J/MNRAS/498/1920ivo://CDS.VizieR/J/MNRAS/498/1920doi:10.26093/cds/vizier.74981920CDSOh S.Evans N.W.2025-02-28T20:16:00Z2023-11-03T09:49:20ZCDS support team

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

cds-question@unistra.fropen-star-clustersastrometryvisible-astronomytrigonometric-parallaxproper-motionsradial-velocityastronomical-modelsThe precision of the Gaia data offers a unique opportunity to study the internal velocity field of star clusters. We develop and validate a forward-modelling method for the internal motions of stars in a cluster. The model allows an anisotropic velocity dispersion matrix and linear velocity gradient describing rotation and shear, combines radial velocities available for a subset of stars, and accounts for contamination from background sources via a mixture model. We apply the method to Gaia DR2 data of the Hyades cluster and its tidal tails, dividing and comparing the kinematics of stars within and beyond 10pc, which is roughly the tidal radius of the cluster. While the velocity dispersion for the cluster is nearly isotropic, the velocity ellipsoid for the tails is clearly elongated with the major axis pointing towards the Galactic centre. We find positive and negative expansions at ~2{sigma} significance in Galactic azimuthal and vertical directions for the cluster but no rotation. The tidal tails are stretching in a direction tilted from the Galactic centre while equally contracting as the cluster in Galactic vertical direction. The tails have a shear (A) of 16.90+/-0.92m/s/pc and a vorticity (B) of -6.48+/-1.15m/s/pc, values distinct from the local Oort constants. By solving the Jeans equations for flattened models of the Hyades, we show that the observed velocity dispersions are a factor of ~2 greater than required for virial equilibrium due to tidal heating and disruption. From simple models of the mass loss, we estimate that the Hyades is close to final dissolution with only a further ~<30Myr left.2020MNRAS.498.1920Ohttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/498/1920CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)J/A+A/616/A10 : 46 open clusters GaiaDR2 HR diagramsJ/A+A/621/L3 : Hyades tidal tails with Gaia DR2 (Meingast+, 2019)J/A+A/621/L2 : Hyades tidal tails revealed by Gaia DR2 (Roeser+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/498/1920https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/498/1920http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/498/1920https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/498/1920https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/498/1920http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/498/1920GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/498/1920/table2 (The merged Hyades used for kinematic modelling)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/498/1920/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/498/1920/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/498/1920/table2?GETtext/xml+votable180.050000true64.8746088921.753716110.0055555555555555565/80 84 87 256 261 5869 5873-5876 5880-5881 5883-5884 5886-5887 6050 6052 6058-6059 6/60 78 95 197 211 247 260 265 272-274 276 279 287 303 305 309 311 313 315 318 324-326 330 333-335 340-342 344 353 355 357-358 360 363 365-369 373-374 378-379 381-383 401 405 407 426-427 450 456 458 462 465 470 472 478 481 483 490 499 507 663 671 701 706 712 729 770 780 784 835 840 847 879 882 890 917 989 997 1009 1029 1031-1033 1035-1038 1041-1042 1049-1050 1052 1057-1058 1060-1062 1065 1072 1075 1077 1090 1096-1097 1159 1163 1166 1196 1199 1201 1211 1234 1272 1312 1554 1564 1568 1577 1580 1611 1614 1640 1661 1720 1810 2052 2086 2152 2163 2178 2183 2211 2228 2274 2293 2296 2325 2328 2335 2350 2356 2368 2375 2383 2418 2426 2446 2456 2466 2468 2483 2525 2535 2577 2583 2589 2609 2618 2634 2686 2711 2715 2739 2744 2788-2789 2792 2802 2804 2806 2809 2811 2813 2827-2828 2830 2838 2866 2880 2893 2915 2924 2949 2974 2981 2992 2995 3032 3045 3056 3066 3117 3133 3335 3593 3625 4796 6174 6232 6363 6711 6748 6802 6809 6867 12440 12655 12667 12760 12789 13312 13351 13376 13389 13412 13432 13443 13472 13503 13542 13578-13579 13591 13643 13650 13654 13667 13669 13681 13702 13714 