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The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics
Context: Ages, chemical compositions, velocity vectors, and Galacticorbits for stars in the solar neighbourhood are fundamental test datafor models of Galactic evolution. The Geneva-Copenhagen Survey of theSolar Neighbourhood (Nordström et al. 2004; GCS), amagnitude-complete, kinematically unbiased sample of 16 682 nearby F andG dwarfs, is the largest available sample with complete data for starswith ages spanning that of the disk. Aims: We aim to improve theaccuracy of the GCS data by implementing the recent revision of theHipparcos parallaxes. Methods: The new parallaxes yield improvedastrometric distances for 12 506 stars in the GCS. We also use theparallaxes to verify the distance calibration for uvby? photometryby Holmberg et al. (2007, A&A, 475, 519; GCS II). We add newselection criteria to exclude evolved cool stars giving unreliableresults and derive distances for 3580 stars with large parallax errorsor not observed by Hipparcos. We also check the GCS II scales of T_effand [Fe/H] and find no need for change. Results: Introducing thenew distances, we recompute MV for 16 086 stars, and U, V, W,and Galactic orbital parameters for the 13 520 stars that also haveradial-velocity measurements. We also recompute stellar ages from thePadova stellar evolution models used in GCS I-II, using the new valuesof M_V, and compare them with ages from the Yale-Yonsei andVictoria-Regina models. Finally, we compare the observed age-velocityrelation in W with three simulated disk heating scenarios to show thepotential of the data. Conclusions: With these revisions, thebasic data for the GCS stars should now be as reliable as is possiblewith existing techniques. Further improvement must await consolidationof the T_eff scale from angular diameters and fluxes, and the Gaiatrigonometric parallaxes. We discuss the conditions for improvingcomputed stellar ages from new input data, and for distinguishingdifferent disk heating scenarios from data sets of the size andprecision of the GCS.Full Table 1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/501/941
| The central region of M83
We combine VLT/ISAAC near-infrared (NIR) spectroscopy with archivalHST/WFPC2 and HST/NICMOS imaging to study the central 20 ×20arcsec2 of M83. Our NIR indices for clusters in thecircumnuclear starburst region are inconsistent with simpleinstantaneous burst models. However, models of a single burst dispersedover a duration of 6 Myr fit the data well and provide the clearestevidence yet of an age gradient along the star-forming arc, with theyoungest clusters nearest the north-east dust lane. The long-slitkinematics show no evidence to support previous claims of a secondhidden mass concentration, although we do observe changes in moleculargas velocity consistent with the presence of a shock at the edge of thedust lane.Based on observations made with ESO Telescopes at the La Silla orParanal Observatories under programme IDs: 64.N-0100(B), 265.B-5723(A)and 65.O-0612(A). Also based on observations made with the NASA/ESAHubble Space Telescope (HST), obtained from the data archive at theSpace Telescope Science Institute (STScI). STScI is operated by theassociation of Universities for Research in Astronomy, Inc., under theNASA contract NAS 5-26555.E-mail: rcwh@astro.ox.ac.uk
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| 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
| Stellar dynamics observations of a double nucleus in M 83
We report on the discovery of a double nucleus in M 83, based onmeasurements of the line of sight velocity distribution of starsobserved at near infrared wavelengths with the VLT ISAAC spectrograph.We observe two peaks separated by 2\farcs 7 in the velocity dispersionprofile of light from late-type stars measured along a slit 0\farcs 6wide, centered on the peak of K band emission and with P.A. 51.7°.The first peak coincides with the peak of the K band light distribution,widely assumed to be the galaxy nucleus. The second peak, of almostequal strength, almost coincides with the center of symmetry of theouter isophotes of the galaxy. The secondary peak location has little Kband emission, and appears to be significantly extincted, even at nearinfrared wavelengths. It also lies along a mid-infrared bar, previouslyidentified by Gallais et al. (1991) and shows strong hydrogenrecombination emission at 1.875mu m. If we interpret the observedstellar velocity dispersion as coming from a virialized system, the twonuclei would each contain an enclosed mass of 13.2 x106Msun within a radius of 5.4 pc. These couldeither be massive star clusters, or supermassive dark objects.
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Datos observacionales y astrométricos
| Constelación: | Virgo |
| Ascensión Recta: | 13h35m31.65s |
| Declinación: | -22°01'28.4" |
| Magnitud Aparente: | 7.108 |
| Distancia: | 49.652 parsecs |
| Movimiento Propio en Ascensión Recta: | -130.7 |
| Movimiento Propio en Declinación: | -37.2 |
| B-T magnitude: | 7.706 |
| V-T magnitude: | 7.158 |
Catálogos y designaciones:
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