G. Meylan

Publications (112)85.38 Total impact

• Source

  Available from: Marc Sauvage

  Dataset: EUCLID RB Issue 1.1 2011-09-29HighQ

  R. Laureijs, J. Amiaux, S. Arduini, J. L. Auguères, J. Brinchmann, R. Cole, M. Cropper, C. Dabin, L. Duvet, A Ealet, [......], S. Serrano, N. Shane, J. -L. Starck, C. Surace, A Taylor, G. Verdoes Kleijn, C. Vuerli, O. R. Williams, A. Zacchei, B. Altieri
• Source

  Available from: Dominique Sluse

  Article: Probing the inner structure of distant AGNs with gravitational lensing

  D. Sluse, D. Hutsemékers, F. Courbin, G. Meylan, J. Wambsganss
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  ABSTRACT: Microlensing is a powerful technique which can be used to study the continuum and the broad line emitting regions in distant AGNs. After a brief description of the methods and required data, we present recent applications of this technique. We show that microlensing allows one to measure the temperature profile of the accretion disc, estimate the size and study the geometry of the region emitting the broad emission lines.
  02/2013;
• Source

  Available from: Eva Eulaers

  Article: COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XIII. Time delays of the doubly lensed quasars SDSS J1206+4332 and HS 2209+1914

  E.Eulaers, M. Tewes, P. Magain, F. Courbin, I. Asfandiyarov, Sh. Ehgamberdiev, S. Rathna Kumar, C.S. Stalin, T.P. Prabhu, G. Meylan, H. Van Winckel
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  ABSTRACT: Aims. Within the framework of the COSMOGRAIL collaboration we present 7- and 8.5-year-long light curves and time delay esti- mates for two gravitationally lensed quasars: SDSS J1206+4332 and HS 2209+1914. Methods. We have monitored these doubly lensed quasars in the R-band using four telescopes: the Mercator, Maidanak, Himalayan Chandra and Euler Telescopes, together spanning a period of 7 to 8.5 observing seasons from mid-2004 to mid-2011. The photom- etry of the quasar images is obtained through simultaneous deconvolution of these data. The time delays are determined from these resulting light curves using four very different techniques: a dispersion method, a spline fit, a regression difference technique, and a numerical model fit, thus minimizing the bias that might be introduced by the use of a single method. Results. The time delay for SDSS J1206+4332 is ∆tAB = 111.3 ± 3 days with A leading B, confirming within the error bars a previ- ously published result. For HS 2209+1914 we present a new time delay of ∆tBA = 20.0 ± 5 days with B leading A. Conclusions. The combination of data from up to four telescopes have lead to well-sampled and nearly 9-season-long light curves, which was necessary to obtain these results, especially for the compact doubly lensed quasar HS 2209+1914.
  Astronomy and Astrophysics 01/2013; · 4.59 Impact Factor
• Article: Interpolating point spread function anisotropy

  M. Gentile, F. Courbin, G. Meylan
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  ABSTRACT: Planned wide-field weak lensing surveys are expected to reduce the statistical errors on the shear field to unprecedented levels. In contrast, systematic errors like those induced by the convolution with the point spread function (PSF) will not benefit from that scaling effect and will require very accurate modeling and correction. While numerous methods have been devised to carry out the PSF correction itself, modeling of the PSF shape and its spatial variations across the instrument field of view has, so far, attracted much less attention. This step is nevertheless crucial because the PSF is only known at star positions while the correction has to be performed at any position on the sky. A reliable interpolation scheme is therefore mandatory and a popular approach has been to use low-order bivariate polynomials. In the present paper, we evaluate four other classical spatial interpolation methods based on splines (B-splines), inverse distance weighting (IDW), radial basis functions (RBF) and ordinary Kriging (OK). These methods are tested on the Star-challenge part of the GRavitational lEnsing Accuracy Testing 2010 (GREAT10) simulated data and are compared with the classical polynomial fitting (Polyfit). We also test all our interpolation methods independently of the way the PSF is modeled, by interpolating the GREAT10 star fields themselves (i.e., the PSF parameters are known exactly at star positions). We find in that case RBF to be the clear winner, closely followed by the other local methods, IDW and OK. The global methods, Polyfit and B-splines, are largely behind, especially in fields with (ground-based) turbulent PSFs. In fields with non-turbulent PSFs, all interpolators reach a variance on PSF systematics $\sigma_{sys}^2$ better than the $1\times10^{-7}$ upper bound expected by future space-based surveys, with the local interpolators performing better than the global ones.
  10/2012;
• Article: Image Analysis for Cosmology: Results from the GREAT10 Star Challenge

