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Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| Radial velocities in the globular cluster ? Centauri
We have used the ARGUS multi-object spectrometer at the CTIO 4 m Blancotelescope to obtain 2756 radial velocity measurements for 1966individual stars in the globular cluster ? Centauri brighter thanblue photographic magnitude of about 16.5. Of these, 1589 stars arecluster members. A comparison with two independent radial velocitystudies, carried out by Suntzeff & Kraft and by Mayor et al.,demonstrates that the median error of our measurements is below 2 kms-1 for the stars brighter than B-magnitude 15, whichconstitute the bulk of the sample. The observed velocity dispersiondecreases from about 15 km s-1 in the inner few arcmin toabout 6 km s-1 at a radius of 25'. The cluster showssignificant rotation, with a maximum amplitude of about 6 kms-1 in the radial zone between 6' and 10'. In a companionpaper by van de Ven et al., we correct these radial velocities for theperspective rotation caused by the space motion of the cluster, andcombine them with the internal proper motions of nearly 8000 clustermembers measured by van Leeuwen et al., to construct a detaileddynamical model of ? Centauri and to measure its distance.
| Elemental Abundance Ratios in Stars of the Outer Galactic Disk. II. Field Red Giants
We summarize a selection process to identify red giants in the directionof the southern warp of the Galactic disk, employing VICphotometry and multiobject spectroscopy. We also present results fromfollow-up high-resolution, high signal-to-noise echelle spectroscopy ofthree field red giants, finding [Fe/H] values of about -0.5. The fieldstars, with galactocentric distances estimated at 10-15 kpc, support theconclusion of Yong and coworkers that the Galactic metallicity gradientdisappears beyond RGC values of 10-12 kpc for the older starsand clusters of the outer disk. We summarize the detailed abundancepatterns for 15 other elements for these stars and compare them withrecently obtained results for old open cluster red giants in the outerdisk. The field and cluster stars at such large distances show verysimilar abundance patterns, and, in particular, all show enhancements ofthe α-elements O, Mg, Si, Ca, and Ti and the r-process element Eu.These results suggest that Type II supernovae have been significantcontributors to star formation in the outer disk relative to Type Iasupernovae within the past few gigayears. We also compare our resultswith those available for much younger objects. The limited results forthe H II regions and B stars in the outer disk also suggest that theradial metallicity gradient in the outer disk is shallow or absent. Themuch more extensive results for Cepheids confirm these trends and thatthe change in slope of the metallicity gradient may occur at a largergalactocentric distance than for the older stars and clusters. However,the younger stars also show rising α-element enhancements withincreasing RGC, at least beyond 12 kpc. These trends areconsistent with the idea of a progressive growth in the size of theGalactic disk with time and episodic enrichment by Type II supernovae aspart of the disk's growth.This paper makes use of observations obtained at the National OpticalAstronomy Observatory, which is operated by the Association ofUniversities for Research in Astronomy (AURA), Inc., under contract fromthe National Science Foundation. We also employ data products from theTwo Micron All Sky Survey, which is a joint project of the University ofMassachusetts and the Infrared Processing and Analysis Center,California Institute of Technology, funded by the National Aeronauticsand Space Administration and the National Science Foundation.
| A Two Micron All Sky Survey View of the Sagittarius Dwarf Galaxy. II. Swope Telescope Spectroscopy of M Giant Stars in the Dynamically Cold Sagittarius Tidal Stream
We have obtained moderate resolution (~6 km s-1) spectroscopyof several hundred M giant candidates selected from Two Micron All SkySurvey photometry. Radial velocities are presented for stars mainly inthe southern Galactic hemisphere, and the primary targets have Galacticpositions consistent with association to the tidal tail system of theSagittarius (Sgr) dwarf galaxy. M giant stars selected from the apparenttrailing debris arm of Sgr have velocities showing a clear trend withorbital longitude, as expected from models of the orbit and destructionof Sgr. A minimum 8 kpc width of the trailing stream about the Sgrorbital midplane is implied by verified radial velocity members. Thecoldness of this stream (σv~10 km s-1)provides upper limits on the combined contributions of stream heating bya lumpy Galactic halo and the intrinsic dispersion of released stars,which is a function of the Sgr core mass. We find that the Sgr trailingarm is consistent with a Galactic halo that contains one dominant,LMC-like lump; however, some lumpier halos are not ruled out. An upperlimit to the total mass-to-light ratio of the Sgr core is 21 in solarunits. Evidence for other velocity structures is found among the moredistant (>13 kpc) M giants. A second structure that roughly mimicsexpectations for wrapped, leading Sgr arm debris crosses the trailingarm in the southern hemisphere; however, this may also be an unrelatedtidal feature. Among the bright, nearby (<13 kpc) M giants toward thesouth Galactic pole are a number with large velocities that identifythem as halo stars; these too may trace halo substructure, perhaps partof the Sgr leading arm near the Sun. The positions and velocities ofsouthern hemisphere M giants are compared with those of southernhemisphere globular clusters potentially stripped from the Sgr system.Support for association of the globular clusters Pal 2 and Pal 12 withSgr debris is found, based on positional and radial velocity matches.Our discussion includes description of a masked-filteredcross-correlation methodology that achieves better than 1/20 of aresolution element velocities in moderate-resolution spectra. Theimproved velocity resolution achieved allows tighter constraints to beplaced on the coldness of the Sgr stream than previously established.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Spectroscopy of giants in LMC clusters. I - Velocities, abundances, and the age-metallicity relation
Velocities and equivalent widths are presented for a large sample of LMCclusters. The calcium abundance is found to be a sensitive abundanceindicator over a very wide range of (Fe/H) between 0.0 and -2.2. Theage-metallicity relation is constructed for the inner and outer parts ofthe LMC. This relationsip can be characterized by a simple one-zoneenrichment model. The abundances for the inner and outer clusters at anage of 2 Gyr are nearly identical, so that little radial abundancegradient is evident in the cluster system.
