Survey of galaxy redshifts. III. The density field and the induced gravity field

Journal Article · Mon Mar 15 04:00:00 EST 1982 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/159751· OSTI ID:5169498

Davis, M; Huchra, J

We have recently completed a redshift survey of galaxies complete to 14.5 m/sub Z/ in the north and south galactic polar caps containing some 2400 objects. Using an estimator unbiased by the known inhomogeneity of matter, we here compute the number density and luminosity density of bright galaxies to a distance of 80 Mpc (H/sub 0/ = 100) over the 2.7 sr of the survey. A plot of density versus distance vividly demonstrates the existence of a region 30 Mpc in extent beyond the Virgo cluster that is underdense by nearly a factor of 2 from the mean. However, averaging over the full sample volume of 4 x 10/sup 5/ Mpc/sup 3/, the number density and luminosity density given in the north catalogs agree to within 7%, suggesting that the survey is perhaps approaching a fair sample volume of the universe. The mean overdensity delta-bar toward the Virgo cluster is measured to be 2.0 +- 0.2, an important number for Virgocentric estimates of ..cap omega... Finally, we examine the local peculiar gravity g induced by the inhomogeneous distribution of matter at large distances, assuming mass density to be at least approximately distributed as the large scale number density of galaxies. In the limit of linear perturbation theory, g is proportional to the expected peculiar motion of the local group v/sub p/, for which we derived Vertical Bar v/sub p/ Vertical Barapprox.670 ..cap omega../sup 0.6/, directed roughly toward the Virgo cluster. The assumptions of this cosmological test are quite different from the nonlinear spherically symmetric Virgo infall test, and yet they both yield estimates of ..cap omega.. that are quite high, 0.4<..cap omega..<0.5, for an adopted infall velocity of 400 km s/sup -1/. If the infall is as high as 500 km s/sup -1/, the universe could very well be closed. However, if the infall is only 300 km s/sup -1/, ..cap omega.. is roughly one-third of the closure density.

• Research Organization: Harvard-Smithsonian Center for Astrophysics
• OSTI ID: 5169498
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 254:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics &amp; Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMOLOGY
DISTRIBUTION
GALAXY CLUSTERS
GRAVITATION
LUMINOSITY
MATHEMATICS
OPTICAL PROPERTIES
PERTURBATION THEORY
PHYSICAL PROPERTIES
RED SHIFT
SPATIAL DISTRIBUTION
STATISTICS
UNIVERSE