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Diffraction-limited bispectrum speckle interferometry of the nuclear region of the Seyfert galaxy NGC 1068 in the H and K' bands
We present near-infrared bispectrum speckle interferometry studies ofthe nuclear region of the Seyfert 2 galaxy NGC 1068.A diffraction-limited K'-band image with 74 mas resolution and the firstH-band image with 57 mas resolution were reconstructed from speckleinterferograms obtained with the SAO 6 m telescope. The resolvedstructure consists of a compact core and an extended northern andsouth-eastern component. The compact core is resolved at all positionangles and has a north-western, tail-shaped extension as well as afainter, south-eastern extension. The K'-band FWHM diameter of thiscompact core is approximately 18 × 39 mas or 1.3 × 2.8 pc(FWHM of a single-component Gaussian fit; fit range 30-80&%slash; ofthe telescope cut-off frequency; the diameter errors are ±4 mas),and the position angle (PA) of the north-western extension is -16± 4 °. If 40% of the flux from the compact K' core isemission from a point source and 60% from a Gaussian intensitydistribution, then a slightly larger FWHM of approximately 26 × 58mas is obtained for the compact K' component. In the H band, the FWHMdiameter of the compact core is approximately 18 × 45 mas(±4 mas), and the PA is -18 ± 4 °. The extendednorthern component (PA 0 °) has an elongated structure with alength of about 400 mas or 29 pc. The extended south-eastern componentis fainter than the northern component. The K'- and H-band fluxes fromthe resolved compact core were measured to be 350 ± 90 mJy (i.e.,K' 8.2m) and 70 ± 20 mJy (H 10.4m), respectively. The PA of -16 ± 4 ° of thecompact 18 × 39 mas core is very similar to that of the westernwall (PA -15 °) of the bright region of the ionization cone.This suggests that the H- and K'-band emission from the compact core isboth thermal emission and scattered light from dust near the westernwall of a low-density, conical cavity or from the innermost region of aparsec-scale dusty torus that is heated by the central source (the dustsublimation radius of NGC 1068 is approximately 0.1-1pc). The northern extended 400 mas structure lies near the western wallof the ionization cone and coincides with the inner radio jet (PA 11 °). The large distance from the core suggests that the K'-bandemission of the northern extended component is scattered light from thewestern cavity region and the radio jet region.Based on observations made with the 6 m BTA telescope, which is operatedby the Special Astrophysical Observatory (SAO), Russia.
| 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
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
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Pozíciós és asztrometriai adatok
| Csillagkép: | Kos |
| Rektaszcenzió: | 02h44m45.06s |
| Deklináció: | +24°11'03.7" |
| Vizuális fényesség: | 8.214 |
| Távolság: | 230.947 parszek |
| RA sajátmozgás: | 51.9 |
| Dec sajátmozgás: | -42.3 |
| B-T magnitude: | 8.685 |
| V-T magnitude: | 8.253 |
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