2017/08/25 by S. A. Mao, Sui Ann Mao, C. Carilli +11 · 1 citation
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #Dynamo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy cluster #Magnetic field #Physics #Radio Astronomy Observations and Technology #Radio galaxy #Redshift #astro-ph.GA
paper · pdf · doi:10.1038/s41550-017-0218-x
29 pages, 5 figures (including Supplementary Information). Published in Nature Astronomy on August 28, 2017
arxiv created 2017/08/25 · openalex publication_date 2017/08/25 · arxiv updated 2017/08/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Magnetic fields play a pivotal role in the physics of interstellar medium in galaxies, but there are few observational constraints on how they evolve across cosmic time. Spatially resolved synchrotron polarization maps at radio wavelengths reveal well-ordered large-scale magnetic fields in nearby galaxies that are believed to grow from a seed field via a dynamo effect. To directly test and characterize this theory requires magnetic field strength and geometry measurements in cosmologically distant galaxies, which are challenging to obtain due to the limited sensitivity and angular resolution of current radio telescopes. Here, we report the cleanest measurements yet of magnetic fields in a galaxy beyond the local volume, free of the systematics traditional techniques would encounter. By exploiting the scenario where the polarized radio emission from a background source is gravitationally lensed by a foreground galaxy at z = 0.439 using broadband radio polarization data, we detected coherent μG magnetic fields in the lensing disk galaxy as seen 4.6 Gyrs ago, with similar strength and geometry to local volume galaxies. This is the highest redshift galaxy whose observed coherent magnetic field property is compatible with a mean-field dynamo origin.