The formation of large-scale structures in the universe and galaxy evolution within this complex environment is a key issue in observational cosmology. On this context we analyze data coming from surveys at different wavelengths on galaxies infalling to clusters between z=0.02 and z=0.20. For nearby clusters we review the late-type galaxy distribution throughout a big volume fraction (1.5 Abell radius), as well as the HI gas content in individual galaxies. This provides us with an independent method to search for substructures around clusters. We analyse the whole HI-gas distribution across the cluster and complement this picture with spatial and dynamical analysis of substructures. We discuss our results within the context of different scenarios, mainly the pre-processing versus cluster-galaxy interactions.

NGC4038/4039, nicknamed “the Antennae” is a prototypical galaxy merger whose close proximity (D~20 Mpc) and relatively simple morphology have made it a favorite target of observational and theoretical studies. Two long, symmetric tidal tails extend off two overlapping disk galaxies and cross to give the merger the appearance of a pair of antennae. The most recent model of the Antennae reproduces many of its key morphological features using collisionless N-Body simulations including a disk, bulge and a King model dark matter halo (Barnes 1988). However, in the last 20 years there have been large advances in both modeling and observations which have not yet been implemented in an updated model. Detailed optical (Whitmore & Schweizer 1995), infrared (Wang et al. 2004) and HI (Hibbard et al. 2001, Gordon et al. 2001) observations give new constraints on the morphology and kinematics of the Antennae and improved simulations allow us to implement more realistic galaxy models and include collisional particles. We revisit the Antennae with GADGET simulations, implementing a Hernquist profile for the dark matter halo and adding gas to update the simulations of this system. We examine which galaxy models are consistent with creating a system such as the Antennae, and comment on the outlook for constraining disk and halo models with detailed simulations of nearby mergers.

Disk galaxies with a spheroidal component host supermassive black holes in their center. While the connection between major mergers and the growth of SMBHs has been investigated extensively in the literature, unequal mass mergers have been rarely studied, despite the fact that they are the large majority of merging events by number and they are associated with the typical targets of gravitational wave experiments such as LISA. We performed N-body/SPH simulations of disk galaxy mergers with mass ratios 1:4 and 1:10 at redshifts z=0 and z=3. They have the highest resolution achieved so far for merging galaxies, and include star formation and feedback from supernovae as well as AGN feedback. Gas dissipation is found to be necessary to the pairing of the SMBHs in these minor mergers, since it prevents tidal disruption and helps the sinking of the lighter SMBH by enhancing dynamical friction. Still, 1:10 mergers with gas allow an efficient pairing only at high z when orbital times are short enough compared to the Hubble time. The relative importance of tides drives stronger central gaseous inflows in the smaller disk, and we discuss its consequences on star formation and the expected SMBH accretion and nuclear activity.

We will discuss the possibility of forming old stellar counter-rotating components in early-type galaxies, by dissipative and dissipationless mergers. To this aim, we will present the results obtained exploring the GalMer database, a library containing hundreds of simulations of galaxy mergers. In particular, a new scenario will be proposed, according to which stellar counter-rotation can form both in dissipative and dissipationless mergers of elliptical-spiral galaxies. In this scenario, stars in the external regions of the galaxies involved in the encounter acquire orbital angular momentum, at first pericenter passage, and, mostly, in the last phases of the merging process, while those in the most inner regions can maintain some of their initial spin (antiparallel to the orbital one), producing decoupled counter-rotating central components. The redistribution of the angular momentum between the different galactic components (gas, stars and dark matter) will be also discussed.

We present a study of one of the closest collisional ring galaxies, from the X-ray to the far-infrared. Chandra data show the presence of very luminous point sources, associated with the ring. Galex observations reveal massive ongoing star formation localized in the ring, confirmed by the Spitzer broad-band dataset. The morphology of AM0644-741 and of its companions appears strongly perturbed by the interactions. This study allows us to understand how disc galaxies collisionally evolve into rings.

