4 research outputs found
Scaling Evolution of Universal Dark-Matter Halo Density Profiles
Dark-matter halos show a universal density profile with a scaling such that
less massive systems are typically denser. This mass-density relation is well
described by a proportionality between the characteristic density of halos and
the mean cosmic density at halo formation time. It has recently been shown that
this proportionality could be the result of the following simple evolutionary
picture. Halos form in major mergers with essentially the same,
cosmogony-dependent, dimensionless profile, and then grow inside-outside, as a
consequence of accretion. Here we verify the consistency of this picture and
show that it predicts the correct zero point of the mass-density relation.Comment: 9 pages, 1 Table and 1 postscript figure, latex uses aaspp4.sty,
accepted for publication in The Astrophysical Journal Letter
The Effects of the Peak-Peak Correlation on the Peak Model of Hierarchical Clustering
In two previous papers a semi-analytical model was presented for the
hierarchical clustering of halos via gravitational instability from peaks in a
random Gaussian field of density fluctuations. This model is better founded
than the extended Press-Schechter model, which is known to agree with numerical
simulations and to make similar predictions. The specific merger rate, however,
shows a significant departure at intermediate captured masses. The origin of
this was suspected as being the rather crude approximation used for the density
of nested peaks. Here, we seek to verify this suspicion by implementing a more
accurate expression for the latter quantity which accounts for the correlation
among peaks. We confirm that the inclusion of the peak-peak correlation
improves the specific merger rate, while the good behavior of the remaining
quantities is preserved.Comment: ApJ accepted. 15 pages, including 4 figures. Also available at
ftp://pcess1.am.ub.es/pub/ApJ/effectpp.ps.g
Scaling Evolution Of Universal Dark-Matter Halo Density Profiles
Dark-matter halos show a universal density profile with a scaling such that less massive systems are typically denser. This mass-density relation is well described by a proportionality between the characteristic density of halos and the mean cosmic density at halo formation time. It has recently been shown that this proportionality could be the result of the following simple evolutionary picture. Halos form in major mergers with essentially the same, cosmogony-dependent, dimensionless profile, and then grow inside-outside, as a consequence of accretion. Here we verify the consistency of this picture and show that it predicts the correct zero point of the mass-density relation. Subject headings: cosmology: theory --- galaxies: formation --- galaxies: evolution --- galaxies: structure 1. INTRODUCTION High resolution cosmological N-body simulations show that the spherically averaged density profile of dark-matter halos has the following universal form (Navarro, Frenk, & White 1997, herea..