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Aims. We report on the redshift of the lensing galaxy and of the quasar QJ 0158-4325  and on the lens model of the system.

Aims. We present a sample of candidate quasars selected using the KX-technique. The data cover 0.68 deg2of the X-ray Multi-Mirror (XMM) Large-Scale Structure (LSS) survey area where overlapping multi-wavelength imaging data permits an investigation of the physical nature of selected sources.

Context. In the course of a mid-infrared imaging campaign of close-by active galaxies, we discovered the mid-infrared counterparts of bright compact radio sources in the central star-forming region of NGC 1808.

Context. Gravitationally lensed quasars constitute an independent tool to derive the Hubble constant through the time-delays of their different images; they offer as well the opportunity to study the mass distribution and interstellar medium of their lensing galaxies and, through microlensing due to stars in their lensing galaxy, they also allow one to study details of the emitting source.

Context.Gravitational lenses offer unique opportunities to explore the molecular content around active galactic nuclei at high redshift, through the magnification and gain in angular resolution.

We analyze X-ray sources detected over 4.2 pseudo-contiguous sq. deg. in the 0.5–2 keV and 2–10 keV bands down to fluxes of $2\times 10^{-15}$and $8\times 10^{-15}$erg s-1cm-2respectively, as part of the XMM-NewtonLarge Scale Structure Survey. The log N–log Sin both bands shows a steep slope at bright fluxes, but agrees well with other determinations below ~$2 \times 10^{-14}$erg s-1cm-2. The detected sources resolve close to 30 per cent of the X-ray background in the 2–10 keV band. We study the two-point angular clustering of point sources using nearest neighbours and correlation function statistics and find a weak, positive signal for ~1130 sources in the 0.5–2 keV band, but no correlation for ~400 sources in the 2–10 keV band below scales of 100 arcsec. A sub-sample of ~200 faint sources with hard X-ray count ratios, that is likely to be dominated by obscured AGN, does show a positive signal with the data allowing for a large angular correlation length, but only at the ~2 (3)σlevel, based on re-sampling (Poisson) statistics. We discuss possible implications and emphasize the importance of wider, complete surveys in order to fully understand the large scale structure of the X-ray sky.

High resolution, mid-infrared (MIR) images of nine nearby active galaxies are presented. The data were obtained with the TIMMI 2 instrument mounted at the ESO 3.6 m telescope using a set of N-band narrow filters. The resulting images have an angular resolution of 0.6´´-1´´. The MIR emission has been resolved in four galaxies: NGC 253, NGC 1365, NGC 1808 and NGC 7469. The images show a circumnuclear population of unknown MIR sources in NGC 1365 and NGC 1808, coincident with radio sources. These MIR/radio sources are interpreted in terms of embedded young star clusters. A high-resolution MIR map of NGC 253 is also presented, and enables the identification of a previously unknown MIR counterpart to the radio nucleus. Extended MIR emission is detected in NGC 7469, and concurs with previous observations in the NIR and radio. For this source, an interesting morphological difference between the 10.4 $\rm \,\mu m$and the 11.9 $\rm \,\mu m$emission is observed, suggesting the presence of a dust-rich micro-bar. Our MIR images of Circinus do not show resolved emission from the nucleus down to an angular scale of 0.5´´. In the case of NGC 2992, an upper limit to the extended MIR emission can be set. We provide new MIR flux measurements for the unresolved AGN in NGC 5995, IZw1 and IIZw136.

In this paper we present new ESO/VLT FORS1 and ISAAC images of the fields around eight gravitationally lensed quasars: CTQ 414, HE 0230-2130, LBQS 1009-0252, B 1030+074, HE 1104-1805, B 1359+154, H 1413+117 and HE 2149-2745. When available and deep enough, HST/WFPC2 data were also used to infer the photometric redshifts of the galaxies around the quasars. The search of galaxy overdensities in space and redshift, as well as a weak-shear analysis and a mass reconstruction are presented in this paper. We find that there are most probably galaxy groups towards CTQ 414, HE 0230-2130, B 1359+154, H 1413+117 and HE 2149-2745, with masses ≤$4\times 10^{14}$$M_\odot$h-1. Considering its photometric redshift, the galaxy group discovered in the field around HE 1104-1805 is associated with the quasar rather than with the lensing potential.

