New Survey Reveals Complex Magnetic Structures in the Milky Way

A research team led by the University of British Columbia Okanagan (UBCO) has created the first broadband map of Faraday rotation, providing an unprecedented view of the Milky Way's magnetic field. The study reveals that the galaxy's magnetic structure is more intricate than previously understood.

Dr. Alex Hill, Assistant Professor in the Irving K. Barber Faculty of Science at UBCO, and his team utilized data from the Dominion Radio Astrophysical Observatory's (DRAO) 15-metre telescope near Penticton, British Columbia. This effort resulted in the Dominion Radio Astrophysical Observatory GMIMS of the northern sky (DRAGONS) dataset, capturing polarized radio emissions across a wide frequency range. This comprehensive data allows astronomers to detect magnetic structures that were previously invisible.

Dr. Anna Ordog, former UBCO postdoctoral researcher and lead of the DRAGONS project, noted that the dataset enables observation of polarized emissions from within the galaxy, revealing significant structural complexity in the magnetic field. She emphasized that DRAGONS is the first to display this level of detail on such large spatial scales across the entire northern sky.

The research builds upon a theoretical concept proposed in 1966, which suggested that observing polarized radio waves at multiple frequencies could measure the three-dimensional structure of the Milky Way's magnetic field. Advancements in broadband telescope technology, such as the DRAO 15-metre telescope, have now made this research feasible.

The project marks the first scientific use of the 15-metre telescope, originally built as a prototype for the Square Kilometre Array (SKA), a large radio telescope under construction in Southern Africa and Western Australia. Dr. Ordog led the setup for the DRAGONS project, supported by students from UBCO and the University of Calgary, along with DRAO engineers and technologists.

The study, recently published in The Astrophysical Journal Supplement Series, tracks how polarized radio waves twist as they travel through the galaxy, revealing the strength, structure, and direction of magnetic fields along the line of sight. The survey indicates that more than half the sky contains complex magnetic structures rather than simple, uniform fields.

Dr. Tom Landecker, an astronomer emeritus at DRAO and adjunct professor at both UBCO and the University of Calgary, highlighted the unexpected complexity of the magnetic field revealed by the new dataset. He described DRAGONS as a tool that illustrates how matter and magnetic fields in the galaxy are organized and interact with phenomena such as supernova explosions and spiral arms.

Dr. Hill emphasized the importance of understanding the Milky Way's magnetic field, noting that it is a crucial component in comprehending the universe's operations and origins. He pointed out that, for decades, measurements of the galaxy's magnetic field were simplified, but the new data provides a more detailed picture.

The DRAGONS data has already been utilized in a study led by University of Calgary doctoral student Rebecca Booth, focusing on the large-scale reversal in the galactic magnetic field. This research, published in an accompanying paper in The Astrophysical Journal, exemplifies the dataset's potential for ongoing studies in this field.

Dr. Ordog noted that DRAGONS is part of a new generation of radio surveys that allow scientists to map the Milky Way's three-dimensional magnetic field structure in the space between the stars, representing a significant Canadian contribution to the global astronomical community.