Large Magellanic Cloud stellar clusters

Brocato, E.; Carlo, E. Di; Menna, G.

doi:10.1051/0004-6361:20010711

Cited by 35 publications

(60 citation statements)

References 44 publications

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“…In this figure they follow the same sequence as suggested by Brocato et al (2001) to reveal the age effect in a LMC cluster. As the cluster becomes older, both the MS termination and the RC become less bright.…”

Section: The Datasupporting

confidence: 71%

“…These data were selected from the HST archive and reduced by Brocato et al (2001). Their original cluster sample has 21 LMC clusters and one SMC cluster, covering a wider range in age (0.1 < ∼ τ < ∼ 13 Gyr).…”

Section: The Datamentioning

confidence: 99%

“…The final (V, B − V) CMDs from Brocato et al (2001) for the 15 intermediate-age LMC clusters are presented in Fig. 1.…”

Section: The Datamentioning

confidence: 99%

“…We generate synthetic CMDs that reproduce as accurately as possible the main features found in the observed CMD, finding the best model CMDs based on statistical comparisons in the Brocato et al (2001); only stars with R ≤ 2 R c (R ≤ 1 R c for NGC 2121) are shown. This sequence was suggested by those authors to reveal the "evolution" effect in the sample.…”

Section: Cmd Modellingmentioning

confidence: 99%

“…3 we present examples of synthetic CMDs of rich LMC clusters. The CMDs are disposed in an age sequence, approximately covering the age range expected for the IACs from Brocato et al (2001). As in Fig.…”

Section: Cmd Modellingmentioning

confidence: 99%

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Physical parameters of 15 intermediate-age LMC clusters from modelling of HST colour–magnitude diagrams

Kerber¹,

Santiago

Brocato

2006

A&A

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Aims. We analyzed HST/WFPC2 colour-magnitude diagrams (CMDs) of 15 populous Large Magellanic Cloud (LMC) stellar clusters with ages between ∼0.3 Gyr and ∼3 Gyr. These (V, B − V) CMDs are photometrically homogeneous and typically reach V ∼ 22. Accurate and self-consistent physical parameters (age, metallicity, distance modulus and reddening) were extracted for each cluster by comparing the observed CMDs with synthetic ones. Methods. These determinations involved simultaneous statistical comparisons of the main-sequence fiducial line and the red clump position, offering objective and robust criteria to determine the best models. The models explored a regular grid in the parameter space covered by previous results found in the literature. Control experiments were used to test our approach and to quantify formal uncertainties.Results. In general, the best models show a satisfactory fit to the data, constraining well the physical parameters of each cluster. The age-metallicity relation derived by us presents a lower spread than similar results found in the literature for the same clusters. Our results are in accordance with the published ages for the oldest clusters, but reveal a possible underestimation of ages by previous authors for the youngest clusters. Our metallicity results in general agree with the ones based on spectroscopy of giant stars and with recent works involving CMD analyses. The derived distance moduli implied by the most reliable solutions, correlate with the reddening values, as expected from the non-negligible three-dimensional distribution of the clusters within the LMC. Conclusions. The inferred spatial distribution for these clusters is roughly aligned with the LMC disk, being also more scattered than recent numerical predictions, indicating that they were not formed in the LMC disk. The set of ages and metallicities homogeneously derived here can be used to calibrate integrated light studies applied to distant galaxies.

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Section: The Datasupporting

confidence: 71%

Section: The Datamentioning

confidence: 99%

“…The final (V, B − V) CMDs from Brocato et al (2001) for the 15 intermediate-age LMC clusters are presented in Fig. 1.…”

Section: The Datamentioning

confidence: 99%

Section: Cmd Modellingmentioning

confidence: 99%

Section: Cmd Modellingmentioning

confidence: 99%

See 3 more Smart Citations

Physical parameters of 15 intermediate-age LMC clusters from modelling of HST colour–magnitude diagrams

Kerber¹,

Santiago

Brocato

2006

A&A

Self Cite

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Horizontal branch stars: the interplay between observations and theory, and insights into the formation of the Galaxy

