Mass Function of Low Mass Dark Halos

The mass function of dark halos in a Λ-dominated cold dark matter (ΛCDM) universe is investigated. 529 output files from five runs of N-body simulations are analyzed using the friends-of-friends cluster finding algorithm. All the runs use 5123 particles in the box size of 35 h−1Mpc to 140 h−1Mpc. Mass of particles for 35 h−1 Mpc runs is 2.67 ×107h−1 M⊙. Because of the high mass resolution of our simulations, the multiplicity function in the low-mass range, where the mass is well below the characteristic mass and ν = δc/σ . 1.0, is evaluated in the present work, and is well fitted by the functional form proposed by Sheth & Tormen (ST). However, the maximum value of the multiplicity function from our simulations at ν ∼ 1 is smaller, and its low mass tail is shallower when compared with the ST multiplicity function. Subject headings: cosmology: theory — dark matter — galaxies: luminosity function, mass function