Kazuya MATSUBAYASHI
(Kyoto University)
The M82 "cap" is a gas cloud at a projected radius of 11.6 kpc along the minor axis of this well-known superwind source. The cap has been detected in optical line emission and X-ray emission and therefore provides an important probe of the wind energetics. In order to investigate the ionization source of the cap, we observed it with the Kyoto3DII Fabry-Perot instrument mounted on the Subaru Telescope. The superior spatial resolution compared to earlier studies reveals a number of bright Hα emitting clouds within the cap. The emission line widths (< 100 km/s FWHM) and line ratios in the newly identified knots are most reasonably explained by slow to moderate shocks velocities (v_shock = 40-80 km/s) driven by a fast wind into dense clouds. The momentum input from the M82 nuclear starburst region is enough to produce the observed shock.