Characterizing SL2S galaxy groups using the Einstein radius

Abstract

Aims. We aim to study the reliability of R A (the distance from the arcs to the center of the lens) as a measure of the Einstein radius in galaxy groups. In addition, we want to analyze the possibility of using R A as a proxy to characterize some properties of galaxy groups, such as luminosity (L) and richness (N). Methods. We analyzed the Einstein radius, θ E , in our sample of Strong Lensing Legacy Survey (SL2S) galaxy groups, and compared it with R A , using three different approaches: 1) the velocity dispersion obtained from weak lensing assuming a singular isothermal sphere profile (θ E,I ); 2) a strong lensing analytical method (θ E,II ) combined with a velocity dispersion-concentration relation derived from numerical simulations designed to mimic our group sample; and 3) strong lensing modeling (θ E,III ) of eleven groups (with four new models presented in this work) using Hubble Space Telescope (HST) and Canada-France-Hawaii Telescope (CFHT) images. Finally, R A was analyzed as a function of redshift z to investigate possible correlations with L, N, and the richness-to-luminosity ratio (N/L). Results. We found a correlation between θ E and R A , but with large scatter. We estimate θ E,I = (2.2 ± 0.9) + (0.7 ± 0.2)R A , θ E,II = (0.4 ± 1.5) + (1.1 ± 0.4)R A , and θ E,III = (0.4 ± 1.5) + (0.9 ± 0.3)R A for each method respectively. We found weak evidence of anticorrelation between R A and z, with Log R A = (0.58 ± 0.06) − (0.04 ± 0.1)z, suggesting a possible evolution of the Einstein radius with z, as reported previously by other authors. Our results also show that R A is correlated with L and N (more luminous and richer groups have greater R A ), and a possible correlation between R A and the N/L ratio. Conclusions. Our analysis indicates that R A is correlated with θ E in our sample, making R A useful for characterizing properties like L and N (and possibly N/L) in galaxy groups. Additionally, we present evidence suggesting that the Einstein radius evolves with z.

SARCS strong-lensing galaxy groups

“…Finally, we have the direct observable of the arc radius R A , values estimated in More et al (2012). We have shown in Verdugo et al (2014) that R A correlates with the groups' total mass, even though a large intrinsic scatter was found. This quantity is tightly related to the central mass distribution, thus, we expect it to be a better tracer of the dark matter halo concentration.…”

“…While this model has proven to give a good description for the mass distribution of individual galaxies, it is not expected to accurately reproduce more massive dark matter haloes, which are expected to present a steeper density profile at large scales. However, the SIS velocity dispersion σ v can be easily compared with results from a dynamical analysis (e.g., Muñoz et al 2013) or strong-lensing models providing an estimate of the Einstein radius (e.g., Verdugo et al 2014). The shear produced by an SIS scales as γ(r) ∝ σ…”

“…To check the robustness of our results, in particular the determination of the NFW concentrations, we combined our weaklensing measurements with the strong-lensing models obtained for eleven SARCS galaxy groups (see Limousin et al 2009;Verdugo et al 2011Verdugo et al , 2014. These strong-lensing constraints were stacked as follows: using Lenstool, we constructed mass maps for each of the eleven objects (SA22, SA39, SA50, SA63, SA66, SA72, SA80, SA83, SA112, SA123, and SA127) and we calculated the mass inside their respective Einstein radius.…”

Combining strong lensing and dynamics in galaxy clusters: integrating MAMPOSSt within LENSTOOL

“…SL2S J02140-0535 was observed in five filters (u * , g ′ , r ′ , i ′ , z ′ ) as part of the CFHTLS (Canada-France-Hawaii Telescope Legacy Survey) 5 using the wide field imager MegaPrime (Gwyn 2011), and in the infrared using WIRCam (Wide-field InfraRed Camera, the near infrared mosaic imager at CFHT) as part of the proposal 07BF15 (P.I. G. Soucail), see Verdugo et al (2014) for Fig. 6: The adaptively smoothed image of SL2S J02140-0535 in the 0.5-2.0 keV band.…”

Survey of Gravitationally lensed Objects in HSC Imaging (SuGOHI) – V. Group-to-cluster scale lens search from the HSC–SSP Survey

“…Furthermore, since galaxy groups are quite abundant compared to massive structures like galaxy clusters, the probability of finding group-scale lenses is also large. Hence, strong lensing can be successfully used to study group-scale halos (Limousin et al 2009;More et al 2012;Foëx et al 2013Foëx et al , 2014Verdugo et al 2014;Newman et al 2015).…”