The role of luminous substructure in the gravitational lens system MG 2016+112 (2008)
More, A., McKean, J. P., More, S., Porcas, R. W., Koopmans, L. V. E., Garrett, M. A.
MG 2016+112 is a quadruply imaged lens system with two complete images A and B and a pair of merging partial images in region C as seen in the radio. The merging images are found to violate the...
Treu, T., Gavazzi, R., Gorecki, A., Marshall, P. J., Koopmans, L. V. E., Bolton, A. S., ...
We study the relation between the internal structure of early-type galaxies and their environment using 70 strong gravitational lenses from the Sloan ACS Lens Survey. The Sloan database is used to...
Vegetti, S., Koopmans, L. V. E.
We introduce a new adaptive and fully Bayesian grid-based method to model strong gravitational lenses with extended images. The primary goal of this method is to quantify the level of luminous and...
Dissecting the Gravitational Lens B1608+656: I. Lens Potential Reconstruction (2008)
Suyu, S. H., Marshall, P. J., Blandford, R. D., Fassnacht, C. D., Koopmans, L. V. E., McKean, J. P., ...
Strong gravitational lensing is a powerful technique for probing galaxy mass distributions and for measuring cosmological parameters. We present a pixelated approach to modeling simultaneously the...
Foreground simulations for the LOFAR–epoch of reionization experiment (2008)
Jelic, V., Zaroubi, S., Labropoulos, P., Thomas, R. M., Bernardi, G., Brentjens, M. A., ...
Probing a massive radio galaxy with gravitational lensing (2007)
More, A., McKean, J. P., Muxlow, T. W. B., Porcas, R. W., Fassnacht, C. D., Koopmans, L. V. E.
The gravitational lens system CLASS B2108+213 has two lensed images separated by 4.56 arcsec. Such a wide image separation suggests that the lens is either a massive galaxy, or is composed of a group...
Marshall, P. J., Treu, T., Melbourne, J., Gavazzi, R., Bundy, K., Ammons, S. M., ...
We combine high-resolution images in four optical/infra-red bands, obtained with the laser guide star adaptive optics system on the Keck Telescope and with the Hubble Space Telescope, to study the...
Koopmans, L. V. E., Barnabe', M.
Abstract: Gravitational lensing and stellar dynamics are two independent methods, based solely on gravity, to study the mass distributions of galaxies. Both methods suffer from degeneracies, however,...
McKean, J. P., Koopmans, L. V. E., Flack, C. E., Fassnacht, C. D., Thompson, D., Matthews, K., ...
The existence of flux-ratio anomalies between fold and cusp images in galaxy-scale strong-lens systems has led to an interpretation based on the presence of a high mass-fraction of cold-dark-matter...
Alba, A. Berciano, Garrett, M. A., Koopmans, L. V. E., Wucknitz, O.
Previous authors have reported the detection of intrinsically faint sub-mm emission lensed by the cluster MS0451.6-0305. They suggest that this emission arises from a merging system composed of a...
Fassnacht, C. D., McKean, J. P., Koopmans, L. V. E., Treu, T., Blandford, R. D., Auger, M. W., ...
We report the serendipitous discovery of two strong gravitational lens candidates (ACS J160919+6532 and ACS J160910+6532) in deep images obtained with the Advanced Camera for Surveys on the Hubble...
Koopmans, L. V. E., Treu, T., Bolton, A. S., Burles, S., Moustakas, L. A.
(Abridged) We present a joint gravitational lensing and stellar dynamical analysis of fifteen massive field early-type galaxies, selected from the Sloan Lens (SLACS) Survey. The following numerical...
Gravitational Lensing & Stellar Dynamics (2005)
Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it...
CLASS B0631+519: Last of the CLASS lenses (2005)
York, T., Jackson, N., Browne, I. W. A., Koopmans, L. V. E., McKean, J. P., Norbury, M. A., ...
We report the discovery of a new gravitational lens system from the CLASS survey, CLASS B0631+519. VLA, MERLIN and VLBA observations show a doubly-imaged radio core, a doubly-imaged lobe and a second...
Gravitational Imaging of CDM Substructure (2005)
We propose the novel method of ``gravitational imaging'' to detect and quantify luminous and dark-matter substructure in gravitational-lens galaxies. The method utilizes highly-magnified Einstein...