We revisit in this paper the location of the various components observed in the AGN of NGC 1068. Discrepancies between previously published studies are explained, and a new measurement for the absolute location of the K-band emission peak is provided. It is found to be consistent with the position of the central engine as derived by Gallimore et al. (1997), Capetti et al. (1997) and Kishimoto (1999). A series of map overlays is then presented and discussed. Model predictions of dusty tori show that the nuclear unresolved NIR-MIR emission is compatible with a broad range of models: the nuclear SED alone does not strongly constrain the torus geometry, while placing reasonable constraints on its size and thickness. The extended MIR emission observed within the ionizing cone is shown to be well explained by the presence of optically thick dust clouds exposed to the central engine radiation and having a small covering factor. Conversely, a distribution of diffuse dust particles within the ionizing cone is discarded. A simple model for the H2and CO emission observed perpendicularly to the axis of the ionizing cone is proposed. We show that a slight tilt between the molecular disc and the Compton thick central absorber naturally reproduces the observed distribution of H2of CO emission.

Very deep ESO/VLT FORS1 and ISAAC images, as well as HST NICMOS2 data are used to infer the nature of the quasar pair LBQS 1429-0053 A and B, either a binary quasar or a doubly-imaged lensed quasar. Direct search of a putative lensing galaxy is unsuccessful down to $R=27$, $J=24$, $Ks=22.5$and $H=22.5$. Moreover, no galaxy overdensity close to the quasar pair is found. A weak shear analysis of the FORS1 R-band 6.8´ $\times$6.8´  field also fails at detecting any concentration of dark matter more massive than $\sigma=500$km s-1and weakens the hypothesis of a dark lens. The only sign of a possible lens consists in a group of 5 objects having colors consistent with galaxies at $z \sim 1$, within a radius of 5´´  from the quasar pair. Considering this group as the lensing potential does not allow to reproduce the image position and flux ratio of LBQS 1429-0053 A and B. Our deep R-band image shows a blue, previously unknown, extended object at the position of LBQS 1429-0053 A, which is consistent with either being the lensed quasar A host, or being an intervening galaxy at lower redshift. Unless future very deep optical images demonstrate that this object is actually the lensed host of LBQS 1429-0053, we conclude that there is very little evidence for LBQS 1429-0053 being lensed. Therefore, we are led to declare LBQS 1429-0053 A and B a genuine binary quasar.

We present the first result of a comprehensive spectroscopic study of quasar host galaxies. On-axis, spatially resolved spectra of low redshift quasars have been obtained with FORS1, mounted on the 8.2 m ESO Very Large Telescope, Antu. The spectra are spatially deconvolvedusing a spectroscopic version of the “MCS deconvolution algorithm”. The algorithm decomposes two dimensional spectra into the individual spectra of the central point-like nucleus and of its host galaxy. Applied to HE 1503+0228  at $z=0.135$(MB=-23.0), it provides us with the spectrum of the host galaxy between 3600 Å  and 8500 Å  (rest-frame), at a mean resolving power of 700. The data allow us to measure several of the important Lick indices. The stellar populations and gas ionization state of the host galaxy of HE 1503+0228 are very similar to the ones measured for normal non-AGN galaxies. Dynamical information is also available for the gas and stellar components of the galaxy. Using deconvolution and a deprojection algorithm, velocity curves are derived for emission lines, from the center up to 4´´  away from the nucleus of the galaxy. Fitting a simple three-components mass model (point mass, spherical halo of dark matter, disk) to the position-velocity diagram, we infer a mass of $M(r<1~{\rm kpc}) = (2.0 \pm 0.3)\times 10^{10}~M_{\odot}$within the central kiloparsec of the galaxy, and a mass integrated over 10 kpc of $M(r<10~{\rm kpc}) = (1.9 \pm 0.3) \times 10^{11}~ M_{\odot}$, with an additional 10% error due to the uncertainty on the inclination of the galaxy. This, in combination with the analysis of the stellar populations indicates that the host galaxy of HE 1503+0228  is a normal spiral galaxy.

