标题： 光学和亚毫米波段对博克球状体的观测——从低密度到高密度追踪磁场 显示英文标题

标题： Optical and submillimetre observations of Bok globules -- tracing the magnetic field from low to high density

摘要： 我们展示了Bok球状云CB3的光学和亚毫米偏振数据以及Bok球状云CB246的光学偏振数据。 我们使用每组偏振数据来推断每个云中的磁场方向。 光学数据只能用于云的低密度、低消光边缘区域。 亚毫米数据只能用于云的高柱密度、中心区域。 此前已发现，背景恒星的近红外偏振绘图不能准确追踪密集云区的磁场。 这可能是由于密集区域缺乏排列整齐的颗粒。 我们通过比较两种独立偏振方法测量的场向来测试这一点。 我们发现，从光学数据推断出的场向与从亚毫米数据估计出的方向很好地吻合。 因此，我们声称这两种方法都在CB3中准确地追踪相同的磁场。 因此，在这种情况下，高密度区域必须存在大量排列整齐的尘埃颗粒，并且它们确实追踪了亚毫米区域的磁场。 我们发现，磁场方向与球状云短轴之间的偏移量为40$\pm$14度。 这与我们在前期关于原恒星核的工作中发现的平均值31$\pm$3度一致，尽管CB3是一个原恒星核。 综合来看，我们已经用这种方法研究的六个原恒星核显示，磁场方向与核短轴之间的平均偏移量为$\sim30\pm$3度，这似乎与某些磁主导恒星形成模型相矛盾。 显示英文摘要

摘要： We present optical and submillimetre polarimetry data of the Bok globule CB3 and optical polarimetry data of the Bok globule CB246. We use each set of polarimetry data to infer the B-field orientation in each of the clouds. The optical data can only be used in the low density, low extinction edge regions of clouds. The submillimetre data can only be used in the high column-density, central regions of the clouds. It has previously been found that near-infrared polarisation mapping of background stars does not accurately trace the magnetic field in dense cloud regions. This may be due to a lack of aligned grains in dense regions. We test this by comparing the field orientations measured by our two independent polarimetry methods. We find that the field orientation deduced from the optical data matches up well with the orientation estimated from the submillimetre data. We therefore claim that both methods are accurately tracing the same magnetic field in CB3. Hence, in this case, there must be significant numbers of aligned dust grains in the high density region, and they do indeed trace the magnetic field in the submillimetre. We find an offset of 40$\pm$14 degrees between the magnetic field orientation and the short axis of the globule. This is consistent with the mean value of 31$\pm$3 degrees found in our previous work on prestellar cores, even though CB3 is a protostellar core. Taken together, the six prestellar cores that we have now studied in this way show a mean offset between magnetic field orientation and core short axis of $\sim30\pm$3 degrees, in apparent contradiction with some models of magnetically dominated star formation.