A sample of relatively unstudied star clusters in the Large Magellanic Cloud: fundamental parameters determined from Washington photometry

To enlarge our growing sample of well-studied star clusters in the Large Magellanic Cloud (LMC), we present CCD Washington CT1 photometry to T1 ~ 23 in the fields of twenty-three mostly unstudied clusters located in the inner disc and outer regions of the LMC. We estimated cluster radii from star counts. Using the cluster Washington (T1,C-T1) colour-magnitude diagrams, statistically cleaned from field star contamination, we derived cluster ages and metallicities from a comparison with theoretical isochrones of the Padova group. Whenever possible, we also derived ages using delta_T1 - the magnitude difference between the red giant clump and the main sequence turn off - and estimated metallicities from the standard giant branch procedure. We enlarged our sample by adding clusters with published ages and metallicities determined on a similar scale by applying the same methods. We examined relationships between their positions in the LMC, ages and metallicities. We find that the two methods for age and metallicity determination agree well with each other. Fourteen clusters are found to be intermediate-age clusters (1-2 Gyr), with [Fe/H] values ranging from -0.4 to -0.7. The remaining nine clusters turn out to be younger than 1 Gyr, with metallicities between 0.0 and -0.4. Our 23 clusters represent an increase of ~ 30% in the current total amount number of well-studied LMC clusters using Washington photometry. In agreement with previous studies, we find no evidence for a metallicity gradient. We also find that the younger clusters were formed closer to the LMC centre than the older ones.Comment: 11 pages, 10 figures. A&A, in pres

Probing the Large Magellanic Cloud's recent chemical enrichment history through its star clusters

We present Washington system colour-magnitude diagrams (CMDs) for 17 practically unstudied star clusters located in the bar as well as in the inner disc and outer regions of the Large Magellanic Cloud (LMC). Cluster sizes were estimated from star counts distributed throughout the entire observed fields. Based on the best fits of theoretical isochrones to the cleaned $(C-T_1,T_1)$ CMDs, as well as on the $\delta T_1$ parameter and the standard giant branch method, we derive ages and metallicities for the cluster sample. Four objects are found to be intermediate-age clusters (1.8-2.5 Gyr), with [Fe/H] ranging from -0.66 to -0.84. With the exception of SL263, a very young cluster ($\sim$ 16 Myr), the remaining 12 objects are aged between 0.32 and 0.89 Gyr, with their [Fe/H] values ranging from -0.19 to -0.50. We combined our results with those for other 231 clusters studied in a similar way using the Washington system. The resulting age-metallicity relationship shows a significant dispersion in metallicities, whatever age is considered. Although there is a clear tendency for the younger clusters to be more metal-rich than the intermediate ones, we believe that none of the chemical evolution models currently available in the literature reasonably well represents the recent chemical enrichment processes in the LMC clusters. The present sample of 17 clusters is part of our ongoing project of generating a database of LMC clusters homogeneously studied using the Washington photometric system and applying the same analysis procedureComment: 11 pages, 20 figures, 3 tables, Accepted for publication in MNRA

A study of the recent chemical evolution of the Large Magellanic Cloud

Abstract: we present the results of a study of the Large Magellanic Cloud (LMC) chemical evolution during the last 2.2 Gyr. This study is based on Washington photometric observations of LMC's star clusters carried out with the Cerro Tololo Inter-American Observatory (CTIO) 4 m telescope, using the C and T_1 filters. As tracers of the LMC's chemical enrichment we used 83 star clusters, from which 40 clusters are projected onto the bar region, 23 in the inner disc and 20 in the outer disc. More than half of the total sample has not been previously studied. We determine size, reddening, deprojected distance, age and metallicity of the observed star clusters.Fil: Palma, Tali. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Palma, Tali. Ministerio de Ciencia, Tecnología e Innovación de la Nación. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Clariá Olmedo, Juan José. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Clariá Olmedo, Juan José. Ministerio de Ciencia, Tecnología e Innovación de la Nación. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Ahumada, Andrea. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Ahumada, Andrea. Ministerio de Ciencia, Tecnología e Innovación de la Nación. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Astronomía (incluye Astrofísica y Ciencias del Espacio