In recent years, it has become clear that large quantities of cool gas reside in the halos of many normal spiral galaxies. Whether the presence of this gas is ultimately a consequence of star formation activity within the disk, or accretion from without, is not yet understood. In order to help answer this question, it is important to also study galaxies with very low rates of star formation, where possible accretion effects should dominate. To that end, deep HI observations of the nearby face-on dwarf spiral NGC4395 have recently been performed. The data were obtained using the WSRT for a total of 8x12 hr. This object was chosen because it is nearby, relatively isolated, and has a very low rate of current star formation. Yet our observations reveal the presence of a huge amount of gas at “anomalous” velocities; the gas behaves much like that observed recently in more actively star forming galaxies such as NGC6946, suggesting that accretion plays a role. I will present a preliminary analysis of the anomalous gas in NGC4395, and discuss implications for the origins of the gas and the evolution of the galaxy.

The cluster environment is host to an array of processes such as galaxy-galaxy interactions, harassment, and ram pressure stripping, which can dramatically influence the evolution of galaxies. In order to constrain the frequency of these environmental processes and their consequences, we analyze the morphological properties and asymmetries of galaxies in the Abell 901/902 Supercluster. As part of the STAGES (Space Telescope Abell 901/902 Galaxy Evolution Survey) collaboration, we have a unique multi-wavelength dataset that includes HST ACS F606W, Spitzer IRAC and MIPS, GALEX, XMM-Newton x-ray, and gravitational lensing maps. We characterize morphologically disturbed and normal galaxies using quantitative CAS parameters and a multi-parameter visual classification system. We present preliminary results on how star formation and AGN activity vary between normal and morphologically disturbed galaxies, as a function of cluster properties including radius, galaxy number density, and intracluster medium (ICM) density. The work will afford important insights as to how the environment shapes the evolution of cluster galaxies.

The interaction of High Velocity Clouds (HVC) with the galactic disk plays an important role in the evolution of galactic structure. In this work, we present preliminary results of the Virtual Catalog of Remote Numerical Simulations associated with the evolution of HVC in a magnetized medium. We have developed an intuitive graphical user interface (GUI) and one database produced by numerical calculations. The development of this prototype was made using Linux, Apache, MySQL, and PHP (LAMP), based on the open source philosophy. All the calculations were performed with the MHD code ZEUS-3D, which solves the ideal MHD equations by finite differences on a fixed Eulerian mesh. The user can specify the existing numerical simulations of the database or run a new simulation introducing initial conditions such as temperature, density, velocity, and magnetic field intensity.

We study the influence of a time-varying ram pressure on spiral galaxies in clusters with a SPH/tree simulation method. As galaxies arrive on highly radial orbits from outskirts to cluster center, they cross the density peak of the intracluster medium and experience a wind. Depending on the duration and intensity of the operation, the distribution of the ISM and star formation in the disk are affected. When the pressure is strong enough the ISM can be swept out and HI-deficient galaxies with a quenched star formation form. Galaxies of different types orbiting in clusters with various ICM distributions show different amounts of reaccretion of the extra-planar gas and final masses.

We investigate the time evolution of warped discs in the triaxial haloes using N-body simulations. Triaxial haloes were represented by fixed external potentials in which self-gravitating discs were embedded. The density distributions of the haloes were modeled by triaxial modification of Hernquist models. We find the warped configurations in the triaxial haloes, and that the shape and persistence of warps depend sensitively on the halo triaxiality. Our simulation results are in agreement with those predicted by simple analytical models. We attribute the development of warps to the torque between a halo and disc and that between the inner and outer regions of the disc. We also present the results from simulations by replacing the fixed haloes with live ones to include a mutual back reaction of disc on the halo using GRAPE-6a.

We have made B-, V-, and I-band observations of satellite galaxies which lie around isolated disk galaxies, using the satellite sample of Zaritsky et al. (1997). We present 3-dimensional light and mass profiles of the centers of these satellites, and discuss how we plan to use the profiles to study the survival or disruption of satellites in minor mergers, an issue that has several important implications.

Shell galaxies are widely considered the debris of recent accretion/merging episodes. Their high frequency in low density environment suggests that such episodes could be among the drivers of the early-type galaxy secular evolution. We present far UV (GALEX) and X-ray (XMM-Newton) photometric properties of a sample of shell galaxies. We interpret the data at the light of the current models with the aim of gain insight about their overall evolution, traced by star formation history and by their hot gas content.

