Asymmetries in galactic potentials, either self-induced, or caused by a passing companion, play an important role in global gas dynamics ingalaxies. In particular, they are able to trigger gas inflow, which in turn feeds nuclear activity. In the inner kiloparsec, the inflowing gas becomes subject to various resonances induced by asymmetry in the potential. This produces complicated gas morphology and dynamics seen in the nuclear rings and spirals. Formation of nuclear rings is relatedto barred galaxies, and explained by the orbital structure in bars.One can get basic understanding of weak nuclear spirals from the linear wave theory, but stronger spirals are likely to be out of the linear regime, and they appear as spiral shocks in hydrodynamical models. In addition, nuclear stellar bars are observed in a considerable fraction of disc galaxies, often nested inside the large bar; their orbital structure further modifies the nuclear gas dynamics. If a massive black hole (MBH) is present in the galactic centre, it governs the resonances even beyond its classically defined sphere of influence. Since resonances shape gas dynamics in the nuclear region, the central black hole should be able to regulate gas flow around itself.

The analysis of a sample of 30 isolated spiral galaxies with andwithout an Active Galactic Nucleus (AGN) results in active and control galaxies having similarbulge and disk properties. Secondary bars also seem to beindistinguishable. Circumnuclear kinematics are also analyzed todisentangle what kind of mechanisms are taking place in thecircumnuclear regions. From long slit spectra of a subsample ofisolated active and non-active spiral galaxies in the Hαemission line region, the shape and properties of the rotation curvesare obtained together with the line ratios used to estimate themetallicity of all the detected HII regions. Kinematics andmetallicities are also studied in comparison with the propertiesdetermined for a family of 111 spiral galaxies with a welldetermined environmental status, ranging from isolation to close, though not disruptive, interaction with satellites or companions. Thestellar kinematics are also studied in some cases, with as mainresult the detection of a stellar velocity dispersion drop in thecenters of four Seyfert galaxies. Together with previous findings, ourresults from the comparison between active and non-active isolatedgalaxies point to AGNs being an episode in the life of galaxies,provided that the fuel is available and the accumulation mechanismsare at work.

Recent progress on the structure and dynamics of bulges is reviewed.Those aspects that link galaxy bulges either to oblate spheroids akin toelliptical galaxies or to rapidly-rotating, flattened systems more nearlyresembling the products of disk internal transformations, are highlighted. Theanalysis of surface brightness profiles derived from HST data is reviewed toshow that unresolved nuclear components detected by HST have biased thedetermination of surface brightness profiles obtained from the ground; r1/4 profiles are virtually nonexistent in galaxybulges. Predictions from accretion N-body models on the shape of surfacebrightness profiles are discussed. The position of bulges on the FundamentalPlane (FP) of elliptical galaxies is examined to infer clues on bulgepopulation ages and bulge dynamical structure. Kinematic diagnostics on theinternal dynamics of bulges are examined. Finally, a new approach to thekinematic analysis of galaxies, based on the use of synthetic spectra of singlestellar population models instead of the standard stellar templates, ispresented.

The kinematics of the inner zones of disc galaxies have recently been shown to be much more complicated than previously thought. New instruments and more sensitive detectors have allowed us to obtain spectra of higher S/N ratio and resolution, as well as images, for a more refined study of these inner zones. Decoupled kinematic cores have been known for some time to exist in ellipticals, but complex structures and their kinematic counterparts are now showing up in disc galaxies also. There is a variety of dynamical origins for these structures, and they can be detected sometimes in the gaseous component, sometimes in the stellar component, and sometimes in both. Here we give an overview of the components which are found with significant frequency, and explain how we can distinguish one from another. The components covered include black holes, inner cores, inner bars, inner discs, inner annuli, inner bulges, etc. In most cases a reliable diagnostic of the component structure would not be possible without combining high quality photometric observations with high quality kinematic observations.

In the present project we apply a 3D MHD numerical model to simulate the evolution of a large-scale magnetic field in a barred galaxy possessing a gaseous halo. A time-dependent velocity field of molecular gas resulting fromself-consistent 3D N-body simulations of a galactic diskis used to solve the induction equation. Thegaseous halo rotates differentially, co-rotating with the disk.In order to form field structures high above the galactic diskin our model, we introduce the dynamo process causing, as well, theamplification of the magnetic field. The simulated magnetic fieldsare used to construct the maps of a high-frequency (Faraday rotation-free)polarized radio emission that accounts for effects of projectionand limited resolution, and is thussuitable for direct comparison with observations. The magnetic field obtained correctly reproduces the observed structures of polarization B-vectors. They formcoherent patterns well aligned with spiral arms and with the bar. We found the dynamical process which initializes a wave-like behavior of the magnetic fieldefficiently forming magnetic maxima between the spiral arms. The magnetic structuresin a form of flux tubes extending along the spiral arms are found, as well.

A sample of nearly 400 stars, selected from the Tycho-2 catalog, has beenobserved towards the North Galactic Pole with the high resolution echellespectrograph Elodie. Combining those data with a local sample from the Hipparcos catalog, adetailed study of the disk components is done. A dynamical analysis is alsoperformed, enabling us to put new constraints on the local mass density.

