High resolution B, V, I imaging of the inner region of the spiral barred galaxy NGC 7479 suggests this galaxy contains a pseudo nuclear ring and possibly a nuclear bar.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We investigate the relation between the asymptotic circular velocity, $V_{\rm circ}$, and the central stellar velocity dispersion, $\sigma_{\rm c}$, in galaxies. We consider a new sample of high surface brightness spiral galaxies (HSB), low surface brightness spiral galaxies (LSB), and elliptical galaxies with HI-based $V_{\rm circ}$ measurements. We find that: 1) elliptical galaxies with HI measurements fit well within the relation; 2) a linear law can reproduce the data as well as a power law (used in previous works) even for galaxies with $\sigma_{\rm c} \lt 70$ km/s; 3) LSB galaxies, considered for the first time with this respect, seem to behave differently, showing either larger $V_{\rm circ}$ values or smaller $\sigma_{\rm c}$ values.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present near-IR, diffraction limited imaging of the nucleus of NGC 1068 obtained with NAOS-CONICA at VLT. These observations provide an accute view on the distribution of hot dust in the vicinity of the central source, at a 0.1” resolution. The use of a new type of coronagraph allowed us to detect and identify new structures at K, to calculate more accurate color indices, and derive the state of the dust in this very complex morphology. We also used deconvolution on images aquired in other bands to get an accute view of these structures.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Modern kinematic diagnostics from high-S/N spectroscopy provide useful tests on the collisionless merger hypothesis for the formation of elliptical galaxies. Bender, Saglia & Gerhard (1994) show that the skewness of the line-of-sight velocity distributions (LOSVD) has opposite sign to the rotation velocity and follows a distinct pattern. Previous N-body experiments (Bendo & Barnes 2000, Naab & Burkert 2001) disagree as to whether the relation is reproduced by the models.

We present first results from an ongoing effort to explain the skewness properties of the LOSVD's of ellipticals. We use large N-body simulations of disk-disk galaxy mergers ($10^6$ particles), with mass ratios 1:1 and 3:1. Our 1:1 models fail to reproduce the H3 vs. $V/\sigma$ relation, in agreement with Naab & Burkert (2001). 3:1 mergers yield trends similar to the observations for large values of $V/\sigma$, but with overall lower H3 values in the models than in real galaxies. And we fail to reproduce high H3 values for low $V/\sigma$. So far, it is unclear whether the disagreement is related to the lack of rotation in the bulge components of our initial model galaxies, or to a more general shortcoming of dissipationless mergers to reproduce the properties of real ellipticals.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Surface brightness measurements of the diffuse intracluster light (ICL) in centrally concentrated, relaxed clusters have demonstrated that stars bound only to the cluster potential can contain anywhere from 5 to 50% of the total cluster flux. These stars are a by-product of the evolution of galaxies in clusters, and can be used to constrain models for the structure and evolution of clusters and their member galaxies. The ICL will be an important test of cosmological models as it is a baryonic component of clusters that is likely to evolve with redshift. To learn about these processes we are undertaking a program to measure the characteristics of the ICL (total flux, color, and substructure) as a function of cluster mass, morphology, and redshift. We have obtained data for a sample of 10 clusters at low and moderate redshifts. We discuss here our preliminary results for one cluster in that sample, A3888. With 4-5 hour integration times on-source per filter (V & gunn-r), we reach a 1 sigma surface brightness limit of 29.9 mag/arcsec$^{2}$ in the V band. We have identified an intracluster light component that is $\sim10\%$ of total cluster light, extends to 600 kpc from the center of the cluster, and is redder in color than the cluster galaxies ($V-r = 0.4$ near the center, increasing to $V-r = 0.8$ at r = 500 kpc). In addition we find 3 low surface brightness features which are blue ($V-r \simeq 0$), and in total are equivalent to one $m_V = 20.8$ mag galaxy.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Low-luminosity nebular emission is found in the centers of a large fraction of galaxies, and in many cases the energy source powering these systems is ambiguous. This is particularly true for H II/LINER “transition” objects, although a reasonable explanation for these sources is that their emission is the composite result of a weak accretion-powered system surrounded by star-forming regions. This contribution describes results from a Hubble Space Telescope spectroscopic survey that probes the structure of nearby transition objects and other emission nuclei. The results provide only limited support for the composite picture for these sources; the emission nuclei do not show a strong tendency for the nebular classification to depend on aperture size. The strongest variations in forbidden line ratios appear to be mediated by a gradient of decreasing nebular density with increasing radius.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The gravitationally lensing clusters A370, A2218, A1689 and Cl0024+1654 were observed with the Infrared Space Observatory (ISO) using ISOCAM at 6.7 $\mu$m and 14.3 $\mu$m (hereafter 7 $\mu$m and 15 $\mu$m respectively).

