Arc statistics in cosmological models with dark energy

¹ Max-Planck-Institut für Astrophysik, PO Box 1317, 85741 Garching, Germany
² Dipartimento di Astronomia, Università di Padova, vicolo dell'Osservatorio 2, 35122 Padova, Italy
³ Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
⁴ Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
⁵ SISSA/ISAS, via Beirut 4, 34014 Trieste, Italy
⁶ Dipartimento di Astronomia, via Ranzani 1, 40127 Bologna, Italy

Corresponding author: M. Bartelmann, msb@mpa-garching.mpg.de

Received: 2 October 2002
Accepted: 18 July 2003

Abstract

We investigate how the probability of the formation of giant arcs in galaxy clusters is expected to change in cosmological models dominated by dark energy with an equation of state compared to cosmological-constant or open models. To do so, we use a simple analytic model for arc cross sections based on the Navarro-Frenk-White density profile which we demonstrate reproduces essential features of numerically determined arc cross sections. Since analytic lens models are known to be inadequate for accurate absolute quantifications of arc probabilities, we use them only for studying changes relative to cosmological-constant models. Our main results are (1) the order of magnitude difference between the arc probabilities in low density, spatially flat and open CDM models found numerically is reproduced by our analytic model, and (2) dark-energy cosmologies with increase the arc optical depth by at most a factor of two and are thus unlikely to reconcile arc statistics with spatially flat cosmological models with low matter density.