Magnetic Fields Detected in Early Galaxy Proto-Cluster at High Redshift
Researchers have measured magnetic fields in the proto-cluster CARLA J1510+5958 at redshift z = 1.72, roughly 10 billion years ago, constraining the proto-intra-cluster medium field to a lower limit of 0.4 microgauss. The study used the JVLA radio telescope to analyze Faraday rotation in polarized emission from a central radio-loud active galactic nucleus (AGN), finding asymmetric polarization properties between its two lobes. The findings suggest that AGN can seed and amplify magnetic fields in the early universe during the initial stages of galaxy cluster formation.
A new study accepted for publication in Astronomy & Astrophysics presents radio observations of the proto-cluster CARLA J1510+5958 at redshift z = 1.72, using the Jansky Very Large Array (JVLA) in the L-band (1–2 GHz). By analyzing Faraday rotation measure (RM) synthesis and QU fitting of polarized emission from the central radio-loud AGN, the team found that the Western lobe displays a relatively uniform rotation measure (average −115 ± 32 rad m⁻²) indicative of a locally ordered, compressed magnetic field, while the Eastern lobe is fully depolarized, pointing to a turbulent, magnetized surrounding medium. Three-dimensional simulations of gas density and turbulent magnetic fields were used to interpret the asymmetry, ruling out a purely isotropic random field for the Western lobe. QU fitting further revealed an internal Faraday component, suggesting that magnetized relativistic plasma from the AGN lobe is mixing with ambient gas and potentially seeding the surrounding proto-intra-cluster medium (proto-ICM) with magnetic fields. From this analysis, the researchers derive a lower limit of 0.4 microgauss for the average physical magnetic field in the proto-ICM, confirming that significant magnetization and field amplification were already underway during early cluster assembly more than 10 billion years ago.
What's missing
The study derives only a lower limit on the proto-ICM magnetic field strength. The depolarization mechanism of the Eastern lobe is not fully resolved, and the generalizability of these results to other proto-clusters at similar redshifts remains an open question. Additionally, the role of other magnetization mechanisms (e.g., primordial fields, turbulent dynamo) relative to AGN seeding is not fully disentangled in this single-system study.
What different sources said
- arXiv astro-phCenter
Magnetic fields at the dawn of structure formation I. The CARLA J1510+5958 proto-cluster
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