Adaptive Optics Systems are now routinely operated on several 4 meter class telescopes, allowing to achieve angular resolutions down to 70 msec in the near-infrared. Although these Systems have excellent performances, their use for exploring the physics and structure of AGN is still limited for the following reasons: the limiting magnitude of the wavefront sensor is too high, the sensitivity of infrared detectors does not give access to medium/high spectral resolution spectroscopy and the angular resolution achieved does not always fit the apparent size of the physical components responsible for emission features close to the central engine. The new generation of 8 — 10 m class telescopes bring improvements in this matter. However, some interesting results have been obtained so far with Adonis, the ESO La Silla adaptive optics System on the 3.60 meter telescope, in the investigation of AGN structure. In particular, a prominent structure has been detected in the central arcsec core of NGC 1068, which might feature the dusty/molecular torus expected on theoretical grounds.

Seyfert galaxies have been shown to exhibit a large variety of features in their X-ray spectra from which the environment of the central engine can lie deduced. We focus on the two following aspects: the Warm Absorber, mainly responsible of the soft X-ray properties. and the reprocessing/reflecting plasma medium at the origin of the iron Kα fluorescent line. The physical parameters and the location of the so-called Warm Absorber (WA), a photoionized medium along the line of sight to the nuclear region, are more strongly constrained by optical coronal lines than by the oxygen edges observed in the soft X-rays and produced by the WA. The photoionization models atso predict the intensities of the X-ray (-mission lines which are going to be detected with the new generation of X-ray satellites. An alternative model to the relativistic accretion disc is proposed to explain the profile of the X-ray iron Kα line observed in the Seyfert 1. This line can be formed in the framework of a quasi-spherical accretion of optically thick clouds. An optically thick photoionization code coupled with a Monte-Carlo code has been developed to compute the entire spectrum from the IR to the hard X-rays for a dose geometry with a large covering factor. The multiple Compton reflections allow to reproduce the redshifted broad iron line as detected in several Seyfert 1 galaxies and in MCG-6-30-15.

The development of a variety of non-electromagnetic detectors will drastically enlarge our global view on Galactic Nuclei and AGNs in the future. The possibility of detecting their non-photonic emission, namely ultra-high energy cosmic rays (UHECRs) and gravitational waves, may open new Windows on AGN physics in coming years.

The main characteristics of the average spectrum of radio quiet AGN in the UV and X-ray range are reviewed, and the emission mechanisms are discussed in the framework of accretion disk models, in particular the "irradiated cold relativistic disk". It is shown that some problems arise in confronting the predictions of the model to the observations. We propose an alternative model in terms of a hot disk surrounded by a cold Compton thick medium. Finally we mention problems with remote regions of the accretion disk.

Early, it has been suggested that Keplerian flows should be unstable regarding shear instabilities. This hypothesis, not seriously considered nowadays, is strongly sustained by a recent re-analysis of experimental data on shear flows and new laboratory experiments. We review some consequences on steady state accretion dises of a viscosity law derived from shear experiments. In particular, we show that it wholly suppresses the thermal and viscous instabilities within the radiation pressure dominated region, unlike the standard theory.

The modclling of plasma outfiows from central gravitating objects such as AGN is bricfly discussed via analytic examples in the context of ideal MHD. The exact solutions are produced via a nonlinear separation of the variables in the full set of the MHD equations. Attention is given to the questions of initial acceleration and collimation of the outflow. A quantitative: criterion is provided for the transition of the morphologies from highly collimated jets to non collimated winds.

Hydrodynamical simulations have played an important role in the understanding of extragalactic jets since the late seventies. In this talk, recent simulations of jets in the relativistic regime are reviewed. Special attention is payed to simulations of jets at parsec scale which, for the first time. have allowed to probe the current models of superluminal radio sources.

Very Long Baseline Interferometry (VLBI) can be used to construct images of the radio emission of active galactic nuclei on scales of parsecs. Although BL Lacertac objects distinguished from other core-dominated AGN primarily in the absence of strong optical line emission - have "core-jet" structures similar to those seen in other types of compact extragalactic radio sources, their parsec-scale structure shows a number of distinctive features, such as the dominance of transverse magnetic fields. This B-field structure may be due to the presence of relativistic shocks: alternatively, it may reflect the dominance of the toroidal comportent of an underlying helical B field. The superluminal speeds observed in the VLBI jets of BL Lac objects are somewhat lower than those in quasars, suggesting that the typical Lorentz factors for the jet flows are smaller.

