We study the interaction of relativistic jets with their environment, using 3-dimen- sional relativistic particle-in-cell simulations for two cases of jet composition: (i) electron-proton (e− − p+) and (ii) electron-positron (e±) plasmas containing helical magnetic fields. We have performed simulations of “global” jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities such as the Weibel instability, the kinetic Kelvin-Helmholtz instability and the Mushroom instability. We have found that these kinetic instabilities are suppressed and new types of instabilities can grow. For the e− − p+ jet, a recollimation-like instability occurs and jet electrons are strongly perturbed, whereas for the e± jet, a recollimation-like instability occurs at early times followed by kinetic instability and the general structure is similar to a simulation without a helical magnetic field. We plan to perform further simulations using much larger systems to confirm these new findings.

We investigated particle acceleration and shock structure associated with an unmagnetizedrelativistic jet propagating into an unmagnetized plasma. Strong magnetic fields generatedin the trailing shock contribute to the electrons transverse deflection and acceleration.We have calculated, self-consistently, the radiation from electrons accelerated in theseturbulent magnetic fields. We found that the synthetic spectra depend on the bulk Lorentzfactor of the jet, its temperature and strength of the generated magnetic fields. We havealso investigated accelerated electrons in strong magnetic fields generated by kineticshear (Kelvin-Helmholtz) instabilities. The calculated properties of the emergingradiation will guide our understanding of the complex time evolution and/or spectralstructure in gamma-ray bursts, relativistic jets in general, and supernova remnants.

Recent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs in the shocked regions. Simulations show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields and for particle acceleration. These magnetic fields contribute to the electron's transverse deflection behind the shock. The “jitter” radiation from deflected electrons in turbulent magnetic fields has properties different from synchrotron radiation calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure of gamma-ray bursts, relativistic jets in general, and supernova remnants. In order to calculate radiation from first principles and go beyond the standard synchrotron model, we have used PIC simulations. We present synthetic spectra to compare with the spectra obtained from Fermi observations.

Recent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs in the shocked regions. Simulations show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields and for particle acceleration. These magnetic fields contribute to the electron's transverse deflection behind the shock. The “jitter” radiation from deflected electrons in turbulent magnetic fields has different properties from synchrotron radiation calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure of gamma-ray bursts, relativistic jets in general, and supernova remnants. In order to calculate radiation from first principles and go beyond the standard synchrotron model, we have used PIC simulations. We will present detailed spectra for conditions relevant to various astrophysical sites of collisionless shock formation. In particular we will discuss application to GRBs and SNRs.

A confocal x-ray fluorescence microscope was built at the Cornell High Energy Synchrotron Source (CHESS) to determine the composition of buried paint layers that range from 10–80 μm thick in paintings. The microscope consists of a borosilicate monocapillary optic to focus the incident beam and a borosilicate polycapillary lens to collect the fluorescent x-rays. The overlap of the two focal regions is several tens of microns in extent, and defines the active, or confocal, volume of the microscope. The capabilities of the technique were tested using acrylic paint films with distinct layers brushed onto glass slides and a twentieth century oil painting on canvas. The position and thickness of individual layers were extracted from their fluorescence profiles by fitting to a simple, semi-empirical model.

We present the analysis of emission line spectra of AGNs andstarbursts with the help of models coupling shocks and photoionizationby AGNs and by massive stars. We show how shocks and photoionizationby the central source have to coexist in AGNs in order to reproducethe observed emission line ratios. We also show how stellar photoionizationmodels can be reconciled with the values of the [OI]/Hα and[SII]/Hα ratios observed in starbursts, without requiring an additionalionizing source such as shocks.

Using integral field spectroscopy, we detected the broad featuresof massive Wolf-Rayet stars in the core of three Seyfert galaxies.The observed high value of the WR/O number ratio is a clear signatureof a young and powerful starburst. The star-forming regions are distributedin an arc/ring-like structure around the AGN, at a distanceof about 200 pc. These are the first spatially-resolved detections ofmassive starbursts so close of an AGN.

