Polarized Infrared Emission from Polycyclic Aromatic Hydrocarbons and Implications

Polarized mid-infrared emission from polycyclic aromatic hydrocarbons (PAHs) can provide a crucial test of basic physics of alignment of nanoparticles and opens a potential new window into studying magnetic fields. In this talk, I will present a new model of polarized PAH emission that takes into account the effect of PAH alignment with the magnetic field due to resonance paramagnetic relaxation. I will then present our predictions for the polarization level of the strong PAH emission features from the interstellar medium. I will present the first detection of polarization of PAH emission at 11.3micron which is consistent with our theoretical prediction. Finally, I will discuss important implications of this work for tracing magnetic fields via mid-IR PAH features and for constraining the polarization of anomalous microwave emission that is useful for the quest of CMB B-modes.