High Resolution VLA Radio Observations of the Boomerang Pulsar Wind Nebula

TL;DR

This study uses high-resolution VLA radio observations to reveal detailed structures and magnetic field properties of the Boomerang pulsar wind nebula, including polarization and interaction features.

Contribution

It provides the first high-resolution polarimetric imaging of the nebula, uncovering small-scale features and a highly ordered magnetic field structure.

Findings

Discovered small-scale elliptical core and arc features.

Measured high polarization fraction (~60%) in the nebula.

Inferred magnetic field strength of 50-105 μG.

Abstract

We present a radio polarimetric study of the Boomerang pulsar wind nebula G106.65+2.96 with VLA observations at the 6 GHz band. Our high-resolution image discovers new small-scale features in the nebula, including an elliptical core of $40''\times20''$ surrounding the central pulsar and a $2'$-long arc wrapping around the core in the north. The latter shows a clear 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 $\sim$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 infer a magnetic field strength of $\sim$50-105$\mu$G.