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

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Abstract 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.