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**Session 85 - Quasar Absorption Line Systems.**

*Display session, Wednesday, January 17*

*North Banquet Hall, Convention Center*

## [85.02] Wavelet Space-Scale-Decomposition Analysis of Spectrum of Density Perturbations from QSO's Ly\alpha Forests

*J. Pando, L. Fang (Univ. of Arizona)*
A method for measuring the spectrum of a density field by a discrete
wavelet space-scale decomposition (SSD) has been studied. We show how
the power spectrum can effectively be described by the father function
coefficients (FFC) of the wavelet SSD. We demonstrate that the features
of the spectrum, such as the magnitude, the index of a power law, and the
typical scales, can be determined with high precision by the FFC
reconstructed spectrum. This method does not require the mean density,
which normally is poorly determined. The problem of the complex geometry
of observed samples can also be easily solved because the basis are always
orthogonal, regardless the geometry of the samples. Using this method,
we examine the spectra inferred from Ly\alpha forests of both simulated
and real samples. We find that
1.) the magnitude of the 1-D spectra is significantly different from a
Poisson process; 2.) the 1-D spectra are flat on scales
less than about 5 h^-1 Mpc, and show a slow increase with the
scale in a range larger than 5 h^-1 Mpc; 3.) the reconstructed
3-D spectra have about the same power as the COBE normalized linear
spectrum of the SCDM model
on scales less than 40 h^-1 Mpc, but the larger than the SCDM model on
scales larger than 40 h^-1 Mpc; 4) the magnitudes of high redshift
(z>2.51) spectra generally are larger than those of low redshift (z<2.51)
results. Points 3) and 4) are probably caused by large geometric
biasing on large scales and high redshifts.

**Program
listing for Wednesday**