J/A+A/620/A27ivo://CDS.VizieR/J/A+A/620/A27doi:10.26093/cds/vizier.36200027CDSJoncour I.Duchene G.Moraux E.Motte F.2018-11-30T08:56:00Z2018-11-26T08:01:32ZCDS support team

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

cds-question@unistra.frmolecular-cloudsmultiple-starsMultiplicity and clustering of young pre-main sequence stars appear as critical clues to understand and constrain the star formation process. Taurus is the archetypical example of the most quiescent star forming regions that may still retain primeval signatures of star formation. This work identifies local overdense stellar structures as a critical scale between wide pairs and loose groups in Taurus. Using the density-based spatial clustering of applications with noise (dbscan) algorithm, and setting its free parameters based on the one-point correlation function and the k-nearest neighbor statistics, we have extracted reliably overdense structures from the sky-projected spatial distribution of stars. Nearly half of the entire stellar population in Taurus is found to be concentrated in 20 very dense, tiny and prolate regions called NESTs (for Nested Elementary STructures). They are regularly spaced (~2pc) and mainly oriented along the principal gas filaments axes. Each NEST contains between four and 23 stars. Inside NESTs, the surface density of stars may be as high as 2500pc^-2^ and the mean value is 340pc^-2^. Nearly half (11) of these NESTs contain about 75% of the class 0 and I objects. The balance between Class I, II, and, III fraction within the NESTs suggests that they may be ordered as an evolutionary temporal scheme, some of them getting infertile with time, while other still giving birth to young stars. We have inferred that only 20% of stars in Taurus do not belong to any kind of stellar groups (either multiple system, ultra wide pairs or NESTs). The mass-size relation for stellar NESTs is very close to the Bonnor-Ebert expectation. The range in mass is about the same as that of dense molecular cores. The distribution in size is bimodal peaking at 12.5 and 50kAU and the distribution of the number of YSOs in NESTs as a function of size exhibits two regimes. We propose that the NESTs in their two size regimes represent the spatial imprints of stellar distribution at birth as they may have emerged within few millions years from their natal cloud either from a single core or from a chain of cores. We have identified them as the preferred sites of star formation in Taurus. These NESTs are the regions of highest stellar density and intermediate spatial scale structures between ultra-wide pairs and loose groups.2018A&A...620A..27Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/620/A27CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/135/2496 : Near-IR survey of Class I protostars (Connelley+, 2008)J/ApJS/186/111 : Spitzer observations of Taurus members (Luhman+, 2010)J/ApJS/186/259 : Taurus Spitzer survey: new candidate members (Rebull+, 2010)J/ApJ/731/8 : Multiple star formation in Taurus-Auriga (Kraus+, 2011)J/ApJ/727/64 : Young stellar groups 7 their most massive stars (Kirk+, 2011)J/ApJ/757/141 : Companion IR detection limits in young associationsJ/ApJ/784/126 : Infrared photometry of all known members in TaurusJ/ApJ/799/155 : Sub-stellar companions in Taurus (Daemgen+, 2015)J/A+A/599/A14 : Taurus ultra-wide pairs (Joncour+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/620/A27https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/620/A27http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/620/A27https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/620/A27https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/620/A27http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/620/A27GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/620/A27/tablea1 (Young stars in NESTs (Taurus))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/620/A27/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/620/A27/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/620/A27/tablea1?GETtext/xml+votable180.050000true63.47228.190.0055555555555555566/1031 1037 1039 1042 1048 1050 1052-1054 1061 1073-1075 1082 1114-1115 1159 1168-1170 23549https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/620/A27?format=asciidefaultJ/A+A/620/A27/tablea1Young stars in NESTs (Taurus)SimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeq[1/151] Index number of star in NESTsmeta.numberintNEST[1/20] Identification number of NEST structuremeta.id.parentint2MASS2MASS ID (star)meta.idcharNameName (Star)meta.idcharRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainSpTypeSpectral Type of (primary) starsrc.spTypecharMassMass of the (primary) starsolMassphys.massfloatClassClass of the (primary) starmeta.code.classcharNstarTotal number of star included in the systemmeta.numberint