  T. D. Kitching, B. Rowe, M. Gill, C. Heymans, R. Massey, D. Witherick, F. Courbin, K. Georgatzis, M. Gentile, D. Gruen, M. Kilbinger, G. L. Li, A. P. Mariglis, G. Meylan, A. Storkey, B. Xin
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  ABSTRACT: We present the results from the first public blind PSF reconstruction challenge, the GRavitational lEnsing Accuracy Testing 2010 (GREAT10) Star Challenge. Reconstruction of a spatially varying PSF, sparsely sampled by stars, at non-star positions is a critical part in the image analysis for weak lensing where inaccuracies in the modelled ellipticity and size-squared can impact the ability to measure the shapes of galaxies. This is of importance because weak lensing is a particularly sensitive probe of dark energy, and can be used to map the mass distribution of large scale structure. Participants in the challenge were presented with 27,500 stars over 1300 images subdivided into 26 sets, where in each set a category change was made in the type or spatial variation of the PSF. Thirty submissions were made by 9 teams. The best methods reconstructed the PSF with an accuracy of ~0.00025 in ellipticity and ~0.00074 in size squared. For a fixed pixel scale narrower PSFs were found to be more difficult to model than larger PSFs, and the PSF reconstruction was severely degraded with the inclusion of an atmospheric turbulence model (although this result is likely to be a strong function of the amplitude of the turbulence power spectrum).
  10/2012;
• Article: COSMOGRAIL XII: Time delays and 9-yr optical monitoring of the lensed quasar RX J1131-1231

  M. Tewes, F. Courbin, G. Meylan, C. S. Kochanek, E. Eulaers, N. Cantale, A. M. Mosquera, P. Magain, H. Van Winckel, D. Sluse, G. Cataldi, D. Voros, S. Dye
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  ABSTRACT: We present the results from 9 years of optically monitoring the gravitationally lensed z=0.658 quasar RX J1131-1231. The R band light curves of the 4 individual images of the quasar are obtained using deconvolution photometry, for a total of 707 epochs. Several sharp quasar variability features strongly constrain the time delays between the quasar images. Using three different numerical techniques, we measure these delays for all possible pairs of quasar images, while always processing the 4 light curves simultaneously. For all three methods, the delays between the 3 close images A, B and C are compatible with being 0, while we measure the delay of image D to be 91 days, with a fractional uncertainty of 1.5% (1 sigma), including systematic errors. Our analysis of random and systematic errors accounts in a realistic way for the observed quasar variability, fluctuating microlensing magnification over a broad range of temporal scales, noise properties, and seasonal gaps. Finally, we find that our time delay measurement methods yield compatible results when applied to subsets of the data.
  08/2012;
• Article: Two accurate time-delay distances from strong lensing: Implications for cosmology