New near-IR long slit spectroscopic data obtained with ISAAC on VLT/ANTU (ESO/Paranal) complement and extend our previously published near-IR data (Alloin et al. [CITE]) to produce Br$_{\gamma}$and H2emission line maps and line profile grids of the central $4'' \times 4''$region surrounding the central engine of NGC 1068. The seeing quality together with the use of an $0.3''$wide slit and $0.3''$slit position offsets allow one to perform 2D-spectroscopy at a spatial resolution $\approx 0.5''$. Slit orientations (PA = 102° and PA = 12°) were chosen so as to match respectively the equatorial plane and the axis of the suspected molecular/dusty torus in NGC 1068. The selected wavelength range from 2.1 to 2.2$\rm ~\mu m$is suitable to detect and analyze the Br$_{\gamma}$and H2emission lines at a spectral resolution corresponding to 35$\rm ~km\,s^{-1}$. An asymmetric distribution of H2emission around the continuum peak is observed. No H2emission is detected at the location of the strong 2.2$\rm ~\mu m$continuum core (coincident within error-bars with the central engine location), while two conspicuous knots of H2emission are detected at about 1''on each side of the central engine along PA = 90°, with a projected velocity difference of 140$\rm ~km\,s^{-1}$: this velocity jump has been interpreted in Alloin et al. ([CITE]) as the signature of a rotating disk of molecular material. From this new data set, we find that only very low intensity Br$_{\gamma}$emission is detected at the location of the two main knots of H2emission. Another knot with both H2and Br$_{\gamma}$emission is detected to the North of the central engine, close to the radio source C where the small scale radio jet is redirected and close to the brightest [OIII] cloud NLR-B. It has a counterpart to the South, placed almost symmetrically with respect to the central engine, although mainly visible in the Br$_{\gamma}$emission. The northern and southern knots appear to be related to the ionization cone. At the achieved spectral resolution, the H2emission line profiles appear highly asymmetric with their low velocity wing being systematically more extended than their high velocity wing. A simple way to account for the changes of the H2line profiles (peak-shift with respect to the systemic velocity, width, asymmetry) over the entire $4'' \times 4''$region, is to consider that a radial outflow is superimposed over the emission of the rotating molecular disk. We present a model of such a kinematical configuration and compare our predicted H2emission profiles to the observed ones. Excitation of the H2line is briefly discussed: X-ray irradiation from the central engine is found to be the most likely source of excitation. Given the fact that the material obscuring our direct view toward the central engine is Compton thick ($N_{\rm H} \geq 10^{24}\,\rm{cm^{-2}}$), the observed location of the main H2knots at a distance of 70 pc from the central engine suggests that the rotating molecular disk is warped.

The gravitational potential responsible for the lensing effect in SBS 1520+530  is studied over length scales from a few arc-seconds to a few arc-minutes. For this purpose, we use sharply deconvolved Hubble Space Telescope images in the optical and near-IR, in combination with ground based optical data obtained over a wider field-of-view. In particular, we have carried out a multi-color analysis in order to identify groups or clusters of galaxies along the line of sight. Photometric redshifts are measured for 139 galaxies unveiling significant excesses of galaxies 1.0´  NW and 1.7´  SW of the main lensing galaxy. The photometric redshift inferred both for the main lensing galaxy and for the galaxy concentrations is $z=0.9^{+0.10}_{-0.25}$. This is in rough agreement with the measured spectroscopic redshift of the main lensing galaxy, $z=0.71$(Burud et al. [CITE]), suggesting that it is part of a larger group or cluster. We investigate the impact of including the galaxy cluster, first on the modelling of the lensing system, and second on the expected time–delay between the two quasar images.

