Search

We present the spectral energy distributions (SEDs) of a hard X-ray selected sample. The sample contains 136 sources with F(2-10 keV)>10^-14 erg/cm^2/s and 132 are AGNs. The sources are detected in a 1 square degree area of the XMM-Newton-Medium Deep Survey where optical data from the VVDS, CFHTLS surveys, and infrared data from the SWIRE survey are available. Based on a SED fitting technique we derive photometric redshifts with sigma(1+z)=0.11 and 6% of outliers and identify AGN signatures in 83% of the objects. This fraction is higher than derived when a spectroscopic classification is available. The remaining 17+9-6% of AGNs shows star-forming galaxy SEDs (SF class). The sources with AGN signatures are divided in two classes, AGN1 (33+6-1%) and AGN2 (50+6-11). The AGN1 and AGN2 classes include sources whose SEDs are fitted by type 1 and type 2 AGN templates, respectively. On average, AGN1s show soft X-ray spectra, consistent with being unabsorbed, while AGN2s and SFs show hard X-ray spectra, consistent with being absorbed. The analysis of the average SEDs as a function of X-ray luminosity shows a reddening of the IR SEDs, consistent with a decreasing contribution from the host galaxy at higher luminosities. The AGNs in the SF classes are likely obscured in the mid-infrared, as suggested by their low L(3-20micron)/Lcorr(0.5-10 keV) ratios. We confirm the previously found correlation for AGNs between the radio luminosity and the X-ray and the mid-infrared luminosities. The X-ray-radio correlation can be used to identify heavily absorbed AGNs. However, the estimated radio fluxes for the missing AGN population responsible for the bulk of the background at E>10 keV are too faint to be detected even in the deepest current radio surveys., Accepted for publication in ApJ

We present the SEDs of a hard X-ray selected sample containing 136 sources with F_(2-10 keV) > 10^(-14) erg cm^(-2) s^(-1); 132 are AGNs. The sources are detected in a 1 deg^2 area of the XMM-Newton Medium Deep Survey where optical data from the VVDS and CFHTLS and infrared data from the SWIRE survey are available. Based on a SED fitting technique we derive photometric redshifts with σ(1 + z) = 0.11 and 6% of outliers and identify AGN signatures in 83% of the objects. This fraction is higher than derived when a spectroscopic classification is available. The remaining 17^(+9)_(-6)% of AGNs show star-forming galaxy SEDs (SF class). The sources with AGN signatures are divided in two classes, AGN1 (33^(+6)_(-1)%) and AGN2 (50^(+6)_(-11)%). The AGN1 and AGN2 classes include sources whose SEDs are fitted by type 1 and type 2 AGN templates, respectively. On average, AGN1s show soft X-ray spectra, consistent with being unabsorbed, while AGN2s and SFs show hard X-ray spectra, consistent with being absorbed. The analysis of the average SEDs as a function of X-ray luminosity shows a reddening of the infrared SEDs, consistent with a decreasing contribution from the host galaxy at higher luminosities. The AGNs in the SF classes are likely obscured in the mid-infrared, as suggested by their low L_(3-20 μm)/L^(corr)_(0.5-10 keV) ratios. We confirm the previously found correlation for AGNs between the radio luminosity and the X-ray and the mid-infrared luminosities. The X-ray-radio correlation can be used to identify heavily absorbed AGNs. However, the estimated radio fluxes for the missing AGN population responsible for the bulk of the background at E > 10 keV are too faint to be detected even in the deepest current radio surveys.

We present a sample of 29 galaxy clusters from the XMM-LSS survey over an area of some 5deg2 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. 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-T(z) relation points toward 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-T relation, which may explain the contradictory results from previous studies. Extensive simulations show that extending the survey area to 10deg2 has the potential to exclude the non-evolution hypothesis, but that constraints on more refined ICM models will probably be limited by the large intrinsic dispersion of the L-T relation. We further demonstrate that increasing the dispersion in the scaling laws increases the number of detectable clusters, hence generating further degeneracy [in addition to sigma8, Omega_m, L(M,z) and T(M,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 SZ surveys., Comment: Accepted for publication by MNRAS. Full resolution images as well as additional cluster data are available through a dedicated database at http://l3sdb.in2p3.fr:8080/l3sdb/

