An innovative blazar classification based on radio jet kinematics

Blazars are usually classified following their synchrotron peak frequency ($\nu F(\nu)$ scale) as high, intermediate, low frequency peaked BL Lacs (HBLs, IBLs, LBLs), and flat spectrum radio quasars (FSRQs), or, according to their radio morphology at large scale, FR~I or FR~II. However, the diversity of blazars is such that these classes seem insufficient to chart the specific properties of each source. We propose to classify a wide sample of blazars following the kinematic features of their radio jets seen in very long baseline interferometry (VLBI). For this purpose we use public data from the MOJAVE collaboration in which we select a sample of blazars with known redshift and sufficient monitoring to constrain apparent velocities. We selected 161 blazars from a sample of 200 sources. We identify three distinct classes of VLBI jets depending on radio knot kinematics: class I with quasi-stationary knots, class II with knots in relativistic motion from the radio core, and class I/II, intermediate, showing quasi-stationary knots at the jet base and relativistic motions downstream. A notable result is the good overlap of this kinematic classification with the usual spectral classification; class I corresponds to HBLs, class II to FSRQs, and class I/II to IBLs/LBLs. We deepen this study by characterizing the physical parameters of jets from VLBI radio data. Hence we focus on the singular case of the class I/II by the study of the blazar BL Lac itself. Finally we show how the interpretation that radio knots are recollimation shocks is fully appropriate to describe the characteristics of these three classes.Comment: 12 pages, 13 figures, accepted by A&

Régulation multidimensionnelle d’un monopole polluant et majorité politique aléatoire

Le contrat de régulation optimale d'un monopole avec deux paramètres d'information privée et d'antisélection (productivité et niveau d'émissions polluantes) est caractérisé. Dans ce contexte de screening bidimensionnel, un aspect d'économie politique est introduit en considérant l'objectif du régulateur comme le résultat d'un processus électoral majoritaire. En fonction du régime politique, deux types de contrats apparaissent : l'un est séparateur, l'autre mélangeant. Leur occurrence dépend de la confrontation des incitations sociales et privées qui résultent de l'arbitrage effectué par le régulateur entre l'extraction de la rente informationnelle et le gain d'efficacité allocative.Régulation de monopole, Screening multidimensionnel, Economie politique

Spectroscopy of High Energy BL Lac Objects with X-shooter on the VLT

Context. The study of BL Lac objects (BLL) detected in gamma-rays gives insights on the acceleration mechanisms in play in such systems and is also a valuable tool to constrain the density of the extragalactic background light. As their spectra are dominated by the non-thermal emission of the jet and the spectral features are weak and narrow in the optical domain, measuring their redshift is challenging. However such a measure is fundamental as it allows a firm determination of the distance and luminosity of the source, and therefore a consistent model of its emission. Aims. Measurement of the redshift of BLL detected in gamma-rays and determination of global properties of their host galaxies. Methods. We observed a sample of eight BLL (KUV 00311-1938, PKS 0447-439, PKS 0301-243, BZB J0238-3116, BZB J0543-5532, BZB J0505+0415, BZB J0816-1311 and RBS 334) with the X-shooter spectrograph installed at the ESO Very Large Telescope in order to take advantage of its unprecedented wavelength coverage and of its resolution about 5 times higher than generally used in such studies. We extracted UVB to NIR spectra that we then corrected for telluric absorption and calibrated in flux. We systematically searched for spectral features. When possible, we determined the contribution of the host galaxy to the overall emission. Results. Of the eight BLL, we measured the redshift of five of them and determined lower limits for two through the detection of intervening systems. All seven of these objects have redshifts greater than 0.2. In two cases, we refuted redshift values reported in other publications. Through careful modelling, we determined the magnitude of the host galaxies. In two cases, the detection of emission lines allowed to provide hints on the overall properties of the gas in the host galaxies.Comment: 19 pages, 10 figures, 7 tables, in press on A&

Prospect on intergalactic magnetic field measurements with gamma-ray instruments

Observing high-energy gamma-rays from Active Galactic Nuclei (AGN) offers a unique potential to probe extremely tiny values of the intergalactic magnetic field (IGMF), a long standing question of astrophysics, astroparticle physics and cosmology. Very high energy (VHE) photons from blazars propagating along the line of sight interact with the extragalactic background light (EBL) and produce e + e − pairs. Through inverse-Compton interaction, mainly on the cosmic microwave background (CMB), these pairs generate secondary GeV-TeV components accompanying the primary VHE signal. Such secondary components would be detected in the gamma-ray range as delayed "pair echos” for very weak IGMF (B 10−16 G). Coordinated observations with space (i.e. Fermi) and ground-based gamma-ray instruments, such as the present Cherenkov experiments H.E.S.S., MAGIC and VERITAS, the future Cherenkov Telescope Array (CTA) Observatory, and the wide-field detectors such as HAWC and LHAASO, should allow to analyze and finally detect such echos, extended emission or pair halos, and to further characterize the IGM

Régulation multidimensionnelle d'un monopole polluant et majorité politique aléatoire

We characterize the optimal regulation contract of a monopoly with two private information parameters of adverse selection (productivity and polluting emissions levels). In this bidimensional screening framework, we introduce a political economy approach, considering that the social objective of the regulator depends on the outcome of a majority vote. Two main types of contracts appear : the first is a separating one, the second is a pooling or bunching one. Their occurrence depends on the conflict between the private and social incentives, which are the result of the regulator?s trade-o. between informational rents extraction and allocative efficiency.

Expériences de conversion

Consacré à des expériences de conversions, ce numéro des Cahiers  donne à voir le vécu de la conversion et ses liens avec le contexte. À  travers l’étude de Raymond Mentzer, nous découvrons l’influence exercée par le « milieu » sur le processus de conversion, au XVII ème siècle.  Ce texte met en lumière les facteurs qui ont pu jouer un rôle, parfois non négligeable,  sur la conversion,  et les stratégies auxquelles elle obéissait. Didier Boisson s’intéresse à l’accueil, qui était réservé aux catholiques, membres du Clergé, convertis au protestantisme,  par les États protestants et les communautés françaises du Refuge. C’est la méfiance qui prédomine, face à ces conversions dont on mettait en doute  la sincérité. Enfin, le dernier texte, écrit par Hélène Baillot, est consacré à la conversion des peuples dits « non-civilisés », telle qu’elle est analysée, interprétée, dans une vision psycho-anthropologique,  par un intellectuel protestant, théologien, Raoul Allier (1862-1939)  à partir des écrits missionnaires

Gamma radiation from active galactic nuclei observed at very high energies with H.E.S.S. : multiwavelength studies and radiative modeling

PARIS-Observatoire (751142302) / SudocSudocFranceF

SSC Scenario for Tev Emission from Non-Blazar AGNs

International audienceM 87 is the first extragalactic source detected in the TeV gamma-ray domain that is not a blazar, its large scale jet not being aligned to the line of sight. We present here a multi-blob synchrotron self-Compton model accounting explicitly for large viewing angles and moderate Lorentz factors as inferred from magnetohydrodynamic simulations of jet formation, motivated by the detection of M 87 at very high energies (VHE; E > 100 GeV). Predictions are presented for the very high-energy emission of active galactic nuclei with extended optical or X-ray jet, which could be misaligned blazars but still show some moderate beaming. We include predictions for 3C 273, Cen A and PKS 0521-36