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Abstract: We measure the mass function of dark matter halos in a large set ofcollisionless cosmological simulations of flat LCDM cosmology and investigateits evolution at z<~2. Halos are identified as isolated density peaks, andtheir masses are measured within a series of radii enclosing specificoverdensities. We argue that these spherical overdensity masses are moredirectly linked to cluster observables than masses measured using thefriends-of-friends algorithm FOF, and are therefore preferable for accurateforecasts of halo abundances. Our simulation set allows us to calibrate themass function at z=0 for virial masses in the range 10^{11} Msol-h < M <10^{15} Msol-h, to <~ 5%. We derive fitting functions for the halo massfunction in this mass range for a wide range of overdensities, both at z=0 andearlier epochs. In addition to these formulae, which improve on previousapproximations by 10-20%, our main finding is that the mass function cannot berepresented by a universal fitting function at this level of accuracy. Theamplitude of the -universal- function decreases monotonically by ~20-50%,depending on the mass definition, from z=0 to 2.5. We also find evidence forredshift evolution in the overall shape of the mass function.

Author: Jeremy L Tinker, Andrey V Kravtsov, Anatoly Klypin, Kevork Abazajian, Michael S Warren, Gustavo Yepes, Stefan Gottlober, Daniel E


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