1 Centro de Investigaciones de Astronomía, Apartado Postal 264, 5101-A Mérida, Venezuela
2 Universidad de Valparaíso, Departamento de Física y Astronomía, Avenida Gran Bretaña 1111, Casilla 5030 Valparaíso, Chile
3 Departamento de Física, Universidad de los Andes, Cra. 1 No. 18A-10, Edificio Ip, A. A. 4976 Bogotá, Colombia
4 Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
5 Laboratoire d’Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 57 avenue d’Azereix, 65000 Tarbes, France
6 Laboratoire d’Astrophysique de Marseille, Université de Provence, CNRS, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
7 Dark Cosmology Center, Niels Bohr Institute, University of Copenhagen, Juliane Marie Vej 30, 2100 Copenhagen, Denmark
8 Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), The University of Tokyo, 5-1-5 Kashiwanoha, 277-8583 Kashiwa-shi, Chiba, Japan
9 Université de Toulouse, UPS-Observatoire Midi-Pyrénées, IRAP, 31400 Toulouse, France
10 Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC V9E 2E7, Canada
11 Universidad de Los Andes, Posgrado de Física Fundamental, La Hechicera, 5101 Mérida, Venezuela
12 Institute Utinam, CNRS UMR6213, Université de Franche-Comté, OSU THETA de Franche-Comté-Bourgogne, 25010 Besançon, France
Received: 22 February 2014
Accepted: 9 September 2014
Aims. We aim to study the reliability of RA (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 RA as a proxy to characterize some properties of galaxy groups, such as luminosity (L) and richness (N).
Methods. We analyzed the Einstein radius, θE, in our sample of Strong Lensing Legacy Survey (SL2S) galaxy groups, and compared it with RA, using three different approaches: 1) the velocity dispersion obtained from weak lensing assuming a singular isothermal sphere profile (θE,I); 2) a strong lensing analytical method (θE,II) combined with a velocity dispersion-concentration relation derived from numerical simulations designed to mimic our group sample; and 3) strong lensing modeling (θE,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, RA 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 θE and RA, but with large scatter. We estimate θE,I = (2.2 ± 0.9) + (0.7 ± 0.2)RA, θE,II = (0.4 ± 1.5) + (1.1 ± 0.4)RA, and θE,III = (0.4 ± 1.5) + (0.9 ± 0.3)RA for each method respectively. We found weak evidence of anti-correlation between RA and z, with Log RA = (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 RA is correlated with L and N (more luminous and richer groups have greater RA), and a possible correlation between RA and the N/L ratio.
Conclusions. Our analysis indicates that RA is correlated with θE in our sample, making RA 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.
Key words: gravitational lensing: strong / galaxies: groups: general
Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l’Univers of the center National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data center as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. Also based on Hubble Space Telescope (HST) data as well as Magellan (IMACS) and VLT (FORS 2) data.
Appendix A is available in electronic form at http://www.aanda.org
© ESO, 2014