Precision Determination of the Mass Function of Dark Matter Halos

The predicted mass function of dark matter halos is essential in connectingobserved galaxy cluster counts and models of galaxy clustering to theproperties of the primordial density field. We determine the mass function inthe concordance $\Lambda$CDM cosmology, as well as its uncertainty, usingsixteen $1024^3$-particle nested-volume dark-matter simulations, spanning amass range of over five orders of magnitude. Using the nested volumes andsingle-halo tests, we find and correct for a systematic error in thefriends-of-friends halo-finding algorithm. We find a fitting form and fullerror covariance for the mass function that successfully describes thesimulations' mass function and is well-behaved outside the simulations'resolutions. Estimated forecasts of uncertainty in cosmological parameters fromfuture cluster count surveys have negligible contribution from remainingstatistical uncertainties in the central cosmology multiplicity function. Thereexists a potentially non-negligible cosmological dependence (non-universality)of the halo multiplicity function.Comment: 4 pages, 3 figures, submitted to ApJ