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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
| Very Large Telescope three micron spectra of dust-enshrouded red giants in the Large Magellanic Cloud
We present ESO/VLT spectra in the 2.9-4.1 μm range for a large sampleof infrared stars in the Large Magellanic Cloud (LMC), selected on thebasis of MSX and 2MASS colours to be extremely dust-enshrouded AGB starcandidates. Out of 30 targets, 28 are positively identified as carbonstars, significantly adding to the known population of opticallyinvisible carbon stars in the LMC. We also present spectra for sixIR-bright stars in or near three clusters in the LMC, identifying fourof them as carbon stars and two as oxygen-rich supergiants. We analysethe molecular bands of C2H2 at 3.1 and 3.8 μm, HCN at 3.57 μm, andsharp absorption features in the 3.70-3.78 μm region that weattribute to C2H2. There is evidence for a generally high abundance ofC2H2 in LMC carbon stars, suggestive of high carbon-to-oxygen abundanceratios at the low metallicity in the LMC. The low initial metallicity isalso likely to have resulted in less abundant HCN and CS. The sample ofIR carbon stars exhibits a range in C2H2:HCN abundance ratio. We do notfind strong correlations between the properties of the molecularatmosphere and circumstellar dust envelope, but the observed differencesin the strengths and shapes of the absorption bands can be explained bydifferences in excitation temperature. High mass-loss rates and strongpulsation would then be seen to be associated with a large scale heightof the molecular atmosphere.
| Dust-enshrouded giants in clusters in the Magellanic Clouds
We present the results of an investigation of post-Main Sequence massloss from stars in clusters in the Magellanic Clouds, based around animaging survey in the L'-band (3.8 μm) performed with the VLT at ESO.The data are complemented with JHKs (ESO and 2MASS) andmid-IR photometry (TIMMI2 at ESO, ISOCAM on-board ISO, and data fromIRAS and MSX). The goal is to determine the influence of initialmetallicity and initial mass on the mass loss and evolution during thelatest stages of stellar evolution. Dust-enshrouded giants areidentified by their reddened near-IR colours and thermal-IR dust excessemission. Most of these objects are Asymptotic Giant Branch (AGB) carbonstars in intermediate-age clusters, with progenitor masses between 1.3and ~5 M_ȯ. Red supergiants with circumstellar dust envelopes arefound in young clusters, and have progenitor masses between 13 and 20M_ȯ. Post-AGB objects (e.g., Planetary Nebulae) and massive starswith detached envelopes and/or hot central stars are found in severalclusters. We model the spectral energy distributions of the cluster IRobjects, in order to estimate their bolometric luminosities andmass-loss rates. The IR objects are the most luminous cluster objects,and have luminosities as expected for their initial mass andmetallicity. They experience mass-loss rates in the range from a few10-6 up to 10-4 M_ȯ yr-1 (ormore), with most of the spread being due to evolutionary effects andonly a weak dependence on progenitor mass and/or initial metallicity.About half of the mass lost by 1.3-3 M_ȯ stars is shed during thesuperwind phase, which lasts of order 105 yr. Objects withdetached shells are found to have experienced the highest mass-lossrates, and are therefore interpreted as post-superwind objects. We alsopropose a simple method to measure the cluster mass from L'-band images.
| Infrared Surface Brightness Fluctuations of Magellanic Star Clusters
We present surface brightness fluctuations (SBFs) in the near-IR for 191Magellanic star clusters available in the Second Incremental and All SkyData releases of the Two Micron All Sky Survey (2MASS) and compare themwith SBFs of Fornax Cluster galaxies and with predictions from stellarpopulation models as well. We also construct color-magnitude diagrams(CMDs) for these clusters using the 2MASS Point Source Catalog (PSC).Our goals are twofold. The first is to provide an empirical calibrationof near-IR SBFs, given that existing stellar population synthesis modelsare particularly discrepant in the near-IR. Second, whereas mostprevious SBF studies have focused on old, metal-rich populations, thisis the first application to a system with such a wide range of ages(~106 to more than 1010 yr, i.e., 4 orders ofmagnitude), at the same time that the clusters have a very narrow rangeof metallicities (Z~0.0006-0.01, i.e., 1 order of magnitude only). Sincestellar population synthesis models predict a more complex sensitivityof SBFs to metallicity and age in the near-IR than in the optical, thisanalysis offers a unique way of disentangling the effects of age andmetallicity. We find a satisfactory agreement between models and data.We also confirm that near-IR fluctuations and fluctuation colors aremostly driven by age in the Magellanic cluster populations and that inthis respect they constitute a sequence in which the Fornax Clustergalaxies fit adequately. Fluctuations are powered by red supergiantswith high-mass precursors in young populations and by intermediate-massstars populating the asymptotic giant branch in intermediate-agepopulations. For old populations, the trend with age of both fluctuationmagnitudes and colors can be explained straightforwardly by evolution inthe structure and morphology of the red giant branch. Moreover,fluctuation colors display a tendency to redden with age that can befitted by a straight line. For the star clusters only,(H-Ks)=(0.21+/-0.03)log(age)-(1.29+/-0.22) once galaxies areincluded, (H-Ks)=(0.20+/-0.02)log(age)-(1.25+/-0.16).Finally, we use for the first time a Poissonian approach to establishthe error bars of fluctuation measurements, instead of the customaryMonte Carlo simulations.This research has made use of the NASA/ IPAC Infrared Science Archive,which is operated by the Jet Propulsion Laboratory, California Instituteof Technology, under contract with the National Aeronautics and SpaceAdministration.