I review the current paradigm for extragalactic radio sources including their classification, relationship to their host galaxies, their environments, their propagation, and their lifetimes. I emphasize recent progress in our understanding of radio source evolution and I discuss the current open questions. In spite of the many outstanding questions, there remains the following "working" paradigm. Massive BHs are present in many (all?) bright galaxies. Activity is triggered when gas reaches the central accretion disk - possibly with the assistance of an interaction. The type of resultant activity depends on the fueling rate and BH properties (Mass and Spin) which in turn may be related to the host galaxy and its immediate environment. The radio jets in the classical doubles power an over-pressured cocoon which propagates through the ISM/ICM in a roughly self-similar way. The GPS and CSS sources are likely to be the young progenitors of the powerful large-scale radio sources and if so can be used to constrain their evolution. Current constraints imply that sources evolve with roughly constant expansion speed and decline in radio power with linear size as P ∝ l-0.5. Lifetimes of canonical powerful radio sources are in the range l06-8 yr (with the less powerful oncs living longer). Finally, activity may be repetitive.

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

We present and discuss near-ultraviolet and optical groundbased spectra of the 20 brightest Seyfert 2 nuclei, and HST ultraviolet images and ultraviolet spectroscopy for a few of them. The goal is to study the starburst-AGN connection and the origin of the featureless continuum. The results indicate that half of the nuclei in the sample harbor a young and/or intermediate age population. These stars are formed in powerful and dusty starbursts of short duration, that have bolometric luminosities similar to the estimated bolometric luminosities of their obscured Seyfert 1 nuclei.

Star formation rates in distant radio galaxies are crucial for understanding the evolution of galaxies. Most processes at works in these targets observed at the most remote epochs are directly or not related to primeval sources of star formation: interplays of starbursts and AGNs, interactions of radio jets with environmental clouds. cooling flows, metal enrichment and dust distributions. Signatures of typical star formation (emission line ratios, equivalent widths, stellar continua) are observed in distant galaxies. However in most cases, they are superimposed to signatures of other processes (shocks, AGN light scattering). in particular at high z with the decrease of angular resolution and surface brightness. A larger variety of environmental components (lobes, jets, clouds and nucleus) simultaneously contribute to the global emission. So that to separate the varions emission processes becomes rapidly essential with higher distances. The 3D spectroscopy is unique to disentangle the various physical processes triggering star formation at high redshifts. Shocks and regions photoionized by the central AGN are identified from their typical features and may be localized in the various zones of the radio galaxy extended to its environment. We present results of a long term observationnal prograin with the successive Integral Field Units (IFU) TIGER and OASIS at CFHT. The present sample consists of three galaxies of increasing z: 3C 171 {z = 0.238), 3C 435A (z = 0.470) and 4C 41.17 (z = 3.8). Line ratios, continua and velocity fields are locallv measured. Interpretations of emission line ratios, velocity fields, equivalent widths, are possible with a coupled code based on CLOUDY and MAPPINGSIII results, as proposed by Moy et al. (2000, 2001). Stellar and nebular continua are interpretcd with the help of our evolutionary synthesis model PEGASE2. Ail models take into account metallicity effects.

We are interested in the stellar content in the central region of active galaxies. In this aim, we perform stellar population synthesis of the integrated starlight in the Optical and NIR using a mathematical method (Pelat, 1997, MNRAS 284, 365) dedicated to the determination of the best solution (among the many local solutions) in the stellar population synthesis problem which is a complex inverse problem. A new development of the code allows the determination of the error zone around the solution, expected from the observational uncertainties. In the next sections, we present this very powerful method and results obtained from a sample of AGN.

We present a new method based on mid-IR (5 — 16 µm) emission for classifying the origin of the mid-IR activity in galaxies. Our method was devefoped using a set of 33 ISOCAM spectra of extragalactic sources which exhibit diverse mid-IR spectral features. Detailed analysis of our sample enables us to identify the general properties of mid-IR emission from active galactic nuclei (AGNs), starbursts, and quiescent star forming regions. The benefits of this mid-IR classification for identifying obscured or faint AGNs and for estimating the star formation intensity in star-forming regions are investigated.

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

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 synthesises the 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 applicable for collisional N-body integrations with extraordinarily large particle numbers (> 105). It opens the perspective to simulate the dynamics of globular clusters with realistic collisional relaxation, as well as stellar Systems surrounding a supermassive black hole in galactic nuclei.

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

Data on continuum variability of the Seyfert galaxy NGC 4151 nucleus are compiled. The most of them related to new cycle of the nucleus activity in 1989-1996. X-ray through the UV and optical data show remarkable similarity in variability characteristics to those of blazars and do not contradict the supposition that new cycle of activity mainly caused by synchrotron jet.