Abstract
The warm-hot intergalactic medium (WHIM) is a candidate for the missing baryons in the Universe. If the WHIM is permeated with the intergalactic magnetic field (IGMF), the Faraday rotation measure (RM) of the WHIM is imprinted in linearly-polarized emission from extragalactic objects. In this article, we discuss strategies to explore the WHIM’s RM from forthcoming radio broadband and wide-field polarization sky surveys. There will be two observational breakthroughs in the coming decades; the RM grid and Faraday tomography. They will allow us to find ideal RM sources for the study of the IGMF and give us unique information of the WHIM along the line of sight.
Highlights
Cosmological structure-formation simulations suggest that the majority of the missing baryons exist as the warm-hot intergalactic medium (WHIM), which resides mostly in galaxy filaments with temperature from 105 K–107 K
The fact that a hotter/X-ray-brighter system has a larger variance of rotation measure (RM) [33] may imply a relation with the development of magneto-hydrodynamic turbulence, though the real origin and history of the intergalactic magnetic field (IGMF) are a longstanding mystery [34,35]
Faraday tomography or Faraday RM synthesis [58,59] is thought to be a revolutionary technique in cosmic magnetism
Summary
The standard theory of big-bang nucleosynthesis predicts the total amount of baryons in the Universe. Cosmological structure-formation simulations suggest that the majority of the missing baryons exist as the warm-hot intergalactic medium (WHIM), which resides mostly in galaxy filaments with temperature from 105 K–107 K. The intergalactic magnetic field (IGMF) is generated in the recombination [6], in the first-star formation [7,8], in the reionization [9,10] and in the structure formation [11] of the Universe. The IGMF influences the configuration of magnetic fields in galaxies [23] These examples tell us the fact that understanding the IGMF is of crucial importance. A firm detection of the IGMF in galaxy filaments brings the discovery of the missing baryons, as well
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