  S. H. Suyu, M. W. Auger, S. Hilbert, P. J. Marshall, M. Tewes, T. Treu, C. D. Fassnacht, L. V. E. Koopmans, D. Sluse, R. D. Blandford, F. Courbin, G. Meylan
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  ABSTRACT: Strong gravitational lenses with measured time delays between the multiple images and models of the lens mass distribution allow a one-step determination of the time-delay distance, and thus a measure of cosmological parameters. We present a blind analysis of the gravitational lens RXJ1131-1231 incorporating (1) the newly measured time delays from COSMOGRAIL, (2) archival HST imaging of the lens system, (3) a new velocity-dispersion measurement of the lens galaxy of 323+/-20km/s based on Keck spectroscopy, and (4) a characterization of the line-of-sight structures via observations of the lens' environment and ray tracing through the Millennium Simulation. Our blind analysis is designed to prevent experimenter bias. The joint analysis of the data sets allows a time-delay distance measurement to 6% precision that takes into account all known systematic uncertainties. In combination with the WMAP7 data set in flat wCDM cosmology, our unblinded cosmological constraints for RXJ1131-1231 are: H_0=80.0+5.8/-5.7km/s/Mpc, OmegaDE=0.79+/-0.03 and w=-1.25+0.17/-0.21. We find the results to be statistically consistent with those from the analysis of the gravitational lens B1608+656. The joint constraints from the two lenses and WMAP7 are H_0=75.2+4.4/-4.2km/s/Mpc, OmegaDE=0.76+0.02/-0.03 and w=-1.14+0.17/-0.20 in flat wCDM, and H_0=73.1+2.4/-3.6km/s/Mpc, OmegaL=0.75+0.01/-0.02 and OmegaK=0.003+0.005/-0.006 in open LCDM. Time-delay lenses constrain especially tightly the Hubble constant (5.7% and 4.0% respectively in wCDM and open LCDM) and curvature of the universe. They complement well other cosmological probes, and provide an independent check of unknown systematics. Our measurement of the Hubble constant is completely independent of those based on the local distance ladder method, providing an important consistency check of the standard cosmological model and of general relativity.
  08/2012;
• Article: COSMOGRAIL XI: Techniques for time delay measurement in presence of microlensing

  M. Tewes, F. Courbin, G. Meylan
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  ABSTRACT: Measuring time delays between the multiple images of gravitationally lensed quasars is now recognized as a competitive way to constrain the cosmological parameters, well complementary with other cosmological probes. This requires long and well sampled optical light curves of numerous lensed quasars, e.g., as obtained by the COSMOGRAIL collaboration. High-quality data from our monitoring campaign calls for novel numerical techniques to robustly measure the delays as well as the associated random and systematic uncertainties, even in presence of microlensing variations. We propose three different point estimators to measure time delays, that are explicitly designed to handle light curves with extrinsic variability. These methods share a common formalism, which enables them to process data from n-image lenses. As the estimators rely on significantly contrasting ideas, we expect them to be sensitive to different bias sources. For each method and data set, we empirically estimate both the precision and accuracy (bias) of the time delay measurement using simulated light curves with known time delays that closely mimic the observations. Eventually, we test the self-consistency of our approach, and we demonstrate that our bias estimation is serviceable. These new methods, including the empirical uncertainty estimator, will represent the standard benchmark for the analysis of the COSMOGRAIL light curves.
  08/2012;
• Article: On the detection of point sources in CMB maps

  H. G. Khachatryan, G. Nurbaeva, D. Pfenniger, G. Meylan
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  ABSTRACT: We use the Wilkinson Microwave Anisotropy Probe 7-year data (WMAP7) to further probe point source detection technique in the sky maps of the cosmic microwave background (CMB) radiation. The method by Tegmark et al. for foreground reduced maps and the Kolmogorov parameter as the descriptor are adopted for the analysis of WMAP satellite CMB temperature data. Part of the detected points coincide with point sources already revealed by other methods. However, we have also found 2 source candidates for which still no counterparts are known, and identified 7 point sources listed in Planck Early Release Compact Source Catalogue as high reliability sources.
  06/2012;
• Article: A seven square degrees survey for galaxy-scale gravitational lenses with the HST imaging archive

  R. S. Pawase, C. Faure, F. Courbin, R. Kokotanekova, G. Meylan
  [show abstract] [hide abstract]
  ABSTRACT: We present the results of a visual search for galaxy-scale gravitational lenses in ~7 square degrees of Hubble Space Telescope (HST) images. The dataset comprises the whole imaging data ever taken with the Advanced Camera for Surveys (ACS) in the filter F814W (I-band) up to August 31st, 2011, i.e. 6.03 square degrees excluding the field of the Cosmic Evolution Survey (COSMOS). In addition, we have searched for lenses in the whole Wide Field Camera 3 (WFC3) near-IR imaging dataset in all filters 1.01 square degree up to the same date. Our primary goal is to provide a sample of lenses with a broad range of different morphologies and lens-source brightness contrast in order to design and train future automated lens finders in view of all-sky surveys. Our criteria to select lenses are purely morphological as we do not use any color or redshift information. The final candidate selection is very conservative hence leading to a nearly pure but incomplete sample. We find 49 new lens candidates: 40 in the ACS images and 9 in the WFC3 images. Out of these, 16 candidates are secure lenses owe to their highly recognizable morphology, 21 more are very good candidates, and 12 more have morphologies compatible with gravitational lensing. The imaging dataset is heterogeneous in depth and spans a broad range of galactic latitudes. It is therefore insensitive to cosmic variance and allows to estimate the number of galaxy-scale strong lenses on the sky for a putative survey depth. Because of the incompleteness of the sample, the estimated lensing rates should be taken as lower limits. Using these, we anticipate that a 15000 square degrees space survey such as Euclid will find at least 60000 galaxy-scale strong lenses down to a limiting AB magnitude of I=24.5 (10-sigma) or I=25.8 (3-sigma).
  06/2012;
• Source

