EDP Sciences
Free access
Volume 372, Number 2, June III 2001
Page(s) 381 - 385
Section Cosmology
DOI http://dx.doi.org/10.1051/0004-6361:20010507

A&A 372, 381-385 (2001)
DOI: 10.1051/0004-6361:20010507

Observational tests of the $\delta_{\mathsf{c}}{-}$ $\vec M$ $_{\mathsf{vir}}$ relation in hierarchical clustering models

L.-M. Cheng1, 2 and X.-P. Wu1, 2

1  National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
2  Department of Astronomy, Beijing Normal University, Beijing 100875, PR China

(Received 22 February 2001 / Accepted 2 April 2001)

Observational determinations of the correlation between the characteristic density $\delta_{\rm c}$ and the virial mass $M_{\rm vir}$ of dark halos constitute a critical test for models of hierarchical structure formation. Using the dynamical properties of dark halos reconstructed from the galaxy distributions in massive systems (groups/clusters) and the rotation curves in less massive systems (dwarf, low surface brightness and spiral galaxies) drawn from the literature, we confirm the existence of the $\delta_{\rm c}$- $M_{\rm vir}$ relation over a broad mass range from $10^{10} M_{\odot}$ to $10^{15} M_{\odot}$, which is in gross consistency with the prediction of a flat cosmological model with $\Omega_{\rm M}=0.3$ and $\Omega_{\Lambda}=0.7$. It is pointed out that previous analyses based on the measurements of X-ray emitting gas and the hydrostatic equilibrium hypothesis, which claimed a shallower scale-free spectrum of $n\approx-1$ for initial density fluctuations, may suffer from nongravitational heating influence especially in low-mass systems.

Key words: cosmology: observations -- dark matter -- galaxies: formation

Offprint request: L.-M. Cheng, clm@class2.bao.ac.cn

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