CCD SDSS Photometry of Poorly Studied Star Clusters in the Large Magellanic Cloud

We present for the first time CCD SDSS푔푟photometry, obtained at the Gemini South telescope with the GMOS attached, of stars inthe field of the poorly studied star clusters NGC1768, HS 85, SL 676, NGC2107, NGC2190, and SL 866, which are distributed in themain body of the Large Magellanic Cloud. We applied a subtraction procedure to statistically clean the cluster CMDs from field starcontamination. In order to disentangle cluster features from those belonging to their surrounding fields, we applied a subtractionprocedure which makes use of variable cells to reproduce the field star color-magnitude diagrams (CMDs) as closely as possible. Wethentraced theirstellardensity radialprofilesfromstarcountsperformedover thecleaned field starsdataset and derivedtheir radii.Using the cleaned cluster CMDs, we estimated ages and metallicities from matching theoretical isochrones computed for the SDSSsystem. The studied star clusters have ages from 0.1 up to 2.0Gyr and are of slightly metal-poor metal content ([Fe/H]≈−0.4dex).Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentin

Towards a comprehensive knowledge of the open cluster Haffner 9

We turn our attention to Haffner 9, aMilkyWay open cluster whose previous fundamental parameter estimates are far from being in agreement. In order to provide with accurate estimates, we present high-quality Washington CT1 and Johnson BVI photometry of the cluster field.We put particular care in statistically cleaning the colour-magnitude diagrams (CMDs) from field star contamination, which was found a common source in previous works for the discordant fundamental parameter estimates. The resulting cluster CMD fiducial features were confirmed from a proper motion membership analysis. Haffner 9 is a moderately young object (age ~350 Myr), placed in the Perseus arm - at a heliocentric distance of ~3.2 kpc -, with a lower limit for its present mass of ~160 M ⊙ and of nearly metal solar content. The combination of the cluster structural and fundamental parameters suggest that it is in an advanced stage of internal dynamical evolution, possibly in the phase typical of those with mass segregation in their core regions. However, the cluster still keeps its mass function close to that of the Salpeter's law.Fil: Piatti, Andres Eduardo. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentin

Washington photometry of 26 moderately young small angular size clusters in the Large Magellanic Cloud

Aims. With the aim of enlarging the number of studied LMC clusters in the age ange 8.0 <∼ log(t) <∼ 9.0, we focus here on a sample of mostly unstudied cluster candidates. Methods. We present for the first time CCD Washington CT1T2 photometry of stars in the field of 26 LMC clusters. Results. The studied clusters turned out to be small angular size objects with ages within the age range 8.0 <∼ log(t) <∼ 9.0, which are projected or immersed in dense star fields.Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

New insights on the bursting formation of star clusters in the large magellanic cloud

We present the results on the age estimates of 36 Large Magellanic Cloud (LMC) clusters obtained for the first time from CCD Washington CT1T2 photometry. By using the (T1, C − T1) and (T1, T1 − T2) diagrams, we estimated ages for the cluster sample using the δT1 index. We confirm that the studied cluster sample belong to the ∼2 Gyr bursting formation epoch of the LMC. Furthermore, when rebuiling the cluster age distribution – taken into account the estimated age errors – we found that the number of clusters with ages between 1 and 3 Gyr now doubles that of the known bursting cluster population, which suggests that the tidal interaction between both Magellanic Clouds and, perhaps, also the Milky Way, was more stronger than expected.Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Propiedades astrofísicas de objetos catalogados como cúmulos estelares en la Nube Menor de Magallanes

We present the results on the age estimates of 11 Small Magellanic Cloud (SMC) clusters obtained for the first time from CCD Washington CT1T2 photometry. CMD cluster features - mainly cluster RCs and MSTOs - turn out to be identificable when performing annular extractions around their respective centres, once they were cleaned from field star contamination. We estimated ages for the cluster sample using the δT1 index, and metallicities from the SGB technique. The resultant ages and metallicities for the control clusters are in excellent agreement with those previously published, thus confirming our present age/metallicity scale. We also confirmed the ages and metallicities derived for the clusters by fitting theoretical isochrones.Presentamos los resultados de las edades estimadas de 11 cumulos de la Nube Menor de Magallanes (NMM) obtenidas por primera vez a partir de fotometrıa CCD en el sistema de Washington CT1T2. Las caracterısticas de los cumulos en los diagramas color-magnitud (DCM) -principalmente el clump de las gigantes y el turnoff de la Secuencia Principal- se identificaron a partir de extracciones circulares alrededor de los centros de los cumulos, una vez que los DCM fueron limpiados de la contaminacion de estrellas del campo. Estimamos las edades de la muestra de cumulos empleando el ındice δT1, y las metalicidades a partir de la tecnica SGB. Las edades y las metalicidades resultantes para cumulos de control estan en excelente acuerdo con estimaciones previamente publicadas, confirmando ası nuestra presente escala de edad/metalicidad. Confirmamos tambien las edades y las metalicidades derivadas para los cumulos a partir de ajustes de isocronas teoricas.Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Towards a comprehensive picture of the star cluster age–metallicity relationship in the Small Magellanic Cloud