Following the presentation of the XMM-LSS X-ray source detection package by Pacaud et al., we provide the source lists for the first 5.5 surveyed square degrees. The catalogues pertain to the [0.5-2] and [2-10] keV bands and contain in total 3385 point-like or extended sources above a detection likelihood of 15 in either band. The agreement with deep logN-logS is excellent. The main parameters considered are position, countrate, 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 countrate are deduced from simulations. We describe the construction of the band-merged catalogue allowing rapid sub-sample selection and easy cross-correlation with external multi-wavelength catalogues. A small optical CFHTLS multi-band subset of objects is associated wich 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 CDS and, in a more extended form, at the Milan XMM-LSS database., 13 pages, 7 figures and 11 tables (fig. 1 and 6 are enclosed in reduced resolution), MNRAS Latex, accepted by MNRAS

International audience; We present a sample of 29 galaxy clusters from the XMM-LSS survey over an area of some 5 deg2 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 LX-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 LX-T relation, which may explain the contradictory results from previous studies. Extensive simulations show that extending the survey area to 10 deg2 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 LX-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 sigma8,Omegam, LX-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.

High resolution mid-infrared (MIR) images of the central region of NGC1068 have been obtained with VISIR, the multi-mode MIR instrument recently installed at the ESO/VLT on Paranal. A map of the emission at 12.8mic with increased sensitivity over the central 8"x 8" area is discussed. It shows a central core (unresolved along the E-W direction) and an extended emission which draws a spiral pattern similar to that observed on near-infrared images. Patches of MIR emission can be detected up to a distance of 4" from the core. The deconvolved 12.8mic map is fully consistent with previous high-resolution MIR observations. It highlights the structure of the extended emission, already seen on the un-deconvolved image, and allows to identify a set of mid-infrared sources: 7 in the NE quadrant and 5 in the SW quadrant. The MIR emission map is compared with those obtained at comparable angular resolution in the near-infrared and in the [OIII] line emission. The very good correlation between the VISIR map and the HST optical map supports the idea that the MIR emission not associated with the torus arises from dust associated with the narrow line region clouds. The N-S extension of the MIR core (0.44") is then probably simply due to the mixing of the MIR emission from the dusty torus and the MIR emission from NLR cloud B, located only 0.1" to the North., 5 pages, 1 figure (reduced quality), accepted MNRAS Letter. The paper with full resolution figure can be downloaded at http://www.sc.eso.org/~egallian/VISIR/N1068_VISIR.ps.gz

We present results about the distribution and kinematics of the molecular environment of the AGN in NGC1068, over a 1.5'' x 3.5'' region around the central engine in NGC1068, derived from H2 line emission detected with ISAAC at VLT/ANTU on ESO/Paranal. The H2 emitting 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 H2 knot is more intense than the western one. The line profiles mapped across the entire 1.5'' x 3.5'' region, at a spatial resolution of 0.3'' x 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 between the two knots; if interpreted as quasi-keplerian velocity, this implies a central enclosed mass of 10^8 solar masses., 4 pages, 3 figures, accepted A&A Letter

We present diffraction-limited IR images at 11.2 and 20.5 microns of the central 6''x6'' region in NGC 1068, collected with the CAMIRAS instrument mounted at the f/36 IR focus of the CFHT/Hawaii 3.6m telescope and at the f/35 IR focus of the ESO/La Silla 3.6m telescope, respectively. After deconvolution, the achieved resolution (0.6'') reveals a prominent central core emitting about 95 % of the total flux at these wavelengths, as well as extended emission, to the South-West and to the North-East, broken into patchy components which are particularly conspicuous at 20.5 microns and can be isolated as individual clouds. The central core shows an East-West FWHM of 0.6'' (hence unresolved) and a North-South FWHM of 0.9'' corresponding to a resolved full size extension of abound 100 pc. Such an elongated shape is in agreement with model predictions of a dusty/molecular torus surrounding the central engine in NGC 1068, observed under an inclination angle around 65 degrees., 7 pages, 2 figures To appear in Astronomy and Astrophysics

