We present a model for the distribution of void sizes and its evolution within the context of hierarchical scenarios of gravitational structure formation. For a proper description of the hierarchical buildup of the system of voids in the matter distribution, not only the void-in-void problem should be taken into account, but also that of the void-in-cloud issue. Within the context of the excursion set formulation of an evolving void hierarchy is one involving a two-barrier excursion problem, unlike the one-barrier problem for the dark halo evolution. This leads to voids having a peaked size distribution at any cosmic epoch, centered on a characteristic void size that evolves self-similarly in time, in distinct contrast to the distribution of virialized halo masses in not having a small-scale cut-off.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

High velocity shocks may provide an important source of ionizing radiation in the NLR of active galaxies. Here we present preliminary results of a new grid of MAPPINGS III shock models for shock velocities up to 1000 km s−1. This grid significantly extends the parameter space covered by the previous models, and will serve as an important component in building multi-process models of the NLR.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The recent discovery of hidden non-axysimmetric and disk-like structures in bright Virgo dwarf elliptical and lenticular galaxies indicates that they may have late-type progenitors. Using high resolution N-body simulations we follow the evolution of disk galaxies within a $\Lambda\textrm{CDM}$ cluster simulated with $10^7$ particles where the hierarchical growth and galaxy harassment are modelled self-consistently. Most of the galaxies undergo significant morphological transformation, even at the outskirts of the cluster, and move through the Hubble sequence from disks to spheroidals. The time evolution of the simulated galaxies is compared with unsharp-masked images from the VLT and we compare the kinematics of our models with the latest high resolution spectroscopic studies from the Keck telescope. We will also discuss the properties of diffuse intra-cluster light formed by tidal debris stripped away from the infalling disks by gravitational interactions.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present results from 547 optical galaxy redshifts obtained in the region of Horologium-Reticulum (HR) using the 6dF (six-degree field) multi-fiber spectrograph on the United Kingdom Schmidt Telescope. Concentrating upon the inter-cluster regions of the HR Supercluster (HRS), we derive three primary results from our 6dF observations. First, the HRS covers a redshift range from at least 16000 to 22500 kms−1. Second, these HRS galaxies exhibit an overall gradient with increasing redshift along a spatial axis of SE-NW with high statistical probability. Third, along the best-fit line from the spatial-redshift linear regression, HRS galaxies comprising the redshift trend are distinctly split into a high- and low-redshift component. Finally, comparisons of the spatial-redshift distribution are made between the HRS and the Shapley supercluster.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of UV spectroscopy of AGNs with double-peaked Balmer emission lines. In 2/3 of the objects, the far-UV resonance lines are strong, with single-peaked profiles resembling those of Seyfert galaxies. The Mg II line is the only UV line with a double-peaked profile. In the remaining objects, the far-UV resonance lines are relatively weak but still single-peaked. The latter group also displays prominent UV absorption lines, indicative of a low-ionization absorber. We interpret the difference in the profiles of the emission lines as resulting from two different regions: a dense, low-ionization accretion disk (the predominant source of the Balmer and Mg II lines), and a lower density, higher-ionization wind (the predominant source of the far-UV resonance lines). These results suggest a way of connecting the double-peaked emitters with the greater AGN population: in double-peaked emitters the accretion rate onto the black hole is low, making the wind feeble and allowing the lines from the underlying disk to shine through. This scenario also implies that in the majority of AGNs, the wind is the source of the broad emission lines.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present theoretical Fe I-III emission-line strengths for physical conditions typical of Active Galactic Nuclei with Broad-Line Regions. We can satisfactorily reproduce the empirical UV Fe II-III emission-line template of Vestergaard & Wilkes (2001) for the prototypical narrow-line Seyfert 1 galaxy I Zw 1, although a number of detailed discrepancies remain.