Accurate radial velocity and metallicity of the Large Magellanic Cloud old globular clusters NGC1928 and NGC1939

We present results obtained from spectroscopic observations of red giants located in the fields of the Large Magellanic Cloud (LMC) globular clusters (GCs) NGC1928 and NGC1939. We used the GMOS and AAOmega+2dF spectrographs to obtain spectra centred on the Ca II triplet, from which we derived individual radial velocities (RVs) and metallicities. From cluster members we derived mean RVs of RVNGC1928 = 249.58±4.65 km s-1 and RVNGC1939 = 258.85±2.08 km s-1, and mean metallicities of [Fe/H]NGC1928 = -1.30±0.15 dex and [Fe/H]NGC1939 = -2.00±0.15 dex. We found that both GCs have RVs and positions consistent with being part of the LMC disc, so that we rule out any possible origin, but in the same galaxy. By computing the best solution of a disc that fully contains each GC, we obtained circular velocities for the 15 known LMC GCs. We found that 11/15 of the GCs share the LMC rotation derived from HST and Gaia DR2 proper motions. This outcome reveals that the LMC disc existed since the very early epoch of the galaxy formation and experienced the steep relatively fast chemical enrichment shown by its GC metallicities. The four remaining GCs turned out to have circular velocities not compatible with an in situ cluster formation, but rather with being stripped from the SMC.Fil: Piatti, Andres Eduardo. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hwang, N.. Korea Astronomy And Space Science Institute; Corea del SurFil: Cole, A. A.. University of Tasmania; AustraliaFil: Angelo, M. S.. Laboratorio Nacional de Astrofisica; BrasilFil: Emptage, B.. University of Tasmania; Australi

Probing the LMC age gap at intermediate cluster masses

The LMC has a rich star cluster system spanning a wide range of ages and masses. One striking feature of the LMC cluster system is the existence of an age gap between 3-10 Gyrs. But this feature is not as clearly seen among field stars. Three LMC fields containing relatively poor and sparse clusters whose integrated colours are consistent with those of intermediate age simple stellar populations have been imaged in BVI with the Optical Imager (SOI) at the Southern Telescope for Astrophysical Research (SOAR). A total of 6 clusters, 5 of them with estimated initial masses M < 10^4M_sun, were studied in these fields. Photometry was performed and Colour-Magnitude Diagrams (CMD) were built using standard point spread function fitting methods. The faintest stars measured reach V ~ 23. The CMD was cleaned from field contamination by making use of the three-dimensional colour and magnitude space available in order to select stars in excess relative to the field. A statistical CMD comparison method was developed for this purpose. The subtraction method has proven to be successful, yielding cleaned CMDs consistent with a simple stellar population. The intermediate age candidates were found to be the oldest in our sample, with ages between 1-2 Gyrs. The remaining clusters found in the SOAR/SOI have ages ranging from 100 to 200 Myrs. Our analysis has conclusively shown that none of the relatively low-mass clusters studied by us belongs to the LMC age-gap.Comment: 9 pages, 8 figures. Accepted to MNRA

Open Cluster Characterization via Cross-Correlation with Spectral Library

We present a characterization method based on spectral cross-correlation to obtain the physical parameters of the controversial stellar aggregate ESO442-SC04. The data used was obtained with GMOS at Gemini-South telescope including 17 stars in the central region of the ob ject and 6 standard-stars. FXCOR was used in an iterative process to obtain self-consistent radial velocities for the standard-stars and averaged radial velocities for the science spectra. Spectral types, effective temperature, suface gravity and metallicities parameters were determined using FXCOR to correlate cluster spectra with ELODIE spectral library and selecting the best correlation matches using the Tonry and Davis Ratio (TDR). Analysis of the results suggests that the stars in ESO442-SC04 are not bound and therefore they do not constitute a physical system.Comment: 4-page paper from IAU symposium 266. Contains 3 eps figures and IAU document class file 'iau.cls

