The impact of coupled dark energy cosmologies on the high-redshift intergalactic medium

We present an analysis of high-resolution hydrodynamical N-body simulations of coupled dark energy cosmologies which focuses on the statistical properties of the transmitted Lyman α flux in the high-redshift intergalactic medium (IGM). In these models the growth of the diffuse cosmic web differs from the standard ΛCDM case: the density distribution is skewed towards underdense regions and the matter power spectra are typically larger (in a scale-dependent way). These differences are also appreciable in the Lyman α flux and are larger than 5 per cent (10 per cent) at z = 2-4 in the flux probability distribution function (pdf) for high-transmissivity regions and for values of the coupling parameter β = 0.08 (β = 0.2). The flux power spectrum is also affected at the ~2 per cent (~5-10 per cent) level for β = 0.08 (β = 0.2) in a redshift-dependent way. We infer the behaviour of flux pdf and flux power for a reasonable range of couplings and present constraints using present high- and low-resolution data sets. We find an upper limit β <~ 0.15 (at 2σ confidence level), which is obtained using only IGM data and is competitive with those inferred from other large-scale structure probes.