Dark energy and substructure effects on the large-scale structure

I consider in detail how the large-scale structure of the universe can provide information about two topics of current interest in cosmology: the nature of dark energy and the abundance of substructure in dark matter halos. Baryonic oscillations in the galaxy power spectrum have been studied as a way of probing dark energy models. While most studies have focused on spectroscopic surveys at high redshift, large multicolor imaging surveys have already been planned for the near future. In view of this, I consider the prospects for measuring baryonic oscillations from angular statistics of galaxies binned using photometric redshifts. I use the galaxy bispectrum in addition to the power spectrum; this allows one to measure and marginalize over possibly complex galaxy bias mechanisms to get robust cosmological constraints. I find that a multicolor imaging survey that probes redshifts beyond unity can give interesting constraints on dark energy parameters. In addition, the shape of the primordial power spectrum can be measured to better accuracy than with the cosmic microwave background alone. In the second example I consider the effects of halo substructure on large-scale structure statistics. The effects on the power spectrum and bispectrum are studied on the smallest scales accessible from future surveys. We compare halo model predictions with results based on N-body simulations, but also extend our predictions to 10 kpc scales which will be probed by future simulations. We find that weak-lensing surveys proposed for the coming decade can probe the power spectrum on small enough scales to detect substructure in massive haloes. We discuss the prospects of constraining the mass fraction in substructure in view of partial degeneracies with parameters such as the tilt and running of the primordial power spectrum.