References of "Vanderriest, C"
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See detailAbout the origin of extinction in the gravitational lens system MG J0414+0534
Angonin-Willaime, M.-C.; Vanderriest, C.; Courbin, F. et al

in Astronomy and Astrophysics (1999), 347

Photometric measurements of the highly reddened gravitational mirage MG J0414+0534 have been carried out either by PSF subtraction or by applying accurate deconvolution algorithms to optical (R, I) and ... [more ▼]

Photometric measurements of the highly reddened gravitational mirage MG J0414+0534 have been carried out either by PSF subtraction or by applying accurate deconvolution algorithms to optical (R, I) and near-infrared (K) images obtained at CFHT and NOT under sub-arcsecond seeing conditions. It is confirmed that the close pair of images A1-A2 suffers a larger extinction than B and C. While the colours of image A2 obtained from ground-based data seem inconsistent with a simple reddening law, higher resolution images available from HST archives reveal an additional extended component (arc) which introduces significant errors in the photometric decomposition. When the arc component is properly taken into account, the colours of the 4 nucleus images do agree with a classical reddening law, with A2 being by far the most obscured component. Such a differential extinction (maximum difference Delta E(R-I) =~ 0.6) is likely due to the lensing galaxy. This does not mean that {all} the extinction occurs into the lens. Indeed, the fact that the arc is much less red than the images of the nucleus suggests that an important part of the reddening is intrinsic to the source. Finally, no significant variability is observed within this data set, i.e. between 1994 and 1997, while a discrepancy from earlier data is noticed for (A1 + A2). Based on observations collected with the Canada-France-Hawaii Telescope at Mauna Kea (Hawaii, USA), the Nordic Optical Telescope (Canary, Spain) and archive data from the Hubble Space Telescope (NASA/ESA) [less ▲]

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See detailHST confirmation of the lensed quasar J03.13.
Surdej, Jean ULg; Claeskens, Jean-François ULg; Remy, M. et al

in Astronomy and Astrophysics (1997), 327

In order to definitely prove the claim by Claeskens et al. (1996A&A...305L...9C) that J03.13 is a doubly imaged quasar, WFPC2 direct imaging and FOS spectroscopy of this compact system have been obtained ... [more ▼]

In order to definitely prove the claim by Claeskens et al. (1996A&A...305L...9C) that J03.13 is a doubly imaged quasar, WFPC2 direct imaging and FOS spectroscopy of this compact system have been obtained with HST. These textbook case observations clearly show that J03.13 consists of two point-like images separated by 0.849"+/-0.001" with a magnitude difference of 2.14+/-0.03 in V and I. We see no trace of a lensing galaxy. From the FOS observations, we find that J03.13 A and B have identical spectra within the measurement uncertainties. The data also show that spectroscopic contamination of B by A is negligible. We do confirm the redshift z=2.545 for J03.13 A and B (emission-lines due to Ly-beta lambda1025 and O VI lambdalambda1031, 1037 are also detected), first derived from an unresolved ground-based spectrum of the two components by Claeskens et al. We also find that the absorption line system at z=2.344 (CIV and Ly-alpha) is present in the spectra of A and B. On the contrary, the absorption line system at z=1.085 (MgII) is only present in the spectrum of J03.13 A. If this latter system is associated with the lens, we may expect that image A consists of two radially merging images with a very small angular separation. From the WFPC2 imagery, we can rule out the presence of a third component fainter than A by up to 5.2mag. with an angular separation >=0.13". [less ▲]

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See detailThe geometry of the quadruply imaged quasar PG 1115+080: implications for H_0_.
Courbin, F.; Magain, Pierre ULg; Keeton, C. R. et al

in Astronomy and Astrophysics (1997), 324

Time delay measurements have recently been reported for the lensed quasar PG 1115+080. These measurements can be used to derive H_0_, but only if we can constrain the lensing potential. We have applied a ... [more ▼]

Time delay measurements have recently been reported for the lensed quasar PG 1115+080. These measurements can be used to derive H_0_, but only if we can constrain the lensing potential. We have applied a recently developed deconvolution technique to analyze sub-arcsecond I band images of PG 1115+080, obtained at the Nordic Optical Telescope (NOT) and the Canada France Hawaii Telescope (CFHT). The high performance of the deconvolution code allows us to derive precise positions and magnitudes for the four lensed images of the quasar, as well as for the lensing galaxy. The new measurement of the galaxy position improves its precision by a factor of 3 and thus strengthens the constraints on the lensing potential. With the new data, a range of models incorporating some of the plausible systematic uncertainties yields H_0_=53^+10^_-7_km/s/Mpc. [less ▲]

