THE IDENTIFICATION OF BALMER-DOMINATED FILAMENTS IN RCW-86

We have identified faint optical filaments in the supernova remnant RCW 86 which emit primarily in Hα in the wavelength range 6250-7450 Å, unlike the brighter radiative filaments that have been reported previously. The new filaments are similar to the nonradiative filaments seen in other supernova remnants which are thought to arise from fast shock waves interacting with partially neutral interstellar matter. Spectra of these filaments show the Hα lines to have two components; the widths of the broad components are consistent with a shock speed in RCW 86 of 500-930 km s-1. These shocks have sufficient velocity to produce the X-ray emission observed in RCW 86 and are likely to be associated with the primary blast wave.