Affiliation: University of Bologna & Ilia State University
Contribution: Poster
Title: What do magnetised jets tell us about the large-scale magnetisation of the Universe?
Abstract: Magnetic fields are observed throughout the universe, on scales ranging from planets and stars to galaxies and galaxy clusters. Observations reveal the large-scale nature of these fields with strengths of microGauss and correlation lengths of the order of kiloparsecs on galaxy and galaxy cluster scales. Despite their ubiquity, the origin of these galaxy and galaxy-cluster magnetics fields (referred to as large-scale magnetic fields, LSMFs) remains an open question in modern astrophysics and cosmology. A commonly accepted hypothesis is that the weak “seed” fields, generated either from an astrophysical scenario (during structure formation) or a cosmological (primordial; in the early Universe) scenario should have significantly been amplified during structure formation. Recent analysis of blazar spectra from the Fermi-LAT and H.E.S.S. (High Energy Stereoscopic System) collaborations favours Megaparsec-correlated magnetic fields with the lower limit of 7.1 × 10-16 Gauss on their field strength in cosmic voids. This supports cosmological (primordial) origin of LSMFs which is often confronted by the astrophysical mechanisms of the seed-field generation in the late Universe. Considered astrophysical sources include powerful events, such as e.g., the Active Galactic Nuclei (AGN) jets and galactic winds, which transfer magnetic fields from the knots of the cosmic web to lower-density regions. The efficiency of magnetising vast voids by such events is expected to be low; however, it is not well understood how from the centers of galaxies these events can magnetize the Universe. In our previous work, we studied the evolution of primordial magnetic fields (PMFs), —seed fields generated in the early Universe—during structure formation. Using the MHD cosmological code Enzo, we investigated their amplification and decay effects in the cosmic web and galaxy clusters. We showed that depending on the correlation length of PMFs, magnetic fields can be efficiently amplified during structure formation. The efficient amplification of large-scale-correlated PMFs (such as those generated during inflation) can be imprinted on the evolution of Faraday Rotation Measure (RM) in the intergalactic medium (IGM). In our current work, we study the magnetisation of lower-density regions, such as the warm-hot ionised medium (WHIM) and IGM by magnetised jets. These jets, driven by AGN, can also contribute to IGM-RM statistics. In this talk, I will present results from my previous work and discuss our ongoing research on studying the AGN-driven jets in cosmological simulations. I will also address the implications of both our previous and current work and explain how distinguishing different large-scale magnetisation scenarios can help us understand some of the unresolved questions of Astrophysics and Cosmology.
This contribution can be found in the Poster Hall.