Understanding Magnetic Fields in the Milky Way Galaxy and in Star Forming Clouds

Trustees Of Boston University, Boston

Investigators

Abstract

The magnetic field that threads through the gas and dust in the Milky Way Galaxy has been mapped by the awardees using their own instrument, Mimir. Mimir was built over a decade ago with support from NSF, NASA, and the W.M. Keck Foundation. Mimir measures the polarization of infrared light produced by the dust in the Milky Way. Most of the dust (and gas) is found in large clouds that drift through space. These clouds collapse under their own weight to form new stars. Careful analysis of the polarized light from these dusty clouds teaches us about the magnetic fields that control the shapes and sizes of each cloud. The magnetic fields also affect the way the clouds collapse to make stars. Much of the data has already been collected. The awardees now need funding to support the careful examination of the data. The data will be used, together with observations from other telescopes such as the Stratospheric Observatory for Infrared Astronomy (SOFIA) and NSF's Atacama Large Millimeter Array (ALMA), to test models of Milky Way clouds and star formation. Students from Boston University will be trained on how to take the Mimir data and examine the polarimetry results. A graduate student will use Mimir, SOFIA and ALMA data to complete their PhD project. Undergraduate students (including many who are not majoring in astronomy) will be brought to Arizona to operate Mimir on the Perkins telescope. These telescope trips often inspire students to follow careers in science. Other students will participate in the observing by videoconference. The team will also pursue outreach opportunities at the Boston Museum of Science, where the Department of Astronomy at Boston University holds weekly open nights. Mimir is being used by the awardees to survey the magnetic field structure along the galactic plane and in various star forming regions via background starlight polarization measurements in the near-infrared H-band. Their survey, dubbed the Galactic Plane Infrared Polarization Survey (GPIPS), covers 76 square degrees of the inner disk and probes up to 20 magnitudes of extinction. Complementary mid-IR polarization measurements are used to probe star forming clouds up to 50 magnitudes of extinction. Various well-known techniques (Zeeman splitting, the Davis-Chandrasekhar-Fermi method, etc.) will be used on these and complementary archival data to infer field strengths and orientations across the surveyed areas. Analysis of these data will provide quantitative tests of models of galactic B-fields and constrain theories of star formation in dense molecular clouds. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.