| A Search for HAeBe stars in the bar of the Large Magellanic Cloud based on optical variability
We searched the EROS1 database consisting of 80 000 stars in the bar ofthe Large Magellanic Cloud for blue objects with irregular photometricbehavior similar to Galactic Herbig Ae/Be (HAeBe) stars. We found 14 newobjects in addition to the discovery of 7 HAeBe candidate stars found inour previous studies. Based on their light curve and colours we classifythese new objects also as EROS LMC HAeBe Candidates (ELHCs). The objectsare located in an area of enhanced 60 mu m emission, which indicates astar forming region. The stars are concentrated in three areas and themajority of the objects are clustered round the N 120 nebular complex.The light curves are interpreted with a simple model, involvingobscuration by an inhomogeneous orbiting circumstellar dust cloud as thedominant cause of the variability. We find that the dust orbiting thestars is at a radial distance in the order of 10 to a few 100 AUs. Mostof the objects are ``bluer-when-fainter''. This is attributed to thepresence of a (blue) scattering nebula with a size smaller than thepoint spread function of the photometric images. The stellar parametersare derived from the photometry. The luminosity of the stars is in therange of 3.4 < log (L/Lsolar) < 4.2 and the coloursindicate spectral types O or B. The stars are located in the HR-diagramabove the birthline for Galactic stars by about 1 dex in luminosity. Themethod used to detect the ELHCs stars on optical variability criteria isdiscussed. We show that our sample of HAeBe candidates in the EROS1field of view is complete up to V =~ 16.5 mfor the typicalamplitude and time scale of the ELHCs.
| A statistical study of binary and multiple clusters in the LMC
Based on the Bica et al. (\cite{bica}) catalogue, we studied the starcluster system of the LMC and provide a new catalogue of all binary andmultiple cluster candidates found. As a selection criterion we used amaximum separation of 1farcm4 corresponding to 20 pc (assuming adistance modulus of 18.5 mag). We performed Monte Carlo simulations andproduced artificial cluster distributions that we compared with the realone in order to check how many of the found cluster pairs and groups canbe expected statistically due to chance superposition on the plane ofthe sky. We found that, depending on the cluster density, between 56%(bar region) and 12% (outer LMC) of the detected pairs can be explainedstatistically. We studied in detail the properties of the multiplecluster candidates. The binary cluster candidates seem to show atendency to form with components of similar size. When possible, westudied the age structure of the cluster groups and found that themultiple clusters are predominantly young with only a few cluster groupsolder than 300 Myr. The spatial distribution of the cluster pairs andgroups coincides with the distribution of clusters in general; however,old groups or groups with large internal age differences are mainlylocated in the densely populated bar region. Thus, they can easily beexplained as chance superpositions. Our findings show that a formationscenario through tidal capture is not only unlikely due to the lowprobability of close encounters of star clusters, and thus the evenlower probability of tidal capture, but the few groups with largeinternal age differences can easily be explained with projectioneffects. We favour a formation scenario as suggested by Fujimoto &Kumai (\cite{fk}) in which the components of a binary cluster formedtogether and thus should be coeval or have small age differencescompatible with cluster formation time scales. Table 6 is only availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/391/547
| The Optical Gravitational Lensing Experiment. Cepheids in Star Clusters from the Magellanic Clouds
We present Cepheids located in the close neighborhood of star clustersfrom the Magellanic Clouds. 204 and 132 such stars were found in the LMCand SMC, respectively. The lists of objects were constructed based oncatalogs of Cepheids and star clusters, recently published by theOGLE-II collaboration. Location of selected Cepheids on the skyindicates that many of them are very likely cluster members. Photometricdata of Cepheids and clusters are available from the OGLE Internetarchive.
