Imprints of Dark Energy on Cosmic Structure Formation. I. Realistic Quintessence Models

摘要

Dark energy as a quintessence component causes a typical modification of thebackground cosmic expansion, which in addition to its clustering properties,can leave a potentially distinctive signature on large scale structures. Manyprevious studies have investigated this topic, particularly in relation to thenon-linear regime of structure formation. However, no careful pre-selection ofviable quintessence models with high precision cosmological data was performed.Here we show that this has led to a misinterpretation (and underestimation) ofthe imprint of quintessence on the distribution of large scale structures. Tothis purpose we perform a likelihood analysis of the combined Supernova IaUNION dataset and WMAP5-years data to identify realistic quintessence models.Differences from the vanilla LambdaCDM are especially manifest in the predictedamplitude and shape of the linear matter power spectrum, though these remainwithin the uncertainties of the SDSS data. We use these models as benchmark forstudying the clustering properties of dark matter halos by performing a seriesof high resolution N-body simulations. We find that realistic quintessencemodels allow for relevant differences of the dark matter distribution with therespect to the LambdaCDM scenario well into the non-linear regime, withdeviations up to 40% in the non-linear power spectrum. Such differences areshown to depend on the nature of DE, as well as the scale and epoch considered.At small scales (k~1-5 h Mpc^{-1}, depending on the redshift) the structureformation process is about 20% more efficient than in LambdaCDM. We show thatthese imprints are a specific record of the cosmic structure formation historyin DE cosmologies and therefore cannot be accounted in standard fittingfunctions of the non-linear matter power spectrum. Comment: 24 pages, 11 figures. Higher resolution paper available at http://cp3.phys.ucl.ac.be/upload/papers/astro-ph-0903.5490.ps (ps) and http://cp3.phys.ucl.ac.be/upload/papers/astro-ph-0903.5490.pdf (pdf). v2: New discussion on the non-linear power spectrum at small scales. v3: same as v2 with corrected references. Matches version to appear in MNRAS