Large-scale power spectrum and structures from the ENEAR galaxy peculiar velocity catalogue

We estimate the mass density fluctuations power spectrum (PS) on large scal es by applying a maximum likelihood technique to the peculiar velocity data of the recently completed redshift-distance survey of early-type galaxies (hereafter ENEAR). Parametric cold dark matter (CDM)-like models for the PS are assumed, and the best-fitting parameters are determined by maximizing the probability of the model given the measured peculiar velocities of the galaxies, their distances and estimated errors. The method has been applied to CDM models with and without COBE normalization. The general results are in agreement with the high-amplitude power spectra found from similar anal yses of other independent all-sky catalogue of peculiar velocity data such as MARK III and SFI, in spite of the differences in the way these samples w ere selected, the fact that they probe different regions of space and galax y distances are computed using different distance relations. For example, a t k = 0. 1 h Mpc(-1) the power spectrum value is P(k)Omega (1.2) (6.5 +/-3) x 10(3)(h(-1) Mpc)(3) and eta (8) = sigma (8)Omega (0.6) = 1.1(-0.35)(+0.2 ); the quoted uncertainties refer to 3 sigma error level. We also find that , for ACDM and OCDM COBE-normalized models, the best-fitting parameters are confined by a contour approximately defined by Omegah(1.3) = 0.377 +/-0.08 and Omegah(0.88) = 0.517 +/-0.083 respectively. Gamma -shape models, free of COBE normalization, result in the weak constraint of Gamma greater than or equal to 0.17 and in the rather stringent constraint of eta (8) = 1.0 +/ -0.25. All quoted uncertainties refer to 3 sigma confidence level (c.l.). The calculated PS has been used as a prior for Wiener reconstruction of the density field at different resolutions and the three-dimensional velocity field within a volume of radius approximate to 80 h(-1) Mpc. Ali major stru ctures in the nearby Universe are recovered and are well matched to those p redicted from all-sky redshift surveys. The robustness of these features ha s been tested with constrained realizations (CR). Analysis of the reconstru cted three-dimensional velocity field yields a small bulk-flow amplitude (s imilar to 160 +/- 60 km s(-1) at 60 h(-1) Mpc) and a very small rms value o f the tidal field (similar to 60 km s(-1)). The results give further suppor t to the picture that most of the motion of the Local Group arises from mas s fluctuations within the volume considered.