| The Optical Gravitational Lensing Experiment. Catalog of Star Clusters from the Large Magellanic Cloud
We present the catalog of star clusters found in the area of about 5.8square degree in the central regions of the Large Magellanic Cloud. Itcontains data for 745 clusters. 126 of them are new objects. For eachcluster equatorial coordinates, radius, approximate number of membersand cross-identification are provided. Photometric data for all clusterspresented in the catalog and Atlas consisting of finding charts andcolor-magnitude diagrams are available electronically from the OGLEInternet archive.
| Star Clusters in Local Group Galaxies
Not Available
| Interacting star clusters in the Large Magellanic Cloud. Overmerging problem solved by cluster group formation
We present the tidal tail distributions of a sample of candidate binaryclusters located in the bar of the Large Magellanic Cloud (LMC). Oneisolated cluster, SL 268, is presented in order to study the effect ofthe LMC tidal field. All the candidate binary clusters show tidal tails,confirming that the pairs are formed by physically linked objects. Thestellar mass in the tails covers a large range, from 1.8x 10(3) to 3x10(4) \msun. We derive a total mass estimate for SL 268 and SL 356. Atlarge radii, the projected density profiles of SL 268 and SL 356 falloff as r(-gamma ) , with gamma = 2.27 and gamma =3.44, respectively. Outof 4 pairs or multiple systems, 2 are older than the theoreticalsurvival time of binary clusters (going from a few 10(6) years to 10(8)years). A pair shows too large age difference between the components tobe consistent with classical theoretical models of binary clusterformation (Fujimoto & Kumai \cite{fujimoto97}). We refer to this asthe ``overmerging'' problem. A different scenario is proposed: theformation proceeds in large molecular complexes giving birth to groupsof clusters over a few 10(7) years. In these groups the expected clusterencounter rate is larger, and tidal capture has higher probability.Cluster pairs are not born together through the splitting of the parentcloud, but formed later by tidal capture. For 3 pairs, we tentativelyidentify the star cluster group (SCG) memberships. The SCG formation,through the recent cluster starburst triggered by the LMC-SMC encounter,in contrast with the quiescent open cluster formation in the Milky Waycan be an explanation to the paucity of binary clusters observed in ourGalaxy. Based on observations collected at the European SouthernObservatory, La Silla, Chile}
| Clusters in the west side of the bar of the Large Magellanic Cloud: interacting pairs?
In this paper, we present the VI-CCD photometry of 11 unstudied clusterslocated in the bar of the Large Magellanic Cloud (LMC), as a part of aproject aimed to infer the star formation history of this galaxy. Wederive the ages of these clusters by means of isochrone fitting. Threeclose pairs of clusters are included in the sample, namely NGC 1903-SL357, SL 349-SL 353, SL 387-SL 385. We discuss the surface photometry ofthese objects: the distortion in the isophotal contours is regarded as asign of interactions between pairs of physically connected clusters.While the systems SL 349-SL 353 and SL 387-SL 385 are likely pairs ofnearly coeval clusters, NGC 1903-SL 357 is not because of the large agedifference between the two. Several possible mechanisms for theformation of this peculiar pair are examined in the context ofinteractions between the Large and Small Magellanic Cloud (SMC).
| Cepheids in MC Clusters: New Observations
Not Available
| The ellipticities of Galactic and Large Magellanic Cloud globular clusters
The correlations between the ellipticity and the age and mass of LMCglobular clusters are examined, and both are found to be weak. It isconcluded that neither of these properties is mainly responsible for theobserved differences in the LMC and Galactic globular clusterellipticity distributions. Most importantly, age cannot be the primaryfactor in the LMC-Galaxy ellipticity differences, even if there is arelationship, as even the oldest LMC clusters are more elliptical thantheir Galactic counterparts. The strength of the tidal field of theparent galaxy is proposed as the dominant factor in determining theellipticities of that galaxy's globular clusters. A strong tidal fieldrapidly destroys velocity anisotropies in initially triaxial, rapidlyrotating elliptical globular clusters. A weak tidal field, however, isunable to remove these anisotropies and the clusters remain close totheir initial shapes.