| Core velocity dispersion and mass-to-light ratio of the old Magellanic globular cluster NGC 1835
The projected velocity dispersion in the core of the old LargeMagellanic Cloud globular cluster NGC 1835 is deduced from integratedlight spectra obtained at the European Southern Observatory (ESO) withCASPEC, the Cassegrain ESO Echelle Spectrograph mounted on the ESO3.6-m telescope at La Silla, Chile. A numerical cross-correlationtechnique gives a projected velocity dispersion ?P(core) = 10.1±0.2km s-1.Multimass anisotropic King-Michie dynamical models are applied to theobservational constraints given by the surface brightness profile andthe above central projected velocity dispersion. Depending on themodel, the values obtained for the total mass of the cluster rangefrom 0.70 to 1.55 106 Msun, with a mean totalmass = 1.0±0.3 106Msun, corresponding to a global mass-to-light ratio = 3.4±1.0(M/LV)sun. The present study shows that when the same kind of dynamical models(King-Michie) constrained by the same kind of observations (surfacebrightness profile and central value of the projected velocitydispersion) are applied to an old rich Magellanic globular cluster,viz., NGC 1835, the results seem similar to those obtained in the caseof galactic globular clusters. Consequently, the rich old globularclusters in the Magellanic clouds could be quite similar (in mass andM/LV) to the rich globular clusters in the Galaxy.
| What is the mass-to-light ratio of the old Magellanic globular cluster NGC 1835?
We astronomers are lucky: our Galaxy as two companion galaxies, theLarge and Small Magellanic Clouds, situated weil above the galacticplane, which Contain a huge potential of astrophysical information. Forexample, concern: ng star clusters, the realm of the globuar clustersis much richer and more Varied in the Magellanic Clouds than in theGalaxy: rich clusters of all ages are observed, from the youngest,having ages of a few tens 10^6 yr to the oldest 1haV'lng ages of theorder"or larger than 10 10^9 yr. In this paper, only old Magellanicand galactic globular clusters are considered.
| NGC 6366 - The most metal-rich halo globular cluster?
Spectra have been obtained at the Ca II IR triplet of four giants in theheavily reddened Galactic globular cluster NGC 6366. These spectra, whencompared with similar spectra of giants in the globular clusters NGC6171 and NGC 1851, suggest, for an adopted reddening of E(B-V) = 0.70mag, that the Fe/H = -0.84 + or - 0.23 dex for NGC 6366. It is concludedthat the Fe/H abundance of NGC 6366 is = -0.85 + or - 0.10 dex. Thespectra also yield a heliocentric velocity of -123.2 + or - 1.0 km/s forthe cluster. This velocity, when analyzed following the precepts ofArmandroff (1989), unambiguously associates NGC 6366 with the slowlyrotating halo cluster system, albeit the most metal-rich member of thispopulation yet identified, rather than with the rapidly rotating disksystem of globular clusters. An improved heliocentric velocity of -34 +or - 3 km/s is also given for NGC 6171, resolving the uncertaintyconcerning the velocity of this cluster.
| The radial velocity, velocity dispersion, and mass-to-light ratio of the Sculptor dwarf galaxy
Radial velocities for 16 K giants in the Sculptor dwarf spheroidalgalaxy are presented. The velocities have been determined viacross-correlation techniques from spectra obtained at the calciuminfrared triplet. They have a single-observation accuracy of 4.7 km/s.The mean velocity of the Sculptor stars is +107.4±2.0 km/s, avalue that supports the adoption of a large mass for the Galaxy. Theone-dimensional velocity dispersion of this sample is 6.3 (+1.1, -1.3)km/s, a value which, when combined with a new estimate of the coreradius of the galaxy and the observed central surface brightness, yieldsa visual mass-to-light ratio of 6.0 in solar units. This value is morethan twice current estimates of global mass-to-light ratios of globularclusters, and thus, if interpreted literally, indicates that Sculptorcontains a substantial amount of additional mass not found in globularclusters.
| A sample of old-disk-population red giants.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976PASP...88..426E&db_key=AST
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Osservazione e dati astrometrici
| Costellazione: | Bulino |
| Ascensione retta: | 04h57m47.27s |
| Declinazione: | -35°11'23.5" |
| Magnitudine apparente: | 8.951 |
| Distanza: | 471.698 parsec |
| Moto proprio RA: | 0.2 |
| Moto proprio Dec: | 12.4 |
| B-T magnitude: | 10.316 |
| V-T magnitude: | 9.064 |
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