J/A+A/695/A22ivo://CDS.VizieR/J/A+A/695/A22doi:10.26093/cds/vizier.36950022CDSQin C.Pang X.Pasquato M.Kouwenhoven M.B.N.Vallenari A.2025-04-01T20:01:01Z2025-02-28T09:09:47ZCDS support team

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

cds-question@unistra.frmilky-way-galaxyopen-star-clustersstellar-agesgalaxy-classification-systemsWe analyzed the fractal dimension of open clusters using 3D spatial data from Gaia DR3 for 93 open clusters from Pang et al. (2024ApJ...966..169P) and 127 open clusters from Hunt & Reffert (2024A&A...686A..42H, Cat. J/A+A/686/A42) mainly within 500pc. The box-counting method was adopted to calculate the fractal dimension of each cluster in three regions: the all- member region, r<=rt (inside the tidal radius), and r>rt (outside the tidal radius). In both the Pang and Hunt catalogs, the fractal dimensions are smaller for the regions r>rt than those for r<=rt, indicating that the stellar distribution is more clumpy in the cluster outskirts. We classified cluster morphology based on the fractal dimension via the Gaussian mixture model. Our study shows that the fractal dimension can efficiently classify clusters in the Pang catalog into two groups. The fractal dimension of the clusters in the Pang catalog declines with age, which is attributed to the development of tidal tails. This is consistent with the expectations from the dynamical evolution of open clusters. We found strong evidence that the fractal dimension increases with cluster mass, which implies that higher-mass clusters are formed hierarchically from the mergers of lower-mass filamentary- type stellar groups. The transition of the fractal dimension for the spatial distribution of open clusters provides a useful tool to trace the Galactic star-forming structures, from the location of the Local Bubble within the solar neighborhood to the spiral arms across the Galaxy.2025A&A...695A..22Qhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/695/A22CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/350 : Gaia EDR3 (Gaia Collaboration, 2020)I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)J/ApJ/877/12 : Coma Ber & Neighbor Stellar Group tidal tails (Tang+, 2019)J/ApJ/923/20 : Hierarchical clustering in Vela OB2 complex (Pang+, 2021)J/A+A/646/A104 : Improving the open cluster census. I. (Hunt+, 2021)J/ApJ/937/L7 : Collinder132-Gulliver21 stream members from Gaia DR3J/A+A/673/A114 : Improving the open cluster census. II. (Hunt+, 2023)J/A+A/686/A42 : Improving the open cluster census. III. (Hunt+, 2024)J/ApJ/912/162 : Open clusters in solar neighborhood (Pang+, 2021)J/ApJ/931/156 : 3D morphology of open clusters with Gaia EDR3. IIhttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/695/A22https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/695/A22http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/695/A22https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/695/A22https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/695/A22http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/695/A22GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/695/A22/tablea1 (Fractal dimension for the Pang catalog clusters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/695/A22/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/695/A22/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/695/A22/tablea1?GETtext/xml+votable180.050000true356.035533956.07858190.005555555555555556Cone search capability for table J/A+A/695/A22/tablea2 (Fractal dimension for the Hunt catalog clusters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/695/A22/tablea2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/695/A22/tablea2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/695/A22/tablea2?GETtext/xml+votable180.050000true301.232286349118-10.5287121110250.0055555555555555566/463 1194 1204 1208 1539 1560 1913 2945 3004 3289 3849 4698 11418 14058 14162 14193 14305 14312 14363 14403 14432 14603 14878 15396 15432 15694 16489 20924 21438 21529 22034 22058 22805 22837 22854 22859-22860 22880 22884 22895 23717 28480 28711 28806 29158 29728 30439 31071 31790 31812 32111 33102 37231 37332 37592 37790 37933 38018 38051 38073 39160 39181 39183 39191 39216 39273 39297 39354 39388 39548 39714 39739 39867 39871 41557 41995 42268 42415 42979 42990 44353 44361 44365 47621https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/695/A22?format=asciiOpticaldefaultJ/A+A/695/A22/tablea1Fractal dimension for the Pang catalog clustersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintClusterCluster Namemeta.id;meta.maincharAgeCluster AgeMyrtime.agefloatTypeMorphological type (1)src.morph.typecharfdim-allFractal dimension for the all-member regionstat.correlationdoublefdim-inrt? Fractal dimension for the region inside the tidal radius (r<=rt)stat.correlationdoublenullablefdim-outrt? Fractal dimension for the region outside the tidal radius (r>rt)stat.correlationdoublenullable_RAPositions from Pang et al., 2022, Cat. J/ApJ/931/156 (right ascension part)degpos.eq.ra;meta.mainnullable_DEPositions from Pang et al., 2022, Cat. J/ApJ/931/156 (declination part)degpos.eq.dec;meta.mainnullableJ/A+A/695/A22/tablea2Fractal dimension for the Hunt catalog clustersClusterCluster Namemeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlogAgeLogarithm of cluster age (1)log(yr)time.agedoublefdim-allFractal dimension for the all-member regionstat.correlationdoublefdim-inrt? Fractal dimension for the region inside the tidal radius (r<=rt)stat.correlationdoublenullablefdim-outrt? Fractal dimension for the region outside the tidal radius (r>rt)stat.correlationdoublenullable_RAPositions from Hunt et al., 2024, Cat. J/A+A/686/A42 (right ascension part)degpos.eq.ra;meta.mainnullable_DEPositions from Hunt et al., 2024, Cat. J/A+A/686/A42 (declination part)degpos.eq.dec;meta.mainnullable