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.

Seyfert galaxies have been shown to exhibit a large varietyof features in their X-ray spectra from which the environment of thecentral 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 ironKα fluorescent line. The physical parameters and the location of theso-called Warm Absorber (WA), a photoionized medium along the lineof sight to the nuclear region, are more strongly constrained by opticalcoronal lines than by the oxygen edges observed in the soft X-raysand produced by the WA. The photoionization models atso predict theintensities of the X-ray (-mission lines which are going to be detectedwith the new generation of X-ray satellites. An alternative model to therelativistic accretion disc is proposed to explain the profile of the X-rayiron Kα line observed in the Seyfert 1. This line can be formed in theframework of a quasi-spherical accretion of optically thick clouds. Anoptically thick photoionization code coupled with a Monte-Carlo codehas been developed to compute the entire spectrum from the IR tothe hard X-rays for a dose geometry with a large covering factor. Themultiple Compton reflections allow to reproduce the redshifted broadiron line as detected in several Seyfert 1 galaxies and in MCG-6-30-15.

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.

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.

Early, it has been suggested that Keplerian flows should beunstable regarding shear instabilities. This hypothesis, not seriouslyconsidered nowadays, is strongly sustained by a recent re-analysis ofexperimental data on shear flows and new laboratory experiments. Wereview some consequences on steady state accretion dises of a viscositylaw derived from shear experiments. In particular, we show thatit wholly suppresses the thermal and viscous instabilities within theradiation pressure dominated region, unlike the standard theory.

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.

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

I review the current paradigm for extragalactic radio sourcesincluding their classification, relationship to their host galaxies, theirenvironments, their propagation, and their lifetimes. I emphasize recentprogress in our understanding of radio source evolution and I discussthe current open questions. In spite of the many outstandingquestions, there remains the following "working" paradigm. MassiveBHs are present in many (all?) bright galaxies. Activity is triggeredwhen gas reaches the central accretion disk - possibly with the assistanceof an interaction. The type of resultant activity depends on thefueling rate and BH properties (Mass and Spin) which in turn may berelated to the host galaxy and its immediate environment. The radiojets in the classical doubles power an over-pressured cocoon whichpropagates through the ISM/ICM in a roughly self-similar way. TheGPS and CSS sources are likely to be the young progenitors of the powerfullarge-scale radio sources and if so can be used to constrain theirevolution. Current constraints imply that sources evolve with roughlyconstant expansion speed and decline in radio power with linear sizeas P ∝ l-0.5. Lifetimes of canonical powerful radio sources are in therange l06-8 yr (with the less powerful oncs living longer). Finally,activity may be repetitive.

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.

We present and discuss near-ultraviolet and optical groundbasedspectra of the 20 brightest Seyfert 2 nuclei, and HST ultravioletimages and ultraviolet spectroscopy for a few of them. The goal is tostudy the starburst-AGN connection and the origin of the featurelesscontinuum. The results indicate that half of the nuclei in the sampleharbor a young and/or intermediate age population. These stars areformed in powerful and dusty starbursts of short duration, that havebolometric luminosities similar to the estimated bolometric luminositiesof their obscured Seyfert 1 nuclei.

Star formation rates in distant radio galaxies are crucial forunderstanding the evolution of galaxies. Most processes at works inthese targets observed at the most remote epochs are directly or notrelated to primeval sources of star formation: interplays of starburstsand AGNs, interactions of radio jets with environmental clouds. coolingflows, metal enrichment and dust distributions. Signatures of typicalstar formation (emission line ratios, equivalent widths, stellar continua)are observed in distant galaxies. However in most cases, they are superimposedto signatures of other processes (shocks, AGN light scattering).in particular at high z with the decrease of angular resolutionand surface brightness. A larger variety of environmental components(lobes, jets, clouds and nucleus) simultaneously contribute to the globalemission. So that to separate the varions emission processes becomesrapidly essential with higher distances. The 3D spectroscopy is uniqueto disentangle the various physical processes triggering star formationat high redshifts. Shocks and regions photoionized by the central AGNare identified from their typical features and may be localized in the variouszones of the radio galaxy extended to its environment. We presentresults of a long term observationnal prograin with the successive IntegralField Units (IFU) TIGER and OASIS at CFHT. The presentsample 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 andvelocity fields are locallv measured. Interpretations of emission line ratios,velocity fields, equivalent widths, are possible with a coupled codebased on CLOUDY and MAPPINGSIII results, as proposed by Moyet al. (2000, 2001). Stellar and nebular continua are interpretcd withthe help of our evolutionary synthesis model PEGASE2. Ail modelstake into account metallicity effects.

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.

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

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.

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.

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.

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