Rattraper ou devancer l’Europe? Politiques françaises des énergies renouvelables et dynamiques d’européanisation

La France a échoué de façon répétée à atteindre ses objectifs européens en matière de consommation d’électricité d’origine renouvelable. Quant au rapide développement des agrocarburants, il tient d’abord au poids et à l’influence du secteur agricole domestique. Cela ne signifie pas pour autant que la construction européenne a été sans influence sur les politiques françaises de soutien aux énergies renouvelables, mais pas nécessairement sur un mode hiérarchique. Afin de rendre compte des interactions entre politiques françaises et européennes, cet article s’inscrit dans une approche de sociologie politique attentive à la diversité des pratiques et « usages de l’Europe », en explorant les dynamiques verticales et horizontales de l’européanisation. France has repeatedly failed to reach its European objectives in terms of renewable electricity consumption. As for the rapid growth of biofuels, it results mainly from the weight and influence of the domestic agriculture sector. Yet, this does not mean that the European integration process has had no influence on French renewable energy policies, although not necessarily in a top-down fashion. In order to account for the interactions between French and European policies, this paper develops an approach centered on the practices and usages of Europe, and explores vertical and horizontal dynamics of Europeanization

VDES J2325−5229 a z = 2.7 gravitationally lensed quasar discovered using morphology-independent supervised machine learning

We present the discovery and preliminary characterization of a gravitationally lensed quasar with a source redshift zs = 2.74 and image separation of 2.9 arcsec lensed by a foreground zl = 0.40 elliptical galaxy. Since optical observations of gravitationally lensed quasars showthe lens system as a superposition of multiple point sources and a foreground lensing galaxy, we have developed a morphology-independent multi-wavelength approach to the photometric selection of lensed quasar candidates based on Gaussian Mixture Models (GMM) supervised machine learning. Using this technique and gi multicolour photometric observations from the Dark Energy Survey (DES), near-IR JK photometry from the VISTA Hemisphere Survey (VHS) and WISE mid-IR photometry, we have identified a candidate system with two catalogue components with iAB = 18.61 and iAB = 20.44 comprising an elliptical galaxy and two blue point sources. Spectroscopic follow-up with NTT and the use of an archival AAT spectrum show that the point sources can be identified as a lensed quasar with an emission line redshift of z = 2.739 ± 0.003 and a foreground early-type galaxy with z = 0.400 ± 0.002.We model the system as a single isothermal ellipsoid and find the Einstein radius θE ∼ 1.47 arcsec, enclosed mass Menc ∼ 4 × 1011 M and a time delay of ∼52 d. The relatively wide separation, month scale time delay duration and high redshift make this an ideal system for constraining the expansion rate beyond a redshift of 1

Searching for dark matter annihilation in recently discovered Milky Way satellites with Fermi-LAT

We search for excess γ-ray emission coincident with the positions of confirmed and candidate Milky Way satellite galaxies using six years of data from the Fermi Large Area Telescope (LAT). Our sample of 45 stellar systems includes 28 kinematically confirmed dark-matter-dominated dwarf spheroidal galaxies (dSphs) and 17 recently discovered systems that have photometric characteristics consistent with the population of known dSphs. For each of these targets, the relative predicted γ-ray flux due to dark matter annihilation is taken from kinematic analysis if available, and estimated from a distance-based scaling relation otherwise, assuming that the stellar systems are DM-dominated dSphs. LAT data coincident with four of the newly discovered targets show a slight preference (each ~2σ local) for γ-ray emission in excess of the background. However, the ensemble of derived γ-ray flux upper limits for individual targets is consistent with the expectation from analyzing random blank-sky regions, and a combined analysis of the population of stellar systems yields no globally significant excess (global significance 1 TeV and mDM,t+t-> 70 GeV) and weakening by a factor of ~1.5 at lower masses relative to previously observed limits

