Steps toward the Power Spectrum of Matter. II. The Biasing Correction with σ8Normalization

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Abstract
We suggest a new method to determine the bias parameter of galaxies relative to matter. The method is based on the assumption that gravity is the dominating force which determines the formation of the structure in the universe. Because of gravitational instability, matter flows out of underdense regions toward overdense regions. To form a galaxy, the density of matter within a certain radius must exceed a critical value (Press-Schechter limit); thus galaxy formation is a threshold process. In low-density environments (voids) galaxies do not form and matter remains in primordial form. We estimate the value of the threshold density which divides the matter into two populations, a low-density population in voids and a clustered population in high-density regions. We investigate the influence of the presence of these two populations on the power spectrum of matter and galaxies. We find that the power spectrum of clustered particles (galaxies) is similar to the power spectrum of matter. We show that the fraction of total matter in the clustered population determines the difference between amplitudes of fluctuations of matter and galaxies, i.e., the bias factor. To determine the fraction of matter in voids and clustered population we perform numerical simulations. The fraction of matter in galaxies at the present epoch is found using a calibration through the σ8 parameter. We find σ8 = 0.89 ± 0.09 for galaxies, σ8 = 0.68 ± 0.09 for matter, and bgal = 1.3 ± 0.13, the biasing factor of the clustered matter (galaxies) relative to all matter.
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