The Next Generation Virgo Cluster Survey - Infrared (NGVS-IR): I. A new Near-UV/Optical/Near-IR Globular Cluster selection tool

The NGVS-IR project (Next Generation Virgo Survey - Infrared) is a contiguous near-infrared imaging survey of the Virgo cluster of galaxies. It complements the optical wide-field survey of Virgo (NGVS). The current state of NGVS-IR consists of Ks-band imaging of 4 deg^2 centered on M87, and J and Ks-band imaging of 16 deg^2 covering the region between M49 and M87. In this paper, we present the observations of the central 4 deg^2 centered on Virgo's core region. The data were acquired with WIRCam on the Canada-France-Hawaii Telescope and the total integration time was 41 hours distributed in 34 contiguous tiles. A survey-specific strategy was designed to account for extended galaxies while still measuring accurate sky brightness within the survey area. The average 5\sigma limiting magnitude is Ks=24.4 AB mag and the 50% completeness limit is Ks=23.75 AB mag for point source detections, when using only images with better than 0.7" seeing (median seeing 0.54"). Star clusters are marginally resolved in these image stacks, and Virgo galaxies with \mu_Ks=24.4 AB mag arcsec^-2 are detected. Combining the Ks data with optical and ultraviolet data, we build the uiK color-color diagram which allows a very clean color-based selection of globular clusters in Virgo. This diagnostic plot will provide reliable globular cluster candidates for spectroscopic follow-up campaigns needed to continue the exploration of Virgo's photometric and kinematic sub-structures, and will help the design of future searches for globular clusters in extragalactic systems. Equipped with this powerful new tool, future NGVS-IR investigations based on the uiK diagram will address the mapping and analysis of extended structures and compact stellar systems in and around Virgo galaxies.Comment: 23 pages, 18 figures. Accepted for publication in ApJ

Gestes et bandes dessinées

avec le soutien de l'université de Poitiers et le Réseau Régional de Recherche Nouvelle Aquitaine en bandes dessinéesInternational audienceSelon Thierry Smolderen, scénariste distingué par plusieurs prix, « la bande dessinée joue à fond de la cinéspective ». En effet, « une planche de BD suscite une sorte de fondu enchaîné ». De la sorte, on comprend mieux comment certains gestes d'action, courir, sauter, trembler, danser, tomber, glissent de cases en cases sans altérer la lecture en créant un phénomène de continuité. Certes, dans une bande dessinée « classique », divisée en plusieurs cases bien séparées par une « gouttière », chaque vignette pourrait être une « image plate » captant l'attention sur elle seule, et arrêtant la lecture. Mais généralement, il n'en est rien, et la magie du 9e art peut s'exercer.Les gestes peuvent être isolés, mais ils peuvent aussi être pensés globalement. Ils forment alors un langage appelé par commodité une gestuelle. Pour cette gestuelle, un geste peut remplacer un énoncé, souligner un mot, contredire aussi le propos formulé par un personnage ou contenu dans une bulle. Les gestes peuvent exprimer la surprise, la colère, l'impuissance, la tendresse, la joie... De la sorte, tout un répertoire de gestes et d'expressions se déploie, certains inscrits dans un contexte historique ou sociétal.Le présent ouvrage est pluridisciplinaire, insistant sur le fait qu'il n'existe pas une méthodologie unique mais des lectures variées « naïves ou savantes », pour s'attacher aux expressions gestuelles, aux gestes porteurs d'émotions et de sensations, aux gestes agressifs ou lents et délicats

Les êtres contrefaits: Corps difformes et corps grotesques dans la bande dessinée

International audienceLa bande dessinée offre un vaste spectre de corps dangereux et de corps ridicules, les premiers incarnant un risque majeur, les seconds exprimant le rire ambigu, car ces corps difformes abritent l’émotion ambivalente du grotesque. Le récit graphique explore les potentialités plastiques du corps, il interroge ses valeurs imaginaires, il invente des contrefaçons qui modifient le regard que nous portons sur les formes corporelles, leurs limites et leurs significations

Massimo Salvatores: integral experiments and their use for the validation of nuclear data and the neutronic design of advanced nuclear systems

Among the many domains of reactor physics on which Massimo Salvatores gave his considerable contributions, he was particularly passionate about integral experiments. In this paper, we make a review of selected experimental campaigns among the numerous ones he has promoted, conceived, designed, directed, or analyzed. They have been regrouped in a temporal sequence corresponding to the different periods of Massimo's career, which exceeded 50 years. When possible, for each of the experiments we provide a brief description, the goal for which it was conceived and carried out, and the practical impact on validation and design improvement. Finally, the conclusions offer thoughts and suggestions for the future of the integral experiments and a possible way of honoring the invaluable legacy that Massimo Salvatores has left to us

Reactor Physics Experiments on Zero Power Reactors

International audienc

Monte Carlo MSM correction factors for control rod worth estimates in subcritical and near-critical fast neutron reactors

The GUINEVERE project was launched in 2006, within the 6th Euratom Framework Program IP-EUROTRANS, in order to study the feasibility of transmutation in Accelerator Driven subcritical Systems (ADS). This zero-power facility hosted at the SCK·CEN site in Mol (Belgium) couples the fast subcritical lead reactor VENUS-F with an external neutron source provided by interaction of deuterons delivered by the GENEPI-3C accelerator and a tritiated target located at the reactor core center. In order to test on-line subcriticality monitoring techniques, the reactivity of all the VENUS-F configurations used must be known beforehand to serve as benchmark values. That is why the Modified Source Multiplication Method (MSM) is under consideration to estimate the reactivity worth of the control rods when the reactor is largely subcritical as well as near-critical. The MSM method appears to be a technique well adapted to measure control rod worth over a large range of subcriticality levels. The MSM factors which are required to account for spatial effects in the reactor can be successfully calculated using a Monte Carlo neutron transport code

Extended MSM method to estimate the reactivity of a sub-critical core driven by an accelerator based neutron source

ISBN 978-1-5272-6447-2International audienceThe Modified Source Multiplication method is used to determine an unknown reactivity level of a reactor from a known one if one has access to the detector counting for both levels when the reactor is fed by a constant neutron source like an Am-Be source. When available, an accelerator driven source, in continuous mode, can be useful as its intensity can be tunable and then adapted to the experimental conditions. However, in that case, the MSM technique must be extended to account for an external source whose intensity, energy and angular distributions can vary from one measurement to another. In this paper, this Modified Multi-Source Multiplication (MMSM) method is applied to measurements done during the FREYA project in the GUINEVERE facility, operated with the GENEPI-3C accelerator providing a mixture of (D,T) and (D,D) neutrons. The monitoring of these sources through the detection of the associated charged particles allows the calculation of the MMSM factors and the estimate of the reactivity values. The results are compared in different configurations with the reactivity obtained with an Am-Be source or in dynamic measurements performed with GENEPI-3C. Their excellent agreement shows the possibility of using such accelerator-based neutron sources for MSM measurements when they are correctly monitored. This is of great interest for deep sub-critical level characterization for which detector count rates per source neutrons might be low