ALMA's Polarized View of 10 Protostars in the Perseus Molecular Cloud

作者：Cox Erin G^*; Harris Robert J; Looney Leslie W; Li Zhi Yun; Yang Haifeng; Tobin John J; Stephens Ian

来源：Astrophysical Journal, 2018, 855(2): 92.

DOI：10.3847/1538-4357/aaacd2

• ISM: magnetic fields
• polarization
• stars: formation
• stars: protostars

We present 870 mu m ALMA dust polarization observations of 10 young Class 0/I protostars in the Perseus Molecular Cloud. At similar to 0.'' 35. (80 au) resolution, all of our sources show some degree of polarization, with most (9/10) showing significantly extended emission in the polarized continuum. Each source has incredibly intricate polarization signatures. In particular, all three disk-candidates have polarization vectors roughly along the minor axis, which is indicative of polarization produced by dust scattering. On similar to 100 au scales, the polarization is at a relatively low level (less than or similar to 1%) and is quite ordered. In sources with significant envelope emission, the envelope is typically polarized at a much higher (less than or similar to 5%) level and has a far more disordered morphology. We compute the cumulative probability distributions for both the small (disk-scale) and large (envelope-scale) polarization percentage. We find that the two are intrinsically different, even after accounting for the different detection thresholds in the high/low surface brightness regions. We perform Kolmogorov-Smirnov and Anderson-Darling tests on the distributions of angle offsets of the polarization from the outflow axis. We find disk-candidate sources are different from the non-disk-candidate sources. We conclude that the polarization on the 100 au scale is consistent with the signature of dust scattering for disk-candidates and that the polarization on the envelope-scale in all sources may come from another mechanism, most likely magnetically aligned grains.

• 出版日期2018-3-10