A low-z test for interacting dark energy

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A non-minimal coupling between the dark matter and dark energy components may offer a way of solving the so-called coincidence problem. In this paper we propose a low-z test for such hypothesis using measurements of the gas mass fraction fgas in relaxed and massive galaxy clusters. The test applies to any model whose dilution of dark matter is modified with respect to the standard a⁻³ scaling, as usual in interacting models, where a is the cosmological scale factor. We apply the test to current fgas data and perform Monte Carlo simulations to forecast the necessary improvements in number and accuracy of upcoming observations to detect a possible interaction in the cosmological dark sector. Our results show that improvements in the present relative error σgas/fgas are more effective to achieve this goal than an increase in the size of the fgas sample.