Bibcode
Munari, E.; Monaco, Pierluigi; Koda, Jun; Kitaura, F.-Sh.; Sefusatti, Emiliano; Borgani, Stefano
Bibliographical reference
Journal of Cosmology and Astroparticle Physics, Issue 07, article id. 050 (2017).
Advertised on:
7
2017
Citations
14
Refereed citations
13
Description
We present a test to quantify how well some approximate methods,
designed to reproduce the mildly non-linear evolution of perturbations,
are able to reproduce the clustering of DM halos once the grouping of
particles into halos is defined and kept fixed. The following methods
have been considered: Lagrangian Perturbation Theory (LPT) up to third
order, Truncated LPT, Augmented LPT, MUSCLE and COLA. The test runs as
follows: halos are defined by applying a friends-of-friends (FoF) halo
finder to the output of an N-body simulation. The approximate methods
are then applied to the same initial conditions of the simulation,
producing for all particles displacements from their starting position
and velocities. The position and velocity of each halo are computed by
averaging over the particles that belong to that halo, according to the
FoF halo finder. This procedure allows us to perform a well-posed test
of how clustering of the matter density and halo density fields are
recovered, without asking to the approximate method an accurate
reconstruction of halos. We have considered the results at z=0,0.5,1,
and we have analysed power spectrum in real and redshift space,
object-by-object difference in position and velocity, density
Probability Distribution Function (PDF) and its moments, phase
difference of Fourier modes. We find that higher LPT orders are
generally able to better reproduce the clustering of halos, while little
or no improvement is found for the matter density field when going to
2LPT and 3LPT. Augmentation provides some improvement when coupled with
2LPT, while its effect is limited when coupled with 3LPT. Little
improvement is brought by MUSCLE with respect to Augmentation. The more
expensive particle-mesh code COLA outperforms all LPT methods, and this
is true even for mesh sizes as large as the inter-particle distance.
This test sets an upper limit on the ability of these methods to
reproduce the clustering of halos, for the cases when these objects are
reconstructed at the object-by-object level.
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