We present low-resolution ultraviolet spectra of 14 low redshift (zem . 0.8) quasars observed with HST/STIS as part of a Snap project to understand the relationship between quasar outflows and luminosity. By design, all observations cover the C IV emission line. Nine of the quasars are from the Hamburg-ESO catalog, three are from the Palomar-Green catalog, and one is from the Parkes catalog. The sample contains a few interesting quasars including two broad absorption line (BAL) quasars (HE 01433535, HE0436-2614), one quasar with a mini-BAL (HE 1105-0746), and one quasar with associated narrow absorption (HE 0409-5004). These BAL quasars are among the brightest known (though not the most luminous) since they lie at zem < 0.8. We compare the properties of these BAL quasars to the zem < 0.5 Palomar-Green and zem > 1.4 Large Bright Quasar samples. By design, our objects sample luminosities in between these two surveys, and our four absorbed objects are consistent with the v ∼ L0.62 relation derived by Laor & Brandt (2002). Another quasar, HE0441-2826, contains extremely weak emission lines and our spectrum is consistent with a simple powerlaw continuum. The quasar is radio-loud, but has a steep spectral index and a lobedominated morphology, which argues against it being a blazar. The unusual spectrum of this quasar resembles the spectra of the quasars PG1407+265, SDSSJ1136+0242, and PKS1004+13 for which several possible explanations have been entertained. Subject headings: quasars: absorption lines — quasars: emission lines — surveys Norman, OK 73019 Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 Spitzer Science Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 Department of Physics, University of Nevada, Las Vegas, NV 89154 Faculty of Natural and Applied Sciences, Notre Dame University, Zouk Mosbeh, Lebanon Department of Physics, Baker University, P.O. Box 65, Baldwin City, Kansas 66006-0065 Apache Point Observatory, 2001 Apache Point Road, P.O. Box 59, Sunspot, NM 88349-0059 Orbital Sciences Steward Observatory, The University of Arizona, 933 Cherry Ave., Tucson, AZ 85721 Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Accurate star formation histories (SFHs) of galaxies are fundamental for understanding the build-up of their stellar content. However, the most accurate SFHs - those obtained from colour-magnitude diagrams (CMDs) of resolved stars reaching the oldest main sequence turnoffs (oMSTO) - are presently limited to a few systems in the Local Group. It is therefore crucial to determine the reliability and range of applicability of SFHs derived from integrated light spectroscopy, as this affects our understanding of unresolved galaxies from low to high redshift. To evaluate the reliability of current full spectral fitting techniques in deriving SFHs from integrated light spectroscopy by comparing SFHs from integrated spectra to those obtained from deep CMDs of resolved stars. We have obtained a high signal--to--noise (S/N $\sim$ 36.3 per \AA) integrated spectrum of a field in the bar of the Large Magellanic Cloud (LMC) using EFOSC2 at the 3.6 meter telescope at La Silla Observatory. For this same field, resolved stellar data reaching the oMSTO are available. We have compared the star formation rate (SFR) as a function of time and the age-metallicity relation (AMR) obtained from the integrated spectrum using {\tt STECKMAP}, and the CMD using the IAC-star/MinnIAC/IAC-pop set of routines. For the sake of completeness we also use and discuss other synthesis codes ({\tt STARLIGHT} and {\tt ULySS}) to derive the SFR and AMR from the integrated LMC spectrum. We find very good agreement (average differences $\sim$ 4.1 $\%$) between the SFR(t) and the AMR obtained using {\tt STECKMAP} on the integrated light spectrum, and the CMD analysis. {\tt STECKMAP} minimizes the impact of the age-metallicity degeneracy and has the advantage of preferring smooth solutions to recover complex SFHs by means of a penalized $\chi^2$. [abridged]

