Ab-initio modeling of galaxy formation is becoming ever more detailed and is including ever more physical processes in a bid to describe the process of galaxy formation more realistically. We will describe some recent advances and applications of the semi-analytic model of galaxy formation, GALFORM. In particular, we will describe a preliminary study of the effects of environment on galaxy morphology in a $z=0.4$ cluster.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a spectroscopic sample of 48 early-type galaxies in the rich cluster Abell 2218 and 50 galaxies in Abell 2390. Since both samples are very similar, we combine them and investigate a total number of 98 early-type galaxies at $z \sim 0.2$. A subsample of 34 galaxies with HST structural properties is used to construct the Fundamental Plane. Elliptical and S0 galaxies show a zeropoint offset of $\overline{m}_{r}\sim0.43$ mag with respect to the local Coma FP. Both sub-samples, ellipticals and lenticulars, exhibit a similar, mild evolution and small scatter. The moderate amount of luminosity evolution is consistent with stellar population models of passive evolution, if $z_{f}\ge2$ is assumed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

WFPC2 continuum images of the low metallicity Blue Compact Dwarf Galaxy SBS 0335-052 revealed 6 intense point source that were deemed to be super star clusters. Subsequent observations with NICMOS in the infrared continuum and Paschen α reveals that only 2 of the sources have very young stars with the other point sources as clusters that may have ended their episodes of star formation. The optical images show a probable supernova created cavity to the north of the present clusters, while the currently active star forming clusters lie at the southern end of the cluster. This indicates a possible string of induced star formation propagating from the north to the south. The presence of a large number of O stars in a small volume raises the question of whether super star clusters might be the breeding grounds for intermediate mass black holes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have investigated the stellar kinematics of two brightest cluster galaxies (BCGs) to large distances from the cluster centre. In both galaxies, the velocity dispersion rises with radius. Orbital anisotropy is ruled out as the cause and we conclude that the kinematics in the outer parts of BCGs are dark matter dominated. This result contrasts with the current problem for intermediate luminosity ellipticals, which appear to have less dark matter than predicted by CDM. Combining the present results with our previous work, the fraction of BCGs with outwardly rising dispersions ($\sim60\%$) is much higher than that found previously ($\sim7\%$) from the inner parts of BCGs. We argue that this phenomenon may be more common than previously thought. The agreement with radial trends expected for a smooth galaxy/cluster transition, and the lack of dependence on cD/BCG dominance and cluster environment, suggest that the outwardly rising dispersion is a genuine response of the stars to the underlying cluster potential. There is evidence that BCG in Abell 2063 is not at the centre of the cluster potential.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We compare the circumnuclear stellar population and environmental properies of Seyfert and Composite (Seyfert + Starburst) nuclei with those of LINERs and LINER/HII transition galaxies (TOs), and discuss evidence for evolution from Seyfert/Composite to LINER/TO nuclei.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have discovered four intergalactic HII regions in the Stephan's quintet, at more than 25 kpc projected distance from the center of the nearest group galaxy, with no apparent optical connection to it. They have ${\rm M}_B$ ranging from −11.9 to −12.5 mag, colors B$-$R=0.7 to 1.1 mag, radial velocities from 6565 to 6651 km/s and they are superposed onto the HI tail east of NGC 7319, with a mean radial velocity of 6610 km/s. In addition, they have metalicities of the order of 12+log(O/H)=8.58$\pm$0.25, which suggests that they were formed from pre-enriched material. We derive a mean age of $4.6 \pm 0.6$ Myr and a mean stellar mass of $(2.9 \pm 1.4)\times10^4~M_\odot$ for the four objects. The masses, ages, colors, velocities, metalicities and location of the objects suggest that they are HII regions that were formed far away from the galaxies through compression of the intergalactic HI gas by galaxy collisions.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The detection of very high energy emission in blazars with the new generation of TeV telescopes rises the question of the origin of this emission and its relation to that at other wavelengths. In this work we present contemporaneous optical and X-ray observations of two bright and close southern hemisphere blazars: PKS 2005-489 and PKS 2155-304, the latter detected at TeV energies. The SED between radio and X-rays is discussed and compared with that of other TeV blazars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Near-infrared spectroscopic observations in the range 0.8-2.4μm are used to study the kinematics and excitation mechanisms of Molecular Hydrogen and [FeII] lines in a sample of AGNs. The width of H2 lines is narrower than [FeII] lines, therefore they do not originate