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|Proper motion determination of open clusters based on the UCAC2 catalogue|
We present the kinematics of hundreds of open clusters, based on theUCAC2 Catalogue positions and proper motions. Membership probabilitieswere obtained for the stars in the cluster fields by applying astatistical method uses stellar proper motions. All open clusters withknown distance were investigated, and for 75 clusters this is the firstdetermination of the mean proper motion. The results, including the DSSimages of the cluster's fields with the kinematic members marked, areincorporated in the Open Clusters Catalogue supported on line by ourgroup.
|CCD photometry of distant open clusters NGC 2425, Haffner 10 and Czernik 29|
We present BVI photometry for the poorly known southern hemisphere openclusters NGC 2425, Haffner 10 and Czernik 29. We have calculated thedensity profile and established the number of stars in each cluster. Thecolour-magnitude diagrams of the objects show a well-defined mainsequence. However, the red giant clump is present only in NGC 2425 andHaffner 10. For these two clusters we estimated the age as 2.5 +/- 0.5Gyr, assuming a metallicity of Z= 0.008. The apparent distance moduliare in the ranges 13.2 < (m-M)V < 13.6 and 14.3 <(m-M)V < 14.7, while the heliocentric distances areestimated to be 2.9 < d < 3.8 kpc and 3.1 < d < 4.3 kpc forNGC 2425 and Haffner 10, respectively. The angular separation of2.4° (150 pc at mean distance) may indicate a common origin of thetwo clusters.
|Open clusters in the Third Galactic Quadrant. II. The intermediate age open clusters NGC 2425 and NGC 2635|
We analyse CCD broad band (UBV(RI)_C) photometric data obtained in thefields of the poorly studied open clusters NGC 2425and NGC 2635. Both clusters are found to be ofintermediate age thus increasing the population of open clusters knownto be of the age of, or older than, the Hyades. More explicitly, we findthat NGC 2425 is a 2.2 Gyr old cluster, probably ofsolar metallicity, located at 3.5 kpc from the Sun. NGC2635 is a Hyades age (600 Myr) cluster located at a distanceof 4.0 kpc from the Sun. Its Colour Magnitude Diagram reveals that it isextremely metal poor for its age and position, thus making it a veryinteresting object in the context of Galactic Disk chemical evolutionmodels.
|Morphology of Galactic Open Clusters|
We analyzed the shapes of Galactic open clusters by the star-countingtechnique with the Two Micron All Sky Survey star catalog database.Morphological parameters such as the ellipticity and size have beenderived via stellar density distribution, weighed by clusteringprobability. We find that most star clusters are elongated, even for theyoungest star clusters of a few million years old, which are locatednear the Galactic disk. The shapes of young star clusters must reflectthe conditions in the parental molecular clouds and during the clusterformation process. As an open cluster ages, stellar dynamics cause theinner part of the cluster to circularize, but the overall radius getslarger and the stellar density becomes sparser. We discuss how theinternal relaxation process competes with Galactic external perturbationduring cluster evolution.
|Open clusters in the third galactic quadrant. I. Photometry|
We have performed a photometric survey of open clusters in the thirdGalactic quadrant in order to study the star formation history andspatial structure in the Canis Major-Puppis-Vela region. In this paperwe describe a catalogue of CCD U BV RI photometry of approximately 65000 stars in the fields of 30 open clusters. The data were obtained andreduced using the same telescope, the same reduction procedures, and thesame standard photometric system, which makes this catalogue the largesthomogeneous source of open cluster photometry so far. In subsequentpapers of this series, colour-colour and colour-magnitude diagrams willbe presented which, amongst other uses, will allow the determination ofan homogeneous set of cluster reddenings, distances, and ages that willconstitute the observational basis for our studies of the spatialstructure and star formation history in the third Galactic quadrant.
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