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|Herbig Ae/Be Stars in the Magellanic Bridge|
We have found Herbig Ae/Be star candidates in the western region of theMagellanic Bridge. Using the near-infrared camera SIRIUS and the 1.4 mtelescope IRSF, we surveyed ~3.0deg×1.3deg(24deg<~α<~36deg,-75.0deg<~δ<~-73.7deg) in the J, H,and Ks bands. On the basis of colors and magnitudes, about200 Herbig Ae/Be star candidates are selected. Considering thecontaminations by miscellaneous sources, such as foreground stars andearly-type dwarfs in the Magellanic Bridge, we estimate that about 80(~40%) of the candidates are likely to be Herbig Ae/Be stars. We alsofound one concentration of the candidates at the young star cluster NGC796, strongly suggesting the existence of pre-main-sequence (PMS) starsin the Magellanic Bridge. This is the first detection of PMS starcandidates in the Magellanic Bridge, and if they are genuine PMS stars,this could be direct evidence of recent star formation. However, theestimate of the number of Herbig Ae/Be stars depends on the fraction ofclassical Be stars, and thus a more precise determination of the Be starfraction or observations to differentiate between the Herbig Ae/Be starsand classical Be stars are required.
|Dating star clusters in the Small Magellanic Cloud by means of integrated spectra|
In this study flux-calibrated integrated spectra in the range(3600-6800) Å are presented for 16 concentrated star clusters inthe Small Magellanic Cloud (SMC), approximately half of which constituteunstudied objects. We have estimated ages and foreground interstellarreddening values from the comparison of the line strengths and continuumdistribution of the cluster spectra with those of template clusterspectra with known parameters. Most of the sample clusters are youngblue clusters (6-50 Myr), while L 28, NGC 643 and L 114 are found to beintermediate-age clusters (1-6 Gyr). One well known SMC cluster (NGC416) was observed for comparison purposes. The sample includes clustersin the surroundings and main body of the SMC, and the derived foregroundreddening values are in the range 0.00 <= E(B-V) <= 0.15. Thepresent data also make up a cluster spectral library at SMC metallicity.Based on observations made at Complejo Astronómico El Leoncito,which is operated under agreement between the Consejo Nacional deInvestigaciones Científicas y Técnicas de laRepública Argentina and the National Universities of La Plata,Córdoba and San Juan, Argentina.
|A Revised and Extended Catalog of Magellanic System Clusters, Associations, and Emission Nebulae. I. Small Magellanic Cloud and Bridge|
A survey of extended objects in the Magellanic System was carried out onthe ESO/SERC R and J Sky Survey Atlases. The present work is dedicatedto the Small Magellanic Cloud and to the inter-Magellanic Cloud region("Bridge") totaling 1188 objects, of which 554 are classified as starclusters, 343 are emissionless associations, and 291 are related toemission nebulae. The survey includes cross-identifications amongcatalogs, and we present 284 new objects. We provide accurate positions,classification, homogeneous sizes, and position angles, as well asinformation on cluster pairs and hierarchical relation for superimposedobjects. Two clumps of extended objects in the Bridge and one at theSmall Magellanic Cloud wing tip might be currently forming dwarfspheroidal galaxies.
|Blue-violet spectral evolution of young Magellanic Cloud clusters|
We study the integrated spectral evolution in the blue-violet range of97 blue star clusters in the Magellanic Clouds, from those associatedwith gas emission to those as old as a few hundred Myr. Some clustersare dominated by the flux of those massive stars that pass throughevolutionary stages such as Wolf-Rayet, Luminous Blue Variable, Be, andsupergiant stars of different temperatures. The relationships amongspectral features such as absorption and emission lines, Balmerdiscontinuity and Balmer continuum are used to study the spectralevolution of the clusters. Finally, we sort into groups spectra ofsimilar evolutionary stages, creating a template spectral library withpossible applications in stellar populations syntheses of star-forminggalaxies and in the spectral simulation of bursts of star formation withdifferent mean ages and durations.
|Accurate positions for SMC clusters|
Positions of 203 SMC clusters accurate to + or - 5 arcsec are reported.The astrometry method used is briefly described. Plans for futureMagellanic Cloud cluster astrometry are summarized.
|Observed radii and structural parameters of star clusters in the SMC. III|
The tidal radii, concentration parameters, and masses of 24 starclusters in the SMC have been derived by means of star counts. In thisinvestigation the seven most distant clusters (with projected distancesfrom the rotation center similar to the halo radius) are included aswell, and their masses are found to be about one hundred times lowerthan those of the halo clusters of the Galaxy.
|Age calibration and age distribution for rich star clusters in the Large Magellanic Cloud|
An empirical relation is presented for estimating the ages of rich starclusters in the Large Magellanic Cloud (LMC), to within a factor ofabout 2, from their integrated UBV colors. The calibration is based onpublished ages for 58 LMC clusters derived from main-sequencephotometry, integrated spectra, or the extent of the asymptotic giantbranches. Using stellar population models, a sample of LMC clusters moremassive than about 10,000 solar masses is isolated, which is correctedfor incompleteness as a function of magnitude. An unbiased agedistribution for three clusters is then determined. The number ofclusters decreases with increasing age in a manner that is qualitativelysimilar to the age distribution for the open clusters in our Galaxy. TheLMC age distribution is, however, flatter, and the median age of theclusters is greater. If the formation rate has been approximatelyconstant over the history of the two galaxies, then the age distributionobtained here implies that clusters are disrupted more slowly in theLMC. The results contain no evidence for bursts in the formation ofclusters, although fluctuations on small time scales and slow variationsover the lifetime of the LMC cannot be ruled out.
|Integrated magnitudes and colors of clusters in the magellanic clouds and Fornax system|
Data from PV, six-color, and four-color photometric observations ofclusters (38 in the Small Magellanic Cloud, 16 in the Large MagellanicCloud, four in the Fornax system, and NGC 1841) are reported. Theobservations were made in 1951, 1960-1961, 1959-1966, and 1974-1975using various telescopes and photometer setups at Mount StromloObservatory in Australia. Tables of integrated magnitudes and colors(both as originally observed and as reduced to the BV system) arepresented, and comparable published data are shown. The combined V dataare fitted to the theoretical luminosity profiles of King (1966) toestimate the total magnitudes and surface brightness distributions of 33of the clusters. Several sample profile fits are shown. A color-colorplot (V-B vs. G-R) is discussed in terms of identification of clustertypes by color: it is found that globular clusters can be separated fromother types, if all have the same amount of reddening.
|On the structure of the wing of the Small Magellanic Cloud.|
Abstract image available at:http://adsabs.harvard.edu/abs/1971A&A....10....1W
|The cluster system of the Small Magellanic Cloud|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958MNRAS.118..172L&db_key=AST
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