Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany.
Nature. 2011 Nov 16;479(7374):499-501. doi: 10.1038/nature10551.
The formation of molecular clouds, which serve as stellar nurseries in galaxies, is poorly understood. A class of cloud formation models suggests that a large-scale galactic magnetic field is irrelevant at the scale of individual clouds, because the turbulence and rotation of a cloud may randomize the orientation of its magnetic field. Alternatively, galactic fields could be strong enough to impose their direction upon individual clouds, thereby regulating cloud accumulation and fragmentation, and affecting the rate and efficiency of star formation. Our location in the disk of the Galaxy makes an assessment of the situation difficult. Here we report observations of the magnetic field orientation of six giant molecular cloud complexes in the nearby, almost face-on, galaxy M33. The fields are aligned with the spiral arms, suggesting that the large-scale field in M33 anchors the clouds.
分子云的形成，这些云团是星系中的恒星托儿所，目前人们对此知之甚少。一类云形成模型表明，在单个云团的尺度上，大尺度的银河磁场是无关紧要的，因为云团的湍流和旋转可能会使磁场的方向随机化。或者，银河场可能强大到足以将其方向强加给单个云团，从而调节云团的积累和碎裂，并影响恒星形成的速度和效率。我们在银河系盘中的位置使得对这种情况进行评估变得困难。在这里，我们报告了对附近、近乎正面的星系 M33 中六个巨大分子云复合体的磁场方向的观测结果。这些场与螺旋臂一致，表明 M33 中的大尺度场固定了云团。
