Wide-angle effects in the power spectrum multipoles for next-generation redshift surveys

Distance measurements from galaxy redshift surveys allow the mapping of the galaxy density field and the measurement of the matter power spectrum, which offers a powerful test of cosmological models. Accurate power spectrum measurement must take into account redshift space distortions, whereby peculiar velocities modify the inferred distances to galaxies via Doppler shift. We quantify such distortions in large-scale surveys, in which the plane-parallel approximation fails, and wide-angle corrections to the power spectrum couple correlation function multipoles with the survey window function. We validate a recently developed formalism to compute these corrections for a general line-of-sight geometry and examine wide-angle effects by comparing with commonly used estimators on mock catalogs for the upcoming SPHEREx survey. This work will be important in determining the magnitude of wide-angle corrections for other next-generation surveys, such as the Nancy Grace Roman Telescope and Euclid.