DG Tau射电节点C频谱低频翻转的意义
Implications of the low frequency turn-over in the spectrum of radio knot C in DG Tau
摘要：
原恒星DG Tau中射电结C的同步辐射谱具有低频翻转。这是用来表明它的磁场强度可能至少是10 mG，这大约是两个数量级大于先前估计。较早的，较低的值是由于高估的发射体积连同省略的最小磁场的同步加速器光谱指数的依赖。由于源是部分解决的，这意味着同步辐射的低体积填充因子。有人认为，解释观测结果所需的高压是由于冲击。此外，为了进一步增强磁场强度以及相对论电子密度，可能需要冷却热气体。据认为，所观察到的光谱指数意味着无线电发射电子的能量是低于需要参加一阶费米加速。因此，无线电发射提供了其加速前阶段的特性的见解。还提请注意射电结C的性质和超新星中的激波诱导的射电辐射之间的相似性。
英文摘要：
The synchrotron spectrum of radio knot C in the protostellar object DG Tau has a low frequency turn-over. This is used to show that its magnetic field strength is likely to be at least 10 mG, which is roughly two orders of magnitude larger than previously estimated. The earlier, lower value is due to an overestimate of the emission volume together with an omission of the dependence of the minimum magnetic field on the synchrotron spectral index. Since the source is partially resolved, this implies a low volume filling factor for the synchrotron emission. It is argued that the high pressure needed to account for the observations is due to shocks. In addition, cooling of the thermal gas is probably necessary in order to further enhance the magnetic field strength as well as the density of relativistic electrons. It is suggested that the observed spectral index implies that the energy of the radio emitting electrons is below that needed to take part in first order Fermi acceleration. Hence, the radio emission gives insights to the properties of its pre-acceleration phase. Attention is also drawn to the similarities between the properties of radio knot C and the shock induced radio emission in supernovae.
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