Corporate social responsibility in the global value chain: a bargaining perspective

Breaches of corporate social responsibility (CSR) in global value chains (GVCs) pose a managerial challenge for multinational enterprises (MNEs) and threaten both their reputations and global sustainability. While an MNE-centric perspective on these issues has dominated existing international business research, we show that a dynamic view of bargaining among actors in the GVC can yield novel insights. We draw on coalitional game theory and develop a model where an MNE collaborates, monitors, and negotiates prices with a supplier whose CSR breaches may be revealed by the MNE, external agents, or remain hidden. Our model illustrates how MNEs may face a hold-up problem when irresponsible actions by suppliers are made public, and the suppliers have the power to engage in opportunistic renegotiation. Interestingly, we show that greater monitoring by MNEs, if not combined with specific strategies, can have negative consequences by weakening the MNE's bargaining position and, in some cases, even prompting more irresponsible actions by the suppliers. Our model advances international business research on GVC sustainability and has important implications for managers and researchers alike

Estudio de cúmulos estelares de la Nube Menor de Magallanes: fotometría de Washington de 14 cúmulos de edad intermedia

We present CCD photometry in the Washington system C and T1 bands of 14 star clusters of the Small Magellanic Cloud (SMC). We determine ages and metallicities using theoretical isochrones, the δT1 parameter and the Red Giant Standard method. Excepting IC 1708, all the observed clusters are aged between 1 and 6.3 Gyr, while their metallicities ([Fe/H]) range between -0.7 and -1.4. Two important cluster formation episodes in the SMC, dated at ∼ 2 Gyr and ∼ 5 Gyr ago, were detected. During approximately the first 4 Gyr in the SMC lifetime, the cluster formation rate turned out to be constant. A detailed version of this work can be seen in Piatti et al. (2011, MNRAS, 417, 1559).Presentamos fotometría CCD en las bandas C y T1 del sistema de Washington de 14 cúmulos estelares de la Nube Menor de Magallanes (NmM). Usando isócronas teóricas, el parámetro δT1 y el método de las Ramas Gigantes Estándar, determinamos edades y metalicidades. Excepto IC 1708, todos los cú- mulos observados tienen edades entre 1000 y 6300 millones de años y valores de [Fe/H] entre -0.7 y -1.4. Constatamos dos importantes episodios de formación de cúmulos en la NmM ocurridos hace ∼ 2 mil y ∼ 5 mil millones de años. Durante los primeros 4 mil millones de años desde que se formaron los cúmulos, la tasa de formación de los mismos se mantuvo constante. Una versión detallada de este trabajo puede verse en Piatti et al. (2011, MNRAS, 417, 1559).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; ArgentinaFil: Claria Olmedo, Juan Jose. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Bica, E.. Universidade Federal do Rio Grande do Sul; BrasilFil: Geisler, D.. Universidad de Concepción; ChileFil: Ahumada, Andrea Veronica. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Girardi, L.. Observatorio di Padova; Itali

Caracterización de tres cúmulos estelares de la Nube Menor de Magallanes

El presente trabajo representa la continuación de un estudio sistemático de cúmulos estelares de las Nubes de Magallanes observados con el telescopio de 4 m del Observatorio Interamericano de Cerro Tololo (Chile), usando el sistema fotométrico de Washington. Se presentan resultados preliminares de 3 cúmulos débiles y compactos de la Nube Menor de Magallanes, uno de los cuales (BS 126) no registra estudios previos. Se caracteriza esta muestra determinando principalmente los radios angulares, enrojecimientos, edades y metalicidades. La determinación de estos parámetros se lleva a cabo de manera homogénea aplicando procedimientos estandares.This work represents the continuation of a systematic study of star clusters belonging to the Magellanic Clouds observed with the Cerro Tololo Interamerican Observatory (Chile) 4 m telescope, using the Washington photometric system. We present preliminary results for 3 faint and compact clusters of the Small Magellanic Cloud, one of which (BS126) has not been previously studied. We characterize the sample by determining mainly angular radii, reddenings, ages and metallicities of the clusters. The determination of these parameters is performed in a homogeneous way by applying standard procedures.publishedVersionFil: Palma, Tali. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Clariá Olmedo, Juan José. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Ahumada, Andrea. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Otras Ciencias Naturales y Exacta

