The Central Mass and Phase-Space Densities of Dark Matter Halos: Cosmological Implications

Abstract

Current data suggest that the central mass densities ${\rho }_0$ and phase-space densities $Q\equiv {\rho }_0/{\sigma }_V^3$ of cosmological halos in the present universe are correlated with their velocity dispersions ${\sigma }_V$ over a very wide range of ${\sigma }_V$ from less than 10 to more than 1000 $\mathrm{km}{\mathrm{s}}^{-1}$. Such correlations are an expected consequence of the statistical correlation of the formation epochs of virialized objects in the CDM model with their masses; the smaller-mass halos typically form first and merge to form larger-mass halos later. We have derived the $Q-{\sigma }_V$ and ${\rho }_0-{\sigma }_V$ correlations for different CDM cosmologies and compared the predicted correlations with the observed properties of a sample of low-redshift halos ranging in size from dwarf spheroidal galaxies to galaxy clusters. Our predictions are generally consistent with the data, with preference for the currently-favored, flat $\Lambda$CDM model. Such a comparison serves to test the basic CDM paradigm while constraining the background cosmology and the power-spectrum of primordial density fluctuations, including larger wavenumbers than have previously been constrained.

12 pages, 3 figures, ApJ Letters, in press (2002); Changed to match the accepted version. Results and figures unchanged; text revisions only

References in corpus (1)

• The Postcollapse Equilibrium Structure of Cosmological Haloes in a Low-Density Universe

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