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Evolution of Mass Distribution in CDM Halos | | Joel R. Primack
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12 Oct 2000 | | Subject: | astro-ph | | Affiliation: | Physics Department, UCSC | | Abstract: | On the basis of a new convergence study of high-resolution N-body simulations, my colleagues and I now agree that the Navarro, Frenk, & White (1996) density profile $
ho_{NFW}(r) propto r^{-1} (r+r_s)^{-2}$ is a good representation of typical dark matter halos of galactic mass. Comparing simulations of the same halo with numbers of particles ranging from $sim10^3$ to $sim10^6$, we have also shown that $r_s$, the radius where the log-slope is -2, can be determined accurately for halos with as few as $sim10^3$ particles. Based on a study of thousands of halos at many redshifts in an Adaptive Refinement Tree (ART) simulation of a cosmological volume in a $Lambda$CDM cosmology, we have found that the concentration $cvir equiv Rvir/
s$ has a log-normal distribution, with $1sigma$ $Delta (log cvir) = 0.18$ at a given mass, corresponding to a scatter in maximum rotation velocities of $Delta Vmax/Vmax = 0.12$. The average concentration declines with redshift at fixed mass as $cvir(z) propto (1+z)^{-1}$. This may have important implications for galaxy rotation curves. Finally, we have found that the velocity function determined from galaxy luminosity functions plus luminosity-velocity relations agrees with the predictions from our $Lambda$CDM simulations. But we also note that the very limited evolution with redshift of the velocity function predicted by $Lambda$CDM conflicts with the data that is becoming available on the number density of bright galaxies unless there is significant evolution of the luminosity-velocity relation at $z>1$. | | Source: | arXiv, astro-ph/0010248 | | Services: | Forum | Review | PDF | Favorites | |
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