A magnetized Galactic halo from inner Galaxy outflows

Abstract

Magnetic halos of galaxies are crucial for understanding galaxy evolution, galactic-scale outflows and feedback from star formation activity. Identifying the magnetized halo of the Milky Way is challenging because of the potential contamination from foreground emission arising in local spiral arms. In addition, it is unclear how our magnetic halo is influenced by recently revealed large-scale structures such as the X-ray-emitting eROSITA Bubbles detected by the extended Roentgen Survey with an Imaging Telescope Array (eROSITA). Here we report the identification of several kiloparsec-scale magnetized structures on the basis of their polarized radio emission and their gamma-ray counterparts, which can be interpreted as the radiation of relativistic electrons in the Galactic magnetic halo. These non-thermal structures extend far above and below the Galactic plane and are spatially coincident with the thermal X-ray emission from the eROSITA Bubbles. The morphological consistency of these structures suggests a common origin, which can be sustained by Galactic outflows driven by active star-forming regions located in the Galactic Disk at 3–5 kpc from the Galactic Centre. These results reveal how X-ray-emitting and magnetized halos of spiral galaxies can be related to intense star formation activities and suggest that the X-shaped coherent magnetic structures observed in their halos can stem from galactic outflows. A magnetic galactic halo featuring coherent ridges several kiloparsecs above and below the Galactic Disk has been detected in multi-wavelength observations. The halo is probably a consequence of outflows driven by active star-forming regions in the disk.