Linking radio and gamma ray emission in Ap Librae

Ap Lib is one of the rare Low Synchrotron Peaked blazars detected so far at TeV energies. This type of source is not properly modelled by standard one-zone leptonic Synchrotron-self-Compton (SSC) emission scenarios. The aim of this paper is to study the relevance of additional components which should naturally occur in a SSC scenario for a better understanding of the emission mechanisms, especially at very high energies (VHE). Methods. We use simultaneous data from a multi-wavelength campaign of Planck, Swift-UVOT and Swift-XRT telescopes carried out in February 2010, as well as quasi-simultaneous data of WISE, Fermi and H.E.S.S. taken in 2010. The multi-lambda emission of Ap Lib is modelled by a blob-in-jet SSC scenario including the contribution of the base of the VLBI extended jet, the radiative blob-jet interaction, the accretion disk and its associated external photon field. We show that signatures of a strong parsec-scale jet and of an accretion disk emission are present in the SED. We can link the observationnal VLBI jet features from MOJAVE to parameters expected for a VHE emitting blob accelerated near the jet base. The VHE emission appears to be dominated by the inverse-Compton effect of the blob relativistic electrons interacting with the jet synchrotron radiation. In such scenario Ap Lib appears as an intermediate source between BL Lac objects and Flat Spectrum Radio Quasars. Ap Lib could be a bright representative of a specific class of blazars, in which the parsec-scale jet luminosity is no more negligible compared to the blob and contributes to the high energy emission via inverse Compton processes.Comment: 12 pages, 7 figures, Accepted for publication in A&

La survie religieuse des communautés protestantes du centre de la France et du Bassin parisien de la Révocation de l’édit de Nantes à l’édit de tolérance (1685-1787)

Le protestantisme du Nord de la France aux XVIIe et XVIIIe siècles se caractérise par sa grande dispersion ainsi que par sa très faible importance numérique. Pourtant, malgré le choc de la Révocation, les conversions et les départs, des communautés vivantes traversent le dernier siècle de l\u27Ancien Régime. Du point de vue religieux, des signes montrent que, tout au long de cette période, les protestants conservent une foi vivante: des assemblées se tiennent dès les premiers mois de l\u27édit de Fontainebleau, des «nouveaux convertis» attaquent le dogme et la discipline de l\u27Église catholique, ou refusent l\u27intervention du curé dans les grands moments de leur vie. Les formes de résistance et les rythmes de persécution sont cependant variables d\u27une communauté, voire d\u27une époque à l\u27autre. Certaines églises, en particulier celles de Picardie, profitent de la proximité de la frontière avec les Pays-Bas autrichiens, ainsi que de la présence des pasteurs qui accompagnent les garnisons de la Barrière. D\u27autres, plus isolées, trouvent dans la capitale un lieu d\u27accueil et leurs membres fréquentent les chapelles d\u27ambassades des pays protestants. Ce n\u27est pourtant que tardivement, et non sans mal, que les structures ecclésiastiques se réorganisent, à partir du milieu des années 1760. L\u27édit de tolérance permet à ces communautés affaiblies démographiquement de reparaître au grand jour, là où elles ont survécu

Host galaxies of AGN

The relationship of an AGN to its host galaxy is a crucial question in the study of galaxy evolution. We perform stellar population synthesis in the central regions of galaxies of different activity levels. A large number of stellar features are measured both in the optical and near-infrared. We find the nuclear stellar population to be related to the level of activity. These differences are no more conspicuous further away in the bulge of the galaxy

Shocks in relativistic transverse stratified jets, a new paradigm for radio-loud AGN

