Large-Scale Mass Power Spectrum from Peculiar Velocities

This is a brief progress report on a long-term collaborative project to measure the power spectrum (PS) of mass density fluctuations from the Mark III and the SFI catalogs of peculiar velocities. The PS is estimated by applying maximum likelihood analysis, using generalized CDM models with and without COBE normalization. The application to both catalogs yields fairly similar results for the PS. The robust result is a relatively high PS, with P(k)\Omega^{1.2}=(4.5+/-2.0)X10^3 (Mpc/h)^3 at k=0.1 h/Mpc. An extrapolation to smaller scales using the different CDM models gives \sigma_8\Omega^{0.6}=0.85+/-0.2. The general constraint on the combination of cosmological parameters is of the sort \Omega \h_{50}^{\mu} n^{\nu}=0.75+/-0.25, where \mu=1.3 and \nu=3.7,2.0 for \Lambda CDM models with and without tensor fluctuations respectively. For open CDM, without tensor fluctuations, the powers are \mu=0.9 and \nu=1.4.