A systematic study of 30 Radio Loud AGNs available in the BeppoSAX archive has been carried out. The sample consists of 9 Broad Line radio Galaxies, 5 Steep Spectrum Radio Quasars and 16 Flat Spectrum Radio Quasars. These objects represent, according to Unified Models, objects with decreasing viewing angles. Our analysis shows considerable differences between FSRQs and BLRGs'SSRQS. As expected in the AGN Unified Model: i) the X-Ray spectrum of FSRQs is a simple power law with a hard spectral slope (the only exception being 3C273), ii) Broad Line and Steep Radio Spectrum AGNs show a steeper X-Ray continuum and Seyfert like features. We also find that the Fe line is weaker than in radio quiet objects. However no strong evidence emerges that a jet contamination may be the main responsible for the EW shrinking in BLRGs and SSRQs. Recent XMM-Newton observations of Pictor A, 3C445 and PKS 2152-69 confirm the nuclear BeppoSAX results and better constrain the Fe line parameters.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

New infrared spectroscopy of 22 high-luminosity high-redshift AGNs helps to test several suggestions regarding the mass, composition and size of the emission line regions in active galacic nuclei (AGN). A plot of the metalicity luminosity correlation over more than five orders of magnitude in luminosity shows that most narrow line Seyfert 1 galaxies fall outside of the general trend. However, when L/LEdd is plotted instead of luminosity, all sources follow the same trend suggesting this to be the primary driver of the correlation. Regarding the narrow emission lines in the most luminous sources, there is a dichotomy in the observed properties where 2/3 of the sources show very strong [O III] lines while the remaining 1/3 have no detectable NLR. On the basis of this I argue that earlier proposed relations of the type $R_{NLR}\propto L_{{\rm [O III]}}^{1/2}$ must break down for RNLR exceeding a few kpc. Thus, NLRs in high luminosity AGN may be very different from those observed in nearby sources. In particular, some high luminosity sources may be in a phase of violent star-formation that produce a large quantity of high density gas in their central kpc.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The NUGA project is a high-resolution (0.5″−1″) CO survey of low luminosity AGN including the full sequence of activity types (Seyferts, LINERs and transition objects). NUGA aims to systematically study the different mechanisms for gas fueling of AGNs in the Local Universe. In this paper we discuss the latest results of this recently completed survey, which now includes newly acquired subarcsec resolution observations for all targets of the sample. The large variety of circumnuclear disk morphologies found in NUGA galaxies (m = 1, m = 2 and stochastic instabilities) is a challenging result that urges the refinement of current dynamical models. In this paper we report on new results obtained in 4 study cases for NUGA: NGC 4826, NGC 7217, NGC 4579 and NGC 6951.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The formation and growth of supermassive black holes (SMBHs) physically linked with bulges are considered. We focus on the radiation hydrodynamic process for the growth of SMBH in the optically thick starburst phase, where radiation from bulge stars drives the mass accretion on to a galactic center through radiation drag effect. In the present scenario, the AGN luminosity-dominant phase (QSO phase) is preceded by the host luminosity-dominat phase, which is called “proto-QSO phase”. In this phase, there exists the massive dusty disks within younger bulges. Also, the proto-QSO phase is anticipated by an optically-thick ultraluminous infrared galaxy (ULIRG) phase. Furthermore, such radiation hydrodynamic model has been also applied to disk galaxies. It turns out that the mass of a SMBH primarily correlates with a bulge component even in a disk galaxy. Thus, by analogy to proto-QSOs, the BH growing phase in disk galaxies may have massive dusty disks within younger bulges.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Despite many years of effort, observational studies have not found a strong correlation between the presence of any proposed fueling mechanism and low-luminosity AGN. After a discussion of the mass requirements for fueling, I summarize this observational work and provide a number of hypotheses for why the nature of AGN fueling has remained unresolved. In particular, I stress the potential importance of the increasing number of candidate fueling mechanisms with decreasing mass accretion rate, the relevant spatial scales for different fueling mechanisms, and the lifetime of an individual episode of nuclear accretion. The episodic AGN lifetime is a particularly relevant complication if it is comparable to or shorter than the time that the responsible fueling mechanisms are observationally detectable. I conclude with a number of relatively accessible areas for future investigation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We summarize the detection rates at wavelengths other than optical for ∼99,000 galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 1 “main” spectroscopic sample. The analysis is based on positional cross-correlation with source catalogs from ROSAT, 2MASS, IRAS, GB6, FIRST, NVSS and WENSS surveys. We find that the rest-frame UV-IR broad-band galaxy SEDs form a remarkably uniform, nearly one parameter, family. As an example, the SDSS u and r band data, supplemented with redshift, can be used to predict K band magnitudes measured by 2MASS with an rms scatter of only 0.2 mag; when measurement uncertainties are taken into account, the astrophysical scatter appears not larger than ∼0.1 mag.