Clump stars in the Solar Neighbourhood

Hipparcos data has allowed the identification of a large number of clump stars in the Solar Neighbourhood. We discuss our present knowledge about their distributions of masses, ages, colours, magnitudes, and metallicities. We point out that the age distribution of clump stars is ``biased'' towards intermediate-ages. Therefore, the metallicity information they contain is different from that provided by the local G dwarfs. Since accurate abundance determinations are about to become available, these may provide useful constraints to chemical evolution models of the local disc.Comment: 6 pages, proc. of the Sept. 20-24, 1999 Vulcano Workshop "The chemical evolution of the Milky Way: stars vs. clusters", eds. F. Matteucci, F. Giovanell

Basis for a SOAR Optical Imager Pipeline

The development of CCD mosaics had been incorporated into the majority of the recent observing facilities, including on SOAR. We discuss the treatment of mosaic CCD exposures including basic instrumental calibration, the creation of bad pixel masks, the removal of cosmic rays and fringes by sky flat-fielding, the set up of a World Coordinate System by astrometric calibration and the removal of the gap by the creation of single, deep images out of a set of dithered exposures. We have assembled these image treatment programs on a series of semi-automated IRAF scripts1 to handle the reduction of general SOAR Optical Imager (SOI) images requiring little on none user interaction.El desarrollo de mosaicos CCD ha sido incorporado recientemente en la mayor´ıa de los observatorios modernos, entre ellos SOAR. En este trabajo describimos el tratamiento de im´agenes mosaico SOAR en sus diferentes etapas: calibraciones instrumentales b´asicas, generaci´on de una m´ascara para eliminaci´on de pixeles malos, remoci´on de rayos c´osmicos y fringes, ajuste del WCS a trav´es de calibraciones astrom´etricas y remoci´on de gaps en la imagen simple profunda generada a partir de varias im´agenes mosaico. Hemos redactado diferentes rutinas de procesamiento de dichas im´agenes para que puedan ser ejecutadas de un modo semi-autom´atico dentro de un entormo IRAF.Fil: Maia, F. F. S.. Universidade Federal do Minas Gerais; BrasilFil: 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: Santos, J. F. C.. Universidade Federal do Minas Gerais; BrasilFil: Corradi, W. J. B.. Universidade Federal do Minas Gerais; Brasi

Educación para la salud en la peatonal Junín de Corrientes

Fundamentación: la Facultad de Odontología de la UNNE, a través de su Secretaría de Extensión conjuntamente con la Cátedra Práctica Clínica Preventiva II, elaboran Proyectos de Extensión  abordados desde las necesidades reales de la población, para promover la Salud Bucal. Nuestra propuesta se basa en la realización de las tareas extramuros, concretadas mediante la estrategia  de dinámica de grupos, y la elaboración de programas preventivos a nivel comunitario. Objetivos: promover en el alumno condiciones  necesarias para la elaboración, ejecución de Programas de Educación  para  la Salud a nivel comunitario, tomando como eje la Prevención - Promover en los destinatarios actitudes de autocuidado de su propia salud buco-dental. Actividades: las tareas se realizan  en víspera al “Día del Odontólogo”; para ello,  docentes y alumnos se distribuyen en todo el trayecto de la peatonal Junín, finalizando en un escenario preparado para este evento, en la Plaza “Juan de Vera”, (ubicada en el centro de dicha peatonal). Las actividades consisten en Promoción de la Salud Bucal, con demostraciones sobre la técnica de higiene oral, entrega de folletos destinados a todos los grupos etáreos, (diseñados por los alumnos), teatralización, stands, canciones, juegos, y varios estudiantes utilizan disfraces alusivos. Resultados: con esta modalidad  de trabajos extramuros se logra que el alumno aplique los conocimientos de contenidos específicos de la Asignatura, llevándolos a la práctica, en la comunidad, brindándoles los recursos para diseñar “Programas Preventivos a nivel Comunitario para distintos grupos etáreos”, que los incentiva para que asuman actitudes de compromiso social. Esta actividad innovadora, tiene un impacto favorable en la sociedad, puesto que se concientiza sobre la importancia de actitudes preventivas en el cuidado de su salud bucal

Caracterización de cúmulos abiertos a través de correlaciones cruzadas con librerías de espectros