A total of 178 sources were detected in the whole set, 70 of them being cluster objects. The spectral energy distribution of a subset of sources was calculated using GRASIL. The results for the total infrared luminosity and the estimation of the star formation rate are presented for the non stellar objects for which the SED has been determined. The majority of the cluster galaxies in A2218 are best fit by models of quiescent ellipticals. In Cl0024+1654, most of the galaxies lying on the Butcher-Oemler region of the colour-magnitude diagram are best fit by disk galaxies, while those on the main sequence area have in general SEDs corresponding to post-starburst galaxies.

The population of each cluster is compared with the field population, as well as with the population of other clusters. A significant number of Luminous IR Galaxies (LIRGs) is detected in Cl0024+1654, while only one LIRG has been observed in total in A370, A1689, and A2218. This result supports the link between LIRGs in clusters and recent or ongoing cluster merger activity as well as the need for extending the observations to the outer parts of clusters.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We analyzed spectra of 15 luminous high-redshift quasars (3.3<z<5.1) and we derived black hole masses that are based on Hβ, MgII, and CIV emission lines, in the range of $2\times10^8<M_{bh}<4\times10^{10} M_\odot$. Assuming exponential growth of the black holes we estimated that it takes about several 100 Myr up to 1 Gyr to accumulate the observed black hole masses, i.e., most of the SMBHs that power these quasars at high-redshifts, started to grow at $z \simeq 5 {\rm to} 10$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We determined a central black hole mass of $M_{\rm virial}=1.8\pm 0.4\times 10^{7} M_{\odot}$ in the Seyfert galaxy Mrk 110 with reverberation mapping methods – i.e. from integrated optical line profile variations as well as from velocity-delay maps. But this black hole mass depends on the unknown orientation of the central accretion disk. Here we report on the detection of gravitational redshifted emission in the variable fraction of all broad optical emission lines in Mrk 110. We derive a central black hole mass of $M_{\rm grav}=14.0\pm 3.0\times 10^{7} M_{\odot}$ with this method. This value is independent on the orientation of the accretion disk. A comparison of both black hole mass estimates allows to determine the central accretion disk inclination angle i to 21° in Mrk 110, and therefore the orientation of the spin axis of the central black hole.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A new volume-limited sample of 84 isolated pairs of galaxies has been selected from the UZC catalogue. Galaxies in pairs are brighter than $M_{Zw}-5\log h =-18.9$. The projected separation between pair members is $r < 200 h^{-1}$ kpc, the isolation criterion requires the pair to have no further companion within a $R=1 h^{-1}$ Mpc distance. Morphological classification for both members is available for 57 pairs. Out of these, 9 are early-type (E+E) pairs, 29 late type (S+S) pairs, and 19 mixed (E+S) pairs. We find a deficit of luminous dominants among E+E and E+S pairs relative to S+S pairs, while the distance between pair members is statistically undistinguishable. However, among the 12 pairs that are not only close but also luminous, the fraction of E+E and S+S pairs is 8% and 83% respectively. This result is consistent with star-formation being enhanced in S+S pairs (but not in spirals in S+E pairs) in extremely close isolated pairs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This contribution reviews two topics of current interest in the study of black hole demographics in active galaxies: Can the stellar velocity dispersions of quasar host galaxies be measured? And can we constrain the black hole mass function below 106 M$_\odot$?To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We explore the stellar halo of the Milky Way to search for fossil signatures of past mergers. We use the Beers et al. (2000) catalog of non-kinematically selected metal poor stars in the solar neighborhood to select subsets of halo stars within 1-2 kpc of the Sun. Motivated by the results of high resolution CDM simulations, we look for substructure in the kinematics of the fastest stars. When a two-point velocity correlation function is applied to these subsets, statistical evidence of substructure is found. This appears to be due to a small moving group with dynamical properties similar to the stellar “stream” previously discovered by Helmi et al. (1999).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a statistical analysis of the Chandra observation of the source field around the 3C 295 galaxy cluster ($z=0.46$). Three different methods of analysis, namely a chip by chip LogN-LogS, a two-dimentional Kolmogorov-Smirnov (KS) test, and the angular correlation function (ACF) show a strong overdensity of sources in the North-East of the field, that may indicate a filament of the large scale structure of the universe towards 3C 295.