J/A+A/711/A138ivo://CDS.VizieR/J/A+A/711/A138CDSZhang S.Huang L.Zhao W.Chi H.Chen J.2026-07-10T07:25:59Z2026-07-10T08:25:26ZCDS support team

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

cds-question@unistra.frmilky-way-galaxyopen-star-clustersvisible-astronomyMass segregation, defined as the preferential concentration of massive stars towards cluster centres, is a well-established outcome of two-body relaxation in star clusters. It is not yet established whether the inverse configuration, in which massive stars are preferentially dispersed to large radii, can survive over dynamical timescales on a population scale. We investigate whether anti-mass-segregated open clusters exist as a statistically significant, dynamically stable population in the Milky Way. We used 2800 open clusters from the Gaia DR3 catalogue and identified mass segregation using two independent diagnostics: the minimum spanning tree ratio (Lambda_MSR_) and the centre-of-mass distance ratio (Lambda_CC_), evaluated for the five and ten most massive members. We further performed direct N-body simulations to test the dynamical stability of anti-segregated configurations. We identify 706 anti-mass-segregated clusters (25.2% of the sample). Compared to the normal population, these systems are systematically more extended (+20% in the half-mass radius), dynamically younger (~39% in dynamical age) and have longer relaxation timescales (+25%). The mass excess of anti-segregated clusters relative to normal clusters increases monotonically with dynamical age, reaching +109% at tau=5-10. Direct N-body simulations confirm that anti-segregated configurations remain stable over multiple relaxation timescales, while mass-segregated and random clusters develop strong positive segregation. Anti-mass segregation is a dynamically stable structural state that likely reflects primordial cluster conditions. The prevalence of this configuration provides indirect constraints on the central mass content of open clusters, as massive central black holes would rapidly disrupt the anti-segregated state.2026A&A...711A.138Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/711/A138CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/686/A42 : Improving the open cluster census. III. (Hunt+, 2024)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/711/A138https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/711/A138http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/711/A138https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/711/A138https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/711/A138http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/711/A138GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/711/A138/clusters (Full parameter catalogue with dynamical ages)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/711/A138/clusters?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/711/A138/clusters?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/711/A138/clusters?GETtext/xml+votable180.050000true71.57603675-9.711044710.0055555555555555565/764-765 3575 3580 3582 3603 3606-3607 3613 3656 3661 3674 3841 3844 3846 3859 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41816-41817 41829 41831 41833-41834 41846 41856-41858 41860 41863-41864 41873-41874 41878-41879 41893 41922 41995 42029 42095 42111 42127 42135 42141 42143 42145 42147 42151 42153-42155 42161-42166 42172-42174 42177 42190 42196-42197 42201-42203 42212-42214 42216-42218 42228 42230 42232 42268 42274 42300 42303 42316 42333-42334 42340 42343 42346-42347 42351 42353 42363-42365 42367 42370 42374 42380 42383-42384 42386-42387 42389-42392 42394 42396 42399-42400 42402 42405 42407 42415 42417 42420-42421 42442-42443 42447-42448 42450 42452 42454-42456 42458 42460 42462-42465 42469-42470 42472 42483 42486-42487 42496-42497 42516 42522 42548 42565 42583 42589 42656 42836 42846 42850 42964 42983 42988 43009 43011-43012 43014 43020-43022 43028 43031 43036 43038 43040-43041 43043-43044 43047-43048 43050 43052 43059 43072 43079 43104 43136-43137 43140 43301 43402 43450 44360 44378 47623 49099https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/711/A138?format=asciiOpticaldefaultJ/A+A/711/A138/clustersFull parameter catalogue with dynamical agesNtotalTotal number of member stars (N_total)meta.numberintLambdaCC10Center-of-mass distance ratio at N=10 (Lambda_CC_10)pos.distance;arith.ratiodoubleLambdaMST15MST segregation ratio evaluated at N=15 (Lambda_MST_15)stat.fit.paramdoublen_RVNumber of stars used for RV (n_RV)meta.noteintrJTotal structural radius (J) (rJ)phot.mag;em.IR.JdoubleXmatchTypeCross-match classification type descriptor (XmatchType)meta.codechartrelaxHalf-mass relaxation time (this work) (t_relax_Myr)Myrtime.relaxdoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintLambdaMST5MST segregation ratio evaluated at N=5 (Lambda_MST_5)stat.fit.paramdoubleLambdaCC5Center-of-mass distance ratio at N=5 (Lambda_CC_5)pos.distance;arith.ratiodoubleLambdaMST10MST segregation ratio evaluated at N=10 (Lambda_MST_10)stat.fit.paramdoubleLambdaCC15Center-of-mass distance ratio at N=15 (Lambda_CC_15)pos.distance;arith.ratiodoubleLambdaMST20MST