  Available from: Dominique Sluse

  Article: Microlensing of the broad line region in 17 lensed quasars

  D. Sluse, D. Hutsemékers, F. Courbin, G. Meylan, J. Wambsganss
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  ABSTRACT: When an image of a strongly lensed quasar is microlensed, the different components of its spectrum are expected to be differentially magnified owing to the different sizes of the corresponding emitting region. Chromatic changes are expected to be observed in the continuum while the emission lines should be deformed as a function of the size, geometry and kinematics of the regions from which they originate. Microlensing of the emission lines has been reported only in a handful of systems so far. In this paper we search for microlensing deformations of the optical spectra of pairs of images in 17 lensed quasars. This sample is composed of 13 pairs of previously unpublished spectra and four pairs of spectra from literature. Our analysis is based on a spectral decomposition technique which allows us to isolate the microlensed fraction of the flux independently of a detailed modeling of the quasar emission lines. Using this technique, we detect microlensing of the continuum in 85% of the systems. Among them, 80% show microlensing of the broad emission lines. Focusing on the most common lines in our spectra (CIII] and MgII) we detect microlensing of either the blue or the red wing, or of both wings with the same amplitude. This observation implies that the broad line region is not in general spherically symmetric. In addition, the frequent detection of microlensing of the blue and red wings independently but not simultaneously with a different amplitude, does not support existing microlensing simulations of a biconical outflow. Our analysis also provides the intrinsic flux ratio between the lensed images and the magnitude of the microlensing affecting the continuum. These two quantities are particularly relevant for the determination of the fraction of matter in clumpy form in galaxies and for the detection of dark matter substructures via the identification of flux ratio anomalies.
  06/2012;
• Article: A fast empirical method for galaxy shape measurements in weak lensing surveys

  M. Tewes, N. Cantale, F. Courbin, T. D. Kitching, G. Meylan
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  ABSTRACT: We describe a simple and fast method to correct ellipticity measurements of galaxies from the distortion by the instrumental and atmospheric point spread function (PSF), in view of weak lensing shear measurements. The method performs a classification of galaxies and associated PSFs according to measured shape parameters, and corrects the measured galaxy ellipticites by querying a large lookup table (LUT), built by supervised learning. We have applied this new method to the GREAT10 image analysis challenge, and present in this paper a refined solution that obtains the competitive quality factor of Q = 104, without any shear power spectrum denoising or training. Of particular interest is the efficiency of the method, with a processing time below 3 ms per galaxy on an ordinary CPU.
  03/2012;
• Source

  Available from: W. Freedman

  Article: The Hubble constant and new discoveries in cosmology

  S. H. Suyu, T. Treu, R. D. Blandford, W. L. Freedman, S. Hilbert, C. Blake, J. Braatz, F. Courbin, J. Dunkley, L. Greenhill, [......], B. F. Madore, P. J. Marshall, G. Meylan, J. Mould, B. Reid, M. Reid, A. Riess, D. Schlegel, V. Scowcroft, L. Verde
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  ABSTRACT: We report the outcome of a 3-day workshop on the Hubble constant (H_0) that took place during February 6-8 2012 at the Kavli Institute for Particle Astrophysics and Cosmology, on the campus of Stanford University. The participants met to address the following questions. Are there compelling scientific reasons to obtain more precise and more accurate measurements of H_0 than currently available? If there are, how can we achieve this goal? The answers that emerged from the workshop are (1) better measurements of H_0 provide critical independent constraints on dark energy, spatial curvature of the Universe, neutrino physics, and validity of general relativity, (2) a measurement of H_0 to 1% in both precision and accuracy, supported by rigorous error budgets, is within reach for several methods, and (3) multiple paths to independent determinations of H_0 are needed in order to access and control systematics.
  02/2012;
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  Available from: Dominique Sluse

