Discovery of a new supernova remnant G21.8-3.0

Abstract

Sensitive radio continuum surveys of the Galactic plane are ideal for discovering new supernova remnants (SNRs). From the Sino-German λ6 cm polarisation survey of the Galactic plane, an extended shell-like structure has been found at l = 21.8 degree, b = -3.0 degree, which has a size of about 1 degree. New observations were made with the Effelsberg 100-m radio telescope at λ11 cm to estimate the source spectrum together with the Urumqi λ6 cm and the Effelsberg λ21 cm data. The spectral index of G21.8-3.0 was found to be α = -0.72 {\pm} 0.16. Polarised emission was mostly detected in the eastern half of G21.8-3.0 at both λ6 cm and λ11 cm. These properties, together with the Hα filament along its northern periphery and the lack of infrared emission, indicate that the emission is non-thermal as is usual in shell-type SNRs.

8 pages, 4 figures (figure quality is reduced due to the size limit), accepted for publication in MNRAS