Is the local Hubble flow consistent with concordance cosmology?

In this paper we review the history of the search for and study of the motions of nearby galaxies with respect to the Hubble Flow. The current status of the field is that (1) convincing infall has been detected into dense clusters, especially the Virgo cluster, (2) the microwave background direction is moderately well aligned with the measured flow nearby but not apparently on larger scales, and (3) there is good but not perfect consistency between the nearby density fields and velocity fields. Particular problems exist in the different Ω's required to fit the density field derived from optically selected and IRAS (60μ) selected galaxy samples.

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Hubble flow variations as a test for inhomogeneous cosmology

Astronomy and Astrophysics ◽

10.1051/0004-6361/201629174 ◽

2019 ◽

Vol 622 ◽

pp. A83 ◽

Cited By ~ 1

Author(s):

Christoph Saulder ◽

Steffen Mieske ◽

Eelco van Kampen ◽

Werner W. Zeilinger

Keyword(s):

Large Scale ◽

Cold Dark Matter ◽

Statistical Tests ◽

Specific Model ◽

Accelerated Expansion ◽

Inhomogeneous Cosmology ◽

Galaxy Surveys ◽

Model Versus ◽

Differential Expansion ◽

Hubble Flow

Context. Backreactions from large-scale inhomogeneities may provide an elegant explanation for the observed accelerated expansion of the universe without the need to introduce dark energy. Aims. We propose a cosmological test for a specific model of inhomogeneous cosmology, called timescape cosmology. Using large-scale galaxy surveys such as SDSS and 2MRS, we test the variation of expansion expected in the Λ-cold dark matter (Λ-CDM) model versus a more generic differential expansion using our own calibrations of bounds suggested by timescape cosmology. Methods. Our test measures the systematic variations of the Hubble flow towards distant galaxies groups as a function of the matter distribution in the lines of sight to those galaxy groups. We compare the observed systematic variation of the Hubble flow to mock catalogues from the Millennium Simulation in the case of the Λ-CDM model, and a deformed version of the same simulation that exhibits more pronounced differential expansion. Results. We perform a series of statistical tests, ranging from linear regressions to Kolmogorov-Smirnov tests, on the obtained data. They consistently yield results preferring Λ-CDM cosmology over our approximated model of timescape cosmology. Conclusions. Our analysis of observational data shows no evidence that the variation of expansion differs from that of the standard Λ-CDM model.

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Dynamical Models for our Virgocentric Deviation from Hubble Flow

Highlights of Astronomy ◽

10.1017/s1539299600005979 ◽

1983 ◽

Vol 6 ◽

pp. 751-752

Author(s):

E. E. Salpeter

Keyword(s):

Mass Density ◽

Galaxy Cluster ◽

Virgo Cluster ◽

Point Of View ◽

Model Fit ◽

Cluster Center ◽

The Core ◽

Wide Range ◽

Range Of Values ◽

Hubble Flow

Spherically symmetric models for the dynamic development of a galaxy cluster from an initial overdensity have been carried out numerically, without dissipation or 2-body relaxation but with shell crossings included. The deviation ∆V from pure Hubble Flow of the Local Group, due to the retardation effect of the Virgo cluster and supercluster, has been calculated from a number of different models by Hoffman and Salpeter (Astrophys. J. 263, 1982, in press). The results are somewhat surprising if one takes the point of view of (a) insisting that the dynamic model fit the observed dispersion of galaxy systemic velocities in the core of the Virgo cluster, but (b) allowing the mass to light ratio M/L to be an arbitrary (but smoothly varying) function of distance from the Virgo cluster center. Point (a) essentially fixes the mass density and M/L in the core, but (b) still allows a wide range of values for the cosmological density parameters Ω (proportional to the average M/L far from the Virgo cluster). With this point of view ∆V actually decreases with increasing Ω: If M/L is constant, Ω ≈ 0.3 and ∆V ≈ 250 km s–1 (Hoffman, Olson and Salpeter, Ap. J. 242, 861, 1980); for Ω ~ 0.05, ∆V would exceed 350 km s–1; for Ω = 1, AV could be less than 150 km s–1.

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Condensations and Cavities

Symposium - International Astronomical Union ◽

10.1017/s0074180900039000 ◽

1983 ◽

Vol 104 ◽

pp. 217-217

Author(s):

F. Occhionero ◽

P. Santangelo ◽

N. Vittorio

Keyword(s):

Spherical Symmetry ◽

Linear Growth ◽

Non Linear ◽

Unified Algorithm ◽

Hubble Flow

We present a unified algorithm which describes the non-linear growth 1) of condensations surrounded by cavities or 2) of cavities surrounded by condensations (i.e. ridges of higher density) in the Hubble flow. The main idealization is that of pressureless spherical symmetry (Tolman-Bondi solution); overall algebraic details and results for problem 1) are given in previous work (Occhionero, et al., 1981 a and b); results for problem 2) will be given elsewhere (Occhionero, et al., 1982).

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The Motion of the Local Group of Galaxies with Respect to the Background of Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900039097 ◽

1983 ◽

Vol 104 ◽

pp. 255-258

Author(s):

R. D. Davies

Keyword(s):

Large Scale ◽

Local Group ◽

Microwave Background ◽

Optical Studies ◽

Group Motion ◽

Gravitational Influence ◽

Nearby Galaxies ◽

Peculiar Motion ◽

The Universe ◽

Hubble Flow

A measurement of the motion of the Local Group of galaxies through the Universe provides an indication of their peculiar motion relative to the Hubble flow consequent upon the gravitational influence of the local large scale mass inhomogeneities. This motion can be measured either relative to the cosmic microwave background at z ∼ 1000 or relative to the background or nearby (z ∼ 0.01) galaxies. The interpretation of published measurements is subject to some uncertainty. As an example, the Local Group motion derived from optical studies of nearby galaxies (Rubin et al. 1976) differs from that derived from radio frequency measurements of the dipole anisotropy in the microwave background. (Boughn et al. 1981, Gorenstein & Smoot 1981).

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