We present the results of a CO survey of gravitationally lensed quasars, conducted with the Plateau de Bure Interferometer over the last three years. Among the 18 objects surveyed, one was detected in CO line emission, while six were detected in the continuum at 3 mm and three in the continuum at 1 mm. The low CO detection rate may at least in part be due to uncertainties in the redshifts derived from quasar broad emission lines. The detected CO source, the $z=3.2$radio quiet quasar MG 0751+2716, is quite strong in the CO(4-3) line and in the millimeter/submillimeter continuum, the latter being emission from cool dust. The integrated CO line flux is $5.96\pm 0.45$Jy$\cdot$kms-1, and the total molecular gas mass is estimated to be in the range $M_{\rm H_2} = 1.6$–$3.1\times 10^9~M_{\odot}$.

We report the discovery of an extremely red object (ERO) in a medium-deep ISOCAM extragalactic survey. The object is also a radio source. Subsequent VLT NIR spectroscopy revealed a prominent Hαline giving a redshift of 1.5. We present the spectrum and photometric data points and discuss evidence that ISO J1324-2016 is a quasar harbouring a significant amount of very hot dust.

Mid-infrared images of the Seyfert 1 galaxy Mrk 279obtained with the ISO satellite are presented together with the results of a one-year monitoring campaign of the 2.5-11.7 μm spectrum. Contemporaneous optical photometric and spectrophotometric observations are also presented. The galaxy appears as a point-like source at the resolution of the ISOCAM instrument (4-5″). The 2.5-11.7 μm average spectrum of the nucleus in Mrk 279shows a strong power law continuum with $\alpha = -0.80\pm0.05$(${ F_{\nu} \propto \nu^{\alpha}}$) and weak PAH emission features. The Mrk 279spectral energy distribution shows a mid-IR bump, which extends from 2 to 15-20 μm. The mid-IR bump is consistent with thermal emission from dust grains at a distance of $\ga 100$lt-d. No significant variations of the mid-IR flux have been detected during our observing campaign, consistent with the relatively low amplitude (~10% rms) of the optical variability during the campaign. The time delay for Hβline emission in response to the optical continuum variations is $\tau = 16.7^{+5.3}_{-5.6}$days, consistent with previous measurements.

We present results about the distribution and kinematics of the molecular environment of the AGN in NGC 1068, over a $1.5'' \times 3.5''$region around the central engine in NGC 1068, derived from H2line emission detected with ISAAC at VLT/ANTU on ESO/Paranal. The H2emitting molecular gas is found to be distributed along the East-West direction and with two main peak emission (knots) located at a distance of about 70 pc from the central engine. The eastern H2knot is more intense than the western one. The line profiles mapped across the entire $1.5'' \times 3.5''$region, at a spatial resolution of $0.3''\times 0.45''$, appear to be quite complex with either a blue or red wing. At first order, we find a velocity difference of 140 km s-1between the two knots; if interpreted as quasi-Keplerian velocity, this implies a central enclosed mass of $10^8 M_{\odot}$.