| Star Clusters Driven to Form by Strong Collisions Between Gas Clouds in High-Velocity Random Motion
Abstract image available at:http://adsabs.harvard.edu/abs/1997AJ....113..249F
| 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.
| 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.
| Bar star clusters in the LMC - Formation history from UBV integrated photometry
The sample of star clusters in the LMC Bar region with integrated UBVphotometry was enlarged by approximately a factor four, totaling 129objects. The (B-V) histogram gap between blue and red clustersdisappears with this deeper sample. Age groups in terms of equivalentSWB types were derived and their spatial distribution studied. Clustersyounger than t about 200 Myr are not homogeneously distributed throughthe bar. In particular a strong star forming event at t about 100 Myrwas detected in the eastern part of the Bar, consisting of a compactgrouping of seven coeval clusters around NGC 2058 and NGC 2065. Also, 11close pairs and two trios are analyzed, and the colors indicate thatonly four pairs are clearly not coeval.
| The evolution of carbon stars in the Magellanic Clouds
This study presents JHK photometric data for over 100 field stars in theSMC and for 10 in the Large Cloud together with spectroscopic resultsfor about half of them. In the Small Cloud carbon stars were found athigher temperatures and lower luminosities than previously observed. Thefaintest are below the top of the red giant branch. The medium- andlow-luminosity C stars in the M-C transition zone have a low C2 content.At these luminosities, most of the J-type stars are found close to theC2-poor stars in the HR diagram. Their C2 content is about as high as inthe coolest, most evolved C stars. The present observations of carbonstars in the SMC show that they cover a range in M(bo) from -3 to 5.9mag. The transitions from M to C via S appear to occur in both Clouds ata rather well-defined range in M(bol) for SWB and classes IV and V.
| A catalogue of binary star cluster candidates in the Large Magellanic Cloud
A photographic atlas of close pairs of star clusters in the LargeMagellanic Cloud is presented here. The criterion for inclusion ofcluster pairs in the atlas was an upper limit of 18.7 pc for theprojected separation between the centers of the clusters in each pair.Accurate coordinates for the clusters, the projected separations andestimates of the diameters and positional angles are given and some ofthe global properties of the cluster-pair population of the LMC arediscussed. It is found that the individual clusters in pairspreferentially have nearly equal sizes.
| Near-infrared spectral evolution of blue LMC clusters : a comparison with galactic open clusters.
Abstract image available at:http://adsabs.harvard.edu/abs/1990RMxAA..21..202B
| Blue Magellanic clusters - Near-infrared spectral evolution
New integrated spectra in the range 5600-10,000 A are presented for 28LMC and 3 SMC young star clusters. The equivalent widths (W) ofprominent features and the continuum distribution are measured. Theanalysis, supplemented by 8 additional LMC clusters from previousstudies, indicates that the red supergiant phase is indeed verytime-peaked, occuring from 7 to 12 Myr. In addition to the previous caseof NGC 2004, it is found that NGC 1805, NGC 1994, NGC 2002, NGC 2098,and NGC 2100 (as well as NGC 2011 to a lesser extent) are undergoingthis phase. The red supergiant phase is clearly denoted by strong TiObands and Ca II triplet as well as a flat continuum or (in extremecases) a continuum with positive slope above 6000 A.
| Ellipticities at R(h) of LMC star clusters
The projected ellipticities of 53 populous LMC star clusters have beenderived by means of PDS 1010A scans and a computer interactive method ofreduction implemented on an Apollo 570 workstation. Film copies of apair of J and U plates taken with the 1.2 m UK Schmidt Telescope inAustralia were used. The ellipticities derived here agree with thosefound by previous investigators, when comparisons were possible at thesame radius. Ellipticity variations within individual globular clustersare seen to be a common phenomenon, so the ellipticities e(h) at adistance corresponding to the half-mass radius R(h) from the center wereadopted to represent the cluster's flatness. Using these values for theLMC clusters, it is found that LMC clusters are more elliptical thanthose of the Galaxy. Although the young LMC globular clusters show atendency to be more elliptical than the old ones, there is no strongevidence for a significant difference among them. Finally, e(h) wasfound to increase with the total mass of the clusters, possiblyindicating that high-mass clusters have higher angular momentum, or havemore difficulty in shedding angular momentum, than do low mass clusters,and remain longer in their initial flattened shape.
