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NGC 1921



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Ages and Metallicities of Extragalactic Globular Clusters from Spectral and Photometric Fits of Stellar Population Synthesis Models
Spectra of galaxies contain an enormous amount of information about therelative mixture of ages and metallicities of constituent stars. Wepresent a comprehensive study designed to extract the maximuminformation from spectra of data quality typical in large galaxysurveys. These techniques are not intended for detailed stellarpopulation studies that use high-quality spectra. We test techniques ona sample of globular clusters, which should consist of single stellarpopulations and provide good test cases, using the Bruzual-Charlothigh-resolution stellar population synthesis models to simultaneouslyestimate the ages and metallicities of 101 globular clusters in M31 andthe Magellanic Clouds. The clusters cover a wide range of ages andmetallicities, 4 Myr

Integrated UBV Photometry of 624 Star Clusters and Associations in the Large Magellanic Cloud
We present a catalog of integrated UBV photometry of 504 star clustersand 120 stellar associations in the LMC, part of them still embedded inemitting gas. We study age groups in terms of equivalent SWB typesderived from the (U-B) X (B-V) diagram. The size of the spatialdistributions increases steadily with age (SWB types), whereas adifference of axial ratio exists between the groups younger than 30 Myrand those older, which implies a nearly face-on orientation for theformer and a tilt of ~45^deg^ for the latter groups. Asymmetries arepresent in the spatial distributions, which, together with thenoncoincidence of the centroids for different age groups, suggest thatthe LMC disk was severely perturbed in the past.

Long-period variables in the Large Magellanic Cloud. I - Search and discovery
A search for long-period variables has been made in the bar and southernregions of the LMC using a series of I band UKST plates, resulting inthe discovery of 471 Mira variables and 572 SRa variables. By usingmainly automated methods of determining periods and amplitudes ofvariability, corrections for incompleteness have been estimated. TheMiras show a trend toward larger amplitudes and brighter luminositieswith period, both of which should contribute to increase mass-lossrates. The period distribution falls abruptly longward of about 420 daysand shortward of about 140 days, whereas the corresponding limits in thesolar neighborhood are about 450 and about 220 days, suggestingdifferent histories of star formation in the LMC and the Galaxy. Inparticular, there appear to be relatively more old stars in the LMC.

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Observation and Astrometry data

Right ascension:05h19m20.00s
Apparent magnitude:99.9

Catalogs and designations:
Proper Names   (Edit)
NGC 2000.0NGC 1921

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