Fast radio burst dispersion measures and rotation measures and the origin of intergalactic magnetic fields

Abstract

We investigate the possibility of measuring intergalactic magnetic fields using the dispersion measures and rotation measures of fast radio bursts. With Bayesian methods, we produce probability density functions for values of these measures. We distinguish between contributions from the intergalactic medium, the host galaxy and the local environment of the progenitor. To this end, we use constrained, magnetohydrodynamic simulations of the local Universe to compute lines-of-sight integrals from the position of the Milky Way. In particular, we differentiate between predominantly astrophysical and primordial origins of magnetic fields in the intergalactic medium. We test different possible types of host galaxies and probe different distribution functions of fast radio burst progenitor locations inside the host galaxy. Under the assumption that fast radio bursts are produced by magnetars, we use analytic predictions to account for the contribution of the local environment. We find that less than 100 fast radio bursts from magnetars in stellar-wind environments hosted by starburst dwarf galaxies at redshift z 0.5 suffice to discriminate between predominantly primordial and astrophysical origins of intergalactic magnetic fields. However, this requires the contribution of the Milky Way to be removed with a precision of ≈ 1 rad m −2 . We show the potential existence of a subset of fast radio bursts whose rotation measure carry information on the strength of the intergalactic magnetic field and its origins.

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

“…Only in the B1 and in the B5 models 10 20 eV protons are not too much deflected after 30 Mpc of propagation, and their deflection also peaks at small angles after 100 Mpc. This is consistent with previous results that investigated the propagation of UHECRs (also taking into account their energy losses) with ENZO simulation and a similarly large primordial field (Hackstein et al 2016(Hackstein et al , 2019.…”

“…However, this simplistic method reproduced the results obtained by other methods (e.g. Ryu et al 2008;Vazza et al 2017a;Hackstein et al 2019). While the application of the sub-grid dynamo model adds realism to the magnetic field distribution in our volume, it has no impact on the intermediate and low-density regime in which we study the differences introduced by our CMB-based magnetic fields.…”

“…Dolag et al 2005;Alves Batista & Sigl 2014;Berezinsky 2014;). We recently studied the propagation of UHECRs in ENZO simulations combined to the CRPROPA code (Alves Batista et al 2016), finding that the observed level of isotropy of ≥10 18 eV UHECRs rules out primordial models with a uniform magnetic field larger than ∼10 nG (Hackstein et al 2016(Hackstein et al , 2019.…”

“…In summary, we find that among the investigated models there is the theoretical possibility of detecting signatures of the topology of seed magnetic fields in voids, through the clustering of 10 20 eV events from very nearby ≤10 Mpc sources. Unluckily, the statistics of such events is presently so small that such analysis will be dominated by sample variance in the real case (Hackstein et al 2019).…”

Polarized radiative transfer, rotation measure fluctuations, and large-scale magnetic fields

“…They are therefore useful probes of the intergalactic magnetic fields (see e.g. Xu & Han 2014b;Zheng et al 2014;Akahori et al 2016;Ravi et al 2016;Vazza et al 2018;Hackstein et al 2019) and their evolution (see e.g. Xu & Han 2014b), if their redshifts and dispersion measures are known (see e.g.…”