Spiral structure of the third galactic quadrant and the solution to the Canis Major debate
With the discovery of the Sagittarius dwarf spheroidal, a galaxy caughtin the process of merging with the Milky Way, the hunt for other suchaccretion events has become a very active field of astrophysicalresearch. The identification of a stellar ring-like structure inMonoceros, spanning more than 100°, and the detection of anoverdensity of stars in the direction of the constellation of CanisMajor (CMa), apparently associated to the ring, has led to thewidespread belief that a second galaxy being cannibalized by the MilkyWay had been found. In this scenario, the overdensity would be theremaining core of the disrupted galaxy and the ring would be the tidaldebris left behind. However, unlike the Sagittarius dwarf, which is wellbelow the Galactic plane and whose orbit, and thus tidal tail, is nearlyperpendicular to the plane of the Milky Way, the putative CMa galaxy andring are nearly co-planar with the Galactic disc. This severelycomplicates the interpretation of observations. In this Letter, we showthat our new description of the Milky Way leads to a completelydifferent picture. We argue that the Norma-Cygnus spiral arm defines adistant stellar ring crossing Monoceros and the overdensity is simply aprojection effect of looking along the nearby local arm. Our perspectivesheds new light on a very poorly known region, the third Galacticquadrant, where CMa is located.
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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.
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Near infrared photometry of the young clusters NGC 1960, NGC 2453 and NGC 2384
Infrared observations of young star clusters provide vital clues to thestar formation process and evolution of stars. This brief report on mythesis gives a brief description of the observations and analysis of theyoung star clusters NGC 1960, NGC 2453 and NGC 2384 observed in the nearinfrared bands at the Mt Abu Infrared Observatory, Gurushikhar inFebruary 2000. Estimates of distance and age for these clusters for thefirst time using JHK data have been obtained. The colour-magnitudediagrams of these clusters have been extended to the fainter end as faras possible. The observed data was compared to that obtained by 2MASS. Amore detailed paper will be published elsewhere.
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Detection of a Young Stellar Population in the Background of Open Clusters in the Third Galactic Quadrant
We report the detection of a young stellar population (<=100 Myr) inthe background of nine young open clusters belonging to a homogenoussample of 30 star clusters in the third Galactic quadrant (at217deg<=l<=260deg). Deep and accurate UBVRIphotometry allows us to measure model-independent age and distance forthe clusters and the background population with high confidence. Thispopulation is exactly the same population (the blue plume) recentlydetected in three intermediate-age open clusters and suggested to be a<=1-2 Gyr old population belonging to the Canis Major (CMa)overdensity (Bellazzini et al.; Martínez-Delgado et al.).However, we find that the young population in those three clusters andin six clusters of our sample follows the pattern of the Norma-Cygnusspiral arm as defined by CO clouds remarkably well, while in the otherthree program clusters it lies in the Perseus arm. We finally provideone example (out of 21) of a cluster that does not show any backgroundpopulation, demonstrating that this population is not ubiquitous towardCMa.
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Near infrared photometry of the young clusters NGC 1960, NGC 2453 and NGC 2384
The present paper gives a brief description of the observations andanalysis of the young star clusters NGC 1960, NGC 2453 and NGC 2384observed in the near infrared bands at the Mt Abu Infrared Observatory,Gurushikhar in February 2000. Estimates of distance and age for theseclusters for the first time using JHK data have been obtained. Thecolour-magnitude diagrams of these clusters have been extended to thefainter end as far as possible. The observed data was found to agreereasonably well with that obtained by 2MASS. A more detailed paper willbe published elsewhere.
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Proper Motions of Open Star Clusters and the Rotation Rate of the Galaxy
The mean proper motions of 167 Galactic open clusters withradial-velocity measurements are computed from the data of the Tycho-2catalog using kinematic and photometric cluster membership criteria. Theresulting catalog is compared to the results of other studies. The newproper motions are used to infer the Galactic rotation rate at the solarcircle, which is found to be ω0=+24.6±0.8 km s-1 kpc-1.Analysis of the dependence of the dispersion of ω0 estimates onheliocentric velocity showed that even the proper motions of clusterswith distances r>3 kpc contain enough useful information to be usedin kinematic studies demonstrating that the determination of propermotions is quite justified even for very distant clusters.
