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ID 46
file
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creator
Liu, Guo-Chin
Sugiyama, Naoshi
Nishioka, Hiroaki
subject
cosmology: theory
Cosmic microwave background
Large-scale structure of universe
NDC
Astronomy. Space sciences
abstract
The evolution of baryon density perturbations on very small scales is investigated. In particular, the nonlinear growth induced by the radiation drag force from the shear velocity field on larger scales during the recombination epoch, originally proposed by Shaviv in 1998, is studied in detail. We find that inclusion of the diffusion term, which Shaviv neglected in his analysis, results in rather mild growth with growth factor ≪ 100, instead of the enormous amplification, ∼ 10[4], of Shaviv's original claim, since the diffusion suppresses the growth. The growth factor strongly depends on the amplitude of the large-scale velocity field. The nonlinear growth mechanism is applied to density perturbations of general adiabatic cold dark matter (CDM) models. For these models, it has been found in previous works that the baryon density perturbations are not completely erased by diffusion damping if there are gravitational potential perturbations from the CDM component. Employing the perturbed rate equation derived in this paper, the nonlinear evolution of baryon density perturbations is investigated. We find that: (1) The nonlinear growth is larger for smaller scales. This mechanism only affects perturbations whose scales are smaller than ∼102 M⊙, comparable to stellar scales. (2) The maximum growth factors of baryon density fluctuations for various COBE-normalized CDM models are typically less than a factor of 10 for 3 σ large-scale velocity peaks. (3) The growth factor depends on Ωb.
journal title
Astrophysical Journal
volume
Volume 547
start page
1
end page
11
date of issued
2001
publisher
University of Chicago Press
issn
0004-637X
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
publisher
rights
Copyright (c) 2001 The American Astronomical Society.
relation is version of URL
http://dx.doi.org/10.1086/318352
department
Graduate School of Science