Host galaxy identification for supernova surveys

Host galaxy identification is a crucial step for modern supernova (SN) surveys such as the Dark Energy Survey (DES) and the Large Synoptic Survey Telescope (LSST), which will discover SNe by the thousands. Spectroscopic resources are limited, so in the absence of real-time SN spectra these surveys must rely on host galaxy spectra to obtain accurate redshifts for the Hubble diagram and to improve photometric classification of SNe. In addition, SN luminosities are known to correlate with host-galaxy properties. Therefore, reliable identification of host galaxies is essential for cosmology and SN science. We simulate SN events and their locations within their host galaxies to develop and test methods for matching SNe to their hosts. We use both real and simulated galaxy catalog data from the Advanced Camera for Surveys General Catalog and MICECATv2.0, respectively. We also incorporate "hostless" SNe residing in undetected faint hosts into our analysis, with an assumed hostless rate of 5%. Our fully automated algorithm is run on catalog data and matches SNe to their hosts with 91% accuracy. We find that including a machine learning component, run after the initial matching algorithm, improves the accuracy (purity) of the matching to 97% with a 2% cost in efficiency (true positive rate). Although the exact results are dependent on the details of the survey and the galaxy catalogs used, the method of identifying host galaxies we outline here can be applied to any transient survey

The Dark Energy Survey : more than dark energy – an overview

This overview paper describes the legacy prospect and discovery potential of the Dark Energy Survey (DES) beyond cosmological studies, illustrating it with examples from the DES early data. DES is using a wide-field camera (DECam) on the 4 m Blanco Telescope in Chile to image 5000 sq deg of the sky in five filters (grizY). By its completion, the survey is expected to have generated a catalogue of 300 million galaxies with photometric redshifts and 100 million stars. In addition, a time-domain survey search over 27 sq deg is expected to yield a sample of thousands of Type Ia supernovae and other transients. The main goals of DES are to characterize dark energy and dark matter, and to test alternative models of gravity; these goals will be pursued by studying large-scale structure, cluster counts, weak gravitational lensing and Type Ia supernovae. However, DES also provides a rich data set which allows us to study many other aspects of astrophysics. In this paper, we focus on additional science with DES, emphasizing areas where the survey makes a difference with respect to other current surveys. The paper illustrates, using early data (from ‘Science Verification’, and from the first, second and third seasons of observations), what DES can tell us about the Solar system, the Milky Way, galaxy evolution, quasars and other topics. In addition, we show that if the cosmological model is assumed to be +cold dark matter, then important astrophysics can be deduced from the primary DES probes. Highlights from DES early data include the discovery of 34 trans-Neptunian objects, 17 dwarf satellites of the Milky Way, one published z > 6 quasar (and more confirmed) and two published superluminous supernovae (and more confirmed)

11. L’intégration des énergies renouvelables aux politiques énergétiques de l’Allemagne et de la France : idées, institutions et stratégies politiques

Les politiques énergétiques, par leur technicité, leurs configurations d’acteurs ou les représentations qu’elles véhiculent, semblent davantage être enclines à l’inertie qu’au changement. Il nous paraît alors d’autant plus intéressant de tenter d’expliquer comment ces politiques réagissent à de nouvelles dynamiques et notamment au développement des énergies renouvelables. Depuis quelques années, ces nouvelles sources d’énergie occupent une place grandissante sur la scène médiatique et les age..

L'Union européenne et les instruments de politique environnementale

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Les énergies renouvelables et l'électricité. À propos d’un conflit entre un secteur et une alternative de politique publique

International audienceAlors que les énergies renouvelables apparaissent souvent comme un sujet consensuel, cet article souligne que leur développement s’inscrit au départ dans une dynamique conflictuelle, puisqu’il vise à transformer radicalement les systèmes énergétiques conventionnels et tout particulièrement celui de l’électricité. Conceptualisant les énergies renouvelables comme une « alternative de politique publique », l’article en dégage les principaux points de conflit avec le secteur électrique. Il montre cependant que cette alternative, loin de parvenir à déstabiliser les logiques sectorielles, semble plutôt avoir été elle-même transformée, voire absorbée par le secteur

Complying with, Resisting or Using Europe? Explaining the Uneven and Diffuse Europeanization of French Renewable Electricity and Biofuels Policies

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