Polarised radio emission associated with HESS J1912+101

Abstract

The shell-type TeV source HESS J1912+101 was tentatively identified as an old supernova remnant, but is missing counterparts at radio and other frequencies. We analysed the Sino-German Urumqi $\lambda$6 cm survey and the Effelsberg $\lambda$11 cm and $\lambda$21 cm surveys to identify radio emission from HESS J1912+101 to clarify the question of a supernova origin. We find a partial shell of excessive polarisation at $\lambda$6 cm at the periphery of HESS J1912+101. At $\lambda$11 cm, its polarised emission is faint and suffers from depolarisation, while at $\lambda$21 cm, no related polarisation is seen. We could not separate the shell's total intensity signal from the confusing intense diffuse emission from the inner Galactic plane. However, a high-percentage polarisation of the shell's synchrotron emission is indicated. Our results support earlier suggestions that HESS J1912+101 is an old supernova remnant. The synchrotron emission is highly polarised, which is typical for evolved supernova remnants of low surface-brightness.