High-resolution Very Large Array Radio Observations of the Boomerang Pulsar Wind Nebula

Abstract We present a radio polarimetric study of the Boomerang pulsar wind nebula G106.65+2.96 with Very Large Array (VLA) observations at the 6 GHz band. Our high-resolution image discovers new small-scale features in the nebula, including an elliptical core of 40″ × 20″ surrounding the central pulsar and a 2 ′ long arc wrapping around the core in the north. The latter shows a gap from the core, and it consists of a bright lobe in the northwest and a tongue-like structure in the northeast. These could be resulting from the pulsar wind interaction with the environment. Our polarization measurement reveals a highly ordered magnetic field with toroidal geometry. The small-scale features are all highly linearly polarized. In particular, the lobe has a polarization fraction of ∼60%, close to the synchrotron limit. This is also much higher than the value measured at a lower frequency, implying significant depolarization. We show that this can be explained by Faraday rotation in the nebula, and we constructed a simple 3D model accordingly to estimate a magnetic field strength of ∼25–70 μ G, assuming a median inclination angle of 60°, which uncertainty arises from the uncertainty in the flux measurement and its distance.