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 focusses on the statistical properties of the transmitted Lyman-alpha flux in the high-redshift intergalactic medium (IGM). In these models the growth of the diffuse cosmic web differs from the standard LCDM 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-alpha flux and are larger than 5% (10%) at z=2-4 in the flux probability distribution function (pdf) for high transmissivity regions and for values of the coupling parameter \beta = 0.08 (\beta = 0.2). The flux power spectrum is also affected at the ~2% (~ 5-10%) level for \beta = 0.08 (\beta = 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 \beta < 0.15 (at 2 sigma confidence level), which is obtained using only IGM data and is competitive with those inferred from other large scale structure probes.