segregation ratio evaluated at N=20 (Lambda_MST_20)stat.fit.paramdoubleLambdaCC20Center-of-mass distance ratio at N=20 (Lambda_CC_20)pos.distance;arith.ratiodoubleIDUnique cluster identifier ID (ID)meta.idintType[o] Cluster type classification (o=open cluster) (Type)src.classcharCSTCluster Structural Parameter (CST)src.morph.paramdoubleNNumber of stars used in structural fit (N)meta.numberintCSTtTidal structural parameter (CSTt)src.morph.paramdoubleNtNumber of stars used in tidal fit (Nt)meta.numberintRAJ2000Right Ascension (J2000) (RAdeg)degpos.eq.ra;meta.mainDEJ2000Declination (J2000) (DEdeg)degpos.eq.dec;meta.mainGLONGalactic longitude (GLON)degpos.galactic.lonGLATGalactic latitude (GLAT)degpos.galactic.latdoubler50Projected half-number angular radius (r50)degphys.angSizedoublercCore angular radius (rc)degphys.angSizedoublertTidal angular radius (rt)degphys.angSizedoublertotTotal angular radius limit (rtot)degphys.angSizedoubler50pcProjected half-number radius in parsecs (r50pc)pcphys.size.radiusdoublercpcCore radius in parsecs (rcpc)pcphys.size.radiusdoublertpcTidal radius in parsecs (rtpc)pcphys.size.radiusdoublertotpcTotal radius limit in parsecs (rtotpc)pcphys.size.radiusdoublepmRAProper motion in Right Ascension direction (pmRA)mas/yrpos.pm;pos.eq.radoubles_pmRAStandard deviation of pmRA (s_pmRA)mas/yrstat.stdev;pos.pm;pos.eq.radoublee_pmRAUncertainty error on pmRA (e_pmRA)mas/yrstat.error;pos.pm;pos.eq.radoublepmDEProper motion in Declination direction (pmDE)mas/yrpos.pm;pos.eq.decdoubles_pmDEStandard deviation of pmDE (s_pmDE)mas/yrstat.stdev;pos.pm;pos.eq.decdoublee_pmDEUncertainty error on pmDE (e_pmDE)mas/yrstat.error;pos.pm;pos.eq.decdoublePlxMedian cluster parallax from Gaia (Plx)maspos.parallax;stat.mediandoubles_PlxStandard deviation of Plx (s_Plx)masstat.stdev;pos.parallaxdoublee_PlxUncertainty error on Plx (e_Plx)masstat.error;pos.parallaxdoubleDist1616th percentile distance (dist16)pcpos.distancedoubleDist50Median cluster distance (Adopted) (dist50)pcpos.distancedoubleDist8484th percentile distance (dist84)pcpos.distancedoubleNdistNumber of stars used for distance (Ndist)meta.numberintglobalPlxGlobal parallax zero-point correction (globalPlx)masstat.fit.paramintXHeliocentric Galactic coordinate X (X)pcpos.cartesian.x;pos.galactic;pos.heliocentricdoubleYHeliocentric Galactic coordinate Y (Y)pcpos.cartesian.y;pos.galactic;pos.heliocentricdoubleZHeliocentric Galactic coordinate Z (Z)pcpos.cartesian.z;pos.heliocentric;pos.galacticdoubleRV? Radial velocity (if available) (RV)km/sphys.veloc;pos.heliocentricdoublenullables_RV? Standard deviation of RV (s_RV)km/sstat.stdevdoublenullablee_RV? Uncertainty error on RV (e_RV)km/sstat.errordoublenullableCMDCl2.52.5th percentile CMD classification score (CMDCl2.5)stat.fit.goodnessdoubleCMDCl1616th percentile CMD classification score (CMDCl16)stat.fit.goodnessdoubleCMDCl50Median CMD classification score (CMDCl50)stat.fit.goodnessdoubleCMDCl8484th percentile CMD classification score (CMDCl84)stat.fit.goodnessdoubleCMDCl97.597.5th percentile CMD classification score (CMDCl97.5)stat.fit.goodnessdoublelogAge1616th percentile of log(Age) (logAge16)log(yr)time.agedoublelogAge50Median cluster log(Age) (logAge50)log(yr)time.agedoublelogAge8484th percentile of log(Age) (logAge84)log(yr)time.agedoubleAV1616th percentile of V-band extinction (AV16)magphys.absorptiondoubleAV50Median cluster V-band extinction (AV50)magphys.absorptiondoubleAV8484th percentile of V-band extinction (AV84)magphys.absorptiondoublediffAV1616th percentile differential extinction (diffAV16)magphys.absorption;arith.diffdoublediffAV50Median differential extinction (diffAV50)magphys.absorption;stat.mediandoublediffAV8484th percentile differential extinction (diffAV84)magphys.absorption;arith.diffdoubleMOD1616th percentile distance modulus (MOD16)magphot.mag.distModdoubleMOD50Median cluster distance modulus (MOD50)magphot.mag.distModdoubleMOD8484th percentile distance modulus (MOD84)magphot.mag.distModdoubler50JProjected half-number angular radius (J) (r50J)phys.size.radiusdoubler50JpcProjected half-number radius (J) in pc (r50Jpc)pcphys.size.radiusdoublerJpcTotal structural radius (J) in pc (rJpc)pcphys.size.radiusdoubleprobJProbability threshold parameter (J) (probJ)stat.fit.goodnessdoubleNJNumber of selected members (J) (NJ)meta.numberintMassJCalculated integrated cluster mass (J) (MassJ)solMassphys.massdoublee_MassJUncertainty on cluster mass (J) (e_MassJ)solMassstat.errordoubleMassTotTotal integrated cluster mass (MassTot)solMassphys.massdoublee_MassTotUncertainty on total cluster mass (e_MassTot)solMassstat.errordoubleminClSizeMinimum cluster size threshold (minClSize)phys.sizeintisMergedCluster merger classification flag (isMerged)src.classintisGMMMembGMM member classification flag (isGMMMemb)src.classintNXmatchesNumber of catalog cross-matches (NXmatches)meta.numberintDynAgeDimensionless dynamical age tau (this work) (Dynamical_Age)time.agedoubleNameCluster designation name (Name)meta.id;meta.maincharAllNamesAlternative cluster names/cross-matches (AllNames)meta.idcharCMDClHumanHuman verification flag for CMD (CMDClHuman)stat.fit.goodnesschar