Gravitational lensing and stellar dynamics provide two complementary, nearly orthogonal, constraints on the mass distribution of early-type lens galaxies. This allows the luminous and dark-matter...
CLASS B2108+213: A new wide separation gravitational lens system (2004)
McKean, J. P., Browne, I. W. A., Jackson, N. J., Koopmans, L. V. E., Norbury, M. A., Treu, T., ...
We present observations of CLASS B2108+213, the widest separation gravitational lens system discovered by the Cosmic Lens All-Sky Survey. Radio imaging using the VLA at 8.46 GHz and MERLIN at 5 GHz...
Strong Gravitational Lensing with SKA (2004)
Koopmans, L. V. E., Browne, I. W. A., Jackson, N. J.
The advent of new observational facilities in the last two decades has allowed the rapid discovery and high-resolution optical imaging of many strong lens systems from galaxy to cluster scales, as...
Stern, Daniel, Van Dokkum, P. G., Nugent, Peter, Sand, D. J., Ellis, R. S., Sullivan, Mark, ...
We report the discovery of a transient source in the central regions of galaxy cluster Abell 267. The object, which we call "PALS1", was found in a survey aimed at identifying highly-magnified...
Keck spectroscopy of CLASS gravitational lenses (2004)
McKean, J. P, Koopmans, L. V. E., Browne, I. W. A., Fassnacht, C. D., Blandford, R. D., Lubin, L. M., ...
We present the optical spectra of four newly discovered gravitational lenses from the Cosmic Lens All-Sky Survey (CLASS). These observations were carried out using the Low Resolution Imaging...
The signature of substructure on gravitational lensing in the Lambda CDM cosmological model (2004)
Bradac, M., Schneider, P., Lombardi, A., Steinmetz, M., Koopmans, L. V. E., Navarro, J. F.
HI kinematics in a massive spiral galaxy at z=0.89 (2003)
Koopmans, L. V. E., De Bruyn, A. G.
We present a kinematic model of the neutral-hydrogen in the spiral galaxy of the lens system PKS1830-211, based on a Multi Element Radio-Linked Interferometer (MERLIN) 1.4-GHz radio map and the...
The dark matter halos of spheroidal galaxies and clusters of galaxies (2003)
Treu, T., Koopmans, L. V. E., Sand, D. J., Smith, G. P., Ellis, R. S.
We describe the first results from two observational projects aimed at measuring the amount and spatial distribution of dark matter in distant early-type galaxies (E/S0s) and clusters of galaxies. At...
Cool White Dwarfs Revisited -- New Spectroscopy and Photometry (2003)
Salim, Samir, Rich, R. Michael, Hansen, Brad M., Koopmans, L. V. E., Oppenheimer, Ben R., Blandford, Roger D.
In this paper we present new and improved data on 38 cool white dwarfs identified by Oppenheimer et al. 2001 (OHDHS) as candidate dark halo objects. Using the high-res spectra obtained with LRIS, we...
The Lenses Structure & Dynamics (LSD) Survey aims at studying the internal structure of luminous and dark matter - as well as their evolution - of field early-type (E/SO) galaxies to z~1. In...
The signature of substructure on gravitational lensing in the LCDM cosmological model (2003)
Bradac, M., Schneider, P., Lombardi, M., Steinmetz, M., Koopmans, L. V. E., Navarro, Julio F.
We present a study of the lens properties of quadruply imaged systems, lensed by numerically simulated galaxies. We investigate a simulated elliptical and disc galaxy drawn from high resolution...
The Hubble Constant from the Gravitational Lens B1608+656 (2003)
Koopmans, L. V. E., Treu, T., Fassnacht, C. D., Blandford, R. D., Surpi, G.
We present a refined gravitational lens model of the four-image lens system B1608+656 based on new and improved observational constraints: (i) the three independent time-delays and flux-ratios from...
Extrinsic Radio Variability of JVAS/CLASS Gravitational Lenses (2003)
Koopmans, L. V. E., Biggs, A., Blandford, R. D., Browne, I. W. A., Jackson, N. J., Mao, S., ...
We present flux-ratio curves of the fold and cusp (i.e. close multiple) images of six JVAS/CLASS gravitational lens systems. The data were obtained over a period of 8.5 months in 2001 with the...
The Cosmic Lens All-Sky Survey:II. Gravitational lens candidate selection and follow-up (2002)
Browne, I. W. A., Wilkinson, P. N., Jackson, N. J. F., Myers, S. T., Fassnacht, C. D., Koopmans, L. V. E., ...
