J/A+A/581/A74ivo://CDS.VizieR/J/A+A/581/A74doi:10.26093/cds/vizier.35810074CDSAbreu-Vicente J.Kainulainen J.Stutz A.Henning T.Beuther H.2017-01-11T12:12:52Z2016-01-15T11:18:42ZCDS support team

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

cds-question@unistra.frmolecular-cloudsgalaxy-classification-systemsWe present the first study of the relationship between the column density distribution of molecular clouds within nearby Galactic spiral arms and their evolutionary status as measured from their stellar content. We analyze a sample of 195 molecular clouds located at distances below 5.5kpc, identified from the ATLASGAL 870{mu}m data. We define three evolutionary classes within this sample: starless clumps, star-forming clouds with associated young stellar objects, and clouds associated with HII regions. We find that the N(H_2_) probability density functions (N-PDFs) of these three classes of objects are clearly different: the N-PDFs of starless clumps are narrowest and close to log-normal in shape, while star-forming clouds and HII regions exhibit a power-law shape over a wide range of column densities and log-normal-like components only at low column densities. We use the N-PDFs to estimate the evolutionary time-scales of the three classes of objects based on a simple analytic model from literature. Finally, we show that the integral of the N-PDFs, the dense gas mass fraction, depends on the total mass of the regions as measured by ATLASGAL: more massive clouds contain greater relative amounts of dense gas across all evolutionary classes.2015A&A...581A..74Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/581/A74CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/549/A45 : ATLASGAL Compact Source Catalog: 330<l<21 (Contreras+, 2013)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/581/A74https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/581/A74http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/581/A74https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/581/A74https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/581/A74http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/581/A74GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/581/A74/tablef1 (Regions studied in this paper)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/581/A74/tablef1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/581/A74/tablef1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/581/A74/tablef1?GETtext/xml+votable180.050000true271.399625-20.87444440.0055555555555555565/7275 7278 7377 6/28919 29088 29090-29092 29094-29097 29116 29118-29119 29162 29456 29461 29463 29504-29506 29522 29528https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/581/A74?format=asciiOpticaldefaultJ/A+A/581/A74/tablef1Regions studied in this paperrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameRegion namemeta.id;obs.fieldintm_NameMultiplicity index on Namemeta.code.multipcharTypeType of regionsrc.classcharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainRadius? Radiusarcsecphys.angSizeintnullableamaj? Major axisarcsecphys.angSizeintnullableamin? Minor axisarcsecphys.angSize;srcintnullableAngle? Angledegpos.posAngintnullableDistDistance (1)kpcpos.distancefloatn_Dist[a] Note on Dist (2)meta.notecharl_e_DistLimit flag on e_Distmeta.code.errorchare_Dist? Distance dispersion (3)kpcstat.errorfloatnullableRefReferences (4)meta.refchar