252 research outputs found

    Introduzione

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    The Universal Initial Mass Function In The XUV Disk of M83

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    We report deep Subaru Halpha observations of the XUV disk of M83. These new observations enable the first complete census of very young stellar clusters over the entire XUV disk. Combining Subaru and GALEX data with a stellar population synthesis model, we find that (1) the standard, but stochastically-sampled, initial mass function (IMF) is preferred over the truncated IMF, because there are low mass stellar clusters (10^{2-3}Msun) that host massive O-type stars; that (2) the standard Salpeter IMF and a simple aging effect explain the counts of FUV-bright and Halpha-bright clusters with masses >10^3Msun; and that (3) the Halpha to FUV flux ratio over the XUV disk supports the standard IMF. The Subaru Prime Focus Camera (Suprime-Cam) covers a large area even outside the XUV disk -- far beyond the detection limit of the HI gas. This enables us to statistically separate the stellar clusters in the disk from background contamination. The new data, model, and previous spectroscopic studies provide overall consistent results with respect to the internal dust extinction (Av~0.1 mag) and low metallicity (~0.2Zsun) using the dust extinction curve of SMC.Comment: 11 pages, 8 figures. Accepted for publication in Ap

    Escala de motivación para el aprendizaje en universitarios : versión abreviada

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    A avaliação da motivação para aprender é um aspecto relevante em contextos educacionais, pois a motivação pode influenciar o engajamento dos estudantes, sua aprendizagem e seu desempenho em tarefas acadêmicas. O objetivo deste estudo foi propor uma versão breve da Escala de Motivação para Aprendizagem em Universitários (EMAPRE-U Breve). A EMAPRE-U é uma escala de 28 itens que avalia três dimensões motivacionais: meta aprender, meta performance-aproximação e meta performance-evitação. Participaram do estudo 525 universitários do primeiro ano de graduação de uma universidade pública. Através de análises fatoriais exploratórias e de conteúdo dos itens chegou-se a uma versão com 15 itens. Análises fatoriais confirmatórias e de correlação com construtos relacionados forneceram evidências de validade para a medida breve, e indicaram um bom ajuste dos dados ao modelo trifatorial. Os resultados sugerem que o instrumento tem o potencial de contribuir para a avaliação da motivação para aprendizagem na educação superior, ainda que aprimoramentos possam ser feitos no futuro.The assessment of motivation to learn is a relevant aspect in educational contexts as motivation can influence student engagement, learning, and performance in academic tasks. The aim of this study was to propose a brief version of the Motivation Scale for Learning in University Students (EMAPRE-U Brief). The EMAPRE-U is a 28-item scale that assesses three motivational dimensions: the learning goal, the performance-approach goal, and the performance-avoidance goal. The study included 525 first-year undergraduate students at a public university. Through exploratory factor analysis and item content analysis, a 15-item version was developed. Confirmatory factor analysis and correlation with theoretically related constructs provided evidence of validity for the brief measure and indicated a good fit of the data to the three-factor model. The results suggest that the instrument has the potential to contribute to the assessment of motivation for learning in higher education, although improvements could be made in the future.La evaluación de la motivación para aprender es un aspecto relevante en los contextos educativos, ya que la motivación puede influir en el compromiso, aprendizaje y desempeño del estudiante en las tareas académicas. El objetivo de este estudio fue proponer una versión breve de la Escala de Motivación para el Aprendizaje en Estudiantes Universitarios (EMAPRE-U Brief). La EMAPRE-U es una escala de 28 ítems que evalúa tres dimensiones motivacionales: metas de aprendizaje, metas de aproximación al rendimiento y metas de evitación del rendimiento. El estudio incluyó a 525 estudiantes de primer año de pregrado de una universidad pública. A través del análisis factorial exploratorio y el contenido de los ítems, se llegó a una versión de 15 ítems. Los análisis factoriales confirmatorios y las correlaciones con constructos relacionados proporcionaron evidencia de validez para la versión breve, e indicaron un buen ajuste de los datos al modelo de tres factores. Los resultados sugieren que el instrumento tiene el potencial de contribuir a la evaluación de la motivación para el aprendizaje en la educación superior, aunque podrían realizarse mejoras en el futuro

