We perform a statistical analysis to study the infall of galaxies onto groups and clusters in the nearby Universe. The study is based on the UZC/SSRS2 group catalogs and galaxy peculiar velocity data. We find a clear signature of infall of galaxies onto groups in a large range of scales 5 Mpc h$^{-1} < r < 30$ Mpc h$^{-1}$. We obtain a significant increase of the infall amplitude with group mass derived from virial equilibrium and from the luminosity of the member galaxies. We compare the observational results with mock catalogs derived from numerical simulations of semi-analytical models where we obtain a behavior similar to observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We investigate the relation between circular velocity vc and bulge velocity dispersion σ in spiral galaxies, based on literature data and new spectroscopic observations. We find a strong, nearly linear vc−σ correlation with a negligible intrinsic scatter, and a striking agreement with the corresponding relation for elliptical galaxies. The least massive galaxies (σ<80 km s−1) significantly deviate from this relation. We combine this vc−σ correlation with the well-known MBHσ relation to obtain a tight correlation between circular velocity and supermassive black hole mass, and interpret this as observational evidence for a close link between supermassive black holes and the dark matter haloes in which they presumably formed. Apart from being an important ingredient for theoretical models of galaxy formation and evolution, the relation between MBH and circular velocity has the potential to become an important practical tool in estimating supermassive black hole masses in spiral galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present results from a set of high ($512^3$ effective resolution), and ultra-high ($1024^3)$ SPH adiabatic cosmological simulations of cluster formation aimed at studying the internal structure of the intracluster medium (ICM). We discuss the radial structure and scaling relations expected from purely gravitational collapse, and show that the choice of a particular halo model can have important consequences on the interpretation of observational data. The validity of the approximations of hydrostatic equilibrium and a polytropic equation of state are checked against results of our simulations. We also show the first results from an unprecedented large-scale simulation of 500 $h^{-1}$ Mpc and $2\times 512^3$ gas and dark matter particles. This experiment will make possible a detailed study of the large-scale distribution of clusters as a function of their X-ray properties.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The nuclear region of the barred spiral galaxy M83 has been imaged at near-infrared wavelengths with the HST NICMOS, showing a new region of star formation activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We analyze quasi-2-dimensional slices of the SDSS EDR. Gaussian smoothing with weighting by the inverse of the selection function provides 2D density fields across the full survey depth. Superclusters (SC) are characterized by a percolation algorithm in the large-scale smoothed field. Group candidates are identified with density maxima in the small-scale smoothed field. The group mass function depends on the SC environmental density. We derive the shape-dependent 3-point correlation function and the void size distribution. These are well reproduced by the galaxies identified in high-resolution $\Lambda$CDM simulations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We announce the construction of an Atlas of STIS-HST Spectra of Seyfert Galaxies, covering the UV and/or optical spectral range. Nuclear spectra of these galaxies have been extracted in windows of width 0.2″ for an optimized sampling (as this is the width of the slit in most cases), from a long-slit spectrum usually covering 52″. Extranuclear spectra have also been extracted, usually using larger windows to improve signal-to-noise ratio. Spectra obtained with different gratings have been combined in order to provide the largest possible wavelength coverage for each galaxy.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have mapped, for the first time, the full velocity extent of the water maser emission in NGC 3079. Based on the analysis of the spectral-line maps, we propose a nearly edge-on, massive, thick, and flared disk for the geometric model of the inner parsec. The disk orbits a mass of $\sim2\times 10^6 M_{\odot}$ enclosed within 0.4 pc, most likely a supermassive black hole. The disk is most likely self-gravitating, clumpy, and supportive of star formation. The presence in our VLBI continuum images of an aging synchrotron component, which is not collinear with the previously imaged jet, might be suggestive of changes in jet orientation. The jet may coexist on pc-scales with a wide-angle outflow, that is related to the kpc-scale superbubble and that is inferred from the observation of dense molecular material at high latitudes above the disk.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present an overview of the initial data processing of near-IR bi-dimensional spectroscopy of the central region of two nearby (v < 3000 km s−1) Active Galactic Nuclei, obtained using the CIRPASS IFU at Gemini South.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We describe a semi-analytic model for the X-ray emitting gas in clusters and groups in which the gas is preheated before halo formation. The model relies on physically sound prescriptions for the formation and evolution of halo structure. For a gas temperature gradient corresponding to a polytropic index of 1.2 and an energy injection of 0.6 keV per gas particle, this model successfully reproduces the observed correlations between gas luminosity, gas temperature and halo mass. We use the model to investigate the detailed entropy structure of groups and clusters of galaxies and compare the results with the observational data.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Can we determine spin parameters of black holes by observations of black hole shadows in accretion disks? In order to answer this question, we have investigated shapes and positions of black hole shadows in optically thick accretion disks around Kerr black holes. In conclusion, in order to measure black hole spin parameters from shapes and positions of black hole shadows, it is crucially important to determine a position of a mass centers of a black hole in a region of a black hole shadow.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This work reports our recent results of an HI line and radio continuum imaging survey of selected southern Active galaxies made with the Very Large Array and the Australian Telescope Compact Array. Radio images are presented and rotation curves for individual galaxies were obtained. The HI total mass content in Seyfert galaxies is larger than those seen in starburst galaxies. Our trends confirm that the infrared luminosity correlates well with the total neutral gas content, which supports the scenario that star formation in the bulges of Seyfert galaxies is considerably higher than in regular late-type galaxies or spirals. We also find a trend between various observational quantities which are also discussed in this work.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The observed properties of supermassive black holes suggest a fundamental link between their assembly and the formation of their host spheroids. We model the growth and activity of black holes in galaxies using ΛCDM cosmological hydrodynamic simulations. We study the evolution of the metal enrichment in quasar hosts and hence explore the relationship between star/spheroid formation and black hole growth/activity in galaxies. Using the simulations we approach the epoch of the first quasars and the first significant star formation activity. We show that the hosts of the rare bright quasars at z∼5−6 have star formation rates of several hundred $\rm\thinspace M_{\odot}\yr^{-1},$ and halo masses of order ∼1012 $\rm\thinspace M_{\odot}$. Already at these redshifts they have supersolar ($Z/Z_{\odot} \sim 2-3$) central metallicities, with a mild dependence of metallicity on luminosity, consistent with observed trends.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In order to analyse the large numbers of Seyfert galaxy spectra available at present, we are testing new techniques to derive their physical parameters fastly and accurately.

