The discovery highlights magnetised structures extending over 16,000 light-years (150 quadrillion kilometers) beyond the Galactic plane. These structures are linked to the origin of the eROSITA Bubbles-vast regions powered by intense gas and energy outflows, primarily caused by supernovae explosions. These bubbles, first observed by the eROSITA satellite, span the sky from horizon to horizon, allowing the first precise measurements of the Milky Way's magnetic halo. The findings were published in 'Nature Astronomy'.
The study reports that magnetic fields within these bubbles are organised into thin filamentary structures stretching up to 150 times the diameter of the full moon. These filaments are connected to hot winds with a temperature of 3.5 million Kelvin, ejected from the Galactic Disc and driven by regions of star formation.
He-Shou Zhang, the study's lead author and an INAF researcher, stated: "Our results find that intense star formation at the end of the Galactic Bar contributes significantly to these expansive, multiphase outflows." He further explained, "This work provides the first detailed measurements of the magnetic fields in the Milky Way's X-ray emitting halo and uncovers new connections between star-forming activities and galactic outflows. Our findings show that the magnetic ridges we observed are not just coincidental structures but are closely related to the star-forming regions in our galaxy."
The research team used a wide-ranging, multi-wavelength survey-from radio to gamma rays-to confirm the connection between these magnetic structures and galactic feedback processes. The study also represents the first observational evidence linking the star-forming ring at the end of the Galactic Bar to large-scale outflows in the Milky Way.
"This study marks a significant step forward in our understanding of the Milky Way," added Gabriele Ponti of INAF. "While outflows from supermassive black holes and starburst events are commonly associated with active galaxies, this research shows that even quiescent galaxies like the Milky Way can generate powerful outflows. The star-forming ring at the end of the Galactic Bar seems to play a key role, potentially shedding light on how similar galaxies grow."
Using data from over ten all-sky surveys, He-Shou Zhang concluded: "Our work is the first comprehensive multi-wavelength study of the eROSITA Bubbles since their discovery in 2020. This study opens new frontiers in our understanding of the Galactic halo and the complex, dynamic star-forming regions of the Milky Way."
Research Report:A magnetised Galactic halo from inner Galaxy outflows
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