How to suppress the shot noise in galaxy surveys

Abstract

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 σn2 relative to the power spectrum P. It is generally assumed that shot noise is white and given by the inverse of the number density n̄. 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 n̄=4×10-3(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. © 2009 The American Physical Society.