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|A low-absorption disk zone at low Galactic latitude in Centaurus|
We investigate the properties of two stellar concentrations in alow-absorption disk zone in Centaurus, located respectively atℓ=306.47°, b=-0.61°, and ℓ=307.01°, b=-0.74°.The present analysis is based mostly on 2MASS photometry, as well asoptical photometry. Based on colour-magnitude diagrams and stellarradial density profiles, we show that these concentrations are not openstar clusters. Instead, they appear to be field stars seen through adifferentially-reddened window. We estimate that the bulk of the starsin both stellar concentrations is located at ~1.5 kpc from the Sun, adistance consistent with that of the Sgr-Car arm in that direction. Thislow-absorption window allows one to probe into distant parts of the diskbesides the Sgr-Car arm, probably the tangent part of the Sct-Cru arm,and/or the far side of the Sgr-Car arm in that direction. The mainsequence associated to the Sgr-Car arm is reddened by E(B-V)0.5, sothat this window through the disk is comparable in reddening to Baade'swindow to the bulge. We also investigate the nature of the open clustercandidate Ru 166. The presently available data do not allow us toconclude whether Ru 166 is an actual open cluster or field stars seenthrough a small-scale low-absorption window.
|On the nature of five open cluster candidates projected close to the Galactic centre|
We present CCD BVI observations obtained for 1759 stars in 4arcminx4arcmin regions around the unstudied southern stellar aggregatesRuprecht 103, 124, 129, 146 and 166, which are described as openclusters in several catalogues. Our analysis shows that none of thesestellar groups are genuine open clusters since no clear main sequencesor other meaningful features can be seen in their colour-magnitudediagrams. Star counts carried out within and outside the clustercandidate fields not only support these results but also show that thestudied objects do not appear to be candidate late stages of starcluster dynamical evolution. Based on observations made at theUniversity of Toronto (David Dunlap Observatory) 24-inch telescope, LasCampanas, Chile. Tables 2 to 6 are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/379/453
|Open clusters and galactic structure|
A total of 610 references to 434 clusters are employed in thecompilation of a catalog of open clusters with color-magnitude diagramson the UBV or RGU systems. Estimates of reddening, distance modulus, ageand number of cluster members are included. Although the sample isconsidered representative of the discoverable clusters in the galaxy,the observed distribution is nonuniform because of interstellarobscuration. Cluster distribution in the galactic plane is found to bedominated by the locations of dust clouds rather than by spiralstructure. The distributions of clusters as a function of age andrichness class show that the lifetimes of poor clusters are much shorterthan rich ones, and that clusters in the outer disk survive longer thanthose in the inner disk. An outer disk age which is only about 50% theage of the globular clusters is indicated by cluster statistics. Thethickening of the galactic disk with increasing galactocentric distancemay be due to either a younger dynamical age or a lower gravitationalpotential in the outer regions.
|Southern open stars clusters. III. UBV-Hbeta photometry of 28 clusters between galactic longitudes 297d and 353d|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS...10..135M&db_key=AST
|Classification of open star clusters|
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