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

Kerber, Leandro; Santiago, B.; Brocato, E.

doi:10.1051/0004-6361:20066128

Cited by 71 publications

(107 citation statements)

References 58 publications

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“…This method was extensively explained in previous works of our group, where it was applied to LMC clusters observed with HST/WFPC2 (Kerber et al 2002(Kerber et al , 2007Kerber & Santiago 2005) and Galactic open clusters from 2MASS (Alves et al 2012). In Paper I we analysed the CMDs of five SMC stellar clusters observed with SOAR/SOI using the same setup as in this paper.…”

Section: Methodsmentioning

confidence: 99%

SMC west halo: a slice of the galaxy that is being tidally stripped?

Dias

Kerber

Barbuy

et al. 2016

A&A

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Context. The evolution and structure of the Magellanic Clouds is currently under debate. The classical scenario in which both the Large and Small Magellanic Clouds (LMC, SMC) are orbiting the Milky Way has been challenged by an alternative in which the LMC and SMC are in their first close passage to our Galaxy. The clouds are close enough to us to allow spatially resolved observation of their stars, and detailed studies of stellar populations in the galaxies are expected to be able to constrain the proposed scenarios. In particular, the west halo (WH) of the SMC was recently characterized with radial trends in age and metallicity that indicate tidal disruption. Aims. We intend to increase the sample of star clusters in the west halo of the SMC with homogeneous age, metallicity, and distance derivations to allow a better determination of age and metallicity gradients in this region. Positions are compared with the orbital plane of the SMC from models. Methods. Comparisons of observed and synthetic V(B − V) colour-magnitude diagrams were used to derive age, metallicity, distance, and reddening for star clusters in the SMC west halo. Observations were carried out using the 4.1 m SOAR telescope. Photometric completeness was determined through artificial star tests, and the members were selected by statistical comparison with a control field. Results. We derived an age of 1.23 ± 0.07 Gyr and [Fe/H] = −0.87 ± 0.07 for the reference cluster NGC 152, compatible with literature parameters. Age and metallicity gradients are confirmed in the WH: 2.6 ± 0.6 Gyr/• and −0.19 ± 0.09 dex/ • , respectively. The age-metallicity relation for the WH has a low dispersion in metallicity and is compatible with a burst model of chemical enrichment. All WH clusters seem to follow the same stellar distribution predicted by dynamical models, with the exception of AM-3, which should belong to the counter-bridge. Brück 6 is the youngest cluster in our sample. It is only 130 ± 40 Myr old and may have been formed during the tidal interaction of SMC-LMC that created the WH and the Magellanic bridge. Conclusions. We suggest that it is crucial to split the SMC cluster population into groups: main body, wing and bridge, counter-bridge, and WH. This is the way to analyse the complex star formation and dynamical history of our neighbour. In particular, we show that the WH has clear age and metallicity gradients and an age-metallicity relation that is also compatible with the dynamical model that claims a tidal influence of the LMC on the SMC.

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Section: Methodsmentioning

confidence: 99%

SMC west halo: a slice of the galaxy that is being tidally stripped?

Dias

Kerber

Barbuy

et al. 2016

A&A

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“…Since then, the "synthetic CMD method" has been widely used on simple stellar populations (Sandrelli et al 1999;Carraro et al 2002;Subramaniam et al 2005;Singh Kalirai 2006;Kerber et al 2007;Girardi et al 2009;Cignoni et al 2011;Donati et al 2014, etc.). An expansion of the method can be found applied with little adjustments to the recovery of SFHs of nearby galaxies (Ferraro et al 1989;Tosi et al 1991;Tolstoy & Saha 1996;Hernandez et al 1999;Dolphin 2002;Frayn & Gilmore 2002;Aparicio & Hidalgo 2009;Small et al 2013) 15 .…”

Section: Cluster Parameters Determinationmentioning

confidence: 99%

ASteCA: Automated Stellar Cluster Analysis

Perren

Vazquez

Piatti

2015

A&A

116

121

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We present the Automated Stellar Cluster Analysis package (ASteCA), a suit of tools designed to fully automate the standard tests applied on stellar clusters to determine their basic parameters. The set of functions included in the code make use of positional and photometric data to obtain precise and objective values for a given cluster's center coordinates, radius, luminosity function and integrated color magnitude, as well as characterizing through a statistical estimator its probability of being a true physical cluster rather than a random overdensity of field stars. ASteCA incorporates a Bayesian field star decontamination algorithm capable of assigning membership probabilities using photometric data alone. An isochrone fitting process based on the generation of synthetic clusters from theoretical isochrones and selection of the best fit through a genetic algorithm is also present, which allows ASteCA to provide accurate estimates for a cluster's metallicity, age, extinction and distance values along with its uncertainties. To validate the code we applied it on a large set of over 400 synthetic The results show that ASteCA is able to recover cluster parameters with an acceptable precision even for those clusters affected by substantial field star contamination. ASteCA is written in Python and is made available as an open source code which can be downloaded ready to be used from its official site.

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“…Such clusters are found mainly in the Large Magellanic Cloud (LMC;Mackey & Broby Nielsen 2007; Mackey et al 2008;Milone et al 2009;Piatti 2013;Kerber et al 2007;Rubele et al 2011), and Small Magellanic Cloud (SMC; Girardi et al 2009Girardi et al , 2013. There has been a long history of explanation for such special CMDs.…”

Section: Introductionmentioning

confidence: 99%

Explanation of a Special Color–magnitude Diagram of Star Cluster NGC 1651 From Different Models

Li¹,

Mao²,

Chen³

2015

ApJ

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The color-magnitude diagram (CMD) of globular cluster NGC 1651 has special structures including a broad main sequence, an extended main sequence turn-off, and an extended red giant clump. The reason for such a special CMDremains unclear. In order to test the difference amongthe results from various stellar population assumptions, we study a high-quality CMD of NGC 1651 from the Hubble Space Telescope archive using eight kinds of models. Distance modulus, extinction, age ranges, star formation mode, fraction of binaries, and fraction of rotational stars are determined and then compared. The results show that stellar populations both with and without age spread can reproduce the special structure of the observed CMD. A composite population with extended star formation from 1.8 Gyrs ago to 1.4 Gyrs ago, which contains 50% binaries and 70% rotational stars, fits the observed CMD best. Meanwhile, a 1.5 Gyr-old simple population that consists of rotational stars can also fit the observed CMD well. The results of CMD fitting are shown to depend strongly on stellar population type (simple or composite), and fraction of rotators. If the member stars of NGC 1651 formed in a single star burst, the effect of stellar rotation should be very important for explaining the observed CMDs. Otherwise, the effect may be small. It is also possible that the special observed CMD is a result of the combined effects of stellar binarity, rotation, and age spread. Therefore, further work on stellar population type and fraction of rotational stars of intermediate-age clusters are necessary to understand their observed CMDs.

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

Cited by 71 publications

References 58 publications

SMC west halo: a slice of the galaxy that is being tidally stripped?

SMC west halo: a slice of the galaxy that is being tidally stripped?

ASteCA: Automated Stellar Cluster Analysis

Explanation of a Special Color–magnitude Diagram of Star Cluster NGC 1651 From Different Models

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