This paper presents and examines new near-infrared integral field observations of the three so-called "embedded star clusters" located in the nuclear region of NGC 1365. Adaptive-optics-corrected K-band data cubes were obtained with the ESO/VLT instrument SINFONI. The continuum in the K-band and emission lines such as He I, Br gamma, and several H-2 lines were mapped at an achieved angular resolution of 0.2 '' over a field of 3 x 3 ''(2) around each source. We find that the continuum emission of the sources is spatially resolved. This means that they are indeed cluster complexes confined to regions of about 50 pc extension. We performed robust measurements of the equivalent width of the CO absorption band at 2.3 mu m and of Br gamma. For the main mid-infrared bright sources, the data only allow us to determine an upper limit to the equivalent width of the CO bands. Under the assumption of an instantaneously formed standard initial mass function Starburst99 model, the new measurements are found to be incompatible with previously published mid-infrared line ratios. We show that an upper mass limit of 25 to 30 M-circle dot, lower than the typically assumed 100 M-circle dot, allows one to simply remove this inconsistency. For such a model, the measurements are consistent with ages in the range of 5.5Myr to 6.5Myr, implying masses in the range from 3 to 10 x 10(6) M-circle dot. We detect extended gas emission both in H II and H-2. We argue that the central cluster complexes are the sources of excitation for the whole nebulae, through ionisation and shock heating. We detect a blue wing on the Br gamma emission profile, suggesting the existence of gas outflows centred on the cluster complexes. We do not find any evidence for the presence of a lower mass cluster population, which would fill up a "traditional" power law cluster mass function.

Context. Nearly 100 new strong-lens candidates have been discovered in the COSMOS field. Among these, 20 lens candidates with 0.34 less than or similar to z(lens) <= 1.13 feature multiple images of background sources.Aims. Using the multi-wavelength coverage of the field and its spectroscopic follow-up, we characterize the evolution with redshift of the environment and of the dark-matter (DM) fraction of the lens galaxies.Methods. We present spectroscopic and new photometric redshifts of the strong-lens candidates. The lens environment is characterized in the following way: we account for the projected 10 closest galaxies around each lens and for galaxies with a projected distance less than 1 Mpc at the lens galaxy redshift. In both cases, we perform similar measurements on a control sample of "twin" non-lens early-type galaxies (ETGs). In addition, we identify group members and field galaxies in the X-ray and optical catalogs of galaxy groups and clusters. From those catalogs, we measure the external shear contribution of the groups/clusters surrounding the lens galaxies. The systems are then modeled using a singular isothermal ellipsoid for the lens galaxies plus the external shear produced by the groups/clusters.Results. We observe that the average stellar mass of lens galaxies increases with redshift. In addition, we measure that the environment of lens galaxies is compatible with that of the twins over the whole redshift range tested here. During the lens modeling, we notice that when let free, the external shear points in a direction which is the mean direction of the external shear produced by the groups/clusters and of the closest galaxy to the lens. We also notice that the DM fraction of the lens galaxies measured within the Einstein radius significantly decreases as the redshift increases.Conclusions. Given these observations, we conclude that while the environment of lens galaxies is compatible with that of non-lens ETGS over a wide range of redshifts, their mass properties evolves significantly with redshift: it is still not clear whether this advocates in favor of a stronger lensing bias toward massive objects at high redshift or if it is simply representative of the high proportion of massive and high stellar density galaxies at high redshift.

AbstractThree radio cm sources in the central star-forming kpc of the closeby barred Seyfert galaxy NGC 1365 are observed. The complete dataset includes VLT infrared J, K, L and N images and spectra. The main observed features include (i) a rising dust continuum towards the mid-infrared (MIR), (ii) bright H emission lines and PAH (polycyclic aromatic hydrocarbon) features, (iii) a bright MIR [Neii] line, and (iv) no detection of MIR [Siv] or [Ariii] lines. For a typical cluster star-formation history and initial mass function, the [Ariii]/[Neii] and [Siv]/[Neii] ratios exhibit an abrupt decrease of several orders of magnitude at an age of ~ 7 Myr. The nondetection of [Ariii] and [Siv] indicates that the clusters are of approximately this age.

