ENEAR Redshift-Distance Survey: Cosmological Constraints

Abstract

We present an analysis of the ENEAR sample of peculiar velocities of field and cluster elliptical galaxies, obtained with Dn-σ distances. We use the velocity correlation function ψ1(r) to analyze the statistics of the field object's velocities, while the analysis of the cluster data is based on the estimate of their rms peculiar velocity Vrms. The results are compared with predictions from cosmological models using linear theory. The statistics of the model velocity field is parameterized by the amplitude η8 = σ8Ω and by the shape parameter Γ of the cold dark matter-like power spectrum. This analysis is performed in redshift space, so as to circumvent the need to address corrections due to inhomogeneous Malmquist bias and to the redshift cutoff adopted in the sample selection. From the velocity correlation statistics, we obtain η8 = 0.51 for Γ = 0.25 at the 2 σ level for one interesting fitting parameter. This result agrees with that obtained from a similar analysis of the SFI I-band Tully-Fisher (TF) survey of field Sc galaxies. Even though less constraining, a consistent result is obtained by comparing the measured Vrms of clusters with linear theory predictions. For Γ = 0.25, we find η8 = 0.63 at 1 σ. Again, this result agrees, within the uncertainties, with that obtained from the SCI cluster sample based on TF distances. Overall, our results point toward a statistical concordance of the cosmic flows traced by spiral and early-type galaxies, with galaxy distances estimated using TF and Dn-σ distance indicators, respectively.