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Morphological analysis of open clusters' propertiesII. Relationships projected onto the galactic plane
A morphological analysis study of open clusters' properties has beenachieved for a sample of 160 UBVCCD open star clusters of approximately128,000 stars near the galactic plane. The data was obtained and reducedfrom using the same reduction procedures, which makes this catalogue thelargest homogeneous source of open clusters' parameters.
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Integrated photometric characteristics of galactic open star clusters
Integrated UBVRI photometric parameters of 140 galactic open clustershave been computed. Integrated I(V-R)0 and I(V-I)0colours as well as integrated parameters for 71 star clusters have beenobtained for the first time. These, in combination with published data,altogether 352 objects, are used to study the integrated photometriccharacteristics of the galactic open clusters. The I(MV)values range from -9.0 to -1.0 mag corresponding to a range in totalmass of the star clusters from ~ 25 to 4*E4 Msun.The integrated colours have a relatively narrow range, e.g., I(B-V){_0}varies from -0.4 to 1.2 mag. The scatter in integrated colours at agiven integrated magnitude can be understood in terms of differences infraction of red giants/supergiants in the clusters. The observedintegrated magnitudes and colours agree with the synthetic ones, exceptthe dependences of I(V-R)0 and I(V-I)0 colours forclusters younger than ~ 100 Myrs and also of the integrated magnitudesof oldest clusters. The large sample provides the most accurate agedependence of integrated magnitudes and colours determined so far. Theluminosity function of the I(MV) has a peak around -3.5 magand its slope indicates that only ~ 1% of the open clusters in thegalactic disc are brighter than I(MV)=-11 mag. No variationhas been found of integrated magnitude with galactocentric distance andmetallicity.
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Near IR study of the young cluster NGC 2453
In an attempt to understand early phases of stellar evolution and starformation, we have taken up the study of extremely young star clustersin the near infrared wavebands. These clusters are deeply embeddedinside the molecular gas and dust but radiate substantially in theinfrared. We have observed one such cluster NGC 2453 from Mt AbuInfrared Observatory (MIRO) operated by the Physical ResearchLaboratory, using the NICMOS-3 infrared array mounted on the 1.2 mCassegrain focus telescope. The observations were made in the J, H andK? wavebands in February 2000. The data reduction and the photometry hasbeen performed using IRAF. Preliminary results are presented.
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Morphological analysis of open clusters' propertiesI. Properties' estimations
A sample of 160 UBVCCD observations of open star clusters near thegalactic plane has been studied, and a catalogue of their propertiesobtained. The main photometrical properties have been re-estimated selfconsistently and the results have been compared with those of Lynga[Lynga, G., 1987. Catalog of Open Cluster Data, 5th Edition, StellarData Centers, Observatoire de Strasbourg, France].
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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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Absolute proper motions of 181 young open clusters.
Not Available
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A deep BVI photometric study of the open cluster NGC 2453.
CCD observations of the open cluster NGC 2453 have been carried out inB, V and I passbands. A total of 356 stars have been observed in a fieldof about 4'x6' of the sky centred on the cluster. Colour-magnitudediagrams in V, B-V and V, V-I have been generated down to V=20 and forthe first time, the unevolved part of the cluster main sequence has beenobserved. The mean true distance modulus derived from these diagrams is13.mag 85+/-0.2 yielding a distance of 5.9+/-0.2kpc. A mean age of 25Myrhas been derived for the cluster by fitting isochrones. The distance ofapproximately 6kpc puts the cluster much beyond the planetary nebula NGC2452 whose largest estimated distance to date is about 3.5kpc. The twoare not physically associated.
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Astronomy with Vainu Bappu Telescope.
Not Available
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Catalogue of blue stragglers in open clusters.
