# Halos and galaxies in the standard cosmological model: results from the Bolshoi simulation - Astrophysics > Cosmology and Nongalactic Astrophysics

Halos and galaxies in the standard cosmological model: results from the Bolshoi simulation - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We present the first results from the new Bolshoi N-body cosmological LCDMsimulation that uses cosmological parameters favored by current observations.The Bolshoi simulation was done in a volume 250Mpc on a side using 8billionparticles with mass and force resolution adequate to follow subhalos down to acompleteness limit of Vcirc=50km- s circular velocity. Using excellentstatistics of halos and subhalos 10M at every moment and 50M over the wholehistory we present accurate approximations for statistics such as the halomass function, the concentrations for distinct halos and subhalos, abundance ofhalos as function of their circular velocity, the abundance and the spatialdistribution of subhalos. We find that at high redshifts the concentrationfalls to a minimum of about 3.8 and then rises slightly for higher values ofhalo mass. We find that while the Sheth-Tormen approximation for the massfunction of halos found by spherical overdensity is accurate at low redshifts,it over-predicts the abundance of halos by nearly an order of magnitude byz=10. We find that the number of subhalos scales with the circular velocity ofthe host halo as Vhost**0.5, and that subhalos have nearly the same radialdistribution as dark matter particles at radii 0.3-2 times the host halo virialradius. The subhalo velocity function n>V behaves as V**-3. We givenormalization of this relation for different masses and redshifts. Finally, weuse an abundance-matching procedure to assign r-band luminosities to darkmatter halos as a function of halo Vcirc, and find that the luminosity-velocityrelation is in remarkably good agreement with the observed Tully-Fisherrelation for galaxies in the range 50-200km-s.

Author: ** A. Klypin, S. Trujillo-Gomez, J. Primack**

Source: https://arxiv.org/