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Metal enrichment of intracluster medium (ICM) is reanalysed in the hierarchical galaxy formation scenario. In order to investigate metal abundances of $\alpha$ and iron-peak elements, we incorporate metal production processes by type Ia supernovae (SNe Ia) as well as type II supernovae (SNe II) into the GALFORM model of semi-analytic galaxy formation. We find that a top-heavy initial mass function (IMF) of stars with a power index $x\simeq 0.35$ for starburst is required under the constraint that the IMF for quiescent disc star formation is the Kennicutt IMF. Our model shows an only mild evolution of [Fe/H] as suggested by a recent observation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The emission line spectra of active galactic nuclei fall into three main categories: star formation nuclei (or HII regions), Seyfert nuclei and LINERs (low ionization narrow emission-line regions). A subset of these galactic nuclei has intermediate characteristics between LINERs and HII regions. These so-called transition objects were the subject of numerous studies in the past, but their true nature has remained elusive. It's almost impossible to explain these objects with models that take into account only one ionization mechanism, being it stars, an AGN or shocks. We show how the use of a set of elaborated photoionization models, that account consistently for these parameters (ionization by stars, shocks and/or AGN and dust), constrained by a detailed study of the stellar population properties, can help us understand the nature of these transition objects.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We use numerical simulations of galaxy clusters to study the dynamical and thermal evolution of the ICM from high redshift to the present time. We measure the properties of the satellites accreting on the cluster main progenitor and then measure their self-bound mass fraction as a function of time after the merging. We also calculate the mean properties of their orbits and investigate the time evolution of their internal velocity dispersion and gas temperature. We measure and model the mean pericentric and apocentric times, distances and velocities. Finally we show how the properties of the ICM at redshift zero can be understood by decomposing them as a function of the cluster merging history.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We analyse the rest–frame (U$-$V) colour–magnitude relation for 2 clusters at redshift 0.7 and 0.8, drawn from the ESO Distant Cluster Survey. By comparing them with the population of red galaxies in the Coma cluster, we show that the high redshift clusters exhibit a deficit of passive faint red galaxies. Our results show that the red–sequence population cannot be explained in terms of a monolithic and synchronous formation scenario. A large fraction of faint passive galaxies in clusters today has moved onto the red sequence relatively recently as a consequence of the fact that their star formation activity has come to an end at $z<0.8$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of a new stellar population synthesis code which mixes both evolutionary and empirical population synthesis techniques. The code decomposes a given galaxy spectrum into a base of high resolution spectra from the recent evolutionary synthesis models of Bruzual & Charlot (2003). The main novelty is that now we synthesize the whole Fλ spectrum, rather than a handful of absorption lines and colors.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have imaged $\sim 1$ deg$^{2}$ in the V-band in the direction of the Hercules cluster (Abell 2151). The data are used to compute, for the first time, the luminosity function (LF) of galaxies in the cluster down to the dwarf regime (M$_{lim}$$\sim -13.85$ ). The global LF is well described by a Schechter function (Schechter 1976) with best-fit parameters $\alpha = -1.30 \pm 0.06$ and M$_V^* = -21.25 \pm 0.25$. The radial dependence of the LF has also been studied, finding that it turns out to be almost constant within the errors even further away than the virial radius. Given the presence of significant substructure within the cluster, we have analized the LFs in different regions. While the LFs of the two subclusters present are consistent with each other and with the global one, the southernmost one exhibits a somewhat steeper faint-end slope.