Numerical study of the cosmological velocity field as a function of density

Free access article

Issue		A&A Volume 419, Number 2, May IV 2004


Page(s)		425 - 437
Section		Cosmology (including clusters of galaxies)
DOI		http://dx.doi.org/10.1051/0004-6361:20034566

A&A 419, 425-437 (2004)
DOI: 10.1051/0004-6361:20034566

Numerical study of the cosmological velocity field as a function of density

A. Domínguez^{1, 2} and A. L. Melott³

¹ Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart, Germany
² Theoretische Physik, Ludwig-Maximilians-Universität, Theresienstr. 37, 80333 München, Germany
³ Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA

(Received 23 October 2003 / Accepted 5 February 2004 )

Abstract
We report on a new study of the velocity distribution in N-body simulations. We investigate the center-of-mass and internal kinetic energies of coarsening cells as a function of time, cell size and cell mass. By using self-similar cosmological models, we are able to derive theoretical predictions for comparison and to assess the influence of finite-size and resolution effects. The most interesting result is the discovery of a polytropic-like relationship between the average velocity dispersion (internal kinetic energy) and the mass density in an intermediate range of densities, ${\kappa}_{\rm int}\propto \varrho^{2-\eta}$ . The exponent $\eta$ measures the deviations from the virial prediction, $\eta_{\rm virial}=0$ . For self-similar models, $\eta$ depends only on the spectral index of the initial power spectrum. We also study CDM models and confirm a previous result that the same polytropic-like dependence exists, with a time and coarsening length dependent $\eta$ . The dependence ${\kappa}_{\rm int}(\varrho)$ is an important input for a recently proposed theoretical model of cosmological structure formation which improves over the standard dust model (pressureless fluid) by regularizing the density singularities.

Key words: gravitation -- methods: N-body simulations -- cosmology: large-scale structure of Universe

Offprint request: A. Domínguez, alvaro@fluids.mpi-stuttgart.mpg.de

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.