THE LOCAL SUPERCLUSTER AS A TEST OF COSMOLOGICAL MODELS

The Local Supercluster kinematic properties (the Local Group infall to ward the Virgo Cluster and galaxy density distribution about the Virgo Cluster) in various cosmological models are examined utilizing large- scale N-body (PM) simulations (500(3) cells, 250(3) particles, and box size of 400 h-1 Mpc) and are compared to observations. Five models ar e investigated: (1) the standard, COBE-normalized CDM model with OMEGA = 1, h = 0.5, and sigma8, = 1.05; (2) the standard HDM model with OME GA = 1, h = 0.75, and sigma8 = 1; (3) the tilted CDM model with OMEGA = 1, h = 0.5, n = 0.7, and sigma8 = 0.5; (4) a CDM + lambda model with OMEGA = 0.3, lambda = 0.7, h = 2/3, and sigma8 = 2/3; (5) the PBI mod el with OMEGA = 0.2, h = 0.8, x = 0.1, m = -0.5, and sigma8 = 0.9. Com parison of the five models with the presently available observational measurements (v(LG) = 85 - 305 km s-1 [with mean of 250 km s-1], DELTA n(g)/n(g)BAR = 1.40 +/- 0.35) suggests that an open universe with OMEG A approximately 0.5 (with or without lambda) and sigma8 approximately 0.8 is preferred, with OMEGA = 0.3-1.0 (with or without lambda) and si gma8, = 0.7-1.0 being the acceptable range. At variance with some prev ious claims based on either direct N-body or spherical nonlinear appro aches, we find that a flat model with sigma8 approximately 0.7-1.0 see ms to be reasonably consistent with observations. However, if one favo rs the low limit of v(LG) = 85 km s-1, then an OMEGA approximately 0.2 -0.3 universe seems to provide a better fit, and flat (OMEGA = 1) mode ls are ruled out at approximately 95% confidence level. On the other h and, if the high limit of v(LG) = 350 km s-1 is closer to the truth, t hen it appears that OMEGA approximately 0.7-0.8 is more consistent. Th is test is insensitive to the shape of the power spectrum, but rather sensitive to the normalization of the perturbation amplitude on the re levant scale (e.g., sigma8) and OMEGA. We find that neither linear nor nonlinear relations (with spherical symmetry) are good approximations for the relation between radial peculiar velocity and density perturb ation, i.e., nonspherical effects and gravitational tidal field are im portant. The derived OMEGA using either of the two relations is undere stimated. In some cases, this error is as large as a factor of 2-4.