    A GALEX Ultraviolet Imaging Survey of Galaxies in the Local Volume

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    We present results from a GALEX ultraviolet (UV) survey of a complete sample of 390 galaxies within ~11 Mpc of the Milky Way. The UV data are a key component of the composite Local Volume Legacy (LVL), an ultraviolet-to-infrared imaging program designed to provide an inventory of dust and star formation in nearby spiral and irregular galaxies. The ensemble dataset is an especially valuable resource for studying star formation in dwarf galaxies, which comprise over 80% of the sample. We describe the GALEX survey programs which obtained the data and provide a catalog of far-UV (~1500 Angstroms) and near-UV (~2200 Angstroms) integrated photometry. General UV properties of the sample are briefly discussed. We compute two measures of the global star formation efficiency, the SFR per unit HI gas mass and the SFR per unit stellar mass, to illustrate the significant differences that can arise in our understanding of dwarf galaxies when the FUV is used to measure the SFR instead of H-alpha. We find that dwarf galaxies may not be as drastically inefficient in coverting gas into stars as suggested by prior H-alpha studies. In this context, we also examine the UV properties of late-type dwarf galaxies that appear to be devoid of star formation because they were not detected in previous H-alpha narrowband observations. Nearly all such galaxies in our sample are detected in the FUV, and have FUV SFRs that fall below the limit where the H-alpha flux is robust to Poisson fluctuations in the formation of massive stars. The UV colors and star formation efficiencies of H-alpha-undetected, UV-bright dwarf irregulars appear to be relatively unremarkable with respect to those exhibited by the general population of star-forming galaxies.Comment: submitted to ApJS, revised per referee's comments; accepted Oct. 30 w/o further revision; 37 pages; figure 6 omitted due to size; figure available from http://users.obs.carnegiescience.edu/jlee/paper

    Search for diboson resonances in hadronic final states in 139 fb −1 of pp collisions at s = 13 TeV with the ATLAS detector

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    Abstract: Narrow resonances decaying into W W, W Z or ZZ boson pairs are searched for in 139 fb−1 of proton-proton collision data at a centre-of-mass energy of s = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider from 2015 to 2018. The diboson system is reconstructed using pairs of high transverse momentum, large-radius jets. These jets are built from a combination of calorimeter- and tracker-inputs compatible with the hadronic decay of a boosted W or Z boson, using jet mass and substructure properties. The search is performed for diboson resonances with masses greater than 1.3 TeV. No significant deviations from the background expectations are observed. Exclusion limits at the 95% confidence level are set on the production cross-section times branching ratio into dibosons for resonances in a range of theories beyond the Standard Model, with the highest excluded mass of a new gauge boson at 3.8 TeV in the context of mass-degenerate resonances that couple predominantly to gauge bosons

    Search for squarks and gluinos in final states with same-sign leptons and jets using 139 fb1^{-1} of data collected with the ATLAS detector

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    A search for supersymmetric partners of gluons and quarks is presented, involving signatures with jets and either two isolated leptons (electrons or muons) with the same electric charge, or at least three isolated leptons. A data sample of proton-proton collisions at s\sqrt{s} = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to a total integrated luminosity of 139 fb1^{-1}, is used for the search. No significant excess over the Standard Model expectation is observed. The results are interpreted in simplified supersymmetric models featuring both R-parity conservation and R-parity violation, raising the exclusion limits beyond those of previous ATLAS searches to 1600 GeV for gluino masses and 750 GeV for bottom and top squark masses in these scenarios

    Search for light long-lived neutral particles produced in pp collisions at s = 13 TeV and decaying into collimated leptons or light hadrons with the ATLAS detector

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    Abstract: Several models of physics beyond the Standard Model predict the existence of dark photons, light neutral particles decaying into collimated leptons or light hadrons. This paper presents a search for long-lived dark photons produced from the decay of a Higgs boson or a heavy scalar boson and decaying into displaced collimated Standard Model fermions. The search uses data corresponding to an integrated luminosity of 36.1 fb-1 collected in proton–proton collisions at s=13 Te recorded in 2015–2016 with the ATLAS detector at the Large Hadron Collider. The observed number of events is consistent with the expected background, and limits on the production cross section times branching fraction as a function of the proper decay length of the dark photon are reported. A cross section times branching fraction above 4 pb is excluded for a Higgs boson decaying into two dark photons for dark-photon decay lengths between 1.5 mm and 307 mm
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