## 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*as a proxy to characterize some properties of galaxy groups, such as luminosity (

_{A}*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*, using three different approaches: 1) the velocity dispersion obtained from weak lensing assuming a singular isothermal sphere profile (

_{A}*θ*); 2) a strong lensing analytical method (

_{E,I}*θ*) combined with a velocity dispersion-concentration relation derived from numerical simulations designed to mimic our group sample; and 3) strong lensing modeling (

_{E,II}*θ*) of eleven groups (with four new models presented in this work) using

_{E,III}*Hubble*Space Telescope (HST) and Canada-France-Hawaii Telescope (CFHT) images. Finally,

*R*was analyzed as a function of redshift

_{A}*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*, but with large scatter. We estimate

_{A}*θ*,

_{E,I}= (2.2 ± 0.9) + (0.7 ± 0.2)*R*_{A}*θ*, and

_{E,II}= (0.4 ± 1.5) + (1.1 ± 0.4)*R*_{A}*θ*for each method respectively. We found weak evidence of anti-correlation between

_{E,III}= (0.4 ± 1.5) + (0.9 ± 0.3)*R*_{A}*R*and

_{A}*z*, with Log

*R*, suggesting a possible evolution of the Einstein radius with

_{A}= (0.58 ± 0.06) − (0.04 ± 0.1)*z**z*, as reported previously by other authors. Our results also show that

*R*is correlated with

_{A}*L*and

*N*(more luminous and richer groups have greater

*R*), and a possible correlation between

_{A}*R*and the

_{A}*N*/

*L*ratio.

*Conclusions. *Our analysis indicates that *R _{A}* is correlated with

*θ*in our sample, making

_{E}*R*useful for characterizing properties like

_{A}*L*and

*N*(and possibly

*N*/

*L*) in galaxy groups. Additionally, we present evidence suggesting that the Einstein radius evolves with

*z*.

Originalsprog | Engelsk |
---|---|

Artikelnummer | A65 |

Tidsskrift | Astronomy & Astrophysics |

Vol/bind | 571 |

ISSN | 0004-6361 |

DOI | |

Status | Udgivet - 1 nov. 2014 |