The evolution of dark matter halo properties in clusters, filaments, sheets and voids

We use a series of high-resolution N-body simulations of the concordance cosmology to investigate the redshift evolution since z= 1 of the properties and alignment with the large-scale structure (LSS) of haloes in clusters, filaments, sheets and voids. We find that (i) once a rescaling of the halo mass with M
*
(z), the typical mass scale collapsing at redshift z, is performed, there is no further significant redshift dependence in the halo properties; (ii) the environment influences the halo shape and formation time at all investigated redshifts for haloes with masses M≲M
*
and (iii) there is a significant alignment of both spin and shape of haloes with filaments and sheets. In detail, at all redshifts up to z= 1: (a) haloes with masses below ∼M
*
tend to be more oblate when located in clusters than in the other environments; this trend is reversed at higher masses: above about M
*
, haloes in clusters are typically more prolate than similar massive haloes in sheets, filaments and voids. (b) The haloes with M≳M
*
in filaments spin more rapidly than similar mass haloes in clusters; haloes in voids have the lowest median spin parameters. (c) Haloes with M≲M
*
tend to be younger in voids and older in clusters. (d) In sheets, halo spin vectors tend to lie preferentially within the sheet plane independent of halo mass; in filaments, instead, haloes with M≲M
*
tend to spin parallel to the filament and higher mass haloes perpendicular to it. For halo masses M≳M
*
, the major axis of haloes in filaments and sheets is strongly aligned with the host filament or the sheet plane, respectively. Such halo–LSS alignments may be of importance in weak lensing analyses of cosmic shear. A question that is opened by our study is why, in the 0 < z < 1 redshift regime that we have investigated, the mass scale for gravitational collapse, M
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, sets roughly the threshold below which the LSS environment either begins to affect, or reverses, fundamental properties of dark matter haloes.