Testing dark matter halo properties using self-similarity. (arXiv:2004.08406v2 [astro-ph.CO] UPDATED)

<a href="http://arxiv.org/find/astro-ph/1/au:+Leroy_M/0/1/0/all/0/1">M. Leroy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Garrison_L/0/1/0/all/0/1">L. Garrison</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eisenstein_D/0/1/0/all/0/1">D. Eisenstein</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Joyce_M/0/1/0/all/0/1">M. Joyce</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Maleubre_S/0/1/0/all/0/1">S. Maleubre</a>

We use self-similarity in N-body simulations of scale-free models to test for

resolution dependence in the mass function and two-point correlation functions

of dark matter halos. We use 1024$^3$ particle simulations performed with

ABACUS, and compare results obtained with two halo finders: friends-of-friends

(FOF) and ROCKSTAR. The FOF mass functions show a systematic deviation from

self-similarity which is explained by resolution dependence of the FOF mass

assignment previously reported in the literature. Weak evidence for convergence

is observed only starting from halos of several thousand particles, and mass

functions are overestimated by at least as much as 20-25 percent for halos of

50 particles. The mass function of the default ROCKSTAR halo catalog (with

bound virial spherical overdensity mass), on the other hand, shows good

convergence from of order 50 to 100 particles per halo, with no detectable

evidence at the few percent level of any systematic dependence for larger

particle number. Tests show that the mass unbinding procedure in ROCKSTAR is

the key factor in obtaining this much improved resolution. Applying the same

analysis to the halo-halo two point correlation function, we find again strong

evidence for convergence only for ROCKSTAR halos, at separations sufficiently

large so that halos do not overlap. At these separations we can exclude

dependence on resolution at the 5-10 percent level once halos have of order 50

to 100 particles. At smaller separations results are not converged even at

significantly larger particle number, and bigger simulations would be required

to establish the resolution required for convergence.

We use self-similarity in N-body simulations of scale-free models to test for

resolution dependence in the mass function and two-point correlation functions

of dark matter halos. We use 1024$^3$ particle simulations performed with

ABACUS, and compare results obtained with two halo finders: friends-of-friends

(FOF) and ROCKSTAR. The FOF mass functions show a systematic deviation from

self-similarity which is explained by resolution dependence of the FOF mass

assignment previously reported in the literature. Weak evidence for convergence

is observed only starting from halos of several thousand particles, and mass

functions are overestimated by at least as much as 20-25 percent for halos of

50 particles. The mass function of the default ROCKSTAR halo catalog (with

bound virial spherical overdensity mass), on the other hand, shows good

convergence from of order 50 to 100 particles per halo, with no detectable

evidence at the few percent level of any systematic dependence for larger

particle number. Tests show that the mass unbinding procedure in ROCKSTAR is

the key factor in obtaining this much improved resolution. Applying the same

analysis to the halo-halo two point correlation function, we find again strong

evidence for convergence only for ROCKSTAR halos, at separations sufficiently

large so that halos do not overlap. At these separations we can exclude

dependence on resolution at the 5-10 percent level once halos have of order 50

to 100 particles. At smaller separations results are not converged even at

significantly larger particle number, and bigger simulations would be required

to establish the resolution required for convergence.

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