  Article: COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses X. Modeling based on high-precision astrometry of a sample of 25 lensed quasars: consequences for ellipticity, shear, and astrometric anomalies

  D. Sluse, V. Chantry, P. Magain, F. Courbin, G. Meylan
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  ABSTRACT: (abridged) Gravitationally lensed quasars can be used as powerful cosmological and astrophysical probes. We can (i) infer the Hubble constant based on the time-delay technique, (ii) unveil substructures along the l.o.s. toward distant galaxies, and (iii) compare the shape and the slope of baryons and dark matter distributions in galaxies. To reach these goals, we need high-accuracy astrometry and morphology measurements of the lens. In this work, we first present new astrometry for 11 lenses with measured time delays. Using MCS deconvolution on NIC2 HST images, we reached an astrometric accuracy of about 1-2.5 mas and an accurate shape measurement of the lens galaxy. Second, we combined these measurements with those of 14 other systems to present new mass models of these lenses. This led to the following results: 1) In 4 double-image quasars, we show that the influence of the lens environment on the time delay can easily be quantified and modeled, hence putting these lenses with high priority for time-delay determination. 2) For quadruple-image quasars, the difficulty often encountered in reproducing the image positions to milli-arcsec accuracy (astrometric anomaly) is overcome by explicitly including the nearest visible galaxy in the model. However, one anomalous system (J1131-1231) does not show any luminous perturber in its vicinity, and three others (WFI2026-4536, WFI2033-4723, and B2045+265) have problematic modeling. These 4 systems are the best candidates for a pertubation by a dark matter substructure. 3) We find a significant correlation between the PA of the light and of the mass distributions in lensing galaxies. In contrast with other studies, we find that the ellipticity of the light and of the mass also correlate well, suggesting that the overall spatial distribution of matter is not very different from the baryon distribution in the inner \sim 5 kpc of lensing galaxies.
  11/2011;
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  Available from: Dominique Sluse

  Article: Three QSOs acting as strong gravitational lenses

  F. Courbin, C. Faure, S. G. Djorgovski, F. Rerat, M. Tewes, G. Meylan, D. Stern, A. Mahabal, T. Boroson, R. Dheeraj, D. Sluse
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  ABSTRACT: We report the discovery of three new cases of QSOs acting as strong gravitational lenses on background emission line galaxies: SDSS J0827+5224 (zQSO = 0.293, zs = 0.412), SDSS J0919+2720 (zQSO = 0.209, zs = 0.558), SDSS J1005+4016 (zQSO = 0.230, zs = 0.441). The selection was carried out using a sample of 22,298 SDSS spectra displaying at least four emission lines at a redshift beyond that of the foreground QSO. The lensing nature is confirmed from Keck imaging and spectroscopy, as well as from HST/WFC3 imaging in the F475W and F814W filters. Two of the QSOs have face-on spiral host galaxies and the third is a QSO+galaxy pair. The velocity dispersion of the host galaxies, inferred from simple lens modeling, is between \sigma_v = 210 and 285 km/s, making these host galaxies comparable in mass with the SLACS sample of early-type strong lenses.
  10/2011;
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  Available from: Frederic Courbin