We present a new investigation of the Cloverleaf (z$=$2.56) based on the HST/WFPC2, IRAM and CFHT/FOCAM images data. The WFPC2 data shows a significant overdensity of galaxies around the Cloverleaf that we interpret as the presence of a distant cluster of galaxies along the line of sight. The Cloverleaf is probably the result of the lensing effects which include, in addition to a single galaxy, a distant clusters of galaxies. We have modelled the lens accordingly. The high-resolution IRAM/CO map provides the orientation and the ellipticity of the CO spots induced by the shear component. Velocity-positional effects are detected at the 8$\sigma$ level in the CO map. A strong limit can then be put on the size, shape and location of the CO source around the quasar. The CO source is found to form a disk- or ring- structure orbiting the central engine at $\sim$ 100km/s at a radial distance of $\sim$ 100pc, leading to a central mass of $\sim$ 10$^{9}$ M$_\odot$ possibly in the form of a black hole., Comment: To appear in "Molecular Lines at High Redshift". Greenbank Oct. 97. C. Arilli, S. Radford, K. Menten eds. Latex with paspconf.sty and psfig.sty. 7 pages, 3 figures only available on ftp.iap.fr: /pub/from_users/mellier/ alloind_fig.tar.gz (486 Kb). 25 Kb gzipped tar file

We present a new investigation of the Cloverleaf (z=2.558) based on the combination of archival HST/WFPC2 data, recent IRAM CO(7-6) maps and wide field CFHT/FOCAM images. The deepest WFPC2 observation shows a significant overdensity of I ~ 23--25 galaxies around the Cloverleaf that we interpret as the presence of a cluster of galaxies along the line of sight. The typical magnitude, red color (R-I ~ 0.9) and small angular size of these galaxies suggest that the cluster is very distant and could be associated with the absorption systems observed in the spectra of the quasar spots. The Cloverleaf is probably the result of the lensing effects of a system which includes a single-galaxy and one of the most distant cluster of galaxies. We have modelled the lens using altogether the WFPC2 data and the IRAM/CO(7-6) map, considereing two cases: one in which the mass model is a galaxy and a dark halo at z=1.7, and a second one in which the mass model is the combination of a cluster and an individual galaxy located amid the Cloverleaf, both at z=1.7. The CO source is found to form a ring-like structure orbiting the central engine at ~ 100km/s at a radial distance of ~ 100pc, leading to a black-hole mass of ~ 10^9 M_solar. The cluster component increases significantly the convergence of the lens and this pulls down the requirement on the mass of the lensing galaxy by a factor 2. This may explain the mystery of the lensing galaxy not detected yet., 12 pages, 4 figures, A&A in press

An 8 month monitoring campaign on the Seyfert 1 galaxy Fairall 9 has been conducted with the International Ultraviolet Explorer in an attempt to obtain reliable estimates of continuum-continuum and continuum-emission-line delays for a high-luminosity active galactic nucleus (AGN). While the results of this campaign are more ambiguous than those of previous monitoring campaigns on lower luminosity sources, we find general agreement with the earlier results: (1) there is no measurable lag between ultraviolet continuum bands, and (2) the measured emission-line time lags are very short. It is especially notable that the Lyα + N v emission-line lag is about 1 order of magnitude smaller than determined from a previous campaign by Clavel, Wamsteker, & Glass (1989) when Fairall 9 was in a more luminous state. In other well-monitored sources, specifically NGC 5548 and NGC 3783, the highest ionization lines are found to respond to continuum variations more rapidly than the lower ionization lines, which suggests a radially ionization-stratified broad-line region. In this case, the results are less certain, since none of the emission-line lags are very well determined. The best-determined emission line lag is Lyα + N v, for which we find that the centroid of the continuum-emission-line cross-correlation function is τcent ≈ 14-20 days. We measure a lag τcent ≲ 4 days for He II λ1640; this result is consistent with the ionization-stratification pattern seen in lower luminosity sources, but the relatively large uncertainties in the emission-line lags measured here cannot rule out similar lags for Lyα + N v and He II λ1640 at a high level of significance. We are unable to determine a reliable lag for C IV λ1550, but we note that the profiles of the variable parts of Lyα and C IV λ1550 are not the same, which does not support the hypothesis that the strongest variations in these two lines arise in the same region.

