我们报告的发现两个超新星遗迹（SNRs）指定G152.4-2.1和G190.9-2.2，使用加拿大银河平面调查数据。本文的目的是，第一，目前的证据，有利于分类的两个来源的信噪比，和，第二，描述基本参数（综合通量密度，频谱和偏振）以及属性（形态，视线速度，距离和物理尺寸），以促进和激励未来的观测。光谱和偏振参数来自现有无线电调查的多波长数据，波长在6和92厘米之间。特别是对于源G152.4-2.1，我们还使用了Effelsberg 100米望远镜在11厘米处进行的新观测。利用中性氢（HI）和45角秒~（12）CO（J=1-0）的1角分谱线数据分析了所发现源周围的星际介质。G152.4-2.1是一个桶形SNR，南北两侧有两个相对的无线电亮极化侧翼。沿着银河平面拉长的残余物正在一种或多或少均匀的介质中演化。G190.9-2.2也是一个壳型残留物，东西两半垂直于平面延伸，并在一个低密度区域内发展，北部和南部是密集的中性氢，东部和西部是分子（12 CO）云。G152.4-2.1和G190.9-2.2的综合射电连续谱指数分别为-0.65+/-0.05和-0.66+/-0.05。两个SNRs的距离约为1千秒差距，G152.4-2.1的直径（32 x30秒差距）大于G190.9-2.2（18x 16秒差距）。这两个残留物是迄今为止最低的表面亮度信噪比，其值为5 x 10 ^-23 W m^-2 Hz^-1 sr^-1。
英文摘要：
We report on the discovery of two supernova remnants (SNRs) designated G152.4-2.1 and G190.9-2.2, using Canadian Galactic Plane Survey data. The aims of this paper are, first, to present evidence that favours the classification of both sources as SNRs, and, second, to describe basic parameters (integrated flux density, spectrum, and polarization) as well as properties (morphology, line-of-sight velocity, distance and physical size) to facilitate and motivate future observations. Spectral and polarization parameters are derived from multiwavelength data from existing radio surveys carried out at wavelengths between 6 and 92cm. In particular for the source G152.4-2.1 we also use new observations at 11cm done with the Effelsberg 100m telescope. The interstellar medium around the discovered sources is analyzed using 1-arcminute line data from neutral hydrogen (HI) and 45-arcsecond 12CO(J=1-0). G152.4-2.1 is a barrel shaped SNR with two opposed radio-bright polarized flanks on the North and South. The remnant, which is elongated along the Galactic plane is evolving in a more-or-less uniform medium. G190.9-2.2 is also a shell-type remnant with East and West halves elongated perpendicular to the plane, and is evolving within a low-density region bounded by dense neutral hydrogen in the North and South, and molecular (12CO) clouds in the East and West. The integrated radio continuum spectral indices are -0.65+/-0.05 and -0.66+/-0.05 for G152.4-2.1 and G190.9-2.2 respectively. Both SNRs are approximately 1 kpc distant, with G152.4-2.1 being larger (32x30 pc in diameter) than G190.9-2.2 (18x16 pc). These two remnants are the lowest surface brightness SNRs yet catalogued at 5x10^-23 W m^-2 Hz^-1 sr^-1.
Odd Radio Circles as supernovae remnants in the intragroup medium
在最近发现的弧分大小的圆形弥散射电源中，有一部分（$\sim8$ %）被称为奇射电圈（Odd Radio Circles）或ORC，它们可能是本星系群及其近邻星系群内群内介质中的超新星遗迹。这一估计是基于光学探测率的群内超新星事件在附近（$z \sim 0.1-0.2$）星系群。在本星系群及其邻近的星系群中，预计每百万年约有5400颗群内超新星。对于一个约为$10^{4}$年的射电可探测周期，平均每1000平方度1.3个群内中等超新星遗迹预计将在射电勘测中被探测到，其灵敏度导致了ORC的发现。在群内介质中，距离$\sim3$ Mpc的超新星遗迹的角大小、表面亮度和射电通量可以预期与五个已知的ORC相似。群内超新星遗迹并不存在于星系的致密和寒冷的星际介质中，而是在星系晕或更远的低密度（$10^{-4}-10^{-5}$ cm $^{-3}$）温暖介质（$10^{5}-10^{6}$ K）中演化，并且可能在与银河系和其他附近星系周围的各种潮汐流光相关的漫射恒星光中找到它们的祖先。