Context. In a previous work, three bright mid-infrared/radio sources were discovered in the nuclear region of starburst/AGN galaxy NGC?1365.Aims. The present study aims to confirm that these sources are indeed young and massive ?embedded? clusters, and derive their physical parameters, such as extinction, age and mass.Methods. Using ISAAC and VISIR at the VLT we obtained maps and low resolution spectra in the near- and mid-infrared. The resulting datasets are first interpreted by comparing the observations with images and spectra of the close-by young cluster R136 in the Large Magellanic Cloud and then by using model predictions for both the nebular emission lines and the spectral energy distribution of the sources.Results. We produce maps of the region containing the three sources in the R, J, Ks, L'?bands and at 12.8?m?and perform their accurate relative positioning. We also provide spectra in the ranges 1.8-2.4?m, 3.3-4.0?m, 8.1-9.3?m?and 10.4-13.2?m. The spectral energy distribution of the three sources rises with wavelength. Emission lines from ionised hydrogen and molecular hydrogen are detected, as well as PAH emission. A conspicuous [NeII]?12.8?m?line is also observed, while neither the [ArIII]?8.9?m?nor the [SIV]?10.4?m?lines are detected. This provides a stringent constraint on the age of the sources: we argue that they are relatively evolved young clusters (6-8?Myr). Owing to their ionising photon emission rates and ages, they must be extremely massive clusters (of the order of 107?M?). Their mid-infrared spectral energy distribution suggests the presence of two components: (1) an optically thin component, with a continuum comparable to that of R136; and?(2)?an optically thick component which might be related to subsequent or on-going episodes of star formation. We anticipate that these sources are good candidates for evolution according to a bi-modal hydrodynamical regime, in which matter is trapped at the centre of a compact and massive cluster and generates further star formation.

Context. The luminosity-metallicity relation is one of the fundamental constraints in the study of galaxy evolution; yet none of the relations available today has been universally accepted by the community.Aims. The present work is a first step to collect homogeneous abundances and near-infrared (NIR) luminosities for a sample of dwarf irregular (dIrr) galaxies, located in nearby groups. The use of NIR?luminosities is intended to provide a better proxy to mass than the blue luminosities commonly used in the literature; in addition, selecting group members reduces the impact of uncertain distances. Accurate abundances are derived to assess the galaxy metallicity.Methods. Optical spectra are collected for Hii?regions in the dIrrs, allowing the determination of oxygen abundances by means of the temperature-sensitive method. For each dIrr?galaxy H-band imaging is performed and the total magnitudes are measured via surface photometry.Results. This high-quality database allows us to build a well-defined luminosity-metallicity relation in the range -13?MH?-20. The scatter around its linear fit is reduced to 0.11?dex, the lowest of all relations currently available. There might exist a difference between the relation for dIrrs and the relation for giant galaxies, although a firm conclusion should await direct abundance determinations for a significant sample of massive galaxies.Conclusions. This new dataset provides an improved luminosity-metallicity relation, based on a standard NIR?band, for dwarf star-forming galaxies. The relation can now be compared with some confidence to the predictions of models of galaxy evolution. Exciting follow-ups of this work are (a) exploring groups with higher densities, (b)?exploring nearby galaxy clusters to probe environmental effects on the luminosity-metallicity relation, and (c)?deriving direct oxygen abundances in the central regions of star-forming giant galaxies, to settle the question of a possible dichotomy between the chemical evolution of dwarfs and that of massive galaxies.

Context. In the course of a mid-infrared imaging campaign of close-by active galaxies, we discovered the mid-infrared counterparts of bright compact radio sources in the central star-forming region of NGC?1808.Aims. We aim at confirming that these sources are deeply embedded, young star clusters and at deriving some of their intrinsic properties.Methods. To complement the mid-infrared images, we have collected a set of near-infrared data with ISAAC at the VLT: J, Ks, and L'?images, as well as low-resolution, long-slit spectra for three of the sources.Results. Surprisingly, the new images unveil a near-infrared counterpart for only one of the mid-infrared/radio sources, namely M?8 in the L'?band. All the other sources are so deeply embedded that their emission does not pop out above the extended diffuse near-infrared emission. The near-infrared spectra of the sources look alike, with intense, ionised hydrogen lines. This supports the interpretation of these sources in terms of embedded young clusters. We derive extinctions and ionising photon production rates for two of the clusters.

Context.Nearly 100 new strong-lens candidates have been discovered in the COSMOS field. Among these, 20 lens candidates with 0.34 ≲ zlens≲ 1.13 feature multiple images of background sources.