With the aim of better understanding the physical processes that produce the continuous emission in active galactic nuclei (AGNs), a snapshot of the overall continuous energy distribution of NGC 3783, from γ-ray to radio wavelengths, has been obtained within the framework of the World Astronomy Days. The data collected in this campaign are from GRO, ROSAT, Voyager 2, IUE, HST, ESO, CTIO, SAAO and the VLA. Great care has been taken in disentangling the genuine AGN continuous emission from other contributions: depending on the waveband, the latter might be (i) unrelated contaminating sources in cases where the instrument field of view is large, (ii) components within which the AGN is embedded, such as the stellar bulge population which accounts for a significant fraction of the optical continuum, and free-bound and FeII blends which contribute to the ultraviolet flux. After correction for these other contributions, the continuous emission of the isolated AGN appears to be rather ftat (i.e., approximately equal energy per unit logarithmic frequency) from soft γ-ray to infrared wavelengths. At high energies (0.1 MeV to 0.1 keV), the AGN continuum can be fitted by a power law Fv ∝ v-α with a spectral index α ≈ 1. At longer wavelengths, two excesses above this power law ("bumps") appear: in the ultraviolet, the classical big blue bump, which can be interpreted as thermal emission from the accretion disc surrounding a massive black hoJe, and in the infrared a second bump which can be ascribed to thermal emission from dust in the vicinity of the AGN, heated by ultraviolet radiation from the central source. By fitting accretion-disc models to the observed AGN spectral energy distribution, we find values for the accretion disc innermost temperature, accretion rate, and black hole mass, with some differences that depend on whether or not we extrapolate the high-energy power law up to infrared wavelengths. A fit to the IR bump above the extended a = 1 power law suggests the presence of a dust component covering the region from a distance r ≈ 80 light days (hot grains at a temperature T ≈ 1500 K) to r ≈ 60 light years (cool grains at T ≈ 200 K). The total mass of dust is around 60 Mʘ.

GALAXIES at high redshift are very faint and difficult to study at optical and near-infrared wavelengths, but detection of far-infrared emission(1) and molecular gas(2,3) in a galaxy at redshift z approximate to 2.3 has suggested that their early evolution may be investigated by these means instead. The host galaxies of quasars are promising candidates for these observations, particularly as quasars might be triggered by interactions and mergers between galaxies(4,5) which result in dust- and gas-rich systems. The Cloverleaf, a gravitationally lensed quasar, has far-infrared/submillimetre emission indicating a substantial dust content(6), and therefore potentially a large amount of gas. Here we report the detection of carbon monoxide emission from the Cloverleaf, which we interpret as indicating a mass of molecular gas that is comparable to the total dynamical mass of the host galaxy, and which is consistent with the total baryonic content of a present-day luminous galaxy. This suggests that, although some processing of gas through stars has taken place in the Cloverleaf at a lookback time of 85% of the current age of the Universe, much of the future stellar content has yet to be formed.

The Seyfert 1 galaxy NGC 3783 was intensely monitored in several bands between 1991 December and 1992 August. This paper presents the results from the ground-based observations in the optical and near-IR bands, which complement the data set formed by the International Ultraviolet Explorer (IUE) spectra, discussed elsewhere. Spectroscopic and photometric data from several observatories were combined in order to obtain well-sampled light curves of the continuum and of H(beta). During the campaign the source underwent significant variability. The light curves of the optical continuum and of H(beta) display strong similarities to those obtained with the IUE. The near-IR flux did not vary significantly except for a slight increase at the end of the campaign. The cross-correlation analysis shows that the variations of the optical continuum have a lag of 1 day or less with respect to those of the UV continuum, with an uncertainty of is less than or equal to 4 days. The integrated flux of H(beta) varies with a delay of about 8 days. These results confirm that (1) the continuum variations occur simultaneously or with a very small lag across the entire UV-optical range, as in the Seyfert galaxy NGC 5548; and (2) the emission lines of NGC 3783 respond to ionizing continuum variations with less delay than those of NGC 5548. As observed in NGC 5548, the lag of H(beta) with respect to the continuum is greater than those of the high-ionization lines.

