J/ApJS/96/175ivo://CDS.VizieR/J/ApJS/96/175doi:10.26093/cds/vizier.20960175CDSBeers T.C.Sommer-Larsen J.2013-02-27T06:18:08Z1997-12-09T21:26:22ZCDS support team

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

cds-question@unistra.frchemically-peculiar-starsastrometryradial-velocitychemical-abundancesWe discuss the kinematic properties of a sample of 1936 Galactic stars, selected without kinematic bias, and with abundances [Fe/H] <= -0.6. The stars selected for this study all have measured radial velocities, and the majority have abundances determined from spectroscopic and narrow-/intermediate-band photometric techniques. In contrast to previous examinations of the kinematics of the metal-poor stars in the Galaxy, our sample contains large numbers of stars that are located at distances in excess of 1 kpc from the Galactic plane. Thus, a much clearer picture of the nature of the metal-deficient populations in the Galaxy can now be drawn. Our present data can be well described in terms of a two-component kinematic model consisting of a thick disk, rotating at roughly 200 km/s (independent of metal abundance), and an essentially nonrotating halo. The kinematics of these two components suggest a very broad overlap in metallicity; the thick disk is shown to possess an extremely metal-weak tail, extending to abundances even lower than previously reported, down to at least [Fe/H] ~ -2.0. A "minimal-assumptions" maximum-likelihood model is used to show that below [Fe/H] = -1.5 roughly 30% of stars in the solar neighbourhood can be kinematically associated with the thick disk. Over the metallicity interval -1.6 <= [Fe/H] <= -1.0, the thick-disk proportion rises to 60%. This fraction is only slightly smaller than contribution of thick-disk stars derived by Morrison, Flynn, and Freeman in the same metallicity interval (80%). Our confirmation that significant numbers of stars with thick-disk-like kinematics exist in the solar neighbourhood at arbitrarily low metal abundance suggests that previous disagreements about the correlation of population rotation velocities and metal abundance (e.g. Sandage & Fouts vs. Norris) may be due primarily to the selection criteria employed, and the resulting different contribution of metal-weak thick-disk stars to the respective data sets. The non-Gaussian nature of the velocity distribution of extremely metal-poor stars ([Fe/H] <= -1.5) in the directions of the Galactic poles reported by previous workers can also be understood as a consequence of the overlap between a cold metal-weak thick-disk population and a hot halo population. A maximum-likelihood technique has been developed in order to estimate the velocity ellipsoids of the thick-disk and halo components of the Galaxy. From the 349 stars in our sample with -1.0 <= [Fe/H] <= -0.6 and |z| <= 1 kpc, the velocity ellipsoid of the thick disk is (sigma_U, sigma_V, sigma_W) = (63 +/- 7, 42 +/- 4, 38 +/- 4) km/s. These values are in remarkably good accord with the predicted thick-disk velocity ellipsoid obtained by Quinn, Hernquist, and Fullagar from simulations of a satellite-merger formation scenario. Based on this velocity ellipsoid, a radial scale length for thick-disk stars of h_R = 4.7 +/- 0.5 kpc is obtained, larger than reported by Morrison, and similar to the value obtained for the old-disk population. However, the apparent equality of sigma_V and sigma_W is evidence that the thick disk is kinematically distinct from the old-disk population, where sigma_V:sigma_W ~ 2^{1/2}:1. We find a substantially smaller asymmetric-drift velocity gradient for presumed thick-disk stars (delta Vrot/delta |z| = -13 +/- 6 km/s/kpc) than reported by Majewski (delta Vrot/delta |z| = -21 +/- 1 km/s/kpc). From 887 stars in our sample with [Fe/H] <= -1.5 the local velocity ellipsoid of the halo is (sigma_r, sigma_phi, sigma_theta) = (153 +/- 10, 93 +/- 18, 107 +/- 7) km/s, that is, strongly radially peaked, as indicated by previous studies. We find little difference in the velocity ellipsoids of this sample when it is split into two roughly equal pieces with -2.2 <= [Fe/H] <= -1.5 and [Fe/H] <= -2.2, which indicates a lack of radial metallicity gradient in the halo, as found from studies of the Galactic globular cluster system. The velocity ellipsoid obtained from the small number of stars in our sample with Galactocentric distances r > 10 kpc (N = 61) is (sigma_r, sigma_phi, sigma_theta) = (115 +/- 18, 138 +/- 78, 110 +/- 24) km/s, much less radially elongated than found for the local sample.1995ApJS...96..175Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/96/175CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/119/2866 : Kinematics of metal-poor stars. II. (Beers+, 2000)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/96/175https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/96/175http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/96/175https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/96/175https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/96/175http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/96/175GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJS/96/175/table2 (Positions, radial velocities, distances, and abundances)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/96/175/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/96/175/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/96/175/table2?GETtext/xml+votable180.050000true0.65126-65.756510.0055555555555555565/2595 2601 4101 4783 6309 6311 7126 8935 8937 8940 8943 9457 11376 11662 11665 11681 11683 11684 11847 11884 12038 12097 6/110 211 212 382 572 608 1280 1281 1663 2058 2089 2173 2426 2629 2921 2997 3176 3712 4286 4322 4373 4479 4762 4942 5182 5226 5621 5708 6051 6301 6386 6390 6391 6530 6551 6555 6556 6560 6561 6563 6565 6577 6601 6740 6744 6934 7251 7456 7518 7710 7767 8064 8294 8314 8354 8366 8367 8410 8439 8466 8502 8584 8652 8716 8779 8866 8994 9065 9095 9138 9172 9363 9509 9635 9938 10169 10328 10334 10362 10363 10377 10379 10394 10398 10401 10416 10476 10524 10541 10569 10584 10602 10638 10661 10757 10758 10764 10792 10797 10802 10811 10862 10904 11098 11123 11197 11961 12308 12353 12355 12356 12358 12359 12512 12626 12632 12696 12743 12773 12904 13205 13680 13803 13972 13983 13991 14013 14017 14034 14035 14038 14042 14058 14216 14373 14857 14874 14994 15043 15106 15220 15375 15427 15440 15714 16018 16115 16401 16409 16411 16414 16419 16421 16427 16433 16443 16450 16451 16452 16453 16456 16458 16461 16462 16463 16465 16467 16470 16473 16475 16477 16478 16479 16485 16486 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18621 18622 18626 18632 18695 18701 18704 18707 18708 18711 18713 18715 18716 18718 18719 18737 18752 18753 18754 18764 18768 18770 18776 18778 18780 18782 18788 18789 18791 18802 18804 18945 18961 18964 18972 18973 18990 19008 19012 19016 19017 19076 19110 19127 19169 19171 19176 19177 19179 19280 19333 19448 19924 20013 20097 20303 20328 20330 20332 20334 20372 20377 20390 20418 20532 20551 20661 20804 20901 21127 21129 21146 21182 21209 21269 21389 21920 22205 22548 22558 22656 22659 22662 22664 23096 23192 23270 23428 23464 23523 23527 23545 24182 24189 24276 24310 24313 24319 24345 24346 24347 24348 24352 24355 24356 24357 24358 24368 24372 24373 24398 24418 24419 24420 24424 24449 24456 24467 24474 24496 24581 24591 24645 24646 24647 24652 24653 24657 24658 24659 24661 24662 24663 24664 24665 24678 24681 24683 24733 24752 24779 24832 24833 24834 24836 24866 24942 25051 25149 25151 25193 25194 25198 25199 25200 25235 25281 25282 25283 25284 25285 25286 25288 25289 25290 25292 25491 25569 25595 25601 25607 25611 25656 25674 25702 25703 25704 25708 25709 25720 25733 25751 25753 25754 25755 25756 25768 25792 25803 25833 25842 25869 25953 25963 26109 26110 26131 26281 26288 26344 26347 26366 26413 26435 26453 26457 26487 26515 26534 26552 26756 26894 26981 27091 27333 27361 27474 27491 27641 27711 27763 27767 27775 27824 27871 27903 27983 27998 28006 28030 28072 28127 28143 28144 28146 28148 28149 28153 28155 28157 28234 28383 28426 28431 28469 28485 28491 28493 28497 28499 28502 28503 28528 28538 28546 28578 28581 28582 28674 28675 28687 28701 28716 28745 28778 28791 28813 28830 28952 28957 28966 29011 29255 29426 29548 29593 29703 29769 29958 30019 30055 30709 30891 30923 30927 30950 30963 30970 30971 31054 31240 31290 31291 31312 31335 31365 31376 31377 31383 31390 31396 31398 31411 31414 31417 31418 31419 31427 31429 31451 31456 31543 31551 31585 31591 31592 31595 31608 31648 31658 31681 31683 31685 31741 31744 31757 31979 32052 32181 32352 32436 32580 32607 32663 32889 32940 32994 33018 33076 33123 33134 33143 33150 33197 33207 33213 33230 33249 33252 33254 33256 33257 33258 33260 33261 33262 33267 33303 33323 33342 33378 33432 33465 33470 33471 33483 33515 33526 33527 33529 33531 33535 33551 33558 33559 33562 33565 33566 33572 33573 33587 33588 33596 33618 33631 33633 33635 33636 33638 33642 33644 33645 33683 33696 33698 33699 33701 33707 33708 33725 33728 33743 33766 33794 33831 33849 33929 33996 34088 34096 34116 34171 34222 34223 34232 34240 34251 34537 34559 34573 34593 34595 34600 34606 34619 34653 34684 34705 34706 34708 34749 34751 34762 34816 34839 34888 34899 34900 34903 34908 34912 34944 35072 35073 35221 35453 35454 35517 35518 35519 35532 