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, b = −3. • 0, which has a size of about 1 • . 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 ± 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.

MeerKAT 1.3 GHz Observations of Supernova Remnants

“…This is a very-low-surface-brightness SNR even for MeerKAT. The integrated flux density from our data is S 1335 = 1.75 ± 0.30 Jy, a little more than 40% of the value expected (Gao et al 2020), which indicates missing large-scale emission. This is not surprising as the SNR has a diameter of about 44′.…”

A Systematic Study of Associations between Supernova Remnants and Molecular Clouds

“…We list all results of SNRC-MC associations in Table 2. Most of SNRCs in our coverage have been recently discovered (Kassim 1988;Gorham 1990;Gray 1994;Trushkin 2001;Brogan et al 2006;Helfand et al 2006;Gerbrandt et al 2014;Anderson et al 2017;Hurley-Walker et al 2019a;Gao et al 2020;Dokara et al 2021;Ranasinghe et al 2021), which are not well studied by multiband observations. A similar approach to study SNR-MC associations is performed to investigate the associations between SNRCs and MCs.…”

Scanning the Milky Way for 10 years: Discoveries from the Sino-German 6 cm polarization survey of the Galactic plane

“…(a) G21.8-3.0 [39] ; (b) G150.3+4.5 [38] ; (c) G178.4-4.2 [37] ; (d) G25.1-2.3 [37] Figure 3 Four new SNRs discovered in the 6 cm survey. (a) G21.8-3.0 [39] ; (b) G150.3+4.5 [38] ; (c) G178.4-4.2 [37] ; (d) G25.1-2.3 [37] (~5 GHz)进行观测, 为HII区的证认工作提供了良好的 数据基础. 2008年, Shi等人 [53] 从部分刚刚处理完成的 6 cm巡天反银心方向的小块天区数据中证认出了3个 延展的HII区: G148.8+2.3、G149.5+0.0(可能为SH 2-205的一部分)和G169.9+2.0(图4第一排), 说明6 cm巡 天数据具有高灵敏度, 能够探测暗弱的延展辐射.…”

“…到目前为止, 银河系内被认知的超新星遗迹仅约 300颗. 甚为欣喜的是, 基于6 cm巡天数据并结合多波 段观测数据, 我们团队先后发现了4颗新的银河系超新 星遗迹: G178.2-4.2和G25.1-2.3 [37] 、G150.3+4.5 [38] 和 2020年新发现的G21.8-3.0 [39] (图3). 其中, 于2011年发…”