New fundamental parameters of the Galactic open clusters Berkeley 26, Czernik 27, Melotte 72, NGC 2479 and BH 37

We have obtained CCD UBVI_{KC} photometry down to V ~ 21.0 for the open clusters Berkeley 26, Czernik 27, Melotte 72, NGC 2479 and BH 37. The latter has never been studied before. Cluster stellar density profiles were obtained from star counts in appropriate-sized boxes distributed throughout the entire observed fields. Based on different measured indices, we estimate the ages of Berkeley 26, Melotte 72 and NGC 2479. On the other hand, we indicate possible solutions for the cluster fundamental parameters by matching theoretical isochrones which reasonably reproduce the main cluster features in their CMDs. In the case of NGC 2479, the cluster E(B-V) and E(V-I) colour excesses and apparent distance modulus were estimated from the fit of the Zero-Age Main Sequence (ZAMS) to the colour-colour and colour-magnitude diagrams, respectively.Comment: MNRAS accepte

Chemical abundances and ages of the bulge stars in APOGEE high-velocity peaks

A cold high-velocity (HV, $\sim$ 200 km/s) peak was first reported in several Galactic bulge fields based on the APOGEE commissioning observations. Both the existence and the nature of the high-velocity peak are still under debate. Here we revisit this feature with the latest APOGEE DR13 data. We find that most of the low latitude bulge fields display a skewed Gaussian distribution with a HV shoulder. However, only 3 out of 53 fields show distinct high-velocity peaks around 200 km/s. The velocity distribution can be well described by Gauss-Hermite polynomials, except the three fields showing clear HV peaks. We find that the correlation between the skewness parameter ($h_{3}$) and the mean velocity ($\bar{v}$), instead of a distinctive HV peak, is a strong indicator of the bar. It was recently suggested that the HV peak is composed of preferentially young stars. We choose three fields showing clear HV peaks to test this hypothesis using the metallicity, [$\alpha$/M] and [C/N] as age proxies. We find that both young and old stars show HV features. The similarity between the chemical abundances of stars in the HV peaks and the main component indicates that they are not systematically different in terms of chemical abundance or age. In contrast, there are clear differences in chemical space between stars in the Sagittarius dwarf and the bulge stars. The strong HV peaks off-plane are still to be explained properly, and could be different in nature.Comment: 13 pages, 10 figures, published in ApJ. Updated to match the final ApJ published version. Minor revisions to the text and Figure

Estudio fotométrico de sistemas binarios y múltiples de cúmulos estelares de la Nube Mayor de Magallanes

Resumen. Estudiamos 11 probables sistemas binarios o múltiples de cúmulos estelares (CEs) de la Nube Mayor de Magallanes. Estos sistemas están conformados por 31 CEs, 19 de los cuales han sido observados con el telescopio “Víctor Blanco” de 4 m de Cerro Tololo en el sistema de Washington. Confirmamos una alta probabilidad de realidad física de algunos de los candidatos estudiados, determinamos sus probables épocas de formación y mostramos, además, que algunos candidatos catalogados podrían no tener realidad física. En todos los casos recomendamos confirmar la asociación física de dichos sistemas mediante estudios de sus distancias heliocéntricas y velocidades radiales relativas.Abstract. We study 11 probable binary or multiple systems of star clusters (SCs) of the Large Magellanic Cloud. They are formed by 31 SCs, out of which 19 have been observed in the Washington system with the Cerro Tololo “Victor Blanco” 4 m telescope. We confirm a high probability of physical reality for some of the studied binary or multiple system candidates. We also determine their probable formation epochs and show that some of them could not be genuine physical systems. In all cases we recommend to confirm the physical association of these SC systems by examining their heliocentric distances and relative radial velocities.publishedVersionFil: Palma, Tali. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Palma, Tali. Conicet, Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Argentina.Fil: Clariá Olmedo, Juan José. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Clariá Olmedo, Juan José. Conicet, Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Argentina.Fil: Ahumada, Andrea Verónica. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; ArgentinaFil: Ahumada, Andrea Verónica. Conicet, Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Argentina.Astronomía (incluye Astrofísica y Ciencias del Espacio