Wide angle effects for peculiar velocities

Understand

The line-of-sight peculiar velocities of galaxies contribute to their observed redshifts, breaking the translational invariance of galaxy clustering down to a rotational invariance around the observer.

• This becomes important when the line-of-sight direction varies significantly across a survey, leading to what are known as `wide angle' effects in redshift space distortions.
• Wide-angle effects will also be present in measurements of the momentum field, i.e.
• the galaxy density-weighted velocity field, in upcoming peculiar velocity surveys.