The transverse stratification of active galactic nuclei (AGN) jets is suggested by observations and theoretical arguments, as a consequence of intrinsic properties of the central engine (accretion disc + black hole) and external medium. On the other hand, the one-component jet approaches are heavily challenged by the various observed properties of plasmoids in radio jets (knots), often associated with internal shocks. Given that such a transverse stratification plays an important role on the jets acceleration, stability, and interaction with the external medium, it should also induce internal shocks with various strengths and configurations, able to describe the observed knots behaviours. By establishing a relation between the transverse stratification of the jets, the internal shock properties, and the multiple observed AGN jet morphologies and behaviours, our aim is to provide a consistent global scheme of the various AGN jet structures. Working on a large sample of AGN radio jets monitored in very long baseline interferometry (VLBI) by the MOJAVE collaboration, we determined the consistency of a systematic association of the multiple knots with successive re-collimation shocks. We then investigated the re-collimation shock formation and the influence of different transverse stratified structures by parametrically exploring the two relativistic outflow components with the specific relativistic hydrodynamic (SRHD) code AMRVAC. We were able to link the different spectral classes of AGN with specific stratified jet characteristics, in good accordance with their VLBI radio properties and their accretion regimes.Comment: 16 pages, 12 figures, accepted for publication in A&

H.E.S.S. discovery of very-high-energy gamma-ray emission of PKS 1440-389

Blazars are the most abundant class of known extragalactic very-high-energy (VHE, E>100 GeV) gamma-ray sources. However, one of the biggest difficulties in investigating their VHE emission resides in their limited number, since less than 60 of them are known by now. In this contribution we report on H.E.S.S. observations of the BL Lac object PKS 1440-389. This source has been selected as target for H.E.S.S. based on its high-energy gamma-ray properties measured by Fermi-LAT. The extrapolation of this bright, hard-spectrum gamma-ray blazar into the VHE regime made a detection on a relatively short time scale very likely, despite its uncertain redshift. H.E.S.S. observations were carried out with the 4-telescope array from February to May 2012 and resulted in a clear detection of the source. Contemporaneous multi-wavelength data are used to construct the spectral energy distribution of PKS 1440-389 which can be described by a simple one-zone synchrotron-self Compton model.Comment: In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherland

Inertial waves and modes excited by the libration of a rotating cube

We report experimental measurements of the flow in a cubic container submitted to a longitudinal libration, i.e. a rotation modulated in time. Velocity fields in a vertical and a horizontal plane are measured in the librating frame using a corotating particle image velocimetry system. When the libration frequency $\sigma_0$ is smaller than twice the mean rotation rate $\Omega_0$, inertial waves can propagate in the interior of the fluid. At arbitrary excitation frequencies $\sigma_0<2\Omega_0$, the oscillating flow shows two contributions: (i) a basic flow induced by the libration motion, and (ii) inertial wave beams propagating obliquely upward and downward from the horizontal edges of the cube. In addition to these two contributions, inertial modes may also be excited at some specific resonant frequencies. We characterize in particular the resonance of the mode of lowest order compatible with the symmetries of the forcing, noted [2,1,+]. By comparing the measured flow fields to the expected inviscid inertial modes computed numerically [L.R.M. Maas, Fluid Dyn. Res. \textbf{33}, 373 (2003)], we show that only a subset of inertial modes, matching the symmetries of the forcing, can be excited by the libration.Comment: Phys. Fluids (in press

Les Eglises réformées aux XVIIe et XVIIIe siècles

Entre la signature de l’édit de Nantes par Henri IV le 30 avril 1598 et les débuts de la Révolution française, le calvinisme français a connu deux principales phases. Jusqu’en 1685, il a une existence légale, même si les persécutions sont nombreuses et l’exercice du culte progressivement limité. L’édit de Fontainebleau de 1685 révoque l’édit de Nantes et interdit désormais officiellement le culte réformé jusqu’à la Révolution : c’est sous le terme de Désert que les protestants français désignent cette période. Malgré la poursuite de la répression, les Églises réformées réussissent à se réorganiser au cours du XVIIIe siècle. À partir des années 1760, le pouvoir se voit progressivement contraint de tolérer cette minorité religieuse. En raison de ces conditions politiques, le calvinisme français a connu au cours de ces deux siècles de profondes mutations