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We identify 175 Seyfert galaxies from the Southern Sky Redshift Survey – SSRS2. We use the entire SSRS2 catalog to investigate the correlation between the presence of AGN with host environment. The AGN phenomenon is more strongly correlated with the internal host properties than with the external environment. In particular, we find that Seyferts reside in more luminous galaxies, and are twice as frequent in barred galaxies and systems showing signs of advanced merger condition, when compared to a control sample.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a numerical code to synthesize the stellar population of galaxies, using the observed flux as observable, for the visible and IR range This code is an evolution of a previous one, which used the equivalent widths.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of over 20 years of optical spectroscopic monitoring of the prototypical double-peaked emitter, Arp 102B. Its distinct double-peaked, extremely broad (FWHM ≈15,000 km s−1) low-ionization lines (Hα, Hβ, and Mg II) are well-modeled by emission from photoionized gas in a relativistic Keplerian accretion disk around a central black hole (Chen & Halpern 1989; Halpern et al. 1996). A ubiquitous property of double-peaked emitters is long-term variability in the shape of their line profiles on the timescale of months to years, which is consistent with the dynamical timescale of an accretion disk. This variability can be attributed to inhomogeneities in the line-emitting disk, i.e., hot spots, spiral arms, eccentricity, and warps. We characterize the profile variability of Arp 102B in detail, and use it to constrain physical models for the structure and dynamics of its line-emitting accretion disk.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this short letter we present our new work on the coronal emission in a sample of AGN. We used the adaptive optics system NACO on the VLT to obtain high angular resolution images (∼0.15”) of the coronal emission in the vicinity of the central engine.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The observed infall of galaxies into the Virgo cluster puts strong constraints on the mass of the cluster. A non-parametric fully non-linear description of the infall can be made with orbit reconstructions based on Numerical Action Methods. The mass of the cluster is determined to be $1.2 \times 10^{15} M_{\odot}$. The mass-to-light ratio for the cluster is found to be seven times higher than the mean ratio found across the region within $V=3000$ km/s.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this work I present the survey which is searching for the rise in the volume-averaged star formation rate at intermediate redshifts (z<1). This survey is a combination of the data taken with Advanced Camera for Surveys in parallel with WFPC2 (U band) of the GOODS fields. We use template fitting of the spectral energy distributions to obtain photometric redshifts and classify the objects as starbursts, early- and late-types. The colors of the starbursts were reproduced and ages were estimated with the stellar evolutionary synthesis code Starburst99. By matching the optical catalog with the Chandra X-ray catalog we have identified the X-ray sources and possible candidates for having a combination of active nuclei and starburst at intermediate redshifts. Analysis of the light concentration, asymmetry and clumpiness, shows that this sample is a mixed bag, containing dwarf ellipticals, early and late-spirals and peculiar objects which resemble mergers in progress. These results have strong implications for galaxy evolution since it shows for the first time who are the candidates for the rise of the SFR at intermediate-z.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present long-slit HST/STIS measurements of the ionized-gas kinematics in the nucleus of three disk galaxies, namely NGC 2179, NGC 4343, NGC 4435. The sample galaxies have been selected on the basis of their ground-based spectroscopy, for displaying a strong central velocity gradient for the ionized gas, which is consistent with the presence of a circum nuclear keplerian disk (CNKD, Bertola et al. 1998; Funes et al. 2002) rotating around a super massive black hole (SMBH). For each target galaxy we obtained the Hα and [NII] 6583 Å kinematics along the major axis and two 0."25 parallel offset positions. Out of three objects only NGC 4435 turned out to have a disk of ionized gas in regular motion and a regular dust-lane morphology. Preliminary modeling indicates a SMBH mass (M[bull ]) one order of magnitude lower than the one expected from the M[bull ]−σc relation for galaxies (Ferrarese & Merritt 2000; Gebhardt et al. 2000).