(Proposal ID) S14A-082

(PI) Ueta Toshiya

(Proposal Title)
 Spectropolarimetric Dust Kinematic Measurements in the Circumstellar Shells

(Abstract)
We propose a pilot study of measuring velocities of dust grains in dusty 
stellar outflows of a Wolf-Rayet star, HD 56925, and a planetary nebula, 
NGC 6543, by adopting the spectropolarimetric technique as has been used to 
investigate dusty outflows from a starburst galaxy, M82. Dust grains flowing 
in stellar winds scatter line emission emanating from the central star in a 
particular scattering angle with respect to the observer. Hence, such line 
emission is singly scattered, and thus, linearly polarized. On the contrary, 
both intrinsic line emission from the local gas component and diffuse line 
emission permeating through the ambient circumstellar matter after many 
scattering are unpolarized. Therefore, the polarized line emission reveals 
the dust grain velocities, because these polarized lines are Doppler-shifted 
according to the outflow speed of the local dust grains. We will thus directly 
measure v_dust at various locations within the target nebulae. In the ALMA 
era, the circumstellar velocity structure of the molecular gas component v_gas 
will be probed extensively. Our study will pave the way, for the first time, 
for providing the matching velocity information for the dust component as 
observational constraints to be compared against theoretical considerations of 
dust-driven wind models.