We report the final results of the search for gravitationally lensed flat-spectrum radio sources found in the combination of CLASS (Cosmic Lens All Sky Survey) and JVAS (Jodrell-Bank VLA Astrometric...
The Cosmic Lens All-Sky Survey: I. Source selection and observations (2002)
Myers, S. T., Jackson, N. J., Browne, I. W. A., De Bruyn, A. G., Pearson, T. J., Readhead, A. C. S., ...
The Cosmic Lens All-Sky Survey (CLASS) is an international collaborative program which has obtained high-resolution radio images of over 10000 flat-spectrum radio sources in order to create the...
B0850+054: a new gravitational lens system from CLASS (2002)
Biggs, A. D., Rusin, D., Browne, I. W. A., De Bruyn, A. G., Jackson, N. J., Koopmans, L. V. E., ...
We report the discovery of a new gravitational lens system from the CLASS survey. Radio observations with the VLA, the WSRT and MERLIN show that the radio source B0850+054 is comprised of two compact...
CLASS B0445+123 : a new two-image gravitational lens system (2002)
Norbury, M. A., Myers, S. T., Marlow, D. R., Koopmans, L. V. E., Fassnacht, C. D., Chae, K. H., ...
Submitted to: Mon. Not. R. Astron. Soc. Abstract: A new two-image gravitational lens system has been discovered as a result of the Cosmic Lens All-Sky Survey (CLASS). Radio observations with the VLA,...
CLASS B0445+123: a new two-image gravitational lens system (2002)
Argo, M. K., Jackson, N. J., Browne, I. W. A., York, T., McKean, J. P., Biggs, A. D., ...
A new two-image gravitational lens system has been discovered as a result of the Cosmic Lens All-Sky Survey (CLASS). Radio observations with the VLA, MERLIN and the VLBA at increasingly higher...
Biggs, A. D., Blandford, R. D., Browne, I. W. A., De Bruyn, A. G., Fassnacht, C. D., ...
We derive constraints on cosmological parameters and the properties of the lensing galaxies from gravitational lens statistics based on the final Cosmic Lens All Sky Survey (CLASS) data. For a flat...
Fassnacht, C. D., Xanthopoulos, E., Koopmans, L. V. E., Rusin, D.
The gravitational lens CLASS B1608+656 is the only four-image lens system for which all three independent time delays have been measured. This makes the system an excellent candidate for a...
Probing dark matter distribution with gravitational lensing and stellar dynamics (2002)
The Lenses Structure and Dynamics (LSD) Survey aims at measuring the luminous and dark matter distribution of high redshift early-type galaxies by combining gravitational lens analysis with newly...
We have measured the kinematic profile of the early-type (E/S0) lens galaxy in the system 0047-281 (z=0.485) with the {\sl Echelle Spectrograph and Imager} (ESI) on the W.M. Keck--II Telescope, as...
The stellar velocity dispersion of the lens galaxy in MG2016+112 at z=1.004 (2002)
We present a direct measurement of the stellar velocity dispersion of the early-type lens galaxy D in the system MG2016+112 (z=1.004), determined from a spectrum obtained with the Echelle...
2016+112 : a gravitationally lensed type II quasar (2002)
Koopmans, L. V. E., Garrett, M. A., Blandford, R. D., Lawrence, C. R., Patnaik, A. R., Porcas, R. W.
A single-screen model of the gravitational lens system 2016+112 is proposed, that explains recent Hubble Space Telescope (HST ) infrared (NICMOS-F160W) observations and new high-resolution European...
The Kinematics of High Proper Motion Halo White Dwarfs (2001)
Koopmans, L. V. E., Blandford, R. D.
We analyse the kinematics of the entire spectroscopic sample of 99 recently discovered high proper-motion white dwarfs by Oppenheimer et al. using a maximum-likelihood analysis, and discuss the claim...
2016+112: A Gravitationally Lensed Type-II Quasar (2001)
Koopmans, L. V. E., Garrett, M. A., Blandford, R. D., Lawrence, C. R., Patnaik, A. R., Porcas, R. W.
A single-screen model of the gravitational lens system 2016+112 is proposed, that explains recent Hubble Space Telescope} (HST) infrared (NICMOS-F160W) observations and new high-resolution European...
