J/A+A/657/A30ivo://CDS.VizieR/J/A+A/657/A30doi:10.26093/cds/vizier.36570030CDSTang M.Palau A.Zapata L.Qin S.L.2024-03-01T13:27:39Z2021-12-22T17:47:15ZCDS support team

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

cds-question@unistra.frstar-forming-regionsradio-sourcesThe fragmentation process in massive star-forming regions is one of the contemporary problems in astrophysics, and several physical processes have been proposed to control the fragmentation including turbulence, magnetic field, rotation, stellar feedback, and gravity. However, the fragmentation process has been poorly studied at small spatial scales well below 1000AU. W51 IRS2 is a well known massive star-forming region whose fragmentation properties have not been well investigated yet. We aim to use ALMA (Atacama Large Millimeter and Submillimeter Array) high angular resolution data to identify the fragments in W51 IRS2 and to study the fragmentation properties on a spatial scale of 0.04" (200AU). We used ALMA data of W51 IRS2 from three projects, which give an angular resolution of 0.028" (144AU) at millimeter wavelengths. The continuum images reveal significant substructure in an east-west ridge, where both W51 North and W51d2 are embedded. A spectral index map has been generated from the 3 and 1.3mm high-resolution continuum images.We identified compact fragments by using uv-range constrained 1.3mm continuum data. A Mean Surface Density of Companions (MSDC) analysis has been performed to study the separations between fragments. A total number of 33 continuum sources are identified and 29 out of them are defined as fragments in the surveyed region.The MSDC analysis reveals two breaks corresponding to spatial sales of 1845AU and 7346AU, indicative of a two-level clustering phenomenon, along with a linear regime below 1845AU, mostly associated with W51 North, whose slope is consistent with the slope for the clustering regime of other cluster-like regions in the Galaxy. The typical masses and separations of the fragments as well as the relation between density and number of fragments can be explained through a thermal Jeans process operating at high temperatures of 200-400K, consistent with previous measurements of the temperature in the region, and produced by the nearby massive stars. Therefore, although W51 IRS2 seems to be undergoing a thermally inhibited fragmentation phase, this does not seem to prevent the formation of a protocluster associated with W51 North.2022A&A...657A..30Thttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/657/A30CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/191/232 : CO survey of W51 molecular cloud (Bieging+, 2010)J/A+A/582/A64 : W51/e2 and G34.3+0.2 IRAM spectra (Lykke+, 2015)J/A+A/589/A44 : W51 Main NH_3_ and CH_3_OH data cubes (Goddi+, 2016)J/A+A/595/A27 : JVLA images of W51A (Ginsburg+, 2016)J/A+A/597/A45 : W51 line of sight deuterium fractionation (Vastel+, 2017)J/ApJ/845/116 : 3mm mapping spectral line survey toward W51 (Watanabe+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/657/A30https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/657/A30http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/657/A30https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/657/A30https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/657/A30http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/657/A30GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/657/A30/table1 (Catalogue of identified continuum sources)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/657/A30/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/657/A30/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/657/A30/table1?GETtext/xml+votable180.050000true290.91715937514.51826936110.005555555555555556Cone search capability for table J/A+A/657/A30/list (List of fits images)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/657/A30/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/657/A30/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/657/A30/list?GETtext/xml+votable180.050000true290.9174214.518120.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/657/A306/30694https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/657/A30?format=asciiRadiodefaultJ/A+A/657/A30/table1Catalogue of identified continuum sourcesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameName of identified sourcemeta.id;meta.maincharn_Name[+] + for isolated and point-like sources (1)meta.notecharSimbadSimbad column added by the CDSmeta.ref.urlcharRAJ2000Right ascension (J2000.0)pos.eq.ra;meta.mainDEJ2000Declination (J2000.0)pos.eq.dec;meta.mainMajorMajor axis of source sizearcsecphys.angSizefloate_MajorMajor axis of source size errorarcsecstat.errorfloatMinorMinor axis of source sizearcsecphys.angSizefloate_MinorMinor axis of source size errorarcsecstat.errorfloatPAPosition angle of source sizedegpos.posAngfloatInt1.3mm continuum peak intensity of sourcemJy/beamphot.flux.density;em.mm.200-400GHzfloate_Int1.3mm continuum peak intensity of source errormJy/beamstat.errorfloatSIntegrated intensity of identified sourcemJyphot.flux.density;em.mm.200-400GHzfloate_SIntegrated intensity of identified source errormJystat.errorfloatMassMass estimated from the 1.3mm continuumsolMassphys.massfloate_MassMass estimated from the 1.3mm continuum errorsolMassstat.error;phys.massfloatMasstMass estimated by optically thick assumptionsolMassphys.massfloate_MasstMass estimated by optically thick assumption errorsolMassstat.errorfloatSpIndexSpectral index estimated for continuum sourcespect.indexfloate_SpIndexSpectral index estimated for continuum source errorstat.errorfloatJ/A+A/657/A30/listList of fits imagesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintObs.dateObservation datestime.epoch;obsnullableFreqObserved frequencyGHzem.freqdoublesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitscharAssocDataAssociated Data web pagemeta.ref.urlchar