We present an experiment on such a new technique to segregate old and young stellar populations in galactic spectra using machine learning methods. We used an ensemble of classifiers, each classifier in the ensemble specializes in young or old populations and was trained with locally weighted regression and tested using ten-fold cross-validation. Since the relevant information concentrates in certain regions of the spectra we used the method of sequential floating backward selection offline for feature selection.

Very interestingly, the application to Seyfert galaxies proved that this technique is very insensitive to the dilution by the Active Galactic Nucleus (AGN) continuum. Comparing with exhaustive search we concluded that both methods are similar in terms of accuracy but the machine learning method is faster by about two orders of magnitude.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

I briefly report on the work conducted to probe the gravitational potential of active and non-active disk galaxies using gas and stellar kinematics.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present our recent results from the observation of the O VI λ λ1032,1038 emission doublet in Seyfert galaxies of type 2 with the FUV spectrograph on the FUSE satellite. These observations are part of our investigation to contrast the properties of the OVI emission line and the absorbing outflows in a sample of rigorously matched Seyfert 1s and 2s, in the framework of the Unified Scheme. The OVI emission line is an excellent diagnostic of the outflowing hot gas at temperatures of ∼106K. In the Unified Scheme, Seyferts of type 2 are those whose central regions are obscured by the ubiquitous dusty torus. We interpret our results in this framework.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

