Though the galactic density wave theory is over 50 years old and is well known in science, it has been difficult to say whether it fits our own Milky Way disk. Here we show a substructure inside the spiral arms. This substructure is reversing with respect to the Galactic Meridian (longitude zero), and crosscuts of the arms at negative longitudes appear as mirror images of crosscuts of the arms at positive longitudes. Four lanes are delineated: a mid-arm (extended 12CO gas at the mid-arm, H i atoms), an in-between offset by about 100 pc (synchrotron, radio recombination lines), an in-between offset by about 200 pc (masers, colder dust), and an inner edge (hotter dust seen in mid-IR and near-IR).
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机译：尽管银河系密度波理论已有50多年的历史，并且在科学界广为人知，但很难说它是否适合我们自己的银河系磁盘。在这里，我们显示了螺旋臂内部的子结构。该子结构相对于银河子午线（经度为零）是相反的，负经度上的手臂横切显示为正经度上的手臂横切的镜像。划定了四个通道：中臂（中臂处扩展的12CO气体，H i原子），中间偏移大约100 pc（同步加速器，无线电重组线），中间偏移大约200 pc （大量，较冷的灰尘）和内部边缘（在中红外和近红外中看到较热的灰尘）。
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