Aims. We present a sample of candidate quasars selected using the KX-technique. The data cover 0.68 deg 2 of 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. Methods. The KX method identifies quasars on the basis of their optical (R and z � ) to near-infrared (Ks) photometry and point-like morphology. We combine these data with optical (u ∗ ,g � ,r � ,i � ,z � ) and mid-infrared (3.6−24 μm) wavebands to reconstruct the spectral energy distributions (SEDs) of candidate quasars. Results. Of 93 sources selected as candidate quasars by the KX method, 25 are classified as quasars by the subsequent SED analysis. Spectroscopic observations are available for 12/25 of these sources and confirm the quasar hypothesis in each case. Even more, 90% of the SED-classified quasars show X-ray emission, a property not shared by any of the false candidates in the KX-selected sample. Applying a photometric redshift analysis to the sources without spectroscopy indicates that the 25 sources classified as quasars occupy the interval 0.7 ≤ z ≤ 2.5. The remaining 68/93 sources are classified as stars and unresolved galaxies.

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.Methods. A deep VLT/FORS2 spectrum and HST/NICMOS-F160W images are deconvolved. From the images we derive the light profile of the lensing galaxy and an accurate relative astrometry for the system. In addition we measure the flux ratio between the quasar images in the Mg II emission line to constrain the mass model.Results. From the spectrum we measure the redshift of the lensing galaxy (z = 0.317 +/- 0.001) and of the quasar (z = 1.294 +/- 0.008). Using the flux ratio in the lens model allows us to discard the SIE as a suitable approximation of the lens potential. On the contrary the truncated-PIEMD gives a good fit to the lens and leads to a time delay of Delta t(A-B) = -14.5 +/- 0.1 days, with H(0) = 73 km s(-1) Mpc(-1).Conclusions. Using the flux ratio to constrain the mass model favors the truncated-PIEMD over the SIE, while ignoring this constraint leaves the choice open.

Cluster formation and gas dynamics in the central regions of barred galaxies are not well understood. This paper reviews the environment of three 10(7) M-circle dot clusters near the inner Lindblad resonance (ILR) of the barred spiral NGC 1365. The morphology, mass, and flow of H I and CO gas in the spiral and barred regions are examined for evidence of the location and mechanism of cluster formation. The accretion rate is compared with the star formation rate to infer the lifetime of the starburst. The gas appears to move from inside corotation in the spiral region to looping filaments in the interbar region at a rate of similar to 6 M-circle dot yr(-1) before impacting the bar dustlane somewhere along its length. The gas in this dustlane moves inward, growing in flux as a result of the accretion to similar to 40 M-circle dot yr(-1) near the ILR. This inner rate exceeds the current nuclear star formation rate by a factor of 4, suggesting continued buildup of nuclear mass for another similar to 0.5 Gyr. The bar may be only 1-2 Gyr old. Extrapolating the bar flow back in time, we infer that the clusters formed in the bar dustlane outside the central dust ring at a position where an interbar filament currently impacts the lane. The ram pressure from this impact is comparable to the pressure in the bar dustlane, and both are comparable to the pressure in the massive clusters. Impact triggering is suggested. The isothermal assumption in numerical simulations seems inappropriate for the rarefaction parts of spiral and bar gas flows. The clusters have enough lower-mass counterparts to suggest they are part of a normal power-law mass distribution. Gas trapping in the most massive clusters could explain their [Ne II] emission, which is not evident from the lower-mass clusters nearby.

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 H II 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 >= M-H >= -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.

Aims. We present a sample of candidate quasars selected using the KX-technique. The data cover 0.68 deg2 of 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.Methods. The KX method identifies quasars on the basis of their optical (R and z') to near-infrared photometry and point-like morphology. We combine these data with optical (u*,g', r',i',z') and mid-infrared (3.6-24 μm) wavebands to reconstruct the spectral energy distributions (SEDs) of candidate quasars.Results. Of 93 sources selected as candidate quasars by the KX method, 25 are classified as quasars by the subsequent SED analysis. Spectroscopic observations are available for 12/25 of these sources and confirm the quasar hypothesis in each case. Even more, 90% of the SED-classified quasars show X-ray emission, a property not shared by any of the false candidates in the KX-selected sample. Applying a photometric redshift analysis to the sources without spectroscopy indicates that the 25 sources classified as quasars occupy the interval 0.7 ≤ z ≤ 2.5. The remaining 68/93 sources are classified as stars and unresolved galaxies.

