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

TL;DR

This paper introduces the FITEX-2d method to extract angular diameter distance and expansion rate from two-dimensional galaxy power spectra, demonstrating that full modeling significantly improves accuracy over BAO-only analysis.

Contribution

The paper develops the FITEX-2d method for simultaneous extraction of D_A and H from 2D galaxy power spectra, enhancing previous BAO-only techniques.

Findings

Full modeling improves parameter estimation by over a factor of two.

The method is validated using Millennium Simulation and Monte Carlo simulations.

Non-linear effects are crucial for accurate dark energy parameter constraints.

Abstract

We present a method for extracting the angular diameter distances, $D_A$, and the expansion rates, $H$, of the universe from the {\it 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 two, provided that non-linear effects are under control.