Dark Matter Halo Merger Histories Beyond Cold Dark Matter: I - Methods and Application to Warm Dark Matter

摘要

We describe a methodology to accurately compute halo mass functions,progenitor mass functions, merger rates and merger trees in non-cold darkmatter universes using a self-consistent treatment of the generalized extendedPress-Schechter formalism. Our approach permits rapid exploration of thesubhalo population of galactic halos in dark matter models with a variety ofdifferent particle properties or universes with rolling, truncated, or morecomplicated power spectra. We make detailed comparisons of analytically derivedmass functions and merger histories with recent warm dark matter cosmologicalN-body simulations, and find excellent agreement. We show that, once theaccretion of smoothly distributed matter is accounted for, coarse-grainedstatistics such as the mass accretion history of halos can be almostindistinguishable between cold and warm dark matter cases. However, the halomass function and progenitor mass functions differ significantly, with the warmdark matter cases being strongly suppressed below the free-streaming scale ofthe dark matter. We demonstrate the importance of using the correct solutionfor the excursion set barrier first-crossing distribution in warm dark matter -if the solution for a flat barrier is used instead the truncation of the halomass function is much slower, leading to an overestimate of the number of lowmass halos.