Forecasting the cosmological constraints with anisotropic baryon acoustic oscillations from multipole expansion

Baryon acoustic oscillations imprinted in the galaxy power spectrum can be used as a standard ruler to determine the angular diameter distance and Hubble parameter from high-redshift galaxies. Combining redshift distortion effect which apparently distorts the galaxy clustering pattern, we can also constrain the growth rate of large-scale structure formation. Usually, future forecasts for constraining these parameters from galaxy redshift surveys are made with the full 2D power spectrum characterized as a function of wave number k and directional cosine mu between line-of-sight direction and wave vector, i.e., P(k,mu). Here, we apply the multipole expansion to the full 2D power spectrum, and discuss how much cosmological information can be extracted from the lower-multipole spectra, taking a proper account of the nonlinear effects on gravitational clustering and redshift distortion. Fisher matrix analysis reveals that compared to the analysis with the full 2D spectrum, using only the partial information from the monopole and quadrupole spectra generally degrades the constraints by a factor of similar to 1.3 for each parameter. The additional information from the hexadecapole spectrum helps to improve the constraints, leading to a result that is almost comparable to the one expected from the full 2D spectrum.