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We explore the use of strong lensing by galaxy clusters to constrain the dark energy equation of state and its possible time variation. The cores of massive clusters often contain several multiply imaged systems of background galaxies at…
We present new observations of the lensing cluster SMACSJ2031.8-4036 obtained with the MUSE integral field spectrograph as part of its commissioning on the Very Large Telescope. By providing medium-resolution spectroscopy over the full…
We present a weak lensing analysis of the X-ray luminous cluster CL 0152-1357 at z~0.84 using HST/ACS observations. The unparalleled resolution and sensitivity of ACS enable us to measure weakly distorted, faint background galaxies to the…
We present a lens model for the cluster SPT-CLJ0615$-$5746, which is the highest redshift ($z=0.972$) system in the Reionization of Lensing Clusters Survey (RELICS), making it the highest redshift cluster for which a full strong lens model…
Weak gravitational lensing provides a direct way to study the mass distribution of clusters of galaxies at large radii. Unfortunately, large scale structure along the line of sight also contributes to the lensing signal, and consequently…
Rich and massive clusters of galaxies at intermediate redshift are capable of magnifying and distorting the images of background galaxies. A comparison of different mass estimators among these clusters can provide useful information about…
We present new optical observations of the z=0.282 cluster Abell 697 from the Keck II telescope. Images show an unusual disturbed structure in the cD halo and a previously unknown faint gravitational lens arc. A spectrum of the arc did not…
Clusters of galaxies have a huge mass which can act as gravitational lenses. Galaxies behind clusters can be distorted to form arcs in images by the lenses. Herein a search was done for giant lensed arcs by galaxy clusters using the SDSS…
Identifying galaxy clusters through overdensities of galaxies in photometric surveys is the oldest and arguably the most economic and mass-sensitive detection method, compared to X-ray and Sunyaev-Zel'dovich Effect surveys that detect the…
The observed incidence of strongly lensing clusters exceeds the predictions of a Lambda-CDM model by about a factor of 10. We revisit the observational side of this discrepancy by measuring the incidence of strong lensing in a subsample of…
We present a new high-precision strong lensing model of PLCK G287.0$+$32.9, a massive lens galaxy cluster at $z=0.383$, with the aim to get an accurate estimation of its effective Einstein radius and total mass distribution. We also present…
We present a new high-precision, JWST-based, strong lensing model for the galaxy cluster Abell 2744 at $z=0.3072$. By combining the deep, high-resolution JWST imaging from the GLASS-JWST and UNCOVER programs and a Director's Discretionary…
We present a strong-lensing (SL) analysis of the galaxy cluster MACS J1319.9+7003 ($z=0.33$, also known as Abell 1722), as part of our ongoing effort to analyze massive clusters with archival {\it HST} imaging. We spectroscopically measured…
The E/SO sequence of a cluster defines a boundary redward of which a reliable weak lensing signal can be obtained from background galaxies, uncontaminated by cluster members. For bluer colors, both background and cluster members are…
Aims: We present a wide-field multi-color survey of a homogeneous sample of eleven clusters of galaxies for which we measure total masses and mass distributions from weak lensing. Methods: The eleven clusters in our sample are all X-ray…
We present the first results on the identification and study of very distant field galaxies in the core of cluster-lenses, using a selection criterium based on both lens modelling and photometric redshifts. We concentrate on two…
We determine the nature, redshift, stellar populations and dust properties of optically faint or non-detected extremely red objects (ERO) found from our survey of the lensing clusters A1835 and AC114. We perform SED fitting and use deep…
We study the dipole for a redshift sample of Abell/ACO clusters. To elucidate the constraints it places on dark matter models, we use numerical simulations based on the Zel'dovich approximation. We run 20 realizations of each of six…
We propose a novel method to reconstruct high-resolution three-dimensional mass maps using data from photometric weak-lensing surveys. We apply an adaptive LASSO algorithm to perform a sparsity-based reconstruction on the assumption that…
We present an integral field spectroscopy survey of rich clusters of galaxies aimed at studying their lensing properties. Thanks to knowledge of the spectroscopic caracteristics of more than three families of multiple images in a single…