Catelan

2009

Astrophys Space Sci

359

430

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We review and discuss horizontal branch (HB) stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC-an argument which, due to its strong reliance on the ancient RR Lyrae stars, is essentially independent of the chemical evolution of these systems after the very earliest epochs in the Galaxy's history. Convenient analytical fits to isochrones in the HB type-[Fe/H] plane are also provided. In this sense, a rediscussion of the second-parameter problem is also presented, focusing on the cases of NGC 288/NGC 362, M13/M3, the extreme outer-halo globular clusters with predominantly red HBs, and the metal-rich globular clusters NGC 6388 and NGC 6441. The recently revived possibility that the helium abundance may play an important role as a second parameter is also addressed, and possible constraints on this scenario discussed. We critically discuss the possibility that the observed properties of HB stars in NGC 6388 and NGC 6441 might be accounted for if these clusters possess a relatively minor population of helium-enriched stars. A technique is M. Catelan is John Simon Guggenheim Memorial Foundation Fellow.M. Catelan ( ) proposed to estimate the HB types of extragalactic globular clusters on the basis of integrated far-UV photometry. The importance of bright type II Cepheids as tracers of faint blue HB stars in distant systems is also emphasized. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyr, is also revisited. Taking into due account the evolutionary status of RR Lyr, the derived relation implies a true distance modulus to the LMC of (m-M) 0 = 18.44 ± 0.11. Techniques providing discrepant slopes and zero points for the M V (RRL)-[Fe/H] relation are briefly discussed. We provide a convenient analytical fit to theoretical model predictions for the period change rates of RR Lyrae stars in globular clusters, and compare the model results with the available data. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are also investigated.

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Analysis of HST CMDs of 15 intermediate-age LMC clusters: self-consistent physical parameters and 3D distribution

Kerber¹,

Santiago

Brocato

2006

IAU

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Abstract. We analysed HST/WFPC2 colour-magnitude diagrams (CMDs) from 15 populous Large Magellanic Cloud (LMC) stellar clusters with ages between ∼0.3 Gyr and ∼3 Gyr. These (V, B-V) CMDs are photometrically homogeneous and reach typically V ∼22. Accurate and selfconsistent physical parameters (age, metallicity, distance modulus and reddening) were extracted for each cluster by comparing the observed CMDs with synthetic ones. These determinations were made by means of simultaneous statistical comparison of MS fiducial lines and red clump position, offering objective and robust criteria to determine the best models. In general, the best models show a satisfactory fit to the data, adequately constraining the physical parameters of each cluster. The inferred spatial distribution of these clusters is roughly aligned with the LMC disk. The set of ages and metallicities homogeneously derived here can be used to calibrate integrated light studies applied to distant galaxies. Keywords. galaxies: star clusters, Magellanic Clouds, Hertzsprung-Russell diagramThe LMC is a unique nearby case of a gas rich, star forming, irregular galaxy containing thousands of clusters with varying masses, ages and metallicities (Olszweski et al. 1996). Therefore, this cluster system is a useful record of the history of star formation, chemical enrichment and dynamics of a quite distinct type of galaxy relative to the Galaxy, being a key-piece to the studies in stellar populations. Although global features of this cluster system, like age and metallicity distributions and the age-metallicity relation, are relatively known (Olszewski et al. 1991, Geisler et al. 1997, the physical parameters of each cluster (specially age and distance) can be significantly better determined using sophisticated analysis of CMDs obtained with HST data, capable to resolve stars even in the cluster centre.In the present work (Kerber et al. 2007) we analysed HST/WFPC2 CMDs from 15 populous LMC clusters (NGC 1651, 1718, 1777, 1831, 1856, 1868, 2121, 2155, 2162, 2173, 2209, 2213, 2249 to determine the following physical parameters for each of them: age (τ ), metallicity (Z), distance modulus ((m − M ) 0 ) and reddening (E(B − V )). For each cluster, the observed MS fiducial line and red clump (RC) position were simultaneously and statistically compared with the ones obtained from synthetic CMDs. The CMD models explored a regular grid in the parameter space consistent with previous determinations found in the literature. Control experiments were used to test our approach and to quantify formal uncertainties. Therefore, our determinations, based on photometrically homogeneous data (Brocato et al. 2001), are self-consistent and done by an objective and robust method.

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Large Magellanic Cloud stellar clusters

Cited by 35 publications

References 44 publications

Physical parameters of 15 intermediate-age LMC clusters from modelling of HST colour–magnitude diagrams

Physical parameters of 15 intermediate-age LMC clusters from modelling of HST colour–magnitude diagrams

Horizontal branch stars: the interplay between observations and theory, and insights into the formation of the Galaxy

Analysis of HST CMDs of 15 intermediate-age LMC clusters: self-consistent physical parameters and 3D distribution

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