Ca II TRIPLET SPECTROSCOPY OF SMALL MAGELLANIC CLOUD RED GIANTS. IV. ABUNDANCES FOR A LARGE SAMPLE OF FIELD STARS AND COMPARISON WITH THE CLUSTER SAMPLE

This paper represents a major step forward in the systematic and homogeneous study of Small Magellanic Cloud (SMC) star clusters and field stars carried out by applying the calcium triplet technique. We present in this work the radial velocity and metallicity of approximately 400 red giant stars in 15 SMC fields, with typical errors of about 7 km s-1 and 0.16 dex, respectively. We added to this information our previously determined metallicity values for 29 clusters and approximately 350 field stars using the identical techniques. Using this enlarged sample, we analyze the metallicity distribution and gradient in this galaxy. We also compare the chemical properties of the clusters and of their surrounding fields. We find a number of surprising results. While the clusters, taken as a whole, show no strong evidence for a metallicity gradient (MG), the field stars exhibit a clear negative gradient in the inner region of the SMC, consistent with the recent results of Dobbie et al. For distances to the center of the galaxy less than 4\ub0, field stars show a considerably smaller metallicity dispersion than that of the clusters. However, in the external SMC regions, clusters and field stars exhibit similar metallicity dispersions. Moreover, in the inner region of the SMC, clusters appear to be concentrated in two groups: one more metal-poor and another more metal-rich than field stars. Individually considered, neither cluster group presents an MG. Most surprisingly, the MG for both stellar populations (clusters and field stars) appears to reverse sign in the outer regions of the SMC. The difference between the cluster metallicity and the mean metallicity of the surrounding field stars turns out to be a strong function of the cluster metallicity. These results could be indicating different chemical evolution histories for these two SMC stellar populations. They could also indicate variations in the chemical behavior of the SMC in its internal and external regions

Propiedades qu\uedmicas de estrellas del campo de la Nube Menor de Magallanes

In this paper we analyze the chemical properties of 400 red giant stars belonging to 15 areas spread over the Small Magellanic Cloud (SMC). Metallicities were determined from the equivalent widths of the CaII triplet lines, measured on spectra obtained with the FORS2 instrument at the Very Large Telescope located on Paranal (Chile). We add to this sample other 350 red giant stars previously investigated by our group using the same technique. Using this extended sample, we analyze and discuss the metallicity distribution and the possible existence of a metallicity gradient among the field stars of the SMC. We also compare our results to the chemical properties inferred for the corresponding 30 star clusters of the SMC, whose metallicities have been determined in a homogeneous scale

Determinaci\uf3n de edades de c\ufamulos estelares de la Nube Menor de %Magallanes a partir del par\ue1metro

The morphological age index has been and is still being used to estimate ages of galactic and extragalactic star clusters. Using a sample of 15 clusters in the Small Magellanic Cloud (SMC) observed with the Very Large Telescope (Chile) in the and passbands; we compare age determinations performed by measuring and using calibrations of cc94 cc94 and s04 s04; hereafter CC94 and S04; respectively. We find that S04 calibration leads to older ages than that of CC94; this difference increasing with age. We also show that ages obtained via CC94 show better agreement with those derived by gla08b gla08b; based on data obtained with the HST. The ages of 6 clusters have been significantly underestimated in previous studies in which comparatively small telescopes have been used. FULL TEXT IN SPANIS

Age and Metallicity Analysis of the Small Magellanic Cloud from Star Clusters

We present metallicities for 15 Small Magellanic Cloud (SMC) star clusters. We add to this sample the ages and metallicities of 15 additional star clusters previously studied by Parisi et al. (2009) and Parisi et al. (2013), which were observed and analyzed following the same procedures as in the present work. Therefore, we compiled a sample of 30 SMC star clusters homogeneously studied, the largest sample to date. Metallicities are determined from the Calcium II triplet lines (CaT) in spectra obtained using the FORS2 multi-object spectrograph on the VLT (Paranal, Chile). Ages are determined from color-magnitude diagrams built from photometry of the pre-images. Using this sample, we analyze the chemical properties of the SMC, particularly the age-metallicity relation. We found three new old clusters which help to fill the so called SMC \u201cage gap\u201d between L 1 and NGC 121, the 2 oldest previously known clusters. These new old SMC clusters broadly increase our knowledge of the chemical evolution of this galaxy during the earliest epochs

VISTA Variables in the V\ueda L\ue1ctea (VVV): Current Status and First Results

VISTA Variables in the V\ueda L\ue1ctea (VVV) is a public ESO near-IR variability survey aimed at scanning the Milky Way Bulge and an adjacent section of the mid-plane. VVV observations started in October 2009 during ESO science verification. Regular observations for the first year of the survey have been conducted since February 2010 and will cover a total area of 520 square degrees in five passbands and five epochs. Here we address the first results obtained from the VVV Survey as well as the current status of the observations