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Clusters of galaxies are the largest bound gravitational systems in the universe. They outline the large-scale structure and thus are able to test predictions of cosmological models. Detailed studies of galaxy populations in clusters at high $z$ offer insights into galaxy evolution as a function of look-back time. Unfortunately, large homogeneous samples of galaxy clusters only exist at redshifts $<$0.5. There are around 1000 candidate clusters with photometric or otherwise estimated redshifts above 0.5, but spectroscopically confirmed clusters are still scarce in this redshift regime. Some clusters with $z>1$ have recently been identified from X-ray surveys.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The structure of the universe is believed to have formed by clustering hierarchically from small to large scales. Much of this evolution occurs very slowly but at a few special times more rapid, violent activity may occur as major subunits collide at high velocities. The Abell 2125 complex ($z=0.247$) appears to be undergoing such an event as shown by modeling of the optical velocity field and by the detection with the VLA of an unusually large number of associated radio active galaxies. We present an 80 ksec Chandra imaging of Abell 2125, together with extensive complementary multi-wavelength data. We show direct evidence for galaxy transformation and destruction during the cluster formation. The Chandra data unambiguously separate the X-ray contributions from discrete sources and large-scale diffuse gas in the Abell 2125 complex, which consists of various merging clusters/groups of galaxies and low-surface brightness emission. This enables us to study processes affecting galaxy evolution during this special time from scales of Mpc down to a few kpc. The overall level of activity plus the special time for the cluster-cluster merger suggests that an important phase of galaxy evolution can take place during such events.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a new sample of 30 nearby (z < 0.2) BL Lacs, selected to study the nuclear as well as the large scale properties of low power radio sources. New VLA and VLBA radio data have been obtained to discuss the morphology, physical properties, and overall properties of the sample. We show that the distributions of total radio power and intrinsic core radio power for BL Lacs are consistent with their being drawn from the same population as FR I radio galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

High resolution radio and X-ray observations of a subsample of composite LINER/H II galaxies with arcsec-scale radio cores were obtained. These observations yield a 12% detection rate of low luminosity AGN among the entire composite sample in the Palomar survey. Four of these low luminosity AGN also possess sub-parsec jet-like radio extensions. While canonical advection-dominated accretion flows may be responsible for the radio and X-ray emission in submillijansky cores like NGC 7331, they do not appear consistent with the radio emission in these milliarcsecond-scale radio cores; the latter sources are more likely to have an energetically important contribution from a radio-emitting jet.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We identify the dominant emission processes in 3C 270 in the infrared to be non-thermal, and emission from its dusty disk does not contribute significantly to the total infrared output. This implies that such disks can be hard to find through their infrared emission, and that any circumnuclear torus, if at all present, is small and thin.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We discuss follow-up X-ray observations of giant-amplitude, non-recurrent X-ray flares, interpreted as tidal disruptions of stars by supermassive black holes at the centers of the flaring galaxies. The flare observations open up a new window to study supermassive black holes and their environment, and the physics of accretion events, in non-active galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Galaxy clusters at $z\sim1$ are particularly important in the study of cluster evolution and the application of clusters to cosmological studies. We briefly discuss the difficulties in creating well-defined, large, high-redshift cluster samples, and some of the techniques used in optical/IR imaging to overcome them. We give a summary of the current state of optical/IR observations of the relatively small number of high-redshift clusters identified so far, including discussions of the galaxy luminosity function, the Fundamental Plane, the color-magnitude relation, and the Butcher-Oemler effect. The application of photometric redshift techniques is also highlighted.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html