J/ApJ/871/46ivo://CDS.VizieR/J/ApJ/871/46doi:10.26093/cds/vizier.18710046CDSKarnath N.Prchlik J.J.Gutermuth R.A.Allen T.S.Megeath S.T.,Pipher J.L.Wolk S.Jeffries R.D.2025-05-06T20:10:48Z2023-10-26T14:22:26ZCDS support team

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

cds-question@unistra.fropen-star-clustersvisible-astronomyspectroscopyradial-velocityinfrared-sourcesspectroscopic-binary-starsWe present a study of the kinematics and structure of the Cep OB3b cluster based on new spectra obtained with the Hectoschelle spectrograph on the MMT and data from Spitzer, Chandra, and Gaia. At a distance of 819+/-16pc, Cep OB3b is one of the closest examples of a young (~3-5Myr), large (~3000 total members) cluster at the late stages of gas dispersal. The cluster is broken into two subclusters surrounded by a lower density halo. We fit the empirical density law of King to each subcluster to constrain their sizes and structure. The richer eastern subcluster has circular symmetry, a modest central density, and lacks molecular gas toward its core, suggesting it has undergone expansion due to gas dispersal. In contrast, the western subcluster deviates from circular symmetry, has a smaller core size, and contains significant molecular gas near its core, suggesting that it is in an earlier phase of gas dispersal. We present posterior probability distributions for the velocity dispersions from the Hectoschelle spectra. The east will continue to expand and likely form a bound cluster with ~35% of stars remaining. The west is undergoing slower gas dispersal and will potentially form a bound cluster with ~75% of stars remaining. If the halo dissipates, this will leave two independent clusters with ~300 members; proper motions suggest that the two subcluster are not bound to each other.2019ApJ...871...46Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/871/46CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVI/120 : High-resolution synthetic stellar library (Coelho+, 2005)J/MNRAS/341/805 : UBVI CCD photometry of Cep OB3b (Pozzo+, 2003)J/AJ/129/363 : Spectroscopy in Orion Nebula Cluster (Sicilia-Aguilar+, 2005)J/AJ/129/829 : H{alpha} emission stars in NGC 2264 (Dahm+, 2005)J/A+A/442/1127 : Library of 2500-10500{AA} synthetic spectra (Munari+, 2005)J/ApJ/648/1090 : Radial velocities of NGC 2264 stars (Furesz+, 2006)J/MNRAS/375/1220 : BVI photometry of young stars in 10 clusters (Mayne+, 2007)J/ApJ/676/1109 : Velocities of stars in the ONC (Furesz+, 2008)J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)J/ApJ/697/1103 : Kinematics of Orion Nebula Cluster (Tobin+, 2009)J/ApJ/699/1454 : YSOs around Cepheus B (Getman+, 2009)J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)J/MNRAS/403/545 : Young stars in Cepheus OB3b (Littlefair+, 2010)J/ApJ/750/125 : Spitzer imaging of Cepheus OB3b cluster (Allen+, 2012)J/A+A/563/A94 : Kinematics of the Gamma Vel cluster (Jeffries+, 2014)J/ApJ/786/113 : Extinction law in the Cep OB3b young cluster (Allen+, 2014)J/ApJ/787/107 : Spatial structure of young stellar clusters. I. (Kuhn+, 2014)J/ApJ/794/124 : Star forming region NGC 2264 Spitzer sources (Rapson+, 2014)J/ApJ/799/136 : IN-SYNC. II. Candidate young stars in NGC 1333 (Foster+, 2015)J/AJ/149/119 : Radial velocities of stars in NGC 2264 (Tobin+, 2015)J/ApJ/807/27 : IN-SYNC. III. RVs of IC348 stars (Cottaar+, 2015)J/ApJ/821/8 : Sp. binary population of ONC and NGC2264 (Kounkel+, 2016)J/A+A/601/A97 : Gaia-ESO Survey: Cha I members (Sacco+, 2017)J/ApJ/844/138 : Optical spectroscopy toward Orion B fields (Kounkel+, 2017)J/ApJ/865/73 : GOBELINS. V. Kinematics of Perseus (Ortiz-Leon+, 2018)J/ApJ/870/32 : Kinematics in young star clusters & associations (Kuhn+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/871/46https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/871/46http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/871/46https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/871/46https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/871/46http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/871/46GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/871/46/spectra (2009-2013 radial velocity results (Tables 2-6))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/871/46/spectra?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/871/46/spectra?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/871/46/spectra?GETtext/xml+votable180.050000true343.94962.85121940.005555555555555556Cone search capability for table J/ApJ/871/46/table7 (Potential spectroscopic binary candidates)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/871/46/table7?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/871/46/table7?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/871/46/table7?GETtext/xml+votable180.050000true343.885562.88596670.0055555555555555566/15682-15683 15689https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/871/46?format=asciiOpticalInfrareddefaultJ/ApJ/871/46/spectra2009-2013 radial velocity results (Tables 2-6)m_2MASSNumber of RV measurements for this starmeta.numberintnullableSimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000[22] Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000[62/63] Degree of declination (J2000)pos.eq.dec;meta.mainRV[-122/58]? Radial velocitykm/sphys.veloc;pos.heliocentricfloatnullablee_RV[0.19/30]? RV uncertaintykm/sstat.errorfloatnullableR[0.03/21.2]? R value (not for Table 7) (1)stat.correlationfloatnullableA12Display data from Allen+ 2012, J/ApJ/750/125 within 3"meta.ref.urlintnullableSBpotential spectroscopic binary candidate (Table 7)meta.ref.urlchar2MASS2MASS identifier (JHHMMSSss+DDMMSSs)meta.id;meta.maincharprimaryDateDate of observation (UT)time.epochcharJ/ApJ/871/46/table7Potential spectroscopic binary candidates2MASS2MASS identifier (JHHMMSSss+DDMMSSs)meta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000[22] Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000[62/63] Degree of declination (J2000)pos.eq.dec;meta.mainRV[-122/58]? Radial velocitykm/sphys.veloc;pos.heliocentricfloatnullablee_RV[0.19/30]? RV uncertaintykm/sstat.errorfloatnullableR[0.03/21.2]? R value (not for Table 7) (1)stat.correlationfloatnullable