The Seyfert 1 galaxy NGC 3783 was intensely monitored in several bands between 1991 December and 1992 August. This paper presents the results from the ground-based observations in the optical and near-IR bands, which complement the data set formed by the International Ultraviolet Explorer (IUE) spectra, discussed elsewhere. Spectroscopic and photometric data from several observatories were combined in order to obtain well-sampled light curves of the continuum and of Hβ. During the campaign the source underwent significant variability. The light curves of the optical continuum and of Hβ display strong similarities to those obtained with the IV E. The near-IR flux did not vary significantly except for a slight increase at the end of the campaign. The cross-correlation analysis shows that the variations of the optical continuum have a lag of 1 day or Iess with respect to those of the UV continuum, with an uncertainty of ≤4 days. The integrated flux of Hβ varies with a delay of about 8 days. These results confirm that (1) the continuum variations occur simultaneously or with a very small lag across the entire UV-optical range, as in the Seyfert galaxy NGC 5548; and (2) the emission !ines of NGC 3783 respond to ionizing continuum variations with less delay than those of NGC 5548. As observed in NGC 5548, the lag of Hβ with respect to the continuum is greater than those of the high-ionization !ines.

We present new integrated spectra in the range 5600-10000 Å for 28 LMC and 3 SMC young star clusters. We measure the equivalent widths (W) of prominent features and the continuum distribution. The analysis, supplemented by 8 additional LMC clusters from our previous studies, indicates that the red supergiant phase is indeed very time-peaked, occuring from 7 to 12 Myr. In addition to the previous case of NGC 2004, we find that NGC 1805, NGC 1994, NGC 2002, NGC 2098 and NGC 2100 as well as NGC 2011 to a lesser extent, are undergoing this phase. The red supergiant phase is clearly denoted by strong TiO bands and Ca II triplet as well as a flat continuum or in extreme cases a continuum with positive slope for λ> 6000 Å. In the SMC clusters, the molecular bands are weak, owing to metal deficiency, but we can show nevertheless that NGC 299 clearly belongs to the red supergiant phase as demonstrated by its spectral slope and enhanced Ca II. We also find new evidence of another red phase at t ≈ 100 Myr, possibly produced by AGB stars, in which the clusters NGC 2031 and NGC 2134 exhibit strong molecular bands like NGC 1866, a previously known case. Clusters between 10 and 50 Myr have strong Hα emission arising from Be stars, a phenomenon which occurs also in Galactic open clusters. From the LMC data set, it has been possible to identify 8 stages in the cluster spectral evolution from 5 to 500 Myr. We derive the corresponding average spectra which shall be useful for population synthesis of galaxies in which recent bursts of star formation have occurred.

We briefly describe our on-going investigation of the near-IR luminosity-metallicity relationship for dwarf irregular galaxies in nearby groups of galaxies. The motivations of the project and the observational databases are introduced, and a preliminary result is presented. The 12+log(O/H) vs.H plane must be populated with more low-luminosity galaxies before a definite conclusion can be drawn., Comment: To be published in "Recycling intergalactic and interstellar matter", IAU Symposium Series, Vol. 217, 2004, Pierre-Alain Duc, Jonathan Braine and Elias Brinks, eds

This is an electronic version of an article published in The Astrophysical Journal. Clavel, J. et al. Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. I. An 8 month campaign of monitoring NGC 5548 with IUE. The Astrophysical Journal 366 (1991): 64-81

We report on the results of intensive ultraviolet spectral monitoring of the Seyfert 1 galaxy NGC 3783. The nucleus of NGC 3783 was observed with the International Ultraviolet Explorer satellite on a regular basis for a total of 7 months, once every 4 days for the first 172 days and once every other day for the final 50 days. Significant variability was observed in both continuum and emission-line ftuxes. The light curves for the con­ tinuum ftuxes exhibited two well-defined local mínima or "dips," the first lasting

We present new elements in the identification of the lens-system producing the 4 images of the BAL quasar H1413+117, based on the recent HST/NICMOS-2/F160W observations. After a careful PSF subtraction of the 4 images of the quasar, the residual H image reveals the presence of a faint object (H~20.5) within the region enclosed by the 4 quasar images. This object corresponds to a single galaxy: the primary lens of the lens-system. We also identify the galaxies around the Cloverleaf which had been proposed to belong to a galaxy cluster/group at high redshift (Kneib et al 1998): the other component in the lens-system that provides the additional "external" shear. For these galaxies, we have derived a likely redshift based upon their R, I and H magnitudes. We find that most of them are consistent with belonging to a galaxy cluster/group with mean redshift =0.9 +/- 0.1. Furthermore we detect 2 very red objects (I-H~4): the faintest one has no observed optical (R and I) counterpart, while the brightest has a predicted redshift around z~2, and may be identified with one of the Cloverleaf absorbers. This gravitational-lens system constitutes an excellent target for IR imaging/spectroscopy with the new generation of 8m ground-based telescopes., Comment: Submitted to A&A letters

