How to suppress the shot noise in galaxy surveys.

Galaxy surveys are one of the most powerful means to extract cosmological information and for a given volume the attainable precision is determined by the galaxy shot noise sigma(n);(2) relative to the power spectrum P. It is generally assumed that shot noise is white and given by the inverse of the number density n[over ]. In this Letter we argue one may considerably improve upon this due to mass and momentum conservation. We explore this idea with N-body simulations by weighting central halo galaxies by halo mass and find that the resulting shot noise can be reduced dramatically relative to expectations, with a 10-30 suppression at n[over ] = 4x10(-3) (h/Mpc)(3). These results open up new opportunities to extract cosmological information in galaxy surveys and may have important consequences for the planning of future redshift surveys.