The biasing phenomenon

Context. We study biasing as a physical phenomenon by analysing geometrical and clustering properties of density fields of matter and galaxies. Aims. Our goal is to determine the bias function using a combination of geometrical and power spectrum analyses of simulated and real data. Methods. We apply an algorithm based on the local densities of particles, delta, to form simulated, biased models using particles with delta >= (0). We calculate the bias function of model samples as functions of the particle-density limit delta(0). We compare the biased models with Sloan Digital Sky Survey (SDSS) luminosity-limited samples of galaxies using the extended percolation method. We find density limits delta(0) of biased models that correspond to luminosity-limited SDSS samples. Results. The power spectra of biased model samples allow estimation of the bias function b(> L) of galaxies of luminosity L. We find the estimated bias parameter of L-* galaxies, b(*) = 1.85 +/- 0.15. Conclusions. The absence of galaxy formation in low-density regions of the Universe is the dominant factor of the biasing phenomenon. The second-largest effect is the dependence of the bias function on the luminosity of galaxies. Variations in gravitational and physical processes during the formation and evolution of galaxies have the smallest influence on the bias function.