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Weighted bias and galaxy clustering

Abstract:

We consider a weighted biasing scheme for galaxy clustering. This differs from previous treatments by the fact that the biased density field coincides with the background mass density whenever the latter exceeds a given threshold value. There is some physical motivation for this scheme, and it is in better accord with intuitive ideas than models based on Kaiser's analysis of the clustering of rich clusters. We explain how different classes of object could be biased in different ways with respect to the underlying density distribution but still have b=1, where b is defined by the square root of the ratio of galaxy to mass autocorrelation functions. We also show that if one applies our scheme consistently, a weak dependence of b upon density can be implied. This could also be the reason why the correlation function of galaxies in groups does not differ substantially from the correlation function of all galaxies.