Large-scale magnetic-field structure in the spiral galaxy M83
Large-scale magnetic-field structure in the spiral galaxy M83
复制标题
螺旋星系M83中的大尺度磁场结构
作者：
S. Sukumar;R. Allen
螺旋星系中磁场的大尺度结构，从散射星光的线偏振1和连续谱同步加速器射电发射的强度和线偏振2推断，倾向于遵循可见的螺旋臂结构。轴对称(在星系IC342和M31中；参考文献3和4)和双对称(在M81中；参考文献3和45)可以看到图案，后者显示出臂之间的场反转。我们在空间分辨率为∼2kpc的空间分辨率下测量了来自明亮的、近正面的螺旋星系M83(NGC5236)的20厘米连续射电辐射的VLA(甚大阵列)观测中的线偏振。最强的线偏振发射来自两个巨大的弧线，∼30kpc长，位于银河系黑暗外部区域的大致相对位置，从中心起∼12kpc。这些区域并不与任何突出的螺旋臂示踪器重合，从与早期6厘米波长的结果相比较，我们得出结论，星系中心的低偏振表明星际磁场无序，可能与在那里观察到的恒星形成活动有关。
THE large-scale structure of magnetic fields in spiral galaxies, as deduced from the linear polarization of scattered starlight1and from the intensity and linear polarization of continuum synchrotron radio emission2, tends to follow the visible spiral arm structure. Both axisymmetric (in the galaxies IC342 and M31; refs 3 and 4) and bisymmetric (in M81; ref. 5) patterns are seen, the latter showing a field reversal between the arms. We have measured the linear polarization at a spatial resolution of ∼2 kpc in VLA (Very Large Array) observations of 20-cm continuum radio emission from the bright, nearly face-on, spiral galaxy M83 (NGC5236). The strongest linearly polarized emission is from two giant arcs, ∼30 kpc long, situated roughly opposite each other in the dark outer regions of the galaxy, ∼12 kpc from the centre. These regions do not coincide with any prominent spiral arm tracers, and from a comparison with earlier results at 6-cm wavelength, we conclude that the low polarization in the centre of the galaxy indicates disorder in the interstellar magnetic field, probably connected with star formation activity observed there.