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See detailIntegral Field Spectroscopy of Selected Extragalactic Objects with FUEGOS
Surdej, Jean ULg; Vanderriest, C.; Angonin-Willaime, M.-C. et al

in Walsh, J.; Danziger, J. (Eds.) Science with the VLT (1995)

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See detail(Erratum) Further observational evidence that MG J0414+0534 is a gravitational mirage.
Angonin-Willaime, M.-C.; Vanderriest, C.; Hammer, F. et al

in Astronomy and Astrophysics (1994), 292

In Sect. 3.3, the identifications of components A1 and A2 for the optical data were inadvertently inverted. This does not change substantially the discussion; just read A1 for A2 and vice versa. In ... [more ▼]

In Sect. 3.3, the identifications of components A1 and A2 for the optical data were inadvertently inverted. This does not change substantially the discussion; just read A1 for A2 and vice versa. In particular, the ratio A2/A1 = 0.3 cannot be made compatible with the radio value without one or several of the mechanisms we suggested. We apologize for the error and thank Dr S. Mao for bringing it to our attention. Erratum to Astron. Astrophys. 281, 388-394 (1994) [less ▲]

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See detailFurther observational evidence that MG J0414+0534 is a gravitational mirage
Angonin-Willaime, M.-C.; Vanderriest, C.; Hammer, F. et al

in Astronomy and Astrophysics (1994), 281

Deep imaging of MG J0414+0534 with R and I filters reveals a faint, fuzzy and red object at the exact location expected for a lensing galaxy in the gravitational mirage hypothesis. Furthermore, the ... [more ▼]

Deep imaging of MG J0414+0534 with R and I filters reveals a faint, fuzzy and red object at the exact location expected for a lensing galaxy in the gravitational mirage hypothesis. Furthermore, the (extremely red and almost featureless) spectra of the 2 brightest components are very similar. These are strong indications that the system results from multiple gravitational imaging of a single source, but the nature of this source is not yet clear. It could be the nucleus of a low metallicity galaxy at a high redshift or a new type of object. Significant differences are observed between the flux ratios of the images at radio and optical wavelenghts. The most likely explanation for this effect is a differential amplification of the image pair A[SUB]1[/SUB]-A[SUB]2[/SUB] because of the large magnification gradient near a caustic. [less ▲]

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See detailSystematic Search for Quasar Candidates using the MAMA Microdensitometer
Moreau, O.; Gosset, Eric ULg; Reboul, H. et al

in Mc Gillivray, H. T.; Thomson, E. B.; Lasker, B. M. (Eds.) et al Astronomy from wide-field imaging (1994)

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See detailGravitational lensing statistics based on a large sample of highly luminous quasars
Surdej, Jean ULg; Claeskens, Jean-François ULg; Crampton, D. et al

in Astronomical Journal (The) (1993), 105

Results on gravitational lensing statistics applied to a sample of 469 highly luminous quasars are reported. The objects were directly imaged, either from the ground under optimal seeing conditions, or ... [more ▼]

Results on gravitational lensing statistics applied to a sample of 469 highly luminous quasars are reported. The objects were directly imaged, either from the ground under optimal seeing conditions, or using the HST. We have derived values for the effectiveness parameter F of galaxies, modeled by means of singular isothermal spheres, to produce macrolensed images of distant quasars, and upper limits on the density parameter Omega(L) of compact objects with masses between 10 exp 10 and 10 exp 12 solar masses. Adopting H(0)= 50 km/s/Mpc, Omega(0)= 1, and Lambda = 0, we find that at the 99.7 percent confidence level, F is between 0.005 and 0.478 and that Omega(L) is less than 0.02. A critical discussion of these results is presented. Finally, comparing the efficiencies of ground-based and space instruments used to search for gravitational lens systems among highly luminous quasars, we conclude that for the near future, ground-based direct imaging characterized by a good dynamical range still constitutes the best observational strategy. [less ▲]

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See detailErratum - Q:1208+1011 - the Most Distant Multiply Imaged Quasar or a Binary
Magain, Pierre ULg; Surdej, Jean ULg; Vanderriest, C. et al

in Astronomy and Astrophysics (1993), 272

In the title of this Letter, the word "multiply" was accidentally omitted. The correct title is shown above.

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See detailSearch for gravitational lenses in a large sample of highly luminous quasars and statistical determination of cosmological parameters
Claeskens, Jean-François ULg; Crampton, D.; Filippenko, A. V. et al

in Surdej, Jean; Fraipont-Caro, D.; Gosset, Eric (Eds.) et al The proceedings of the 31st Liège International Astrophysical Colloquium "Gravitational lenses in the Universe" (1993)

Results on gravitational lensing statistics applied to a sample of 469 highly luminous quasars are reported.