Adaptive Optics Systems are now routinely operated on several4 meter class telescopes, allowing to achieve angular resolutionsdown to 70 msec in the near-infrared. Although these Systems have excellentperformances, their use for exploring the physics and structureof AGN is still limited for the following reasons: the limiting magnitudeof the wavefront sensor is too high, the sensitivity of infrareddetectors does not give access to medium/high spectral resolution spectroscopyand the angular resolution achieved does not always fit theapparent size of the physical components responsible for emission featuresclose to the central engine. The new generation of 8 — 10 m classtelescopes bring improvements in this matter. However, some interestingresults have been obtained so far with Adonis, the ESO La Sillaadaptive optics System on the 3.60 meter telescope, in the investigationof AGN structure. In particular, a prominent structure has beendetected in the central arcsec core of NGC 1068, which might featurethe dusty/molecular torus expected on theoretical grounds.

The dynamics of a massive binary System in a galactic nucleus are presented.These are the first results from simulations applying a hybrid "self consistent field"(SCF) 1 and direct Aarseth N body integrator (NBODY6) 2, which synthesisesthe advantages of the direct force calculation with the efficiency of the field method.The code is aimed for use on parallel architectures and is therefore applicablefor collisional N-body integrations with extraordinarily large particle numbers(> 105). It opens the perspective to simulate the dynamics of globular clusters withrealistic collisional relaxation, as well as stellar Systems surrounding a supermassiveblack hole in galactic nuclei.

The main characteristics of the average spectrum of radioquiet AGN in the UV and X-ray range are reviewed, and the emissionmechanisms are discussed in the framework of accretion disk models,in particular the "irradiated cold relativistic disk". It is shown thatsome problems arise in confronting the predictions of the model to theobservations. We propose an alternative model in terms of a hot disksurrounded by a cold Compton thick medium. Finally we mentionproblems with remote regions of the accretion disk.

The modclling of plasma outfiows from central gravitatingobjects such as AGN is bricfly discussed via analytic examples in thecontext of ideal MHD. The exact solutions are produced via a nonlinearseparation of the variables in the full set of the MHD equations. Attentionis given to the questions of initial acceleration and collimationof the outflow. A quantitative: criterion is provided for the transition ofthe morphologies from highly collimated jets to non collimated winds.

Hydrodynamical simulations have played an important rolein the understanding of extragalactic jets since the late seventies. Inthis talk, recent simulations of jets in the relativistic regime are reviewed.Special attention is payed to simulations of jets at parsec scalewhich, for the first time. have allowed to probe the current models ofsuperluminal radio sources.

The development of a variety of non-electromagnetic detectorswill drastically enlarge our global view on Galactic Nuclei andAGNs in the future. The possibility of detecting their non-photonicemission, namely ultra-high energy cosmic rays (UHECRs) and gravitationalwaves, may open new Windows on AGN physics in comingyears.

We are interested in the stellar content in the central regionof active galaxies. In this aim, we perform stellar population synthesisof the integrated starlight in the Optical and NIR using a mathematicalmethod (Pelat, 1997, MNRAS 284, 365) dedicated to the determinationof the best solution (among the many local solutions) in the stellarpopulation synthesis problem which is a complex inverse problem. Anew development of the code allows the determination of the error zonearound the solution, expected from the observational uncertainties. Inthe next sections, we present this very powerful method and resultsobtained from a sample of AGN.

The narrow emission line luminosities of radio-loud AGN arewell-correlated with their low-frequcncy radio luminosities. This correlationis linear and extends over at least four orders of magnitude. Thecorrelation is discussed in terms of a linear relationship between thepower in the radio-emitting jets and the photoionizing (i.e. accretion)luminosity. Support for this theory comes from a direct correlation betweenthe optical continuum and radio luminosities of steep-spectrumquasars. We discuss the dependence of the observed luminosities ofAGN on their black hole masses and how close to the Eddington limitthey are accreting.