The Curious Case of the "Heartworm" Nebula

TL;DR

This paper reports new radio observations of a peculiar nebula near G357.2-0.2, revealing a faint heart-shaped shell and filamentary structures with nonthermal emission, suggesting complex magnetic and particle acceleration processes without confirmed pulsar association.

Contribution

It provides high-resolution radio imaging of the nebula's features and discusses their possible magnetic and energetic origins, expanding understanding of such unusual Galactic structures.

Findings

Discovery of a faint heart-shaped shell structure

Identification of filamentary, nonthermal emission features

No X-ray detection constrains the presence of a pulsar or PWN

Abstract

The curious Galactic features near G357.2$-$0.2 were observed with the MeerKAT radio interferometer array in the UHF and L bands (0.56--1.68 GHz). There are two possibly related features: a newly identified faint heart-shaped partial shell (the "Heart"), and a series of previously known but now much better imaged narrow, curved features (the "Worm") interior to the heart. Polarized emission suggests that much of the emission is nonthermal and is embedded in a dense plasma. The filaments of the worm appear to be magnetic structures powered by embedded knots that are sites of particle acceleration. The morphology of the worm broadly resembles some known pulsar wind nebulae (PWNe) but there is no known pulsar or PWN which could be powering this structure. We also present eROSITA observations of the field; no part of the nebula is detected in X-rays, but the current limits do not preclude the existence of a pulsar/PWN of intermediate spin-down luminosity.