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See detailThe new gravitational lens candidate Q 1208+1011 and the importance of high quality data.
Magain, Pierre ULg; Surdej, Jean ULg; Vanderriest, C. et al

in The Messenger (1992), 67

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See detailQ 1208 + 1011 - The most distant imaged quasar, or a binary?
Magain, Pierre ULg; Surdej, Jean ULg; Vanderriest, C. et al

in Astronomy and Astrophysics (1992), 253(Letters), 13-16

The paper reports the discovery of a new gravitational lens candidate: the high redshift (z = 3.803) and highly luminous (V = 17.5, M[SUB]V[/SUB] = -30.3) quasar Q 1208 + 1011. As derived from the ... [more ▼]

The paper reports the discovery of a new gravitational lens candidate: the high redshift (z = 3.803) and highly luminous (V = 17.5, M[SUB]V[/SUB] = -30.3) quasar Q 1208 + 1011. As derived from the analysis of direct CCD frames taken with the ESO/MPI 2.2 m telescope, this multiple quasar consists of two pointlike images, separated by 0.45 arcsec and characterized by a brightness ratio of 3.5, in red light. Existing spectroscopic data support the gravitational lens interpretation for this system but cannot exclude the hypothesis of a binary quasar. In the former case, the spectrum suggests that, if the metallic absorption line system reported by Steidel (1990) at a redshift z = 2.9157 is associated with the deflector, the mass of the lens should be of the order of M = 7.8 x 10 exp 11 solar masses. Evaluation of a recent HST PC frame obtained for Q 1208 + 1011 within the snapshot survey for gravitational lenses confirms the above results. [less ▲]

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See detailGravitational lensing statistics based on a large sample of highly luminous quasars observed with ground-based telescopes and HST
Surdej, Jean ULg; Claeskens, Jean-François ULg; Crampton, D. et al

in Benvenuti, Piero; Schreier, Ethan J (Eds.) Proceedings of a ST-ECF/STScI Workshop "Science with the Hubble Space Telescope" (1992)

We present here some recent results on gravitational lensing statistics as applied to a sample of 470 highly luminous quasars.

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See detailFirst spectroscopic evidence of microlensing on a BAL quasar? The case of H 1413 + 117
Angonin, M.-C.; Vanderriest, C.; Remy, M. et al

in Astronomy and Astrophysics (1990), 233

New data has been obtained for the quadruply lensed quasar H 1413 + 117 using the bidimensional spectrograph SILFID at the CFH telescope. The spectra recorded for each of the four individual images turn ... [more ▼]

New data has been obtained for the quadruply lensed quasar H 1413 + 117 using the bidimensional spectrograph SILFID at the CFH telescope. The spectra recorded for each of the four individual images turn out to be quite similar, except for the narrow absorption line systems (probably related to the lenses) seen in images A and B and for marked differences in the spectrum of image D. When compared to the three other images, the spectrum of D shows smaller values for the emission lines/continuum ratio and a larger equivalent width for absorption features located in the blueshifted P Cygni profile. The possible explanations of these observations are briefly discussed in terms of micro-lensing and/or intrinsic variability of the source. [less ▲]

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See detailSpectrographie Bidimensionnelle de 2 Mirages Gravitationnels avec SILFID
Angonin, M. C.; Vanderriest, C.; Surdej, Jean ULg

in Bulletin d'Information du Télescope Canada-France-Hawaii (1990), 22

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See detailBidimensional spectrography of the "clover leaf'' H1413+117 at sub-arcsec. Spatial resolution
Angonin, M. C.; Vanderriest, C.; Surdej, Jean ULg

in Mellier, Y.; Fort, B.; Soucail, G. (Eds.) Gravitational Lensing (1990)

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See detailProfiles of a Key Programme: Gravitational Lensing
Surdej, Jean ULg; Arnaud, J.; Borgeest, U. et al

in The Messenger (1989), 55

Prior to Professor van der Laan's enquiry, in the March 1988 issue of the Messenger, on the general interest among astronomers from the European community to possibly participate in Key Programmes (KPs ... [more ▼]

Prior to Professor van der Laan's enquiry, in the March 1988 issue of the Messenger, on the general interest among astronomers from the European community to possibly participate in Key Programmes (KPs) at the European 80uthern Observatory, at least three distinct groups (including more than half of the above authors) were already involved in the study of "gravitational lensing" effects (see box on pages 10-11). Observations were being performed with the help of various telescopes on La 8illa as weil as at other observatories (VLA, CFHT, Palomar, Kitt Peak, etc.). [less ▲]

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