Extracting Angular Diameter Distance And Expansion Rate Of The Universe From Two-Dimensional Galaxy Power Spectrum At High Redshifts: Baryon Acoustic Oscillation Fitting Versus Full Modeling

We present a method for extracting the angular diameter distances, D(A), and the expansion rates, H, of the universe from the two-dimensional baryon acoustic oscillations (BAO) in the galaxy power spectrum. Our method builds upon the existing algorithm called the "fit-and-extract" (FITEX) method, which allows one to extract only D(A)(2)/H from a spherically averaged one-dimensional power spectrum. We develop the FITEX-2d method, an extension of the FITEX method, to include the two-dimensional information, which allows us to extract D(A) and H simultaneously. We test the FITEX-2d method using the Millennium Simulation as well as simplified Monte Carlo simulations with a bigger volume. The BAOs, however, contain only a limited amount of information. We show that the full modeling, including the overall shape of the power spectrum, yields much better determinations of D(A) and H, hence the dark energy equation of Stateparameters such as w(0) and w(a), than the BAO-only analysis by more than a factor of 2, provided that nonlinear effects are under control.