Rachel Harrison

Dust Polarization Up Close and Personal in a Planet-Forming Disk

We present high-resolution ALMA observations of polarized emission in the protoplanetary disk HD 97048 at 870 $\mu$m. A previous study of gas kinematics in HD 97048 found evidence of a Jupiter-mass planet located between two dust rings. Constraining the dust grain properties in this disk therefore gives us insight into dust evolution at the time of planet formation. We observed polarized emission consistent with scattering (i.e., the scattering of thermal emission from dust grains by other dust grains) in the disk. The polarization fraction and angle are correlated with the disk’s ring and gap substructure. The polarization fraction is higher in the gap and inner cavity than in the first ring, and the polarization angles are more azimuthally oriented in the gap while the polarization angle in the first ring is more parallel to the disk’s minor axis. These changes in polarization fraction and angle are expected to arise from variations in optical depth and the direction of the radiation anisotropy within the disk. We model the expected polarization in this disk for dust grain populations with varying sizes and porosities, and discuss the implications for dust evolution this planet-forming disk.