Name: Kensuke Fukunaga
 Institution: The University of Tokyo
 Title: Density Probability Distribution Function of SDSS
 Key Words: large-scale structure of universe, cosmology,observations
 Abstract: We measure the probability distribution function (PDF) of galaxies in the Seventh
Data Release of the Sloan Digital Sky Survey. In particular, we consider the dependence
of PDFs on galaxy properties such as color, luminosity and morphology by
constructing the volume-limited samples. We find that galaxy PDFs in redshift space
are reasonably well approximated by the log-normal function in linear regimes (scales
larger than 8h−1Mpc), almost independently of the galaxy properties. This result is
consistent with several qualitative results in previous literature, but improves its statistical
significance. A systematic departure from the log-normal function, however, is
detected, at the high-density tail. We create mock catalogues of dark matter distribution
from cosmological N-body simulations, and find the similar behavior especially in
redshift space. This implies that the log-normal approximation to the galaxy PDF is
better in real space. In contract, the galaxy PDFs in nonlinear regime (at 4h−1Mpc)
signficantly deviate from the log-normal function. This behavior is not seen in the
dark matter mock catalogues, and may reflect the effect of nonlinear galaxy biasing.