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Title: The second coming of cold dark matter?

Abstract

In recent years standard cold dark matter (CDM) theory, which enjoyed a large following throughout much of the past decade, has been abandoned by virtually all of its early supporters. The most serious argument against CDM was the incompatibility between the relatively high value of the pairwise radial velocity dispersion between galaxies, {sigma}{sub v}, inferred from numerical simulation with the much lower observational estimates. We reexamine this argument in the light of our new, high-resolution, COBE-normalized simulations and conclude that {sigma}{sub v} is significantly overestimated in simulations which do not have sufficient resolution (i.e., which have masses of galaxies comparable to the mass of N-body particles) and that it is also difficult to reliably estimate {sigma}{sub v} from the observational catalogues used for this purpose. We conclude that inflationary cosmology and CDM are not -- contrary to the presently prevailing prejudice -- incompatible with the observations of small scale peculiar velocities, as characterized, for example, by {sigma}{sub v}.

Authors:
;  [1];  [2];  [3]
  1. Los Alamos National Lab., NM (United States)
  2. Mt. Stromlo Observatory, PB Weston Creek, Canberra, ACT (Australia)
  3. Caltech Concurrent Supercomputing Facility, Pasadena, CA (United States)
Publication Date:
Research Org.:
Los Alamos National Lab., NM (United States)
Sponsoring Org.:
Department of Defense, Washington, DC (United States)
OSTI Identifier:
10113653
Report Number(s):
LA-UR-93-4240; CONF-9311156-1
ON: DE94004992
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Cosmic velocity fields,Paris (France),Nov 1993; Other Information: PBD: [1993]
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; NONLUMINOUS MATTER; COSMOLOGICAL MODELS; VELOCITY; COMPUTERIZED SIMULATION; 661300; OTHER ASPECTS OF PHYSICAL SCIENCE

Citation Formats

Zurek, W.H., Warren, M.S., Quinn, P.J., and Salmon, J.K.. The second coming of cold dark matter?. United States: N. p., 1993. Web.
Zurek, W.H., Warren, M.S., Quinn, P.J., & Salmon, J.K.. The second coming of cold dark matter?. United States.
Zurek, W.H., Warren, M.S., Quinn, P.J., and Salmon, J.K.. 1993. "The second coming of cold dark matter?". United States. doi:. https://www.osti.gov/servlets/purl/10113653.
@article{osti_10113653,
title = {The second coming of cold dark matter?},
author = {Zurek, W.H. and Warren, M.S. and Quinn, P.J. and Salmon, J.K.},
abstractNote = {In recent years standard cold dark matter (CDM) theory, which enjoyed a large following throughout much of the past decade, has been abandoned by virtually all of its early supporters. The most serious argument against CDM was the incompatibility between the relatively high value of the pairwise radial velocity dispersion between galaxies, {sigma}{sub v}, inferred from numerical simulation with the much lower observational estimates. We reexamine this argument in the light of our new, high-resolution, COBE-normalized simulations and conclude that {sigma}{sub v} is significantly overestimated in simulations which do not have sufficient resolution (i.e., which have masses of galaxies comparable to the mass of N-body particles) and that it is also difficult to reliably estimate {sigma}{sub v} from the observational catalogues used for this purpose. We conclude that inflationary cosmology and CDM are not -- contrary to the presently prevailing prejudice -- incompatible with the observations of small scale peculiar velocities, as characterized, for example, by {sigma}{sub v}.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1993,
month =
}

