Title: Hot gas and magnetic arms of NGC 6946: indications for reconnection heating? Show Chinese title

Title: NGC 6946的热气体和磁性臂：再连接加热的迹象？

Abstract: The grand-design face-on spiral galaxy NGC6946 is remarkable because of its high star formation activity, the massive northern spiral arm, and the magnetic arms, which are observed in polarized radio synchrotron emission and are located between the optical arms and possibly are magnetic reconnection regions. X-ray observations of NGC6946 performed with XMM-Newton were used to study the emission from X-ray point sources and diffuse hot gas, including the magnetic arms and the halo. Spectral fitting of the diffuse X-ray emission allowed us to derive temperatures of the hot gas. With assumptions about the emission volume, this allowed us to estimate gas densities, masses, and cooling times. To explain the X-ray emission from the spiral arms of NGC6946 two-temperature plasma models are needed to account for the disk and halo emission. The interarm regions show only one thermal component. We observe that the temperature of the hot gas in and above the magnetic arm regions increases slightly when compared to the average temperatures in the areas in and above the spiral arms. For the southwestern part of the disk, which is depolarized in the radio range by Faraday rotation, we find more efficient mixing of disk and halo gas. We propose magnetic reconnection in the magnetic arm regions of NGC6946 as the possible cause of the additional heating of the gas and ordering of the magnetic fields. In the southwestern part of the galactic disk we observed indications of a possible faster outflow of the hot gas. A very hot gas within the MF16 nebula possibly suggests shock heating by a supernova explosion. Show Chinese abstract

Abstract: 漩涡星系 NGC6946 因其高恒星形成活动、巨大的北部旋臂和磁性旋臂而引人注目，这些磁性旋臂在偏振射电同步辐射中被观测到，位于光学旋臂之间，并可能是磁重联区域。 使用 XMM-Newton 对 NGC6946 进行的 X 射线观测被用来研究来自 X 射线点源和弥漫热气体（包括磁性旋臂和星系晕）的辐射。 弥散 X 射线发射的光谱拟合使我们能够推导出热气体的温度。 假设发射体积的情况下，这使得我们能够估算气体密度、质量和冷却时间。 为了解释 NGC6946 螺旋臂的 X 射线发射，需要双温等离子体模型来解释盘面和星系晕的发射。 星系间区域只显示单一热组分。 我们观察到与螺旋臂内及其上方区域的平均温度相比，磁性臂区域内的热气体温度略有升高。 对于因法拉第旋转而在射电波段去极化的盘面西南部分，我们发现盘面和星系晕气体的混合更加高效。 我们提出 NGC6946 的磁性臂区域中的磁重联可能是气体额外加热和磁场有序的原因。 在银河盘面的西南部，我们观察到了可能的热气体更快外流的迹象。 MF16 星云内的非常热的气体可能表明超新星爆炸引起的激波加热。