2025A&A...699A..33B

Pulsar wind nebulae (PWNe) are among the most efficient particle accelerators in the Universe; however, the physical conditions and magnetic geometry in their inner regions remain poorly understood. X-ray polarization now provides a unique opportunity to investigate the magnetic field structure and turbulence properties close to the sites where high energy particles are accelerated. Here, we report on recent X-ray polarization measurements of the PWN 3C 58 by the International X-ray Polarimeter Explorer (IXPE). 3C 58 is a young system that displays a characteristic jet-torus structure that, unlike those in other PWNe, is observed almost edge-on. This nebula exhibits a high level of integrated polarization, approximately 22%, at an angle near 97°, with an implied magnetic field oriented parallel to the major axis of the inner torus. This suggests a toroidal magnetic geometry with little turbulence in the interior and an intrinsic level of polarization possibly approaching the theoretical limit for synchrotron emission. No significant detection of a polarized signal from the associated pulsar was found. These results confirm that the internal structure of young PWNe is far less turbulent than previously predicted and is at odds with multidimensional numerical simulations.