Conference:
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  • While the standard cold dark matter (CDM) model has received numerous marks against it on the basis of a variety of observational data, the prediction of high {Sigma}{Upsilon}, the pairwise-velocity dispersion between galaxies, on small (megaparsec) scales was reported as perhaps one of its greatest failings. Here, we reexamine the case of CDM and {Sigma}{Upsilon}, with high-resolution numerical simulations. The statistic was measured in simulations, in artificial galaxy catalogs, and in the CfA North Forty redshift survey. In our reanalysis of the CfA data, we found that {Sigma}{Upsilon} {approximately} 500 km/s, significantly higher than the original estimates of Davis &more » Peebles (1983). This new value, along with our estimate of the velocity bias, leads to a virial measure of the cosmological density parameter, {Omega} {approximately} 0.9. which is more than four times the traditionally cited CfA result. Analysis the simulations indicates that while the method of Davis and Peebles works well, the {Sigma}{Upsilon} statistic itself is not generally robust: there is large scatter from catalog to catalog and evidence that the recovered {Sigma}{Upsilon} value depends strongly on a small fraction of galaxies in the central regions of rare, massive clusters. Thus, at present the CDM model cannot be deemed incompatible with observed small-scale peculiar velocities.« less
  • While the standard cold dark matter (CDM) model has received numerous marks against it on the basis of a variety of observational data, the prediction of high {sigma}{sub {ital v}}, the pairwise-velocity dispersion between galaxies, on small (megaparsec) scales was reported as perhaps one of its greatest failings. Here, we reexamine the case of CDM and {sigma}{sub {ital v}} with high-resolution numerical simulations. The {sigma}{sub {ital v}} statistic was measured in simulations, in artificial galaxy catalogs, and the CfA North Forty redshift survey. In our reanalysis of the CfA data, we found that {sigma}{sub {ital v}}{similar_to}500 km/s, significantly higher thanmore » the original estimates of Davis & Peebles (1983). This new value, along with our estimate of the velocity bias, leads to a virial measure of the cosmological density parameter, {Omega}{similar_to}0.9, which is more than four times the traditionally cited CfA result. Analysis of the simulations indicates that while the method of Davis and Peebles works well, the {sigma}{sub {ital v}} statistic itself is not generally robust: there is large scatter from catalog to catalog and evidence that the recovered {sigma}{sub {ital v}} value depends strongly on a small fraction of galaxies in the central regions of rare, massive clusters. Thus, at present the CDM model cannot be deemed incompatible with observed small-scale peculiar velocities. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.« less
  • In this Report we discuss the four complementary searches for the identity of dark matter: direct detection experiments that look for dark matter interacting in the lab, indirect detection experiments that connect lab signals to dark matter in our own and other galaxies, collider experiments that elucidate the particle properties of dark matter, and astrophysical probes sensitive to non-gravitational interactions of dark matter. The complementarity among the different dark matter searches is discussed qualitatively and illustrated quantitatively in several theoretical scenarios. Our primary conclusion is that the diversity of possible dark matter candidates requires a balanced program based on allmore » four of those approaches.« less
  • The spatial distribution of the cold-dark-matter (CDM) and baryonic components of CDM-dominated cosmological models are characterized, summarizing the results of recent theoretical investigations. The evolution and distribution of matter in an Einstein-de Sitter universe on length scales small enough so that the Newtonian approximation is valid is followed chronologically, assuming (1) that the galaxies, CDM, and the intergalactic medium (IGM) are coupled by gravity, (2) that galaxies form by taking mass and momentum from the IGM, and (3) that the IGM responds to the energy input from the galaxies. The results of the numerical computations are presented in extensive graphsmore » and discussed in detail. 12 refs.« less
  • The dark matter (DM) that appears to be gravitationally dominant on all astronomical scales larger than the cores of galaxies can be classified, on the basis of its characteristic free-streaming damping mass M/sub D/, as hot (M/sub D/ approx. 10/sup 15/ M/sub mass/), warm (M/sub D/ approx. 10/sup 11/ M/sub mass/), or cold (M/sub D < 10/sup 8/ M/sub mass/). For the case of cold DM, the shape of the DM fluctuation spectrum is determined by (a) the primordial spectrum (on scales larger than the horizon), and (b) stagspansion, the stagnation of the growth of DM fluctuations that enter themore » horizon while the universe is still radiation-dominated. An attractive feature of the cold dark matter hypothesis is its considerable predictive power: the post-recombination fluctuation spectrum is calculable, and it in turn governs the formation of galaxies and clusters. Good agreement with the data is obtained for a Zeldovich spectrum of primordial fluctuations.« less