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| - I. Optical, weak lensing, and scaling laws
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| - SARCS strong-lensing galaxy groups
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| - We present the weak-lensing and optical analysis of the SL2S-ARCS (SARCS) sample of strong-lensing candidates. The sample is based on the Strong Lensing Legacy Survey (SL2S), a systematic search of strong-lensing systems in the photometric Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). The SARCS sample focusses on arc-like features and is designed to contain mostly galaxy groups. We briefly present the weak-lensing methodology that we used to estimate the mass of the SARCS objects. Among 126 candidates, we obtained a weak-lensing detection (at the 1 σ level) for 89 objects with velocity dispersions of the singular isothermal sphere mass model (SIS) ranging from σSIS ~ 350 km s -1 to ~1000 km s -1 with an average value of σSIS ~ 600 km s -1, corresponding to a rich galaxy group (or poor cluster). From the galaxies belonging to the bright end of the group’s red sequence ( Mi < −21), we derived the optical properties of the SARCS candidates. We obtained typical richnesses of N ~ 5−15 galaxies and optical luminosities of L ~ 0.5−1.5 × 10 12 L⊙ (within a radius of 0.5 Mpc). We used these galaxies to compute luminosity density maps, from which a morphological classification reveals that a large fraction of the sample (~45%) are groups with a complex light distribution, either elliptical or multi-modal, suggesting that these objects are dynamically young structures. We finally combined the lensing and optical analyses to define a sample of the 80 most secure group candidates, i.e. weak-lensing detection and over-density at the lens position in the luminosity map, to remove false detections and galaxy-scale systems from the initial sample. We use this reduced sample to probe the optical scaling relations in combination with a sample of massive galaxy clusters. We detect the expected correlations over the probed range in mass with a typical scatter of ~25% in σSIS at a given richness or luminosity, making these scaling laws interesting mass proxies.
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