  Article: Euclid Definition Study Report

  R. Laureijs, J. Amiaux, S. Arduini, J. L. Auguères, J. Brinchmann, R. Cole, M. Cropper, C. Dabin, L. Duvet, A Ealet, [......], S. Spiro, M Sullivan, A Tilquin, R. Trotta, L. Verde, Y Wang, G. Williger, G Zhao, J. Zoubian, E. Zucca
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  ABSTRACT: Euclid is a space-based survey mission from the European Space Agency designed to understand the origin of the Universe's accelerating expansion. It will use cosmological probes to investigate the nature of dark energy, dark matter and gravity by tracking their observational signatures on the geometry of the universe and on the cosmic history of structure formation. The mission is optimised for two independent primary cosmological probes: Weak gravitational Lensing (WL) and Baryonic Acoustic Oscillations (BAO). The Euclid payload consists of a 1.2 m Korsch telescope designed to provide a large field of view. It carries two instruments with a common field-of-view of ~0.54 deg2: the visual imager (VIS) and the near infrared instrument (NISP) which contains a slitless spectrometer and a three bands photometer. The Euclid wide survey will cover 15,000 deg2 of the extragalactic sky and is complemented by two 20 deg2 deep fields. For WL, Euclid measures the shapes of 30-40 resolved galaxies per arcmin2 in one broad visible R+I+Z band (550-920 nm). The photometric redshifts for these galaxies reach a precision of dz/(1+z) < 0.05. They are derived from three additional Euclid NIR bands (Y, J, H in the range 0.92-2.0 micron), complemented by ground based photometry in visible bands derived from public data or through engaged collaborations. The BAO are determined from a spectroscopic survey with a redshift accuracy dz/(1+z) =0.001. The slitless spectrometer, with spectral resolution ~250, predominantly detects Ha emission line galaxies. Euclid is a Medium Class mission of the ESA Cosmic Vision 2015-2025 programme, with a foreseen launch date in 2019. This report (also known as the Euclid Red Book) describes the outcome of the Phase A study.
  10/2011;
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  Available from: Dominique Sluse

  Article: VLT adaptive optics search for luminous substructures in the lens galaxy towards SDSS J0924+0219

  C. Faure, D. Sluse, N. Cantale, M. Tewes, F. Courbin, P. Durrer, G. Meylan
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  ABSTRACT: Anomalous flux ratios between quasar images are suspected to be caused by substructures in lens galaxies. We present new deep and high resolution H and Ks imaging of the strongly lensed quasar SDSS J0924+0219 obtained using the ESO VLT with adaptive optics and the Laser Guide Star system. SDSS J0924+0219 is particularly interesting as the observed flux ratio between the quasar images vastly disagree with the predictions from smooth mass models. With our adaptive optics observations we find a luminous object, Object L, located ~0.3" to the North of the lens galaxy, but we show that it can not be responsible for the anomalous flux ratios. Object L as well as a luminous extension of the lens galaxy to the South are seen in the archival HST/ACS image in the F814W filter. This suggests that Object L is part of a bar in the lens galaxy, as also supported by the presence of a significant disk component in the light profile of the lens galaxy. Finally, we do not find evidence for any other luminous substructure that may explain the quasar images flux ratios. However, owe to the persistence of the flux ratio anomaly over time (~ 7 years) a combination of microlensing and milli-lensing is the favorite explanation for the observations.
  09/2011;
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  Available from: Frederic Courbin

  Article: On the effect of image denoising on galaxy shape measurements

  G. Nurbaeva, F. Courbin, M. Gentile, G. Meylan
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  ABSTRACT: Weak gravitational lensing is a very sensitive way of measuring cosmological parameters, including dark energy, and of testing current theories of gravitation. In practice, this requires exquisite measurement of the shapes of billions of galaxies over large areas of the sky, as may be obtained with the EUCLID and WFIRST satellites. For a given survey depth, applying image denoising to the data both improves the accuracy of the shape measurements and increases the number density of galaxies with a measurable shape. We perform simple tests of three different denoising techniques, using synthetic data. We propose a new and simple denoising method, based on wavelet decomposition of the data and a Wiener filtering of the resulting wavelet coefficients. When applied to the GREAT08 challenge dataset, this technique allows us to improve the quality factor of the measurement (Q; GREAT08 definition), by up to a factor of two. We demonstrate that the typical pixel size of the EUCLID optical channel will allow us to use image denoising.
  06/2011;
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  Available from: Dominique Sluse

  Article: Zooming into the broad line region of the gravitationally lensed quasar Q2237+0305 = the Einstein Cross: III. Determination of the size and structure of the CIV and CIII] emitting regions using microlensing