White Dwarfs: Contributors and Tracers of the Galactic Dark-Matter Halo (2001)
Koopmans, L. V. E., Blandford, R. D.
We examine the claim by Oppenheimer et al. (2001) that the local halo density of white dwarfs is an order of magnitude higher than previously thought. As it stands, the observational data support the...
The new two-image gravitational lens system CLASS B2319+051 (2001)
Rusin, D., Marlow, D. R., Norbury, M., Browne, I. W. A., Jackson, N., Wilkinson, P. N., ...
We report the discovery of a new two-image gravitational lens system from the Cosmic Lens All-Sky Survey, CLASS B2319+051. Radio imaging with the Very Large Array (VLA) and Multi-Element Radio-Linked...
The Hubble Constant from (CLASS) Gravitational Lenses (2001)
Koopmans, L. V. E., Collaboration, The CLASS
One of the main objectives of the Cosmic Lens All-Sky Survey (CLASS) collaboration has been to find gravitational lens (GL) systems at radio wavelengths that are suitable for the determination of...
On the Probability of Microlensing in GRB Afterglows (2000)
Koopmans, L. V. E., Wambsganss, J.
The declining lightcurve of the optical afterglow of gamma-ray burst GRB000301C showed rapid variability with one particularly bright feature at about t-t0=3.8 days. This event was interpreted as...
Radio Microlensing: Past, Present & Near Future (2000)
Koopmans, L. V. E., De Bruyn, A. G., Fassnacht, C. D., Wambsganss, J., Blandford, R. D., Collaboration, + CLASS
Strongly correlated non-intrinsic variability between 5 and 8.5 GHz has been observed in one of the lensed images of the gravitational lens B1600+434. These non-intrinsic (i.e. `external') variations...
A New Quadruple Gravitational Lens System: CLASS B0128+437 (2000)
Phillips, P. M., Norbury, M. A., Koopmans, L. V. E., Browne, I. W. A., Jackson, N. J., Wilkinson, P. N., ...
High resolution MERLIN observations of a newly-discovered four-image gravitational lens system, B0128+437, are presented. The system was found after a careful re-analysis of the entire CLASS dataset....
CLASS B0739+366: A new two-image gravitational lens system (2000)
Marlow, D. R., Rusin, D., Norbury, M., Jackson, N., Browne, I. W. A., Wilkinson, P. N., ...
We present the discovery of CLASS B0739+366, a new gravitational lens system from the Cosmic Lens All-Sky Survey. Radio imaging of the source with the Very Large Array (VLA) shows two compact...
CLASS B0827+525: `Dark lens' or binary radio-loud quasar? (2000)
Koopmans, L. V. E., De Bruyn, A. G., Fassnacht, C. D., Marlow, D. R., Rusin, D., Blandford, R. D., ...
We present radio, optical, near-infrared and spectroscopic observations of the source B0827+525. We consider this source as the best candidate from the Cosmic Lens All-Sky Survey (CLASS) for a `dark...
The Influence of Central Black Holes on Gravitational Lenses (2000)
Mao, S., Witt, H. J., Koopmans, L. V. E.
Recent observations indicate that many if not all galaxies host massive central black holes. In this paper we explore the influence of black holes on the lensing properties. We model the lens as an...
VLA 8.4-GHz monitoring observations of the CLASS gravitational lens B1933+503 (2000)
Biggs, A. D., Xanthopoulos, E., Browne, I. W. A., Koopmans, L. V. E., Fassnacht, C. D.
The complex ten-component gravitational lens system B1933+503 has been monitored with the VLA during the period February to June 1998 with a view to measuring the time delay between the four compact...
VLA 8.4-GHz monitoring observations of the CLASS gravitational lens B1933+503 (2000)
Fassnacht, C. D., Koopmans, L. V. E., Browne, I. W. A., Xanthopoulos, E., Biggs, A. D.
Submitted to: Mon. Not. R. Astron. Soc. Abstract: The complex ten-component gravitational lens system B1933+503 has been monitored with the VLA during the period February to June 1998 with a view to...
A radio-microlensing caustic crossing in B1600+434? (2000)
Koopmans, L. V. E., De Bruyn, A. G., Wambsganss, J., Fassnacht, C. D.
First, we review the current status of the detection of strong `external' variability in the CLASS gravitational B1600+434, focusing on the 1998 VLA 8.5-GHz and 1998/9 WSRT multi-frequency...