The low mass star forming region associated with the Corona Australis cloud hosts an embedded culture of young stellar objects (YSOs), many of which drive molecular outflows associated with shock-excited (HH-objct) emission-line objects. CO(1-0) mapping from the SEST and CO(3-2) mapping from JCMT are presented and analyzed in the context of identifying outflows and associating them with known YSOs and HH-objects. This region hosts far more molecular outflows than previously thought and resembles in some respects the "burst" of outflow activity associated with the star forming region NGC1333.

We report on the redshift of the lensing galaxy and of the quasar QJ 0158-4325 and on the lens model of the system. 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 MgII emission line to constrain the mass model. 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 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 t(A-B)=-14.5+/-0.1 days, with H0=73 km/s/Mpc. Using the flux ratio to constrain the mass model favors the truncated-PIEMD over the SIE, while ignoring this constraint leaves the choice open., Comment: Research Note, Accepted for publication in A&A

CONTEXT: Gravitationally lensed quasars constitute an independent tool to derive H0 through time-delays; they offer as well the opportunity to study the mass distribution and interstellar medium of their lensing galaxies and, through microlensing 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 observational data over a large field-of-view and spectroscopy at high spatial resolution. METHODS: We present VIMOS integral field observations 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, as well as 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. 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., Comment: 13 pages, 18 figures. Accepted for publication in A&A: January 7, 2008

This "pedagogical" review describes the key Chandra and XMM-Newton extragalactic surveys to date and details some of their implications for AGN physics and evolution. We additionally highlight two topics of current widespread interest: (1) X-ray constraints on the AGN content of luminous submillimeter galaxies, and (2) the demography and physics of high-redshift (z > 4) AGN as revealed by X-ray observations. Finally, we discuss prospects for future X-ray surveys with Chandra, XMM-Newton, and upcoming missions., 26 pages, in Physics of Active Galactic Nuclei at All Scales, eds. Alloin D., Johnson R., Lira P. (Springer-Verlag, Berlin), version with all figures at http://www.astro.psu.edu/users/niel/papers/papers.html

We report on the results of intensive ultraviolet spectral monitoring of the Seyfert 1 galaxy NGC 3783. The nucleus of NGC 3783 was observed with the International Ultraviolet Explorer satellite on a regular basis for a total of 7 months, once every 4 days for the first 172 days and once every other day for the final 50 days. Significant variability was observed in both continuum and emission-line fluxes. The light curves for the continuum fluxes exhibited two well-defined local minima or 'dips,' the first lasting is less than or approximately 20 days and the second is less than or approximately 4 days, with additional episodes of relatively rapid flickering of approximately the same amplitude. As in the case of NGC 5548 (the only other Seyfert galaxy that has been the subject of such an intensive, sustained monitoring effort), the largest continuum variations were seen at the shortest wavelengths, so that the continuum became 'harder' when brighter. The variations in the continuum occurred simultaneously at all wavelengths (delta(t) is less than 2 days). Generally, the amplitude of variability of the emission lines was lower than (or comparable to) that of the continuum. Apart from Mg II (which varied little) and N V (which is relatively weak and badly blended with Ly(alpha), the light curves of the emission lines are very similar to the continuum light curves, in each case with a small systematic delay or 'lag.' As for NGC 5548, the highest ionization lines seem to respond with shorter lags than the lower ionization lines. The lags found for NGC 3783 are considerably shorter than those obtained for NGC 5548, with values of (formally) approximately 0 days for He II + O III), and approximately 4 days for Ly(alpha) and C IV. The data further suggest lags of approximately 4 days for Si IV + O IV) and 8-30 days for Si III + C III). Mg II lagged the 1460 A continuum by approximately 9 days, although this result depends on the method of measuring the line flux and may in fact be due to variability of the underlying Fe II lines. Correlation analysis further shows that the power density spectrum contains substantial unresolved power over timescales of is less than or approximately 2 days, and that the character of the continuum variability may change with time.