  D. Sluse, R. Schmidt, F. Courbin, D. Hutsemékers, G. Meylan, A. Eigenbrod, T. Anguita, E. Agol, J. Wambsganss
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  ABSTRACT: We aim to use microlensing taking place in the lensed quasar Q2237+0305 to study the structure of the broad line region and measure the size of the region emitting the CIV and CIII] lines. Methods: Based on 39 spectrophotometric monitoring data points obtained between Oct. 2004 and Dec. 2007, we derived lightcurves for the CIV and CIII] emission lines. We used three different techniques to analyse the microlensing signal. Different components of the lines (narrow, broad and very broad) are identified and studied. We built a library of simulated microlensing lightcurves that reproduce the signal observed in the continuum and in the lines provided only the source size is changed. A Bayesian analysis scheme is then developed to derive the size of the various components of the BLR. Results: 1. The half-light radius of the region emitting the CIV line is found to be R_CIV ~ 66^{+110}_{-46} lt-days = 0.06$^{+0.09}_{-0.04}$ pc = 1.7$^{+2.8}_{-1.1}$\,10$^{17}$ cm (at 68.3% CI). Similar values are obtained for CIII]. Relative sizes of the carbon-line and V-band continuum emitting-regions are also derived with median values of R(line)/R(cont) in the range 4 to 29, depending of the FWHM of the line component. 2. The size of the CIV emitting region agrees with the Radius-Luminosity relationship derived from reverberation mapping. Using the virial theorem we derive the mass of the black hole in Q2237+0305 to be M_BH ~ 10^{8.3+/-0.3} M_sun. 3. We find that the CIV and CIII] lines are produced in at least 2 spatially distinct regions, the most compact one giving rise to the broadest component of the line. The broad and narrow line profiles are slightly different for CIV and CIII]. 4. Our analysis suggests a different structure for the CIV and FeII+III emitting regions, with the latter produced in the inner part of the BLR or in a less extended emitting region than CIV.
  12/2010;
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  Available from: Dominique Sluse

  Article: COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses IX. Time delays, lens dynamics and baryonic fraction in HE 0435-1223

  F. Courbin, V. Chantry, Y. Revaz, D. Sluse, C. Faure, M. Tewes, E. Eulaers, M. Koleva, I. Asfandiyarov, S. Dye, P. Magain, H. Van Winckel, J. Coles, P. Saha, M. Ibrahimov, G. Meylan
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  ABSTRACT: We present accurate time delays for the quadruply imaged quasar HE 0435-1223. The delays were measured from 575 independent photometric points obtained in the R-band between January 2004 and March 2010. With seven years of data, we clearly show that quasar image A is affected by strong microlensing variations and that the time delays are best expressed relative to quasar image B. We measured Delta_t(BC) = 7.8+/-0.8 days, Delta_t(BD) = -6.5+/-0.7 days and Delta_t_CD = -14.3+/-0.8 days. We spacially deconvolved HST NICMOS2 F160W images to derive accurate astrometry of the quasar images and to infer the light profile of the lensing galaxy. We combined these images with a stellar population fitting of a deep VLT spectrum of the lensing galaxy to estimate the baryonic fraction, $f_b$, in the Einstein radius. We measured f_b = 0.65+0.13-0.10 if the lensing galaxy has a Salpeter IMF and f_b = 0.45+0.04-0.07 if it has a Kroupa IMF. The spectrum also allowed us to estimate the velocity dispersion of the lensing galaxy, sigma_ap = 222+/-34 km/s. We used f_b and sigma_ap to constrain an analytical model of the lensing galaxy composed of an Hernquist plus generalized NFW profile. We solve the Jeans equations numerically for the model and explored the parameter space under the additional requirement that the model must predict the correct astrometry for the quasar images. Given the current error bars on f_b and sigma_ap, we did not constrain H0 yet with high accuracy, i.e., we found a broad range of models with chi^2 < 1. However, narrowing this range is possible, provided a better velocity dispersion measurement becomes available. In addition, increasing the depth of the current HST imaging data of HE 0435-1223 will allow us to combine our constraints with lens reconstruction techniques that make use of the full Einstein ring that is visible in this object.
  09/2010;