35533 35535 35551 35553 35556 35558 35560 35561 35565 35566 35567 35568 35569 35574 35578 35582 35598 35599 35607 35632 35637 35640 35649 35686 35695 35712 35715 35716 35718 35723 35726 35727 35729 35730 35731 35734 35737 35738 35739 35747 35753 35756 35758 35759 35764 35766 35768 35769 35771 35786 35803 35811 35816 35817 35822 35824 35825 35852 35875 35907 35989 36048 36135 36174 36186 36187 36193 36199 36208 36209 36211 36215 36217 36221 36223 36281 36286 36295 36365 36407 36414 36474 36564 36605 36628 36642 36651 36652 36653 36673 36684 36688 36690 36704 36705 36737 36739 36745 36755 36764 36770 36772 36781 36799 36814 36826 36827 36835 36837 37185 37232 37244 37282 37367 37369 37371 37375 37386 37709 37711 37712 37733 37735 37746 37757 37758 37789 37836 37842 37843 37844 37855 37869 37895 37910 37911 37915 37934 37947 37952 37966 38019 38087 38216 38255 38304 38506 38570 38583 38755 38809 38868 38942 39030 39152 39221 39244 39247 39270 39273 39281 39284 39357 39372 39379 39388 39396 39406 39413 39415 39475 39629 39647 39692 39760 39761 39763 39765 39771 39802 39888 40133 40214 40222 40333 40337 40351 40526 40553 40567 40624 40651 40722 40750 40767 40806 40988 41080 41191 41285 41318 41659 41660 41721 41831 41991 42260 42308 42331 42333 42496 42735 43041 43062 43360 43445 43498 43534 43546 43575 43613 43660 43735 43750 43756 43769 43773 43775 43786 43788 43838 43848 43888 43905 43911 43912 43944 43945 43947 43960 44106 44208 44219 44222 44259 44265 44268 44281 44326 44347 44541 44542 44565 44575 44615 44621 44624 44625 44634 44645 44657 44771 44786 44793 44851 44869 44883 44907 44914 44940 45395 45397 45401 45403 45404 45410 45412 45430 45431 45460 45463 45465 45466 45468 45470 45478 45479 45482 45483 45489 45491 45513 45514 45694 45711 45718 45720 45722 45727 45735 45746 45752 45753 45765 45773 45787 45788 45790 45793 45796 45797 45800 45801 45803 45804 45808 45812 45818 45825 45827 45829 45830 45837 45859 45861 45868 45871 45881 45907 46023 46039 46053 46069 46080 46083 46084 46086 46090 46096 46098 46130 46163 46205 46302 46316 46317 46319 46327 46330 46334 46370 46373 46399 46445 46446 46447 46448 46458 46462 46471 46485 46506 46510 46530 46531 46532 46533 46534 46540 46541 46543 46551 46553 46554 46557 46558 46559 46561 46562 46563 46565 46567 46574 46575 46576 46577 46579 46580 46584 46585 46605 46623 46632 46637 46638 46639 46640 46641 46642 46646 46652 46655 46656 46657 46665 46666 46667 46668 46673 46676 46678 46679 46685 46686 46689 46691 46694 46695 46696 46699 46700 46703 46704 46705 46707 46721 46722 46723 46728 46729 46740 46742 46744 46746 46747 46749 46751 46753 46755 46756 46759 46760 46761 46763 46764 46766 46770 46771 46776 46778 46780 46782 46783 46787 46790 46791 46792 46793 46795 46796 46797 46816 46837 46839 46844 46845 46851 46853 46856 46909 46923 46933 47009 47014 47017 47018 47019 47020 47022 47023 47092 47094 47147 47172 47175 47182 47184 47193 47204 47207 47216 47217 47306 47311 47332 47333 47344 47347 47387 47412 47414 47415 47421 47432 47433 47435 47436 47451 47458 47459 47467 47471 47472 47476 47478 47480 47483 47484 47512 47518 47519 47540 47541 47542 47544 47545 47548 47549 47556 47557 47558 47563 47584 47596 47698 47821 47850 47876 47961 48113 48129 48131 48133 48135 48138 48143 48144 48145 48147 48148 48150 48151 48158 48160 48162 48194 48221 48223 48228 48281 48315 48316 48360 48362 48363 48374 48375 48378 48387 48397 48423 48501 48510 48511 48517 48519 48526 48527 48531 48540 48542 48544 48555 48557 48560 48562 48585 48591 48599 48602 48603 48612 48613 48625 48636 48660 48662 48663 48665 48669 48670 48707 48711 48719 48720 48722 48728 48731 48732 48734 48744 48753 48764 48766 48798 48824 48848 48849 48851 48854 48856 48859 48862 48880 48911 48916 48937 48946 49063https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJS/96/175?format=asciiOpticaldefaultJ/ApJS/96/175/table2Positions, radial velocities, distances, and abundancesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarStar namemeta.id;meta.maincharRA1950Right ascension (1950.0)pos.eq.ra;meta.mainDE1950Declination (1950.0)pos.eq.dec;meta.mainVmag[]? V magnitudemagphot.mag;em.opt.VfloatnullableTypeObject classificationmeta.code.class;src.classcharRVBest available heliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentric;meta.modelledintDistDistance from Sunpcpos.distanceint[Fe/H]Abundance estimateSunphys.abundfloatr_RVSource code for RVmeta.ref;pos.frameintr_DistSource code for Distmeta.ref;pos.frameintr_[Fe/H]Source code for Fe/Hmeta.refint_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data)pos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data)pos.eq.decnullableindexed