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the first homogeneous sample of intermediate-mass black hole candidates in active galactic nuclei. Starting with broad-line active nuclei from the Sloan Digital Sky Survey, we use the linewidth-luminosity-mass scaling relation to select a sample of 19 galaxies in the mass range $M_{\mathrm{BH}} \approx 8 \times 10^4 - 10^6\,\ensuremath{M_{\odot}}$. In contrast to the local active galaxy population, the host galaxies are ∼1 mag fainter than M* and thus are probably late-type systems. The active nuclei are also faint, with $M_g \approx -15$ to −18 mag, while the bolometric luminosities are close to the Eddington limit. The spectral properties of the sample are compared to the related class of objects known as narrow-line Seyfert 1 galaxies. We discuss the importance of our sample as observational analogues of primordial black holes, contributors to the integrated signal for future gravitational wave experiments, and as a valuable tool in the calibration of the MBM–σ∗ relation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the preliminary results of BVRI imaging of six clusters chosen from a follow-up project of the CNOC cluster survey. In an attempt to ascertain the evolution of galaxies in the cluster environment, we focus on the infalling galaxy groups, especially on their characteristics reflected by their color properties. To investigate the role of cluster environment in the evolution of galaxy groups, the color properties of galaxy groups are explored as a function of cluster radius and the local density of cluster galaxies. Both the radius and the local density affect the properties of groups, but evidence suggests that density may be more important in the relationship between cluster environment and galaxy characteristics.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We investigate whether the spectral-type of a locally dominant (most luminous) galaxy can be used to select sets of galaxies that are physically associated (groups). We assume that passive dominants trace a group-like potential, and SF-dominants a field-like environment. The group sample includes 988 groups selected in the 2dFGRS applying a maximum magnitude difference criterion. We find that the average number of passive galaxies associated to a dominant is larger when the dominant is passive, a result supporting our assumption that galaxy associations around a passive dominant are reliable groups. Finally we show that, to reduce the contamination by unbound galaxy associations (SF-dominant), ${\rm a}\geq 3$ passive-members criterion is more efficient than ${\rm a}\geq 6$ all-members criterion.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of a spectrophotometric study of star forming regions in HII galaxies. In particular, we find that, besides their “blobbiness”, HII galaxies are quite homogenous in their chemical properties, though we do see important fluctuations in some physical properties (e.g. extinction).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present an X-ray binary population synthesis model, and use it to simulate the evolution of X-ray binaries formed in a burst of star formation of duration 20 Myr and star-formation rate 10 M$_{\odot}$ yr−1. We find that the X-ray luminous phase persists long after the star-formation episode has ended. The 2-10 keV X-ray luminosity can reach values of 1040−1041 erg s−1, comparable to those of some Seyfert galaxies. These models are directly applicable to starburst galaxies as well as LINERs powered by vigorous star formation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Seyfert narrow line regions (NLR) have emission line ratios which are remarkably uniform, displaying only ∼0.5 dex variation between different galaxies. Existing models have been unable to explain these observations without the introduction of ad hoc assumptions, geometrical restrictions or new parameters. Here we introduce a new model: dusty radiation pressure dominated photoionization, which provides a natural self-regulating characteristic, leading to an invariance of the spectrum over a very wide range (>100) of ionization parameter. The dusty model is able to reproduce both the range and the absolute value of the observational line ratios not only in the standard optical diagnostic diagrams but also in UV diagnostic plots, providing an explanation to the problem in NLR observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this paper we present results of a detailed morphological and radio polarization study of the nearby radio galaxy 3C33.1 (4C72.01, 0106+729, z = 0.18) made with the Very Large Array at 18 and 21 cm. Recently, this galaxy has been re-classified within a sample of large core-dominated radio sources and it has an exceedingly high projected linear size of ∼450 kpc. The jet shows little Faraday rotation, with rotation measures |RM|<20 rad m−2, whereas the hotspots exhibit higher values. The low rotation measures indicate that this radio source has a visible jet, which can be a naked jet or stripped from a dense environment. A spectral ageing analysis, based on syncrotron power losses arguments of the integrated spectra, suggest that the radio structure is not younger than 20 Myrs. Further observational properties of this radio galaxy are also discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Secular evolution and fueling is driven by bars in spiral galaxies, and the related dynamical processes are reviewed. It is shown that gravity torques dominate over viscous torques, and produce gas infall to the center. In this infall, the bar wave accepts the angular momentum, which produces its destruction. In the end, a central mass concentration is built, which also contributes to this destruction. While gas can be stalled at ILR for a while, secondary bars then take over the fueling. In a galaxy life-time, several bar episodes can successively develop. Through external gas accretion, disks are replenished by intermittence, between two bar phases. While the general trend for a galaxy is to evolve towards early-types, its morphology can oscillate, and turn back transiently to later-types.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html