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We present a multi-wavelength study of the gravitational lens COSMOS J095930+023427 (z=0.89), together with the associated galaxy group located at $zsim0.7$ along the line of sight and the lensed background galaxy. The source redshift is currently unknown, but estimated to be at $z_s sim 2$. The analysis is based on the available public HST, Subaru, Chandra imaging data, and VLT spectroscopy. The lensing system is an early-type galaxy showing a strong [OII] emission line, and produces 4 bright images of the distant background source. It has an Einstein radius of 0.79, about 4 times large than the effective radius. We perform a lensing analysis using both a Singular Isothermal Ellipsoid (SIE) and a Peudo-Isothermal Elliptical Mass Distribution (PIEMD) for the lensing galaxy, and find that the final results on the total mass, the dark matter (DM) fraction within the Einstein radius and the external shear due to a foreground galaxy group are robust with respect of the choice of the parametric model and the source redshift (yet unknown). We measure the luminous mass from the photometric data, and find the DM fraction within the Einstein radius $f_{rm DM}$ to be between $0.71pm 0.13$ and $0.79 pm 0.15$, depending on the unknown source redshift. Meanwhile, the non-null external shear found in our lensing models supports the presence and structure of a galaxy group at $zsim0.7$, and an independent measurement of the 0.5-2 keV X-ray luminosity within 20 around the X-ray centroid provides a group mass of $M=(3-10)times 10^{13}$ M$_{odot}$, in good agreement with the previous estimate derived through weak lensing analysis.
(abridged) Aims: RXS J113155.4-123155 (z=0.66) is a quadruply imaged lensed quasar with a resolved Einstein Ring. The goal of this paper is to provide a full characterization of this system, and more particularly accurate astrometry and photometry.
[Abridged] The environment where galaxies are found heavily influences their evolution. Close groupings, like the cores of galaxy clusters or compact groups, evolve in ways far more dramatic than their isolated counterparts. We have conducted a multi
We present new SDSS and Washington photometry of the young, outer-halo stellar system, Segue 3. Combined with archival VI-observations, our most consistent results yield: $Z=0.006$, $log(Age)=9.42$, $(m-M)_0=17.35$, $E(B-V)=0.09$, with a high binary
(Abridged) We present a spatially-resolved near-UV/optical study of NGC 4150, using the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope. Previous studies of this early-type galaxy (ETG) indicate that it has a large reservoir of molecul
(Abridged) We present the first results from our spectroscopic survey of the environments of strong gravitational lenses. The lens galaxy belongs to a poor group of galaxies in six of the eight systems in our sample. We discover three new groups asso