Gravity Group Seminar, Mark Kamionkowski (JHU), "Dust polarization and interstellar turbulence"

Fri, Sep 30, 2016, 12:00 pm to 1:30 pm
Joseph Henry Room

Perhaps the most surprising result from the Planck satellite is the observation that the E-mode power in the dust polarization is twice that in the B mode, in stark contrast to pre-Planck expectations of roughly equal dust powers in E and B modes. I will show how the E- and B-mode powers are determined by fluctuations in the magnetized interstellar medium, the slow, fast, and Alfv\'en magnetohydrodynamic (MHD) waves. I will argue that the observed E/B ratio, as well as the TE (temperature-polarization) cross-correlation (which is observed to be positive) are not easily reconciled with expectations for the spectrum of fluctuations expected in the models of MHD turbulence usually invoked to account for the fluctuations. I will then discuss some alternative explanations (including the possibility that the scales probed by Planck overlap the outer scale for interstellar turbulence) for the dust-emission patterns seen in the Planck temperature-polarization maps. I will then outline some interesting directions for future related research.