Koopmans, L. V. E., De Bruyn, A. G.
We present the first unambiguous case of external variability of a radio gravitational lens, CLASS B1600+434. The VLA 8.5-GHz difference light curve of the lensed images, taking the proper time-delay...
A time-delay determination from VLA light curves of the CLASS gravitational lens B1600+434 (2000)
Koopmans, L. V. E., De Bruyn, A. G., Xanthopoulos, E., Fassnacht, C. D.
We present Very Large Array (VLA) 8.5-GHz light curves of the two lens images of the Cosmic Lens All Sky Survey (CLASS) gravitational lens B1600+434. We find a nearly linear decrease of 18-19% in the...
Koopmans, L. V. E., De Bruyn, A. G.
We present the results from recent VLA 8.5-GHz and WSRT 1.4 and 4.9-GHz monitoring campaigns of the CLASS gravitational lens B1600+434 and show how the observed variations argue strongly in favor of...
A study of radio-selected gravitational lenses / (2000)
Thesis (Doctoral)--Rijksuniversiteit Groningen, 2000.
Koopmans, L. V. E., De Bruyn, A. G.
We present the first unambiguous case of external variability of an extra-galactic radio source, the CLASS gravitational lens B1600+434, consisting of two images lensed by an edge-on disk galaxy. The...
Xanthopoulos, E., Browne, I. W. A., Wilkinson, P. N., Jackson, N. J., Karidis, A., Porcas, R. W., ...
We present an overview of all the observations (radio - VLA, MERLIN, VLBA,EVN - and optical - WFPC2 and NICMOS -) that were initially used to confirm the gravitational lens nature of the double JVAS...
B0218+357 : Time Delays and New MERLIN/VLA 5GHz Maps of the Einstein Ring (1999)
Helbig, P., Muxlow, T. W. B., Wilkinson, P. N., Browne, I. W. A., Biggs, A. D., Koopmans, L. V. E.
Abstract: This poster presents a new 5 GHz combined MERLIN/VLA map of B0218+357 which shows for the first time believable substructure in the Einstein ring. This will now be exploited for further...
Measuring H_0 with CLASS B1608+656: The Second Season of VLA Monitoring (1999)
Fassnacht, C. D., Xanthopoulos, E., Koopmans, L. V. E., Pearson, T. J., Readhead, A. C. S., Myers, S. T.
The four-component gravitational lens CLASS B1608+656 has been monitored with the VLA for two seasons in order to search for time delays between the components. These time delays can be combined with...
Fassnacht, C. D., Pearson, T. J., Readhead, A. C. S., Browne, I. W. A., Koopmans, L. V. E., Myers, S. T., ...
We present the results of a program to monitor the four-image gravitational lens B1608+656 with the VLA. The system was observed over a seven month period from 1996 October to 1997 May. The 64 epochs...
Koopmans, L. V. E., Fassnacht, C. D.
EDITED FROM PAPER: We present mass models of the four-image gravitational lens system B1608+656. A mass model for the lens galaxies has been determined that reproduces the image positions, two out of...
Myers, S. T., Rusin, D., Fassnacht, C. D., Blandford, R. D., Pearson, T. J., Readhead, A. C. S., ...
The third phase of the Cosmic Lens All-Sky Survey (CLASS) has recently been completed, bringing the total number of sources imaged to over 15000 in the CLASS and JVAS combined survey. In the VLA...
Browne, I. W. A., Wilkinson, P. N., Quast, R., Marlow, D. R., Helbig, P., Koopmans, L. V. E.
Published in: Astron. Astrophys. Suppl. Ser. 136 (1999) no. 2, pp.297-305 citations recorded in [Science Citation Index] Abstract: We present constraints on the cosmological constant $lambda_{0}$...
Helbig, P., Marlow, D. R., Quast, R., Wilkinson, P. N., Browne, I. W. A., Koopmans, L. V. E.
We present constraints on the cosmological constant $\lambda_{0}$ from gravitational lensing statistics of the Jodrell Bank-VLA Astrometric Survey (JVAS). Although this is the largest gravitational...
Measuring Cosmological Parameters with the JVAS and CLASS Gravitational Lens Surveys (1999)
Helbig, P., Blandford, R. D., Browne, I. W. A., De Bruyn, A. G., Fassnacht, C. D., Jackson, N., ...
The JVAS (Jodrell Bank-VLA Astrometric S