(Proposal ID) S17B-068

(PI) Katsuda, Satoru

(Proposal Title)
Measuring a Polarization of H alpha Line Emission in Tycho's Supernova Remnant

(Abstract)
Recent discovery of linearly-polarized line emission from a Balmer-dominated 
shock in the northwestern SN 1006 remnant (Sparks et al.2015, ApJL, 815, L9) 
stimulated us to propose to observe another very interesting Balmer-dominated 
shock in the eastern limb of Tycho's supernova remnant. The polarization degree
in SN 1006 was measured to be ~2%, consistent with an expectation due to highly
anisotropic impacts of energetic protons and electrons behind a collisionless 
shock (Laming 1990, ApJ, 362, 219).  By noting that Tycho's eastern limb is 
likely a more efficient cosmic-ray accelerator than the northwestern SN 1006, 
we expect a higher polarization degree for the former than the latter. 
Specifically, our preliminary cosmic-ray modified shock model predicts a twice 
higher polarization degree for Tycho than SN 1006. By this new pioneering 
approach, we will reveal if Tycho's knot g is really such a highly efficient 
CR accelerator independently from other preceding works.