Impacts des rejets urbains de temps de pluie (RUTP) sur les milieux aquatiques : État des connaissances

En milieu urbain, les flux générés par la pluie peuvent transporter vers les hydrosystèmes une partie des éléments polluants accumulés par temps sec et issus des diverses activités humaines. Ces flux polluants sont qualifiés de « rejets urbains par temps de pluie » (RUTP). Les études menées depuis les années 1960 ont permis d’identifier le problème en évaluant l’origine des polluants, les ordres de grandeur des concentrations et les flux émis. Les RUTP présentent un caractère épisodique, mais peuvent avoir des effets de nature chronique, liés à la répétition des phénomènes. Ils peuvent altérer les différentes composantes des milieux récepteurs : composantes physiques (e.g. modification des écoulements, de la morphodynamique), chimiques (e.g. apports de matières en suspension, fertilisants, micropolluants), biologiques (e.g. sélection des espèces, toxicité, bio-accumulation) et l’hydrosystème dans sa globalité (e.g. eutrophisation). L’intégration d’une caractérisation biologique dans l’évaluation des impacts est reconnue depuis peu, et il existe relativement peu de travaux prenant en compte cette composante. La complexité des rejets (e.g. caractère intermittent, variabilité spatio-temporelle) et la diversité des milieux récepteurs font qu’il est difficile de dresser un bilan exact des impacts. Une approche intégrée, ou holistique, est aujourd’hui préconisée prenant en compte : des descripteurs physico-chimiques, des critères de qualité du milieu (eau et sédiments), de l’habitat, du régime hydraulique, des communautés biologiques autochtones, et des données toxicologiques. Toutefois, une telle approche est difficile à mettre en oeuvre et les travaux s’appuient généralement sur des approches plus simples : études de laboratoire ou de terrain ou combinant les deux.Urbanization greatly disturbs different ecosystems and particularly affects aquatic ecosystems during wet weather. Runoff can transport some of the pollutants accumulated during dry weather towards aquatic ecosystems along with the waste produced by numerous human activities (transport, industry, etc.). These flows of pollution, commonly called «urban wet weather flows», not only affect the physical, chemical and biological properties of receiving aquatic systems, but also modify the intended use of the water. The need to provide a solution to this problem explains the current increase in the number of studies devoted to the environmental impact of urban storm water.Urban wet weather flow studies began in the 1960’s and have permitted the assessment of the sources of pollutants, the order of magnitude of their concentrations and their loads produced. Urban storm-water pollutants are numerous and are of various origins: sewer system cleansing (scoured particles deposited during dry weather); rain wash-out of atmospheric gases and dusts (nitrogen oxides, carbon monoxide, sulphur dioxide, hydrocarbon vapours, trace metals, aerosols, etc.); rainfall on roofs (copper, zinc, lead); and rain runoff from urban areas and waterproofed surfaces, which are covered with particles accumulated during dry weather. These particles have several sources: cars (hydrocarbons, nitrogen oxides, lead, rubber, zinc, cadmium, copper, titanium, chromium, aluminium, etc.); roads (cement and tar, paint used for road markings, sand and chemical de-icers, detergents, surfactants, etc.); industry (organic matter and organic micro-pollutants); animals (manure as a source of organic matter and bacterial and viral contaminations); solid wastes (plastic, various metals, papers, etc.); and plants (more or less easily biodegradable organic matter, nitrogen, phosphate and pesticide discharges). It is very difficult to define the composition of a standard urban wet weather flow, since the concentrations and loads of pollutants vary considerably according to the type of sewer network (combined, storm-water, etc.), the origin of the water (rainfall, road runoff, settling and infiltration tanks, sewer overflows, etc.), and, of course, the characteristics of the watershed (land use, etc.) and the prevailing weather