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 NGC1808. We aim at confirming that these sources are deeply embedded, young star clusters and at deriving some of their intrinsic properties. To complement the mid-infrared data, 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. Surprisingly, the new images unveil a near-infrared counterpart for only one of the mid-infrared/radio sources, namely M8 in the L' band. All the other sources are so deeply embedded that their emission does not pop out above an 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. 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 mu m and perform their accurate relative positioning. We also provide spectra in the ranges 1.8-2.4 mu m, 3.3-4.0 mu m, 8.1-9.3 mu m and 10.4-13.2 mu 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 mu m line is also observed, while neither the [ArIII] 8.9 mu m nor the [SIV] 10.4 mu m lines are detected. This provides a stringent constraint on the age of the sources: we argue that they are relatively evolved young clusters (6-8Myr). Owing to their ionising photon emission rates and ages, they must be extremely massive clusters (of the order of 10(7) M(circle dot)). 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. 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.Aims. For such studies, one needs to have an excellent knowledge of the close environment of the lensed images in order to model the lensing potential: this means, ideally, observational data over a large field-of-view and spectroscopy at high spatial resolution.Methods. We present VIMOS integral field observations of 27 '' x 27 '' fields of view around four lensed quasars: HE 0230-2130, RX J0911.4 + 0551, H 1413 + 117 and B 1359 + 154. Using the low, medium and high resolution modes, we study the quasar images and the quasar environments. Because of the complexity of the reduction of integral field datasets, we provide a detailed report of the data reduction.Results. Comparison between the quasar spectra of the different images reveals differences for HE 0230-2130, RX J0911.4 + 0551 and H 1413+117: flux ratios between the images of the same quasar are different when measured in the emission lines and in the continuum. We have also measured the redshifts of galaxies in the neighborhood of HE 0230-2130 and RX J0911.4 + 0551 which possibly contribute to the total lensing potential, given their close proximity to the line-of-sight toward the quasars.Conclusions. A careful analysis reveals that microlensing is the most natural explanation for the (de) magnification of the continuum emitting region of the background sources. In HE 0230-2130, image D is likely to be affected by microlensing magnification; in RX J0911.4+0551, images A1 and A3 are likely to be modified by microlensing de-magnification and in H 1413+117 at least image D is affected by microlensing. We have not been able to recover any microlensing information or galaxies close to the line-of-sight in the neighborhood of B 1359+154.

We present a sample of 29 galaxy clusters from the XMM-LSS survey over an area of some 5 deg(2) out to a redshift of z = 1.05. The sample clusters, which represent about half of the X-ray clusters identified in the region, follow well-defined X-ray selection criteria and are all spectroscopically confirmed. For all clusters, we provide X-ray luminosities and temperatures as well as masses, obtained from dedicated spatial and spectral fitting. The cluster distribution peaks around z = 0.3 and T = 1.5 keV, half of the objects being groups with a temperature below 2 keV. Our L-X-T(z) relation points towards self-similar evolution, but does not exclude other physically plausible models. Assuming that cluster scaling laws follow self-similar evolution, our number density estimates up to z = 1 are compatible with the predictions of the concordance cosmology and with the findings of previous ROSAT surveys. Our well-monitored selection function allowed us to demonstrate that the inclusion of selection effects is essential for the correct determination of the evolution of the L-X-T relation, which may explain the contradictory results from previous studies. Extensive simulations show that extending the survey area to 10 deg(2) has the potential to exclude the non-evolution hypothesis, but those constraints on more refined intracluster medium models will probably be limited by the large intrinsic dispersion of the L-X-T relation, whatever be the sample size. We further demonstrate that increasing the dispersion in the scaling laws increases the number of detectable clusters, hence generating further degeneracy [in addition to sigma(8), Omega(m), L-X-T(z)] in the cosmological interpretation of the cluster number counts. We provide useful empirical formulae for the cluster mass-flux and mass-count rate relations as well as a comparison between the XMM-LSS mass sensitivity and that of forthcoming Sunyaev-Zel'dovich surveys.