The kinematical parameters of the local field RR Lyrae populationand the zero-point of the log $P-\langle M_K\rangle$ relation for thesevariables are inferred by applying the statistical parallax(maximum-likeli-hood) technique to a sample of 182 RR Lyraes withknown periods, radial-velocities, metallicities, K-bandphotometry, and absolute proper motions on the ICRS system.Hipparcos, Tycho-2, SPM, UCAC, NPM1, and the Four-Million StarCatalog (Volchkov et al. 1992) were used asthe sources of proper motions; the proper motions of the last twocatalogs are reduced to the Hipparcos (ICRS) system (Dambis &Rastorguev 2001). The K-band magnitudes were adopted fromthe list of Fernley et al. (1998) andsupplemented by the data of the 2MASS Second Incremental DataRelease. The parameters of the velocity distribution are found tobe: ($U_0 = -10 \pm 10$, $V_0 = -51 \pm 8$, $W_0 = -14 \pm5)$ km s-1; ($\sigma_U = 62 \pm 10$, $\sigma_V = 45 \pm 8$,$\sigma_W = 28 \pm 6$) km s-1: and ($U_0 = -23 \pm 13$, $V_0 = -213 \pm 12$, $W_0 = -5 \pm 8$) km s-1; ($\sigma_U = 157 \pm 12$, $\sigma_V = 98 \pm 8$, $\sigma_W = 91 \pm 7$) km s-1 for the thick-disk (41 stars) andhalo (141 stars) objects, respectively. The zero-point of theinfrared PL relation of Jones et al. (1992)(based on the results obtained using the Baade-Wesselink method)is confirmed: we find $\langle M_K\rangle= -2.33 \cdot \log P_{\rm F}-0.82 \pm0.12$ compared to $\langle M_K\rangle= -2.33 \cdot \log P_{\rm F}-0.88$ asinferred by Jones et al. (1992). A conversion ofthe resulting log $P-\langle M_K\rangle $ relation to V-band luminositiesyields the metallicity-luminosity relation $\langle M_V\rangle= +1.04 + 0.14\cdot [$Fe/H$] \pm 0.11$. Our results imply a solar Galactocentric distance of $R_0 = 7.6 \pm 0.4$ kpc and an LMC distance modulus of $DM_{\rm LMC} = 18.18 \pm 0.12$ (cluster RR Lyraes) or $DM_{\rm LMC} = 18.11 \pm 0.12$ (field RR Lyraes), thereby favoringthe so-called short distance scale.

We summarize results from the first year of the Lenses Structure andDynamics Survey (LSD). Using the Echelle Imager and Spectrograph atthe Keck-II Telescope, we have measured spatially resolved velocitydispersion profiles of a sample of distant (up to z=1) early-typegalaxies that are gravitational lenses. By combining lensing anddynamical analyses we can set firm limits on the dark matter densityprofile, the controversial inner slope of the dark matter halo, themass-to-light ratio of the luminous component, the total massdistribution, and on the velocity ellipsoid by breaking the massanisotropy-relation. The implications of these measurements in termson the epoch and mechanism of formation of E/S0 galaxies and of thevalue of the Hubble constant are briefly discussed.

We use a Fourier analysis method to study the spiral structure of the discgalaxies in the Frei et al. (1996) sample. We show that m=1components are more often associated with asymmetries between the twoarms of an m=2 spiral than with global lopsidedness of the disc. Thepower in the m=2 components is correlated with the arm class. Themajority of galaxies with arm class 9 or 12 show clear signs ofmodulation in their spiral arms, suggesting the action of anamplification mechanism like the Swing amplification. Finally we report new detections of underlying large-scale bisymmetric components in flocculent spiral galaxies.

The author discusses models of the Milky Way. An interpolation formula for the contribution of the exponential disc to the circular velocity is proposed.

The origin of galactic warps is a long standing mystery. There has beenprogress recently in the theoretical understanding of thegeneration of warps, drawn from a reanalysis of the influence of a companion to a disc galaxy. A prominent example is found in the Milky Way - the LMC systems. Shortly after the discovery of the Milky Way's warp, it was shown thatthe direct torque from the LMC is too small to generate the observedwarp in amount. We have performed numerical simulations in order to examinethe effect of a live halo, as a mediator of the tidal interaction betweenthe companion and the disc. We find with fairly realistic MilkyWay models that the orbiting motion of the LMC excites massive wakesin the DM halo, and that these wakes produce larger torques on the disc than the companion alone. As a result the disc may develop a warp, of amplitude comparable to the one observed.