We present the results of the spectral study of the some candidates to the polar-ring galaxies. New information about structure and kinematics of gaseous and stellar components was obtained using modern observing techniques such as integral-field spectroscopy and high resolution long-slit spectroscopy. Detailed analyses of the data allowed us to conclude that investigated objects have complicated multicomponent structure among which we can distinguish galaxies with classical polar rings, with circumnuclear polar disks, galaxies with warped gaseous disks and rings and even with stellar polar rings.

The results of galactic rings observations on SAO RAS 6-m telescope are presented. The different types of rings are considered: (i) rings on the dynamical resonances in barred as well as in non-barred galaxies; (ii) collisional ring galaxies; (iii) inclined and polar off-plane rings. The kinematics of the galaxies Arp10, Arp148, Arp212, NGC6104, and NGC7742 are described in details. The main attention is given to an analysis of the ionized gas velocity fields using the different assumptions for the non-circular motions of the gas.

Recent simulations have shown that accretion onto galactic disks can proceed by two independent, halo-cloud-generating mechanisms: the tidal stripping of satellite galaxies and the condensation of warm gas out of hot galactic halos. It is not yet known which of these effects dominates the generation of the observed High-Velocity Clouds (HVCs) nor the extent to which HVCs contribute to the continued accretion onto galactic disk in the local universe. We present the results of cosmological simulations detailing the physical signatures of a condensed cloud population, their observational similarities to HVCs and their contribution to ongoing disk accretion. We also show that condensed HVCs have distinct observational signatures from stripped HVCs. A new wide-field, high-resolution Galactic HI survey using ALFA at Arecibo (GALFA) shows evidence for a new type of halo cloud predicted by the condensed HVC model that may be a key to understanding this ongoing process of galactic accretion.

IIZw71 is catalogued as a probable polar ring galaxy. In this type of objects, a late-type galaxy is surrounded by a rotating disk of molecular gas and dust where processes or recent massive star formation takes place, as a consequence of the interaction with other dwarf close companions. In this contribution, I will summarize the results of long-slit WHT spectrophotometric observations of the bursts of star formation in this ring, studying the differences in reddening, physical properties, chemical abundances and star formation history and analizing the effects that the bad slit coverage in some of the weaker knots has in the determination of all these properties.

Using optical and NIR photometrical data (V, I, J, H, K) and HST/WFPC2 morphological data (Stanford et al. 2002), we carry out a photometrical, morphological and dynamical study of galaxies in the field of the radio galaxies 3C220.1 (z = 0.62), 3C34 (z = 0.689), 3C184 (z = 0.996) and 3C210 (z = 1.169). The primary aims of this study are to analyze the properties of galaxy pairs with respect to their parent sample and to analyze the interaction effects (such as mergers) on color and morphology of galaxy pairs, especially for disk galaxy pairs and mixed morphology pairs.

We have analyzed the galaxies with active nuclei, which are suffer an accretion of companion or merging with another galaxy. The main attention is given for connection of phenomenon of Seyfert nucleus with disks reformation as a consequence of accretion or merging events. In our studing we use methods of 3D spectroscopy. The results of panoramic spectroscopy obtained with Russian 6m telescope are presented: the circumnuclear region were observed with integral-field spectrograph MPFS, the large-scale velocity fields of the ionized gas in the emission lines were constructed from observations with scanning Fabry-Perot interferometer. Based on these data we consider gas and stars kinematics in the circumnuclear region as well as in the outer parts of the galaxies. And we can to analyse how interactions events affect on the gas and stars kinematics in the galactic disks and how it can be connect with AGN fuelling.

Most of the galaxies reside in poor groups of the size of the Local Group and the group environment can play an important role in the evolution of its members. We will present the preliminary results of an optical imaging study of the late-type disk galaxies in the Lyon Group of Galaxies LGG16 and LGG165 and analyze them together with available near- and far-IR and HI data in order to study the effects of possible mutual interactions on their morphology, stellar content and star-formation properties.