from the same parcel of gas. The molecular emission is found to be purely thermal but with heating processes which vary among the objects. A clear correlation between H2/Brγ and [FeII] 1.257μm/Paβ is found for our sample objects supplemented with data from the literature. The correlation of these line ratios is a useful diagnostic tool in the NIR to separate emitting line objects by their level of nuclear activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Several radio-loud objects exhibit a complex structure when observed at radio wavelengths: a stationary core, which is thought to harbour the central engine that powers the AGN phenomena, and a relativistic jet, formed by several superluminal components. In some cases, jet components are ejected with different apparent proper motions and directions on the plane of the sky. Moreover, these sources can also show signatures of long-term periodic variability in their historical optical light curve. In this work, we selected the objects 3C 120 and 3C 345, which exhibit both characteristics mentioned above, and interpret them in the framework of jet inlet precession. A brief discussion about what kind of mechanism could be responsible for jet precession is also presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present new observations in X-ray and optical/ultraviolet of the nucleus of NGC 1097 known for the abrupt appearance of broad, double-peaked Balmer lines in its spectrum in 1991. These new observations are used to construct the spectral energy distribution (SED) of the central engine. From the SED we infer that this AGN is radio-loud and has a bolometric luminosity $L_{\rm Bol} \sim 10^{42} \: \textrm{erg s}^{-1}$, implying a low Eddington ratio of $L_{\rm Bol}/L_{\rm Edd} \sim 10^{-4}$. These results suggest that the central ionizing source is an advection-dominated accretion flow (ADAF) in the form of an ellevated structure which photoionizes an outer thin disk. We fit a simplified ADAF model to the SED and obtain limits on the values of the mass accretion rate $\dot{M}$ and accretion efficiency η, namely $\dot{M}/{\dot{M}_{\rm Edd}} \gtrsim 10^{-3}$ and $\eta \lesssim 10^{-2}$. We identify an ‘energy budget’ problem: if the central photoionizing source is isotropic, the covering factor of the line-emitting portion of the thin accretion disk is ≈6, i. e. the central source accounts for only 20% of the energy emitted in the double-peaked Balmer lines.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Our recent Chandra and XMM-Newton observations of two high redshift broad absorption line (BAL) quasars have revealed the presence of massive outflows of highly ionized, high-metallicity material driven from near the black hole (a few gravitational radii) with velocities of up to 0.4c. The inferred mass outflow rates of 1–10 $M_{\odot}$ yr−1 and the measured outflow velocities, that significantly exceed the escape velocities of galaxies and clusters of galaxies, imply that quasar winds provide an important feedback mechanism for kinetic energy injection into the IGM. These quasar outflows may also play an important role in the coevolution of black holes and their host galaxies. We present new constraints on the location of the X-ray BAL material based on our analysis of the variability of the ionization properties of the X-ray absorbers. The location and ionization properties of the X-ray BAL material are crucial in inferring the mass outflow rate and rate of kinetic energy injected into the IGM.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a weak lensing analysis and comparison to optical and X-ray maps of the close pair of massive clusters A222/223. Indications for a filamentary connection between the clusters are found and discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Radio-loud AGNs can inhabit regions with a very rich ISM. The presence of this rich medium is likely related to the origin and evolution of the host galaxy and of the active nucleus. Recent observations show that a large fraction of radio galaxies contains a significant young stellar population. This supports the idea that mergers are responsible for both the starburst phase and the triggering of the nuclear activity. The gas that reaches the central regions can have quite disturbed kinematics, likely due to the effects of the AGN activity and in particular of the powerful radio jets. The recent detection of fast nuclear gas outflows, observed both in ionised and neutral gas, is giving new and important insights into the physical conditions of the gaseous medium around the nucleus and the interaction between the AGN and this medium. Finally, as another example of the interplay between the radio activity and the ISM, the possibility of star formation induced by the passage of the radio jet will be discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Mrk 1210 is an Sa galaxy at z = 0.01350. Its optical spectrum displays a strong featureless continuum and Wolf-Rayet features within the central 200 pc (Storchi-Bergmann et al. 1998), evidencing the presence of a circumnuclear starburst. Here, we present SpeX near-infrared (NIR) spectroscopy in the interval 0.8−2.4 μm, combined with optical (3700Å-7400Å) observations, aimed at studying the physical properties of the nuclear and extended gas. Kinematics derived from the line profiles, extinction