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 state parameters 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.