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The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| 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.
| Toward the HIPPARCOS link: astrometry of stars and extragalactic sources in the field of the spiral galaxy M51.
We present absolute proper motions of 14 Hipparcos stars from groundbased photographic astrometry in a 2x2deg field around the spiral galaxyMessier 51. These are part of a catalogue of 340 stars with B<=16,for which positions, proper motions, and B magnitudes have been derivedfrom a series of 16 photographic plates. Due to large epoch differencesof up to 88 years between the observations, the proper motion accuracyis typically <=1mas/a. An extragalactic calibration of the propermotion zero-point is achieved by measuring the fictitious proper motionsof bright extragalactic objects in the field. For this purpose, across-correlation technique was developed. The resulting precision ofthe proper motion link to an extragalactic frame is estimated as1.0mas/a. Measurements of double stars and high proper motion stars arealso discussed.
| A photometric study of the M51 system
Photoelectric (UBV and I) and photographic observations of the twocomponents of the M51 system, NGC 5194 and NGC 5195, are presented inthe form of photoelectric drift scans, composite photographs, calibratedcontour maps, color-color diagrams, and three-dimensional plots. Thelarge-scale features and symmetries of the system are described, andindividual regions are examined in detail. Approximate luminosities ofthese regions and integrated luminosities of the complete system aredetermined. The results indicate that: (1) the maximum detected extentof the system is 40 arcmin or 120 kpc; (2) the mass in the outerenvelope is equal to the mass obtained for the bright optical componentsif an M/L ratio of 10 is assumed; (3) the east side of NGC 5194 isbrighter than the west side; (4) the faint outer regions of NGC 5194 arelarge and structured; (5) there seems to be internal interaction betweenthe two galaxies; (6) the two galactic nuclei show complex structure;(7) the luminosity profile of NGC 5194 appears to be unique; and (8) thetwo galaxies may belong to a common system or mass aggregate and appearto be interconnected.
| Radial Velocities, Spectral Types, and Luminosity Classes of 820 Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1950ApJ...112...48M&db_key=AST
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Osservazione e dati astrometrici
| Costellazione: | Cani da Caccia |
| Ascensione retta: | 13h29m18.74s |
| Declinazione: | +46°22'15.3" |
| Magnitudine apparente: | 8.162 |
| Distanza: | 197.239 parsec |
| Moto proprio RA: | 1.4 |
| Moto proprio Dec: | 11.5 |
| B-T magnitude: | 8.653 |
| V-T magnitude: | 8.203 |
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