Simulations and observational tests of primordial magnetic fields from Cosmic Microwave Background constraints

Vazza, Franco; Paoletti, D.; Banfi, Serena; Finelli⋆, F.; Gheller, C.; O’Sullivan, Shane; Brüggen, M.

doi:10.1093/mnras/staa3532

Cited by 26 publications

(36 citation statements)

References 161 publications

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“…These small-scale PMFs, however, undergo dissipation during the later cosmic evolution [22,[24][25][26]. This PMF evolution depends upon the helicity and homogeneity of the magnetic fields [24,27], and its behavior in the late non-linear structure formation phase has been investigated in a number of recent three-dimensional simulations [28][29][30][31]. Ultimately, what we can observe with current measurements are signatures of large-scale PMFs which could have been generated in the inflationary epoch before the big bang [32].…”

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confidence: 68%

Distribution function of nuclei from $e^\pm$ scattering in the presence of a strong primordial magnetic field

Kusakabe,

Kedia,

Mathews

et al. 2021

Preprint

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The amplitude of the primordial magnetic field (PMF) is constrained from observational limits on primordial nuclear abundances. Within this constraint, it is possible that nuclear motion is regulated by Coulomb scattering with electrons and positrons (e ± 's), while e ± 's are affected by a PMF rather than collisions. For example, at a temperature of 10 9 K, thermal nuclei typically experience ∼ 10 21 scatterings per second that are dominated by very small angle scattering leading to minuscule changes in the nuclear kinetic energy of order O(1) eV. In this paper the upper limit on the effects of a possible discretization of the e ± momenta by the PMF on the nuclear momentum distribution is estimated under the extreme assumptions that the momentum of the e ± is relaxed before and after Coulomb scattering to Landau levels, and that during Coulomb scattering the PMF is neglected. This assumption explicitly breaks the time reversal invariance of Coulomb scattering, and the Maxwell-Boltzmann distribution is not a trivial steady state solution of the Boltzmann equation under these assumptions. We numerically evaluate the collision terms in the Boltzmann equation, and show that the introduction of a special direction in the e ± distribution by the PMF generates no directional dependence of the collisional destruction term of nuclei. Large anisotropies in the nuclear distribution function are then constrained from big bang nucleosynthesis. Ultimately, we conclude that a PMF does not significantly affect the isotropy or BBN.

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confidence: 68%

Distribution function of nuclei from $e^\pm$ scattering in the presence of a strong primordial magnetic field

Kusakabe,

Kedia,

Mathews

et al. 2021

Preprint

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“…Bykov et al 2019, and references therein): with cosmological simulations we measured that magnetic field lines tend to align to filaments both inside and outside the filament, following the flow direction on the gas, as a consequence of the velocity shear. This effect, which was found to apply to several variations of primordial scenarios of magnetic fields (Vazza et al 2021) as well as to variations of astrophysical seeding scenarios, albeit in a less prominent way (Banfi et al 2020), impacts on obliquity and therefore on cosmic ray acceleration. The trend outlined above, on one hand being extremely relevant for the study of cosmic ray acceleration and cosmic magnetism, is also very challenging to detect in observations.…”

Section: Introductionmentioning

confidence: 74%

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

Banfi

Vazza

Gheller

2021

Monthly Notices of the Royal Astronomical Society

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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.

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“…This paper is not meant to be too detailed on the numerical subtleties of our simulations, which have been documented elsewhere [102][103][104][105]. Here, we review the most relevant physical aspects of the models examined in our old and new runs, and refer to the Appendix A for a more complete overview of the numerical details and code implementation specifics.…”

Section: Methods and Materials: Cosmological Simulations Of The Cosmi...mentioning

confidence: 99%

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

et al. 2021

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The detection of the radio signal from filaments in the cosmic web is crucial to distinguish possible magnetogenesis scenarios. We review the status of the different attempts to detect the cosmic web at radio wavelengths. This is put into the context of the advanced simulations of cosmic magnetism carried out in the last few years by our MAGCOW project. While first attempts of imaging the cosmic web with the MWA and LOFAR have been encouraging and could discard some magnetogenesis models, the complexity behind such observations makes a definitive answer still uncertain. A combination of total intensity and polarimetric data at low radio frequencies that the SKA and LOFAR2.0 will achieve is key to removing the existing uncertainties related to the contribution of many possible sources of signal along deep lines of sight. This will make it possible to isolate the contribution from filaments, and expose its deep physical connection with the origin of extragalactic magnetism.

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Simulations and observational tests of primordial magnetic fields from Cosmic Microwave Background constraints

Cited by 26 publications

References 161 publications

Distribution function of nuclei from $e^\pm$ scattering in the presence of a strong primordial magnetic field

Distribution function of nuclei from $e^\pm$ scattering in the presence of a strong primordial magnetic field

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

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

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