We present the results on the age and metallicity estimates of 11 Small Magellanic Cloud (SMC) clusters obtained from CCD Washington CT1T2 photometry. The 11 clusters reproduce the ∼2 Gyr bursting formation paradigm when entering them into the age–metallicity relationship (AMR). Once these clusters were added to the largest known SMC cluster sample with ages and metallicities put into an homogeneous scale, we found that a comprehensive picture of the cluster AMR can be obtained, which includes the following components: two enhanced formation processes at t ∼ 2 and 5–6 Gyr, which have taken place throughout the entire body of the galaxy; the absent of a metallicity gradient and a relative spread in metallicity for clusters older than ∼7 Gyr. Furthermore, such picture should not significantly change due to incompleteness in the number of studied clusters. Indeed, based on the statistics of catalogued and studied clusters, we found that a total of seven relatively old/old clusters have not yet studied, and even a smaller number is obtained if the cluster spatial distribution is considered.Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

The star field age-metallicity relationship of the Small Magellanic Cloud

We present the results of the age and metallicity estimates for the unprecedented data base of some 3.3 million stars distributed throughout the entire Small Magellanic Cloud main body, obtained for the first time from CCD Washington CT1 photometry. We produce the first comprehensive star field age–metallicity relationship (AMR) from the birth of the galaxy until ∼1 Gyr ago, independent of any other previous approach. We find that the field stars do not possess gradients in age and metallicity, and that stellar populations formed since ∼2 Gyr ago are more metal rich than [Fe/H] ∼−0.8 dex and are confined to the innermost region (semi-major axis ≲ 1°). For the first time, we compare, homogeneously, the present star field AMR to that of the star cluster population with ages and metallicities in the same star field scales, and find that clusters and star fields share similar chemical evolution histories. Both galaxy components have experienced two enhanced formation processes: the most recent peaked at an age of ∼2 Gyr, and an earlier one detected at an age of ∼5–6 and 7.5 Gyr for clusters and star fields, respectively.Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Cúmulos viejos en la Nube Menor de Magallanes

El sorprendente escaso número de cúmulos formados conjuntamente con esta galaxia ha suscitado el interés de toda la comunidad astronómica internacional. Recientemente, se ha identificado un 60% más de cúmulos viejos respecto de los conocidos hasta el presente.Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Nuevos candidatos a cúmulos viejos en la Nube Menor de Magallanes

We present the results on the age and metallicity estimates of nine SMC clusters (AM 3, HW 31, 40, 41, 42, 59, 63, L 91 and NGC 339) obtained from CCD Washington CT1T2 photometry. We confirm AM 3 and NGC 339 as intermediate-age and metal-poor clusters, and report for the first time that the remaining seven clusters are also intermediate-age or old clusters (t ∼ 4.3 - 9.3 Gyr), which represents an increase of ≥ 60% of the total known intermediate-age/old cluster population in the SMC. The studied clusters have metal contents ranging from intermediate metalpoor ([Fe/H] ≈ -0.7 dex) down to metal-poor ([Fe/H] ≈ -1.3 dex) values. A detailed version of this work can be seen in Piatti (2011, MNRAS, 416, L89).Presentamos resultados de edades y metalicidades obtenidas a partir de datos CCD en el sistema fotom´etrico CT1T2 de Washington para nueve c´umulos estelares de la Nube Menor de Magallanes (NMM, AM 3, HW 31, 40, 41, 42, 59, 63, L 91 and NGC 339). Confirmamos a AM 3 y NGC 339 como c´umulos relativamente viejos y pobres en metales, y reportamos por primera vez que los restantes siete c´umulos son objetos relativamente viejos o genuinamente viejos (t ∼ (4.3 - 9.3)×109 a˜nos), lo cual represente un aumento mayor al 60 % del total de los c´umulos viejos conocidos en la Nube Menor de Magallanes. Los c´umulos estudiados tienen contenidos met´alicos desde medianamente pobres ([Fe/H] ∼ -0.7) a pobres ([Fe/H] ∼ -1.3). Una versi´on detallada de este trabajo puede verse en Piatti (2011, MNRAS, 416, L89).Fil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin