University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Friday, September 25th 2015
2:30 pm:
Speaker: Laura Fissel, U Toronto
Subject: Mapping Magnetic Fields in Star Forming Regions with BLASTPol

A key outstanding question in our understanding of star formation is whether magnetic fields provide support against the gravitational collapse of their parent molecular clouds and cores. While direct measurements of magnetic field strength are challenging, observations of polarized thermal emission from dust grains aligned with respect to the local magnetic field can be used to map out the cloud magnetic field. In this talk I present early results from a BLASTPol, a sensitive balloon-borne polarimeter. BLASTPol observed the Vela C cloud during a 2012 Antarctic flight, yielding the most detailed submillimeter polarization map ever made of a molecular cloud forming high mass stars. Statistical comparisons between submillimeter polarization maps and 3-D numerical simulations of magnetized star-forming clouds are a promising method for constraining magnetic field strength, but uncertainty concerning how the dust polarizing efficiency varies as a function of density and other cloud parameters can make such comparisons difficult. Previous work suggests that this uncertainty can be reduced by studying the dependence of observed polarization fraction (p) on column density (N). In Vela C, I find that most of the structure in p can be modeled by a power-law dependence on two quantities: The first is N and the second is the local dispersion in polarization angle (S). This empirical model for p(N,S) provides new constraints for models of magnetized star-forming clouds and an important first step in the interpretation of the BLASTPol 2012 data set. Finally, I discuss a “next-generation” BLAST polarimeter, which is scheduled for a first Antarctic flight in late 2016. BLAST-TNG will have an order of magnitude increase in both spatial resolution and mapping speed and will map dozens of star-forming regions, placing important constraints on the role magnetic fields play in regulating star formation.

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