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We compare recent HST observations of Seyfert and quasar NLRs and find that type–2 AGNs follow a relation consistent with that expected for a distribution of gas ionized by a central source $R_{\rm NLR,2} \propto L^{0.32 \pm 0.05}$, while type–1 objects are fit with a steeper slope of 0.55±0.05. The latter is comparable to the scaling found for the BLR size with continuum luminosity (slope: 0.5–0.7). Therefore, we investigate what we can learn about the BLR size if the NLR size is only determined by the AGN luminosity. We find that NLR and BLR size are related linearly following $R_{\rm BLR} \propto R_{\rm NLR,1}^{0.88 \pm 0.1}$. This relation can be used to estimate BH masses.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The direct comparison of observations to numerical hydro-N-body simulations, although simple in principle, is not always trivial because of possible artificial effects produced by the instrument response and by instrumental and sky background. To overcome this problem we build the software package X-MAS (X-ray MAp Simulator) devoted to simulate X-ray observations of galaxy clusters obtained from hydro-N-body simulations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report the first results from a panoramic spectroscopic survey of galaxies in the rich cluster Cl0024+1654 ($z\simeq 0.4$). Using HST imaging we examine the properties of early-types as a function of cluster radius. At all cluster radii, our sample lies on a self-consistent Fundamental Plane whose zero point implies evolution since $z=0$ corresponding to $\Delta[\log (M/L_V)] = 0.14 \pm 0.06$, an overall trend consistent with previous work. Using diagnostic [O II] emission and Balmer absorption lines, we locate a population of intrinsically faint galaxies at 1–2.4 Mpc radius undergoing a period of star formation. The luminosity-dependent radial trends are suggestive of the gradual quenching of star formation for infalling galaxies. We discuss physical mechanisms that may be responsible for this environmental evolution.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

$K$ band luminosity functions (LFs) of three, massive, high redshift clusters of galaxies are presented. The evolution of $K^{*}$, the characteristic magnitude of the LF, is consistent with purely passive evolution, and a redshift of formation $z_{{\rm f}} \approx 1.5-2$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We discuss results of the mapping of both the stellar and gaseous kinematics of the nuclear region of 4 nearby Seyfert galaxies, on the basis of GMOS IFU observations in the spectral region of the CaII triplet (8500Å). We do not find in any of these galaxies central drops (within the central hundred parsecs or so) in the stellar velocity dispersions, as recently reported in the literature for a number of Seyferts. However, we do conclude that apparent drops are observed when there is contamination of the CaII triplet absorption lines by underlying line emission. When extended gas emission ([SIII]9068Å) is observed, the gas velocity field differs from the stellar velocity field. The latter is usually consistent with the classical “spider diagram” characteristic of disk galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report the first systematic study of the supercluster-void network in the $\Lambda$CDM concordance cosmology treating voids and superclusters on an equal footing. We study the dark matter density field in real space smoothed with the $L_s = 5$ h−1Mpc Gaussian window. Superclusters and voids are defined as individual members of over-dense and under-dense excursion sets respectively. We determine the morphological properties of the cosmic web at a large number of dark matter density levels by computing Minkowski functionals for every supercluster and void. At the adopted smoothing scale individual superclusters totally occupy no more than about 5% of the total volume and contain no more than 20% of mass if the largest supercluster is excluded. Likewise, individual voids totally occupy no more than 14% of volume and contain no more than 4% of mass if the largest void is excluded. The genus of individual superclusters can be $\sim 5$ while the genus of individual voids reaches $\sim 55$, implying significant amount of substructure in superclusters and especially in voids. Large voids are typically distinctly non-spherical.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have taken N-band spectra of the nuclear dust regions of NGC 1068 with the newly commissioned Mid-InfrareD-Interferometer (MIDI), with a spatial resolution of ∼10 milliarcsec (∼1 pc). We resolve the near-nuclear emission into a warm component (∼300 K) 2.1×3.4 pc in size and a smaller hot component. We see a strong silicate absorption in front of the central component that differs in form from normal olivine-type profiles. This thick dust structure cannot be supported for the length of the active phase of the AGN by gas pressure or turbulent motions.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html