First Observation of the Submillimeter Polarization Spectrum in a Translucent Molecular Cloud

Peter C. Ashton, Peter A.R. Ade, Francesco E. Angil, Steven J. Benton, Mark J. Devlin, Bradley Dober, Laura M. Fissel, Yasuo Fukui, Nicholas Galitzki, Natalie N. Gandilo, Jeffrey Klein, Andrei L. Korotkov, Zhi Yun Li, Peter G. Martin, Tristan G. Matthews, Lorenzo Moncelsi, Fumitaka Nakamura, Calvin B. Netterfield, Giles Novak, Enzo PascaleFrédérick Poidevin, Fabio P. Santos, Giorgio Savini, Douglas Scott, Jamil A. Shariff, Juan D. Soler, Nicholas E. Thomas, Carole E. Tucker, Gregory S. Tucker, Derek Ward-Thompson

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Polarized emission from aligned dust is a crucial tool for studies of magnetism in the ISM, but a troublesome contaminant for studies of cosmic microwave background polarization. In each case, an understanding of the significance of the polarization signal requires well-calibrated physical models of dust grains. Despite decades of progress in theory and observation, polarized dust models remain largely underconstrained. During its 2012 flight, the balloon-borne telescope BLASTPol obtained simultaneous broadband polarimetric maps of a translucent molecular cloud at 250, 350, and 500 μm. Combining these data with polarimetry from the Planck 850 μm band, we have produced a submillimeter polarization spectrum, the first for a cloud of this type. We find the polarization degree to be largely constant across the four bands. This result introduces a new observable with the potential to place strong empirical constraints on ISM dust polarization models in a previously inaccessible density regime. Compared to models by Draine & Fraisse, our result disfavors two of their models for which all polarization arises due only to aligned silicate grains. By creating simple models for polarized emission in a translucent cloud, we verify that extinction within the cloud should have only a small effect on the polarization spectrum shape, compared to the diffuse ISM. Thus, we expect the measured polarization spectrum to be a valid check on diffuse ISM dust models. The general flatness of the observed polarization spectrum suggests a challenge to models where temperature and alignment degree are strongly correlated across major dust components.

Original languageEnglish (US)
Article number10
JournalAstrophysical Journal
Volume857
Issue number1
DOIs
StatePublished - Apr 10 2018

Keywords

  • ISM: clouds
  • dust, extinction
  • instrumentation: polarimeters
  • polarization
  • submillimeter: ISM
  • techniques: polarimetric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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