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

Le Chiese riformate nel XVII e XVIII secolo

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

Optical-NIR spectroscopy of the puzzling gamma-ray source 3FGL 1603.9-4903/PMN J1603-4904 with X-shooter

The Fermi/LAT instrument has detected about two thousands Extragalactic High Energy (E > 100 MeV) gamma-ray sources. One of the brightest is 3FGL 1603.9-4903, associated to the radio source PMN J1603-4904. Its nature is not yet clear, it could be either a very peculiar BL Lac or a CSO (Compact Symmetric Object) radio source, considered as the early stage of a radio galaxy. The latter, if confirmed, would be the first detection in gamma-rays for this class of objects. Recently a redshift z=0.18 +/- 0.01 has been claimed on the basis of the detection of a single X-ray line at 5.44 +/- 0.05 keV interpreted as a 6.4 keV (rest frame) fluorescent line. We aim to investigate the nature of 3FGL 1603.9-4903/PMN J1603-4904 using optical to NIR spectroscopy. We observed PMN J1603-4904 with the UV-NIR VLT/X-shooter spectrograph for two hours. We extracted spectra in the VIS and NIR range that we calibrated in flux and corrected for telluric absorption and we systematically searched for absorption and emission features. The source was detected starting from ~6300 Ang down to 24000 Ang with an intensity comparable to the one of its 2MASS counterpart and a mostly featureless spectrum. The continuum lacks absorption features and thus is non-stellar in origin and likely non-thermal. On top of this spectrum we detected three emission lines that we interpret as the Halpha-[NII] complex, the [SII] 6716,6731 doublet and the [SIII] 9530 line, obtaining a redshift estimate of z= 0.2321 +/- 0.0004. The equivalent width of the Halpha-[NII] complex implies that PMN J1603-4904 does not follow the observational definition of BL Lac, the line ratios suggest that a LINER/Seyfert nucleus is powering the emission. This new redshift measurement implies that the X-ray line previously detected should be interpreted as a 6.7 keV line which is very peculiar.Comment: Published in Astronomy and Astrophysic