We present a characterization method based on spectral cross-correlation to obtain the physical parameters of the controversial stellar aggregate ESO 442-SC04. The data used was obtained with GMOS at Gemini-South telescope. Spectral types, effective temperature, suface gravity and metallicities parameters were determined using FXCOR to correlate cluster spectra with ELODIE spectral library and selecting the best correlation matches using the Tonry and Davis Ratio (TDR). Analysis of the results suggests that the stars in ESO 442-SC04 are not bound and therefore they do not constitute a physical system.En este trabajo presentamos un m´etodo de caracterizacion basado en la correlacion cruzada de espectros de estrellas en el controvertido objeto ESO 442-SC04. Utilizamos espectros obtenidos con el multiespectrografo GMOS del telescopio Gemini Sur. Determinamos tipos espectrales, velocidades radiales, temperaturas efectivas y gravedades superficiales empleando la tarea FXCOR de IRAF, para correlacionar los espectros estelares observados con los de la librerıa ELODIE, en combinacion con la razon Tonry-Davis para seleccionar el mejor ajuste. Un analisis de los resultados sugiere que las estrellas observadas en ESO 442- SC04 no constituyen un sistema fısico.Fil: Maia, F. F. S.. Universidade Federal do Minas Gerais; BrasilFil: Santos Jr, Joâo F. C.. Universidade Federal do Minas Gerais; BrasilFil: Corradi, W. J. B.. Universidade Federal do Minas Gerais; BrasilFil: 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 behaviour of copper anodes in aqueous thiourea-containing sulphuric acid solutions. Open circuit potentials and electrochemical kinetics

The electrochemical behaviour of copper anodes in aqueous thiourea (TU)-containing sulphuric acid was followed from open circuit potential measurements, voltammetry and rotating disk and ring-disk electrode data. The open circuit potential of copper is controlled by equilibria involving different Cu(I)–TU complex species. The thiourea electro-oxidation which yields formamidine disulphide and Cu(I)–TU complex species can be described as a process under intermediate kinetics taking place on a partially blocked copper anode. The degree of copper surface coverage and the type of predominant adsorbate depend on the concentration of thiourea and applied electric potential. Depending on the potential range adsorbates can be formed directly from either a strong TU–copper interaction or a relatively weaker formamidine disulphide interaction. The passivating layer can be related to the formation of polymer-like Cu(I)–TU layers and residues resulting both from thiourea and formamidine disulphide electro-oxidation. A previously proposed complex reaction pathway can explain the general behaviour of these systems, including adsorbate formation and the influence of the electrolyte solution constituents.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

On the Nature of the Stellar Group ESO442-SC04

We propose a definitive test on the real physical nature of ESO 442-SC04, an object which has been listed as a possible open cluster remnant (POCR) by Bica et al. (2001). In order to pursue such analysis, we carried out multi-object spectroscopy of stars in its inner area using GMOS at Gemini-South telescope. By determining their radial velocity and metallicity, in conjunction with 2MASS color-magnitude diagrams and proper motion analysis, we aim at evaluating if the stars form a physical system. Our analysis of the radial velocity data suggests that the stars are not dynamically bound, according to the large radial velocity dispersion (& 50 km/s).Proponemos un test definitivo acerca de la verdadera naturaleza fısica de ESO 442-SC04, un objeto catalogado por Bica et al. (2001) como posible remanente de un cumulo abierto. A partir del analisis de sus velocidades radiales y metalicidades -obtenidas con el multiespectrografo GMOS del telescopio Gemini Sur-, en combinacion con movimientos propios y diagramas color-magnitud 2MASS, evaluamos la posibilidad de que dichas estrellas formen un sistema fisico. Nuestro aalisis de las velocidades radiales sugiere que las estrellas no se encuentran ligadas dinamicamente, de acuerdo a su relativamente gran dispersion de velocidades (& 50km/s).Fil: Maia, F. F. S.. Universidade Federal do Minas Gerais; BrasilFil: Santos Jr, Joâo F. C.. Universidade Federal do Minas Gerais; BrasilFil: Corradi, W. J. B.. Universidade Federal do Minas Gerais; BrasilFil: 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