearcsec/pixinstr.scalefloatNx[56/161] Number of pixels along X-axismeta.numberintNy[39/124] Number of pixels along Y-axismeta.numberintsizeSize of the fits fileKibytephys.size;meta.fitsintfitsDownload the FITS filemeta.ref.urlcharFileNameName of the FITS file in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the filemeta.title;meta.filechar_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