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

Erin G. Cox, Robert J. Harris, Leslie W. Looney, Zhi Yun Li, Haifeng Yang, John J. Tobin, Ian Stephens

Research output: Contribution to journalArticlepeer-review


We present 870 μm ALMA dust polarization observations of 10 young Class 0/I protostars in the Perseus Molecular Cloud. At ∼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 ∼100 au scales, the polarization is at a relatively low level (≲1%) and is quite ordered. In sources with significant envelope emission, the envelope is typically polarized at a much higher (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.

Original languageEnglish (US)
Article number92
JournalAstrophysical Journal
Issue number2
StatePublished - Mar 10 2018


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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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