Multipole expansion of the large-scale velocity field - Using the tensor window function

Abstract

view Abstract Citations (31) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multipole Expansion of the Large-Scale Velocity Field: Using the Tensor Window Function Regos, Eniko ; Szalay, Alexander S. Abstract The radial components of the galaxy-peculiar velocities are related to primordial density fluctuations via a tensor window function. For a given shell of galaxies the radial velocity as a function of direction can be expanded into multipoles, the l = 1 term corresponding to the bulk motion, the l = 2 to a quadruple anisotropy of the velocity field. The l = 0 (monopole) term must be present, if the density enhancement inside the shell differs from zero, but it would be at least partially absorbed into the local value of the Hubble constant. We derive the distribution of these bulk velocities and compare it to the results obtained with the usual scalar window function. The estimated dipole velocity and the statistical scatters are significantly affected by sampling anisotropies in the galaxy selection function: the various multipoles all contribute to the apparent dipole velocity. This apparent bulk velocity is most likely to be near the galactic plane, aligned with the dipole anisotropy of the galaxy distribution. We also calculate the angular correlation function of the radial velocity field and show that the coherence angle is large: {THETA}_0_ = 46^deg^. We generate random realizations of the velocity field and compare them to the smoothed elliptical galaxy data. Publication: The Astrophysical Journal Pub Date: October 1989 DOI: 10.1086/167936 Bibcode: 1989ApJ...345..627R Keywords: Cosmology; Galaxies; Red Shift; Anisotropy; Dipoles; Elliptical Galaxies; Radial Velocity; Tensors; Velocity Distribution; Astrophysics; COSMOLOGY; GALAXIES: REDSHIFTS full text sources ADS |