标题： NGC 4449年轻富氧超新星遗迹的首张VLBI图像 显示英文标题

标题： The First VLBI Image of the Young, Oxygen-Rich Supernova Remnant in NGC 4449

摘要： 我们报告了对附近星系NGC 4449中超亮超新星遗迹SNR 4449-1的1.4 GHz高灵敏度甚长基线干涉测量（VLBI）射电观测结果，这使我们首次获得了该天体的清晰图像。 遗迹的射电形态由两条大致平行的明亮脊组成，这与许多银河系老态超新星遗迹所见的圆筒形状相似，也可能与SN 1987A类似。 遗迹的角直径为65×40毫角秒，对应于(3.7×2.3)×10^{18} (以3.8 Mpc为距离D时)厘米。 我们还给出了一个新的、高信噪比的光学光谱。 通过比较遗迹的线性尺寸与从光学谱线测得的最大速度，并结合历史影像的约束条件，我们得出超新星爆炸发生在约1905年至1961年之间，很可能是在1940年左右。 因此，遗迹的年龄很可能约为70年。我们发现SNR 4449-1的激波很可能仍在与近邻恒星介质相互作用，而不是星际介质。 显示英文摘要

摘要： We report on sensitive 1.4-GHz VLBI radio observations of the unusually luminous supernova remnant SNR 4449-1 in the galaxy NGC 4449, which gave us the first well-resolved image of this object. The remnant's radio morphology consists of two approximately parallel bright ridges, suggesting similarities to the barrel shape seen for many older Galactic supernova remnants or possibly to SN 1987A. The angular extent of the remnant is 65 x 40 mas, corresponding to (3.7 x 2.3) x 10^{18} (D/3.8 Mpc) cm. We also present a new, high signal-to-noise optical spectrum. By comparing the remnant's linear size to the maximum velocities measured from optical lines, as well as using constraints from historical images, we conclude that the supernova explosion occurred between ~1905 and 1961, likely around 1940. The age of the remnant is therefore likely ~70 yr. We find that SNR 4449-1's shock wave is likely still interacting with the circumstellar rather than interstellar medium.