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

We present the black hole mass–bulge velocity dispersion relation for a complete sample of 75 soft X-ray selected AGNs. We find that the AGNs with highest accretion rates relative to Eddington lie below the MBH–σ relation of broad line Seyfert 1s, confirming the Mathur et al. (2001) result. The statistical result is robust and not due to any systematic measurement error. This has important consequences towards our understanding of black hole formation and growth: black holes grow by accretion in well formed bulges. As they grow, they get closer to the MBH–σ relation for normal galaxies. The accretion is highest in the beginning and dwindles as time goes by. Our result does not support theories of the MBH–σ relation in which the black hole mass is a constant fraction of the bulge mass/velocity dispersion at all times or those in which bulge growth is controlled by AGN feedback.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The CAIRNS (Cluster And Infall Region Nearby Survey) project is a large spectroscopic survey of the infall regions surrounding nine nearby rich clusters of galaxies. I describe the survey and use the kinematics of galaxies in the infall regions to estimate the cluster mass profiles. At small radii, these mass profiles are consistent with independent mass estimates from X-ray observations and Jeans analysis. I demonstrate the dependence of mass-to-light ratios on environment by combining these mass profiles with Two-Micron All-Sky Survey (2MASS) photometry. Near-infrared light is more extended than mass in these clusters, suggesting that dense cluster cores are less efficient at forming galaxies and/or more efficient at disrupting them. At large radii, galaxy populations in cluster infall regions closely resemble those in the field. The mass-to-light ratio at these radii should therefore be a good probe of the global mass-to-light ratio. The mass-to-light ratio in the infall region yields a surprisingly low estimate of $\Omega_m \sim 0.1$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We analysed 246 scanned ACO clusters and we do not find any dependence of galaxy cluster ellipticity on redshift.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We use the photoionization code MAPPINGS Ic to model optical emission-line ratios of the extended emission-line regions of 24 Seyfert galaxies. Although most line ratios can be reproduced by varying the ionization parameter, gas density and/or the shape of the ionizing continuum, the ratio [NII]λλ6548,84/[OII]λ3727 can only be reproduced if we allow for a range of oxygen abundances of 0.5≤ (O/H)/(O/H)$_{\odot} \leq$ 3 for the whole sample. We propose a calibration to obtain (O/H) in terms of [NII]/[OII]. Also, in order to reproduce the emission-line spectra beyond 2 kpc from the nucleus, we had to introduce the contribution from hot stars to the ionizing spectra. We conclude that this is due to an increasing contribution of HII regions with distance from the nucleus to the emission-line regions.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The “Herschel Space Observatory” is an ESA mission to perform imaging photometry and spectroscopy in the far-IR & submm 57–670 μm range. It carries a 3.5 m diameter radiatively cooled telescope. The scientific instruments – two cameras/medium resolution spectrometers (PACS and SPIRE) and a very high resolution heterodyne spectrometer (HIFI) – are housed in a superfluid helium cryostat. Herschel will be placed in orbit around the Earth-Sun L2 point in 2007 and will operate for a minimum of 3 years. Roughly 2/3 of the observing time is open to the general astronomical community through a competitive proposal procedure.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the values of CN and Mg overabundances with respect to Fe, for early-type galaxies in 8 clusters over a range of richness and morphology. Spectra were taken from the Sloan Digital Sky Survey (SDSS) DR1 spectroscopic database, and from WHT and CAHA observations. Abundances were derived from absorption lines and single burst population models, by comparing galaxy spectra with appropriately broadened synthetic model spectra. We find robust correlations between [Mg/CN] and [CN/Fe] abundance ratios and cluster X-ray luminosity. No correlation was observed for [Mg/Fe]. We also see a clear trend with the richness and morphology of the clusters. This behavior is interpreted given varying formation timescales for CN, Mg and Fe, combined with a different star formation history in early-type galaxies as a function of their environment. This result supports the scenario in which early-type galaxies in more massive clusters are assembled on shorter timescales than those galaxies within less massive clusters.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html