We use numerical simulations to study the dynamical effect of substructure inCold Dark Matter (CDM) halos on stellar galactic disks. Substructure halos withmasses, densities and orbits derived from high-resolution cosmological CDMsimulations play only a minor dynamical role in the heating of the disk overseveral Gyrs. This is because the orbits of dark satellites in CDM halos seldomtake them near the disk, where their tidal effects are greatest. The mostnoticeable effects of substructure in our simulation may be traced to the mostmassive sub-halo and include: (i) the forcing of short-lived stellar warps in thedisk as a result of tidal shocks that arise during each pericentric passage, and(ii) the tilting of the disk caused by the orbital decay of the satellite. These results imply that substructure might not preclude virialized CDM halos from being acceptable hosts of thin stellar disks like that of the Milky Way, and that the ubiquity of minor stellar warps may be associated with the recurrent tidal influence on the disk of the most massive substructure halos.

Motivated by the presence of numerous dark matter clumps in the MilkyWay's halo as expected from the cold dark matter cosmological model,we conduct numerical simulations to examine the heating of the disk. Weconstruct an initial galaxy model in equilibrium, with a stable thin disk.The disk interacts with dark matter clumps forabout 5 Gyr. Three physical effects are examined: first the massspectrum of the dark matter clumps, second the initial thickness ofthe galactic disk, and third the spatial distribution ofthe clumps. We find that the massive end of the mass spectrumdetermines the amount of disk heating. Thicker disks suffer lessheating. There is a certain thickness at which the heating owing to theinteraction with the clumps saturates. We also find that theheating produced by the model which mimics the distribution found inStandard CDM cosmology is significant and too high to explain theobservational constraints. On the other hand, our model that corresponds tothe clump distribution in a ΛCDM cosmology produces no significantheating. This result suggests that the ΛCDM cosmology ispreferable with respect to the Standard CDM cosmology in explaining thethickness of the Milky Way.

A major goal of contemporary astrophysics is understanding theorigin of the most massive galaxies in the universe, particularly nearbyellipticals and spirals. Theoretical models ofgalaxy formation have existed for many decades, although observationalevidence at both low and high redshifts is only beginning to put constraints on different ideas. We briefly describe theseobservations and how they are revealing the methods by which galaxies form by contrastingand comparing fiducial rapid collapse and hierarchical formation modelpredictions. The available data show that cluster ellipticals must haverapidly formed at z > 2, and that up to50% of all massive galaxies at z ~ 2.5 are involved in major mergers.While the former is consistent with the monolithic collapse picture, weargue that hierarchical formation is the only model that can reproduce all the available observations.

It was recently shown in N-body simulations that the simpleadiabatic invariant r M(r) describes the evolution of acontracting spherical density distribution very well. This is surprising as this adiabatic invariant is only valid forcircular orbits. Orbits in spherically symmetric potentialsresemble rather precessing ellipses. We want to highlight someproblems involved in proving the validity of the adiabaticapproximation on a orbit to orbit basis. Statistical methods aremore promising.

New GSC-II proper motions of RR Lyrae and Blue Horizontal Branch (BHB) stars near the North Galactic Pole are used to show that the Galactic Halo 5 kpc above the Plane has a significantly retrograde galactic rotation.

The relationship between geometrical properties of stellar disks(the flatness and the truncation radius) and disk kinematics areconsidered for edge-on galaxies. It is shown that the observedthickness of the disksagrees with the condition of marginal local gravitationalstability. As a consequence, those galaxies whose disks arethinner should harbor more massive dark halos. A correlationbetween the de-projected central brightness of disks and theirflatness is found (low surface brightness disks tend to be thethinnest ones).We also show that the positions of the observed photometricallydetermined truncation radiiRcut of stellar disks agree well with the hypothesisof marginal local gravitational stability of gaseousproto-disks at R = Rcut.

Highly condensed gaseous objects with masses larger than 5 × 104 M⊙ arecalled Supermassive stars. They are thought to be possible precursors ofSupermassive Black Holes in the centres of galaxies. In the quasi-stationary contraction phase the hydrostatic equilibrium is determined by radiationpressure and gravitation. The global structure is an n=3 polytrope which is at the stability limit. Small relativistic corrections for example can initiatea free fall collapse due to the"post Newtonian" instability.Since the outcome of the final collapse - Supermassive Black Hole or Hypernova- depends sensitively on the structure and the size of the object, when theinstability sets in, it is important to investigate in more detail thecontraction phase of the SMS.If the gaseous object is embedded in a dense stellar system, the central starcluster, the interaction and coupling of both components due to dynamicalfriction change the energy balance and evolution of the SMS dramatically. Dynamicalfriction between stars and gas, which can be estimated semi-analytically (see Just et al. 1986), has 3 different effects on the2-component system. 1) The gas is heated by decelerating the stars. This maystall the contraction process for a while until the stars in the "loss cone",these which cross the SMS, lost their kinetic energy (for the total heating rate seeAmaro-Seoane & Spurzem 2001). 2) This cooling of the losscone stars lead to a mass segregation in the stellar component resulting in amuch more condensed central stellar core. 3) The inhomogeneities due to thegravitational wakes in the gas changes the effective absorption coefficient ofthe gas. This affects the condition for hydrostatic equilibrium and may giveessential deviations from the n=3 polytrope. We discuss, in which evolutionarystages and parameter range these interaction processes are relevant and how theycan influence the stability and evolution of the SMS.