13732 13737 13742 13758-13759 13761 13770 13772 13774 13782 13787 13795-13796 13802 13805 13808-13809 13818 13823 13840 13911 13917 13943 14028 14030-14031 14035-14038 14043 14045 14057 14059-14061 14065 14067-14068 14070-14071 14076 14085 14091 14093-14094 14108 14113-14114 14121-14123 14126 14132 14134-14135 14137 14140 14142 14144-14145 14149 14154 14158 14162 14169 14171 14178 14191 14194 14207-14208 14211-14212 14217-14219 14221 14223 14226-14227 14229-14230 14232-14233 14237 14240 14242-14243 14250 14253 14258-14259 14266 14280 14294 15388 15424 15443 15452 15634 17731 17843 17852 18036 18404 18544 18914 19361 19384 19424 19446 19448 19457 19470 19751 19957 20087 20134 20157 20486 20574 20583-20584 20601 20672 20690 20737 20739 20753 20761 20770 20780 20799 20842 20846 20869 20876 20881 20883 20886 20891 20913 20924 20928 20932 20941 20955 20962 20973 20984 20987-20988 21055 21082 21094 21204 21221 21227 21242 21249 21255 21289 21300-21301 21303 21307-21308 21318-21319 21324 21329 21347 21350 21354-21355 21361 21368 21370 21372 21374 21377-21378 21391 21398 21412 21429 21455-21456 21464 21466 21468 21472 21485 21490 21493 21496 21500 22053 22144-22145 22171 22176-22177 22185 22204 22207 22229 22244 22254 22511 22558 22566 22598 22663 22679 22713 22745 22761 22781 22787 22811 22823 22847 22856-22857 22864-22865 22869 22872 22882 22890 22892 22902 22904 22906-22908 22910-22912 22920 22935-22936 22956 23006 23011 23017 23024 23026 23035 23037 23113 23115 23139 23211 23261 23285-23286 23288 23313 23315 23321 23324-23325 23328-23329 23339 23344 23355-23356 23358-23359 23362 23368-23370 23372 23375 23383 23385-23387 23389 23392-23393 23395-23396 23399 23404-23405 23407-23408 23413 23415-23416 23418-23419 23443-23444 23448 23450 23453-23454 23462 23468 23472 23487 23489-23490 23508 23510-23511 23513-23516 23518-23519 23529 23531 23540-23542 23558 23561 23569 23583-23584 23588 23593 23603 23611 23626 23636 23651 23659-23660 23667 23680 23689 23695 23702 23704 23710 23714 23721-23724 23726-23727 23737-23739 23741 23753 23784 23787 23789 23794 23816 23818 23852 23883 23886 23904 23912 23918 23932 23936 23943 23970 24019 24052 24068 24070 24075-24076 24078 24094-24095 24097 24099-24100 24102-24106 24109-24110 24118 24124 24126 24130 24137 24173 24175 24192 24194-24196 24204 24206-24207 24212 24215-24218 24220 24223-24226 24228-24230 24241-24244 24246 24248 24251-24252 24256 24258-24259 24266 24280 24297-24298 24310 24319 24355 24359 24394 24410 24414 24421 24423 34773 36609 36922 38997 39036 39137 39170 39178 39479 39596 39605 39628 39644 39662 39669-39670 39672 39713 39730 39733 39815 39820 39834 39844 39846 39854 39858 39864-39865 40986 45568 489231.9867573869263685e-19 3.916500758235022e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/498/1920?format=asciiOpticaldefaultJ/MNRAS/498/1920/table2The merged Hyades used for kinematic modelling_DE.icrsDeclination (ICRS) at Epoch=J2000, proper motions taken into accountdegpos.eq.decindexedSimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGaiaDR2Gaia DR2 source identifiermeta.id;meta.mainRA_ICRSRight ascension (ICRS) at Ep=2015.5degpos.eq.ra;meta.mainDE_ICRSDeclination (ICRS) at Ep=2015.5degpos.eq.dec;meta.main_RA.icrsRight ascension (ICRS) at Epoch=J2000, proper motions taken into accountdegpos.eq.raindexedplxParallax from Gaia DR2maspos.parallax.trigdoublepmRAProper motion in right ascension from Gaia DR2mas/yrpos.pm;pos.eq.radoublepmDEProper motion in declination from Gaia DR2mas/yrpos.pm;pos.eq.decdoubleRV? Radial velocitykm/sphys.veloc;pos.heliocentricfloatnullableBP-RP? BP-RP colour from Gaia DR2magphot.color;em.opt.B;em.opt.RfloatnullableGmagG-band magnitude from Gaia DR2magphot.mag;em.optfloatinMeingastIndicates if the source was included the membership list of Meingast & Alves (2019A&A...621L...3M, Cat. J/A+A/621/L3)meta.codecharinRoserIndicates if the source was included the membership list of Roser et al. (2019A&A...621L...2R, Cat. J/A+A/621/L2)meta.codecharPmemMean membership probability from kinematic modellingstat.probabilityfloatGroupFit group (1)meta.code.classcharinGaiaIndicates if the source was included the Gaia Collaboration et al. (2018A&A...616A..10G, Cat. J/A+A/616/A10) membership listmeta.codechar