Radio Polarization Observations of G319.9-0.7: A Bow-shock Nebula with an Azimuthal Magnetic Field Powered by Pulsar J1509-5850

TL;DR

This study presents radio polarization observations of the bow-shock pulsar wind nebula G319.9-0.7, revealing a helical magnetic field aligned with the pulsar's motion, and highlights its unique magnetic structure among similar nebulae.

Contribution

First detection of a helical magnetic field in a bow-shock nebula, suggesting an alignment between pulsar spin axis and velocity, expanding understanding of magnetic field geometries in such systems.

Findings

Helical magnetic field trailing the pulsar

Flat radio spectrum with index -0.26

Distinct magnetic and brightness properties compared to other bow-shock nebulae

Abstract

We report radio polarization observations of G319.9-0.7 (MSC 319.9-0.7) at 3 and 6 cm obtained with the Australia Telescope Compact Array. The source shows a highly elongated morphology with the energetic pulsar J1509-5850 located at the tip. We found a flat radio spectrum of index \alpha=-0.26 +/- 0.04 and a high degree of linear polarization. These results confirm G319.9-0.7 as a bow-shock pulsar wind nebula. The polarization maps suggest a helical magnetic field trailing the pulsar, with the symmetry axis parallel to the system's inferred direction of motion. This is the first time such a field geometry has been seen in a bow-shock nebula, and it may be the result of an alignment between the pulsar spin axis and its space velocity. Compared to other bow-shock examples, G319.9-0.7 exhibits very different properties in the field structure and surface brightness distribution, illustrating the large diversity of the population.