Realistic simulations of gravitational lensing by galaxy clusters: extracting arc parameters from mock DUNE images

Aims. We present a newly developed code that allows simulations of optical observations of galaxy fields with a variety of instr uments. The code incorporates gravitational lensing effects and is targetted at simulating lensing by galaxy cluste rs. Our goal is to create the tools required for comparing theoretical expectations with observations to obtain a better understanding of how observational noise affects lensing applications such as mass estimates, studies on the internal properties o f galaxy clusters and arc statistics. Methods. Starting from a set of input parameters, characterizing bot h the instruments and the observational conditions, the simulator provides a virtual observation of a patch of the sky. It includes sever al sources of noise such as photon-noise, sky background, seeing, and instrumental noise. Ray-tracing through simulated mass distributions accounts for gravitational lensing. Source morphologies are realistically simulated based on shapelet decompositions of galaxy images retrieved from the GOODS-ACS archive. According to their morphological class, spectralenergy-distributions are assigned to the source galaxies i n order to reproduce observations of each galaxy in arbitrary photometric bands. Results. We illustrate our techniques showing virtual observations of a galaxy-cluster core as it would be observed with the space telescope DUNE, which was recently proposed to ESA within its ”Cosmic vision” programme. We analyze the simulated images using methods applicable to real observations and measure the properties of gravitat ional arcs. In particular, we focus on the determination of t heir length, width and curvature radius. Conclusions. We find that arc properties strongly depend on several proper ties of the sources. In particular, our results show that com pact, faint or low surface brightness galaxies that are barely detectab le are more easily distorted as arcs with large length-to-wi dth ratios. We conclude that realistic lensing simulations can be obtained with the method proposed here. They will be essential for evaluating and improving analysis techniques currently used for cosmological interpretatio ns of cluster lensing.

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