affecting the emitting gas, temperature and density indicators of the NLR, and excitation sources for the molecular and low-ionization gas are discussed. The presence of high-ionization as well as low-ionization and molecular lines in the optical and NIR spectrum suggests a strong competition between the starburst component and the ionized gas from the central engine. This makes Mrk 1210 an ideal target to study the interplay between starburst and nuclear activity in galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present VLT–ISAAC spectra of unprecedented S/N and resolution for the Hβ region in a sample of n = 17 quasars in the range z=0.8–2.5. The data represent our first attempt to test source occupation and line properties for the Eigenvector 1 parameter space that was defined using a sample of sources with z<0.8. We find no strong luminosity/redshift dependent effects with the possible exception of an increase in the minimum broad line profile width from 1000 to 3000 km s−1 between MB≈−20 and −28.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We discuss some recent results from a program to study the relationships between AGNs, super-massive black holes (SMBHs), and their surrounding host galaxies. The results are based on broad emission-line diagnostics of the SMBH masses and metal abundances in a unique sample of 578 Type 1 AGNs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

During the last decades many authors have concentrated their efforts on understanding what are the most efficient mechanisms to feed an AGN. Several solutions have been proposed, as the presence of circumnuclear star clusters, nuclear bars/disks/spirals, and the interaction between galaxies, in form of close encounters and mergers. Here we present new results about an isolated, intermediate-type Seyfert galaxy, Mrk315. The analysis of broad- and narrow-band images, and integral field spectra revealed a spiral-like structure hidden under the E/S0 morphology of the galaxy, and confirmed the presence of a nuclear jet-like feature, forming a sort of very extended “hook”. Moreover, our data confirmed the supposed nature of the already known knot, located at 2” from the active nucleus, as a secondary nucleus, residual of a minor merger bewteen the galaxy and a small nucleated companion.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The excellent spatial resolution of the Chandra satellite allowed us to see a wide variety of new types of substructures in the intergalactic gas in clusters of galaxies. The most promising scenarios to explain at least some of the phenomenology in the clusters centers involve processes that result from the interaction of the central active galaxy and its surroundings. Here, we present preliminary results of a Chandra velocity analysis of the Centaurus cluster. The results suggest that some of the core features may be interacting with pre-existent bulk gas flows in the cluster.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We use low resolution, near-IR spectra of eight of the most distant quasars known, with redshifts in the range 4.9<z<6.4, to investigate the gas and dust properties in their circumnuclear regions. Half of these quasars are characterized by deep, broad and blueshifted absorption features associated with both high and low ionization species, i.e. they belong to the class of Broad Absorption Line (BAL) quasars, which are associated with powerful outflows of dense gas. The large fraction of BAL quasars, the depth and ionization state of the absorption features suggest that these most distant quasars are surrounded by a much larger amount of dense gas than lower redshift (z<4) quasars. We discuss the possible interpretation of this result in terms of extremely high accretion rates and the association with the early formation of quasars.

The spectral shape of all these very distant quasars, and in particular of the BAL quasars, is bluer than for quasars at z<4, suggesting an evolution of the properties of the dust responsible for the quasar reddening. We show that the observed spectral shape can be explained by an extinction curve due to dust produced by SNe. This finding would address the problem of the dust production at z>6, when the age of the universe was lower than the evolutionary timescales of AGB stars.

Finally, these spectra allow to investigate the Fe/α-element abundance ratio, which is a tracer of the star formation history, through the relative strengths of the FeII UV bump and the MgII doublet. We find indications for a large abundance of Fe even in the most distant quasars at z∼6. This finding requires that a strong burst of star formation occurred in the hosts of these quasars already at z>9.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We analyse the stellar content of a large number of HII galaxies based on the continuum and absorption features of their spectra using population synthesis methods, in order to gain information about the star formation histories of these objects. We find that all galaxies of our sample contain an old stellar population (≥1 Gyr) that dominates the stellar mass, and in a great majority of these, we also found evidence for an intermediate-age population ≥100 Myr apart from the presently bursting, ionizing young generation ≤107 yrs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html