uvby-Hβ CCD photometry of NGC 1817 and NGC 1807
We have investigated the area of two NGC entries, NGC 1817 and NGC 1807,with deep CCD photometry in the uvby-Hβintermediate-band system. The photometric analysis of a selected sampleof stars of the open cluster NGC 1817 yields a reddening value of E(b-y)= 0.19±0.05, a distance modulus of V0-MV =10.9±0.6, a metallicity of [Fe/H] = -0.34±0.26 and an ageof log t = 9.05±0.05. Our measurements allow us to confirm thatNGC 1807 is not a physical cluster.Figure \ref{map} and Tables \ref{log} and \ref{chips} are only availablein electronic form at http://www.edpsciences.orgTables 4 and 5 are 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/426/827
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New membership determination and proper motions of NGC 1817. Parametric and non-parametric approach
We have calculated proper motions and re-evaluated the membershipprobabilities of 810 stars in the area of two NGC objects, NGC 1817 andNGC 1807. We have obtained absolute proper motions from 25 plates in thereference system of the Tycho-2 Catalogue. The plates have a maximumepoch difference of 81 years; and they were taken with the doubleastrograph at Zo-Sèstation of Shanghai Observatory, which has anaperture of 40 cm and a plate scale of 30 arcsec mm-1. Theaverage proper motion precision is 1.55 mas yr-1. Theseproper motions are used to determine the membership probabilities ofstars in the region, based on there being only one very extendedphysical cluster: NGC 1817. With that aim, we have applied and comparedparametric and non-parametric approaches to cluster/field segregation.We have obtained a list of 169 probable member stars.Table 5 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/426/819Tables 1, 2 and 4 and Fig. 1 are only available in electronic form athttp://www.edpsciences.org
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M2000: An astrometric catalog in the Bordeaux Carte du Ciel zone +11degr <= delta <= +18degr
During four years, systematic observations have been conducted in driftscan mode with the Bordeaux automated meridian circle in the declinationband +11degr <= delta <= +18degr . The resulting astrometriccatalog includes about 2.3x 106 stars down to the magnitudelimit VM=16.3. Nearly all stars (96%) have been observed atleast 6 times, the catalog being complete down to VM=15.4.The median internal standard error in position is ~ 35 mas in themagnitude range 11 < VM <15, which degrades to ~ 50 maswhen the faintest stars are considered. M2000 also provides one bandphotometry with a median internal standard error of ~ 0.04 mag.Comparisons with the Hipparcos and bright part of Tycho-2 catalogs haveenabled us to estimate external errors in position to be lower than 40mas. In this zone and at epoch 1998, the faint part of Tycho-2 is foundto have an accuracy of 116 mas in alpha instead of 82 mas deduced fromthe model-based standard errors given in the catalog. The catalog isdistributed on CD-ROM and through the CDS(http://cdsweb.u-strasbg.fr/Cats.html). Further information is given onthe website http://www.observ.u-bordeaux.fr/~soubiran/m2000.htm
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Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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Determination of proper motions and membership of the open clusters NGC 1817 and NGC 1807
Relative proper motions, their corresponding observed errors andmembership probabilities of 722 stars in the old open cluster NGC 1817region are determined from PDS measurements of 12 plate pairs. Theplates have the maximum epoch difference of 81 years and were taken withthe double astrograph at Zǒ-Sè station of ShanghaiObservatory, which has an aperture of 40 cm, a focal length of 6.9 m anda plate scale of 30''/mm. The average proper motion accuracy is 1.6mas/yr. These proper motions are used to determine the membershipprobabilities of stars in the region. The existence of two clusters inthe region (NGC 1817, NGC 1807) is discussed. The number of stars withmembership probability higher than 0.7 is 416 for NGC 1817 and 14 forNGC 1807. Table 5 is only available in electronic form from CDS viaanonymous ftp 130.79.128.5, and by e-mail request tolbalague@pchpc3.am.ub.es
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Chemical Evolution of the Galactic Disk: Evidence for a Gradient Perpendicular to the Galactic Plane
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.2813P&db_key=AST
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Investigation of the anisotropy in the orientations of galaxies of the Uppsala and ESO/Uppsala catalogs
The anisotropy in the orientations of the galaxies of the Uppsala(Northern Hemisphere) and ESO/Uppsala (Southern Hemisphere) catalogs isinvestigated. It is shown that the galaxies of both catalogs exhibit anidentical, statistically significant and clearly expressed anisotropy inthe orientations of the apparent major axes. The effect isdifferentiated with respect to the magnitudes, angular diameters, andmorphological types. Arguments for its being real are advanced. In thespatial respect, a model in which the normals of the galaxies arecoplanar with one and the same plane in space but are oriented randomlyin the other directions is preferred. The effect relates either to theouter regions of the Local Supercluster or has an even larger scale.
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The radial distribution of surface brightness in galactic disks
Surface photometry of 51 galaxies based on a number of deeply exposedIIIa-J Schmidt plates, is reported. A sample of spiral galaxies that iscomplete to a diameter of 2 arcmin at the apparent isophote of 26.5J-mag per square arcsecond has a narrow distribution of central surfacebrightness with mu0 = 21.8 plus or minus 0.6 J-mag per squarearcsecond (mean and standard deviation). This is not produced by sampleselection effects. The bivariate distribution function of mu0and scalelength h shows that the mean value of mu0 changesfrom about 21.5 at h approximately equal to 5 kpc to about 22-22.5 at anh of about 1 kpc. The small spread in mu0 in the universe isprobably a result of a constant ratio of visible to dark matter in allgalaxies, if galaxies collapse with detailed conservation of angularmomentum from uniformly rotating, uniform spheres that derive theirangular momentum from tidal torques in a universe with hierarchicalclustering. This model also explains the approximate exponential natureand the cutoffs in stellar disks at about 4.5 scalelengths.
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Catalogue of UBV Photometry and MK Spectral Types in Open Clusters (Third Edition)
Not Available
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Analysis of groups of galaxies with accurate redshifts
Arecibo radio telescope redshift measurements have been obtained forover 100 galaxies in more than 40 different groups which generallyconsist of a large spiral galaxy with one or more companions. This setof data is supplemented with over 160 galaxies in more than 40 groupswhose dominant galaxy is brighter than 11.8 mag. An analysis of theentire sample indicates that typical structure in extragalactic space isone in which a large central galaxy has smaller and fainter companionsextending from about 20-900 kpc around. The companion galaxies in thesegroups have significantly higher redshifts than the brightest galaxy inthe group, confirming previous studies in whose results the companiongalaxies are systematically redshifted with respect to the dominantgalaxy.
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La constel lacio de Tauro.
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Dreifarbenphotometrie in offenen Sternhaufen sowie in zwei Sternfeldern im Cyg.
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Dreifarbenphotometrie der offenen Sternhaufen NGC 1502, 1807 und 1817. Mit 9 Textabbildungen
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