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.Aims. We study here the molecular and dust content of the high redshift (z = 3.2), gravitationally lensed quasar MG0751 + 2716.Methods. We used the IRAM Plateau de Bure interferometer to measure the CO J = 3-2, J = 4-3 and J = 8-7 rotation lines and continuum flux between 1.1 mm and 3 mm in MG0751 + 2716. We use HST data and constraints from the high resolution MERLIN map at 6.2 cm to build an improved model of the lens.Results. The position agreement between the CO emission and the millimeter continuum suggests that dust and molecules are closely related. A 500 km s(-1) velocity gradient is tentatively detected from the CO lines across the central 0.5 ''. The continuum SED in the range 0.45 mm-204 mm exhibits the signatures of two components: synchrotron emission from a core/jet system, and thermal emission related to warm dust. The CO line intensities are compatible with warm, dense molecular gas, suggesting a location in the close environment of the quasar. These observational constraints lead us to consider a source/quasar model made of a point-like core, a radio jet, and a molecular and dusty ring-like structure (similar to 460 pc in radius) located in a plane perpendicular to the jet axis and seen almost edge-on. For this configuration, we derive a total magnification of 16 for the quasar radiation at rest frequency above 350 GHz and a magnification of 25 below 350 GHz. The dust mass ( assuming a likely temperature T = 50 K) is M-dust = 1.7 x 10(8) M-circle dot, the mass of molecular material is M(H-2) = 6 x 10(10) M-circle dot and a lower limit to the dynamical mass is M-dyn = 1.5 x 10(10) M-circle dot. Such values are comparable to those found in the small sample of CO detected sources at high redshifts.

We present low-resolution ultraviolet spectra of 14 low redshift (z<0.8) quasars observed with HST/STIS as part of a Snap project to understand the relationship between quasar outflows and luminosity. By design, all observations cover the CIV emission line. Nine of the quasars are from the Hamburg-ESO catalog, three are from the Palomar-Green catalog, and one is from the Parkes catalog. The sample contains a few interesting quasars including two broad absorption line (BAL) quasars (HE0143-3535, HE0436-2614), one quasar with a mini-BAL (HE1105-0746), and one quasar with associated narrow absorption (HE0409-5004). These BAL quasars are among the brightest known (though not the most luminous) since they lie at z<0.8. We compare the properties of these BAL quasars to the z<0.5 Palomar-Green and z>1.4 Large Bright Quasar samples. By design, our objects sample luminosities in between these two surveys, and our four absorbed objects are consistent with the v L^0.62 relation derived by Laor Brandt (2002). Another quasar, HE0441-2826, contains extremely weak emission lines and our spectrum is consistent with a simple power-law continuum. The quasar is radio-loud, but has a steep spectral index and a lobe-dominated morphology, which argues against it being a blazar. The unusual spectrum of this quasar resembles the spectra of the quasars PG1407+265, SDSSJ1136+0242, and PKS1004+13 for which several possible explanations have been entertained.

Following the presentation of the XMM-Large Scale Structure (XMM-LSS) survey X-ray source detection package by Pacaud et al., we provide the source lists for the first surveyed 5.5 deg(2). The catalogues pertain to the [0.5-2] and [2-10] keV bands and contain in total 3385 pointlike or extended sources above a detection likelihood of 15 in either band. The agreement with deep log N-log S is excellent. The main parameters considered are position, count rate, source extent with associated likelihood values. A set of additional quantities such as astrometric corrections and fluxes are further calculated while errors on the position and count rate are deduced from simulations. We describe the construction of the band-merged catalogue allowing rapid subsample selection and easy cross-correlation with external multiwavelength catalogues. A small optical Canada-France-Hawaii Telescope Legacy Survey multiband subset of objects are associated with each source along with an X-ray/optical overlay. We make the full X-ray images available in FITS format. The data are available at the Centre de Donnees de Strasbourg and, in a more extended form, at the Milan XMM-LSS survey data base.