An extensive survey of blue straggler candidates in galactic openclusters of both hemispheres is presented. The blue stragglers wereselected considering their positions in the cluster colour-magnitudediagrams.They were categorized according to the accuracy of thephotometric measurements and membership probabilities. An amount of 959blue straggler candidates in 390 open clusters of all ages wereidentified and classified. A set of basic data is given for everycluster and blue straggler. The information is arranged in the form of acatalogue. Blue stragglers are found in clusters of all ages. Thepercentage of clusters with blue stragglers generally grows with age andrichness of the clusters. The mean ratio of the number of bluestragglers to the number of cluster main sequence stars is approximatelyconstant up to a cluster age of about 10^8.6^ yr and rises for olderclusters. In general, the blue stragglers show a remarkable degree ofcentral concentration.
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Photometric Variable Stars Found in Five Southern Open Clusters
Not Available
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A cluster analysis of open clusters
The Galactic distribution of 361 open clusters is studied using acluster analysis method. It is shown that more than half of the clustersenter groups with characteristic dimensions of several hundred parsecs.To distinguish physical clusters from random condensations, criteriabased on age similarity, the color of the main-sequence blue end, andthe integrated color and radial velocity of the clusters are used. Theproximity of these values suggests a physical unity and common origin ofclusters in a group.
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A cluster analysis of young open clusters
Cluster analysis methods are used to consider the galactic distributionof 224 open clusters with an age up to 10 to the 8th yrs. Most of theseclusters enter condensations with characteristic dimensions of a fewhundred parsecs. Some condensations are so similar in terms of the age,integrated color, and radial velocity of their components, that thiscannot be considered a coincidence. This suggests that each condensationis a physical entity consisting of clusters apparently linked by acommon origin.
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Catalogue of UBV Photometry and MK Spectral Types in Open Clusters (Third Edition)
Not Available
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Distances to planetary nebulae. I - The reddening-distance method
Distances to 12 planetary nebulae are derived from the increase ofinterstellar reddening with distance along the lines of sight of thenebulae. The reddening-distance relations are determined using WalravenVBLUW photometry of stars in small fields around the planetary nebulae.With a theoretical calibration of the VBLUW colors the effectivetemperature, surface gravity and reddening are determined for early typestars. Distances are then determined by means of a luminositycalibration which is based on the stellar evolution models of Hejlesen(1980). The reddenings of the planetary nebulae are determined using anumber of different methods. The amount of internal reddening isestimated. The planetary nebula distances derived from thereddening-distance relations have accuracies of 10 to 40 percent. Thisis a substantial improvement compared to accuracies of previouslydetermined distances. As a byproduct, the distance to the young opencluster NGC 2453 is determined.
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IDAM - A catalogue of DM, HD(E) and other cross-identifications for stars in open clusters (magnetic tape)
This catalogue presents cross-identifications between usual numberingsystems for stars in open clusters and several astronomical catalogues:BS, HD-HDE, DM, NLS, LLS, GCVS, IDS, ADS, SAO and miscellaneous lists orcatalogues. It concerns 345 open clusters, for a total of 9543 entries.Inverse tables are given for each catalogue. The present cataloguecompletely supersedes the 1976 version.
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Integrated Photometric Parameters of Open and Globular Clusters
Not Available
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Distances to Planetary Nebulae
Not Available
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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.
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Analysis of UBV Data in Open Clusters
Not Available
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A catalogue of galactic clusters observed in three colours
This catalogue contains photometric data for 190 galactic clusters, allobserved in UBV or RGU. The distances of the young clusters (with spless than b3) have been calculated or recalculated according to method Aof Becker (1963). The galactic distribution of these clusters confirmstheir role of being good spiral tracers.
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NGC 2453, a moderately young open cluster in Puppis
Abstract image available at:http://adsabs.harvard.edu/abs/1974A&AS...18...19M
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Haffner 20 and 21, Two Moderately Old Open Clusters in Puppis
Abstract image available at:http://adsabs.harvard.edu/abs/1974PASP...86..480F
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Photoelectric observations of stars in the Southern open clusters. NGC 2335, 2343, 2453, 4439 and H5.
Not Available
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