As part of a larger program to study spatially resolved jet / interstellar medium interactions in nearby Seyfert galaxies, we have obtained high spatial resolution spectrographic observations of the central regions of M 51 and its extra-nuclear cloud (XNC, Ford et al. 1985), using STIS on-board the Hubble Space Telescope (HST). In this paper, we present very preliminary results from these observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present an overview on the state of the gas in cluster outskirts. We show that the entropy of the gas in the outskirts often exhibit strong deviations from predictions based on the cluster scaling. We identify the cause of these deviations with incomplete shock propagation observed in clusters with ongoing major merging, survival of substructure and incomplete thermalization, and emission from the surrounding large-scale structure seen in projection.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have studied the quantitative morphology of the galaxies of the Coma cluster brighter than $m_{r}=17$. The surface brightness profiles of all galaxies were decomposed into the structural components: bulge and disc. We found a correlation between the scale length of the discs and the location in the cluster. Galaxies located at small projected distances show smaller discs than those located in the outermost regions of the cluster. We have also investigated the correlation betwenn the B$-$r color of the galaxies and their environment. For late-type galaxies there is a correlation between the color and the position in the cluster. The bluest galaxies are located in the outermost regions of the cluster and show the largest discs. These results can be explained in terms of galaxy harassment.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present single-dish observations of a sample of 27 nearby (z<0.018) Seyfert galaxies obtained with the ATNF/Mopra radiotelescope. The total neutral gas content for the sample is derived. We find that Seyfert galaxies are gas-rich objects with a median HI mass to blue luminosity ratio $M_{HI}/L_B\sim 0.38$ M$_\odot$/$L_\odot$, which tends to increase with decreasing optical and far-infrared luminosities. We have also found a correlation among the neutral hydrogen content of Seyfert 2 galaxies and the IRAS luminosities, similar to those found for normal spiral and starburst galaxies. Our results suggest a scenario where the star formation of Seyfert galaxies is similar to that found in starbursts, and that they are dependent of the initial neutral mass content of progenitors of galaxy disks in the blue compact-HII galaxy-Seyfert sequence. Within this sequence, the far-infrared luminosity and the total hydrogen mass correlate as $L_{fir}/L_\odot\propto (M_{HI}/M_\odot)^{1.5\pm 0.4}$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

NGC 1241 is a Sy 2 galaxy with a 1.4 kpc circumnuclear ring (CNR) of star formation revealed in Paα. A 0.3 kpc long Paα emitting bar centered on the nucleus is present, apparently without associated absorption features. GEMINI (+QUIRC+Hokupa) IR pixel-photometry reveals instead an azimuthally symmetric (J−Ks) color which is redder at the nucleus than at the CNR. This property may well be due to the increasing importance of dust when going from the ring inward into the nucleus. Nevertheless the (V−H) color does not indicate special absorption conditions in the nucleus with respect to the CNR, and no absorption features are evident, as normally expected near emitting bars. Then, we propose as an alternative explanation an excess of C-stars in the nuclear region which decreases outwards until reaching the CNR and its colors. We have compared the pixel color-magnitude diagram with the 2-MASS (J−Ks) vs. Ks diagram for the Large Magellanic Cloud: about 5×102 C-stars and 2.5×104 AGB Oxygen-rich stars inside r∼50 pc, are enough to reproduce the observed nuclear tip in the diagram. This stars would release gas that, gravitationally bounded, pollutes the nuclear environment and could amount 10−2 to 10−1 M$_{\odot}$ yr−1 of fuel for the central engine during the lifetime of stars with masses 2 M$_{\odot}\lt M_{CStars} \lt 6{\rm M}_{\odot}$. This scenario may also explain the observed increased strength of the CN-bands in the stellar populations of Sy 2 nuclei, and the recent claim of a significant contribution of intermediate age stars to the optical continuum of low luminosity AGNs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html