| Observed dynamical parameters of the disk clusters of the Large Magellanic Cloud. II
The structural parameters and density profiles for 28 LMC globularclusters (located within 5 kpc from the rotation center) have beenderived by means of star counts. The clusters were measured on plates offour different colors (U, J, V, I) taken with the 1.2-m UK Schmidttelescope. The tidal radii are found to be within 40-65 pc and theirdynamical masses from 10,000 to 100,000 solar masses. Comparing thedynamical parameters of these clusters with those studied by Kontizas etal. (1987), it is found that the most extended and massive clusters ofthis galaxy are in the innermost area, at distances not exceeding 3 kpcfrom the rotation center; the distances have been corrected for theinclination of the LMC.
| Population-I Pulsating Stars. VI - Ages of Star Clusters and Associations
On the basis of our age estimations of Population I pulsating stars inour Galaxy (Tsvetkov, 1986a), the mean ages of 6 open star clusterscontaining 21 Delta Scuti-variables and of 8 star clusters andassociations containing 13 classical cepheids, have been evaluated.These mean cluster age estimations weighted according to theprobabilities for different evolutionary phases of the pulsating stars,are obtained in the evolutionary track systems of Iben (1967) andPaczyñski (1970); the cluster ages are larger in theformer system. Our results are compared with those obtained from variousmethods by other authors. Clusters with classical cepheids and withDelta Scuti-stars have ages, respectively, in the ranges 107_108 yearsand 106_109 years. It is shown that the use of simpleperiod-age(-colour) relations for Population I pulsating stars givessufficiently accurate cluster age estimations. By use of our period-agerelations for classical cepheids (Tsvetkov, 1986a), the mean ages of 56other star clusters and associations in our Galaxy, the MagellanicClouds, and M 31 galaxy have been estimated in both systems of tracks.The results are generally in agreement with those obtained from variousmethods by other authors. The use of Population I pulsating stars instar clusters and associations is one of the simplest and most easilyapplied methods for determining cluster ages; but there are somelimitations in its application
| Integrated UV magnitudes of the Large Magellanic Cloud associations
UV photographs (2600 A, 350 A passband) of the LMC have been obtained bythe S183 experiment during a Skylab mission. The background is estimatedand a method for deriving the integrated fluxes is presented. Theintegrated magnitudes of about 50 associations and isocontours of theirintensities are given, along with the B and V integrated magnitudes of13 associations.
| Binary star clusters in the Large Magellanic Cloud
In a survey of the LMC cluster system, double clusters with acenter-to-center separation of less than 1.3 arcmin (18 pc) have beenidentified. It is inferred that a considerable fraction of these doubleclusters must be binaries since the calculated projection effects canaccount for only 31 of them. This inference is strongly supported by thefact that the ages available for some of the culsters of the sample (asdetermined from UBV photometry) are less than the computed times ofmerger or disruption of the binary cluster system. Furthermore, thespace distribution of these pairs indicates that these clusters belongto a very young or young population.
| 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.
| The kinematics of globular clusters in the Large Magellanic Cloud
Velocities for 35 globular clusters in the LMC have been combined withdata from other sources to yield velocities for a total of 59 clustersthat range in age from 100 million to 10 billion years. Clusters youngerthan one billion years are noted to have motions similar to the gas intheir vicinity and to share the rotation solution previously found onthe basis of H I velocity maps and H II region velocities. These youngclusters therefore constitute a flattened system having a lowline-of-sight velocity dispersion, consistent with that found inprevious kinematic and photometric studies. The older clusters are alsoflattened to a disk-like system, although both the systematic velocityand position angle of the line of nodes are significantly different forthese older clusters. The data presented also suggest that, unlike theMilky Way, there is no evidence for a kinematic halo population amongglobular clusters in the LMG.
| The extended giant branches of intermediate age globular clusters in the Magellanic Clouds. II
In order to obtain a complete sample of upper asymptotic giant branch(AGB) stars in the red globular clusters of the Magellanic Clouds, aphotographic near-infrared survey of the clusters was conducted. Theresults are compared with previous photometry and the problem of errorarising from variability of carbon stars is addressed. Stars withoutspectra are tentatively classified based on their JHK colors. Apparentand absolute bolometric magnitudes and effective temperatures werecalculated from the IR colors, allowing for the location of the redstars and of the cluster giant branches in the physical H-R diagram tobe determined. Stellar evolution on the AGB is discussed, leading toimproved estimates of the extent of the upper AGB. A carbon star censusis presented and the ages of the clusters is derived with suitablycomplete photometry. On this basis, the chemical enrichment history ofthe Clouds is discussed.
| The composite period-age relation for cepheids of the Magellanic Clouds, M 31 and galaxy.
Not Available
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