26 research outputs found
Fourier imaging of non-linear structure formation
We perform a Fourier space decomposition of the dynamics of non-linear
cosmological structure formation in LCDM models. From N-body simulations
involving only cold dark matter we calculate 3-dimensional non-linear density,
velocity divergence and vorticity Fourier realizations, and use these to
calculate the fully non-linear mode coupling integrals in the corresponding
fluid equations. Our approach allows for a reconstruction of the amount of mode
coupling between any two wavenumbers as a function of redshift. With our
Fourier decomposition method we identify the transfer of power from larger to
smaller scales, the stable clustering regime, the scale where vorticity becomes
important, and the suppression of the non-linear divergence power spectrum as
compared to linear theory. Our results can be used to improve and calibrate
semi-analytical structure formation models.Comment: 22 pages, 8 figures, matches published versio
Cosmological N-body simulations with generic hot dark matter
We have calculated the non-linear effects of generic fermionic and bosonic
hot dark matter components in cosmological N-body simulations. For sub-eV
masses, the non-linear power spectrum suppression caused by thermal
free-streaming resembles the one seen for massive neutrinos, whereas for masses
larger than 1eV, the non-linear relative suppression of power is smaller than
in linear theory. We furthermore find that in the non-linear regime, one can
map fermionic to bosonic models by performing a simple transformation.Comment: 19 pages, 9 figure
Resolving Cosmic Neutrino Structure: A Hybrid Neutrino N-body Scheme
We present the first simulation capable of resolving the structure of
neutrino clustering on Mpc scales. The method combines grid- and particle-based
methods and achieves very good accuracy on both small and large scales, while
keeping CPU consumption under control. Such simulations are not only ideal for
calculating the non-linear matter power spectrum but also particularly relevant
for studies of how neutrinos cluster in galaxy- or cluster-sized halos. We
perform the largest neutrino N-body simulation to date, effectively containing
10 different neutrino hot dark matter components with different thermal
properties.Comment: 13 pages, 6 figure
The Effect of Thermal Neutrino Motion on the Non-linear Cosmological Matter Power Spectrum
We have performed detailed studies of non-linear structure formation in
cosmological models with light neutrinos. For the first time the effect of
neutrino thermal velocities has been included in a consistent way, and the
effect on the matter power spectrum is found to be significant. The effect is
large enough to be measured in future, high precision surveys. Additionally, we
provide a simple but accurate analytic expression for the suppression of
fluctuation power due to massive neutrinos. Finally, we describe a simple and
fast method for including the effect of massive neutrinos in large-scale N-body
simulations which is accurate at the 1% level for \sum m_nu < 0.15 eV.Comment: 17 pages, 7 figures. Minimal changes, matches JCAP versio
Neutrinos in Non-linear Structure Formation - The Effect on Halo Properties
We use N-body simulations to find the effect of neutrino masses on halo
properties, and investigate how the density profiles of both the neutrino and
the dark matter components change as a function of the neutrino mass. We
compare our neutrino density profiles with results from the N-one-body method
and find good agreement. We also show and explain why the Tremaine-Gunn bound
for the neutrinos is not saturated. Finally we study how the halo mass function
changes as a function of the neutrino mass and compare our results with the
Sheth-Tormen semi-analytic formulae. Our results are important for surveys
which aim at probing cosmological parameters using clusters, as well as future
experiments aiming at measuring the cosmic neutrino background directly.Comment: 20 pages, 8 figure