Lyman-alpha power spectrum as a probe of modified gravity

Abstract

We investigate the impact of modified-gravity models on the Lyman-$α$ power spectrum. Building a simple analytical modeling, based on a truncated Zeldovich approximation, we estimate the intergalactic medium power spectrum and the Lyman-$α$ flux decrement power spectrum along the line of sight. We recover the results of numerical simulations for $f(R)$-gravity models and present new results for K-mouflage scenarios. We find that the shape of the distortion due to the modified gravity depends on the model, through the scale-dependence or not of their growth rate. This is more clearly seen in the three-dimensional power spectrum than in the one-dimensional power spectrum, where the line-of-sight integration smoothes the deviation. Whilst the Lyman-$α$ power spectrum does not provide competitive bounds for $f(R)$ theories, it could provide useful constraints for the K-mouflage models. Thus, the efficiency of the Lyman-$α$ power spectrum as a probe of modified-gravity scenarios depends on the type of screening mechanism and the related scale dependence it induces. The prospect of a full recovery of the three-dimensional Lyman-$α$ power spectrum from data would also lead to stronger constraints and a better understanding of screening mechanisms.

25 pages