On the alignment of haloes, filaments and magnetic fields in the simulated cosmic web

Abstract

The continuous flow of gas and dark matter across scales in the cosmic web can generate correlated dynamical properties of haloes and filaments (and the magnetic fields they contain). With this work, we study the halo spin properties and orientation with respect to filaments, and the morphology of the magnetic field around these objects, for haloes with masses in the range ∼108 − 1014 M⊙ and filaments up to ∼8 Mpc long. Furthermore, we study how these properties vary in presence, or lack thereof, of different (astro)physical processes and with different magnetic initial conditions. We perform cosmological magnetohydrodynamical simulations with the Eulerian code Enzo and we develop a simple and robust algorithm to study the filamentary connectivity of haloes in three dimensions. We investigate the morphological and magnetic properties and focus on the alignment of the magnetic field along filaments: our analysis suggests that the degree of this alignment is partially dependent on the physical processes involved, as well as on magnetic initial conditions. We discuss the contribution of this effect on a potential attempt to detect the magnetic field surrounding these objects: we find that it introduces a bias in the estimation of the magnetic field from Faraday rotation measure techniques. Specifically, given the strong tendency we find for extragalactic magnetic fields to align with the filaments axis, the value of the magnetic field can be underestimated by a factor ∼3, because this effect contributes to making the line-of-sight magnetic field (for filaments in the plane of the sky) much smaller than the total one.

Magnetogenesis and the Cosmic Web: A Joint Challenge for Radio Observations and Numerical Simulations

“…First, we extract from each three-dimensional volume a catalog of filaments in the given range of lengths, using the algorithm developed in [121] for our simulations. By construction, all detected filaments are delimited by M 100 ≥ 10 13 M halos, and are filled with gas with an average T ≥ 5 × 10 5 K temperature.…”

Magnetogenesis and the Cosmic Web: a joint challenge for radio observations and numerical simulations

“…First, we extract from each 3-dimensional volume a catalog of filaments in the given range of lengths, using the algorithm developed in [121] for our simulations. By construction, all detected filaments are delimited by M 100 ≥ 10 13 M halos, and are filled with gas with an average T ≥ 5 • 10 5 K temperature.…”

Continuous Filament Network of the Local Universe

“…Two principles lie at the heart of the LSS theory: (i) the hypothesis of the Gaussian distribution of initial density perturbations, and (ii) Zeldovich's approximation within which one can describe their evolution (van de Weygaert 2002). Most of the methods for describing the LSS have been tested via numerical simulations (Libeskind et al 2018;Ganeshaiah Veena et al 2019;Bonnaire et al 2020;Banfi et al 2021;Zhang et al 2022), and only a few have been applied to actual observational surveys (Sousbie 2011;Sousbie et al 2011;Tempel et al 2014;Chen et al 2016;Carrón Duque et al 2022). A detailed comparison of several modern methods of filament detection is given by Libeskind et al (2018).…”