THE DISCOVERY OF BALMER-FILAMENTS ENCIRCLING SNR RCW-86

We report the discovery of Balmer-dominated filaments along almost the complete periphery of the supernova remnant RCW 86 (also known as G 3 15.2-2.3 or MSH 14-63). Using the UM/CTIO Curtis Schmidt telescope, we obtained deep CCD images in the emission of H alpha and [S II], toget her with continuum images to remove stellar confusion, After continuum subtraction, we discovered a network of H alpha filaments reaching al most completely around the remnant. Most of the newly identified filam ents show no corresponding [S II] emission, indicating that they belon g to the peculiar ''Balmer-dominated'' class of filaments. Comparison of these Balmer filaments with existing radio and X-ray images of RCW 86 shows an overall similarity, although interesting differences are a pparent upon detailed inspection. While further observations of these newly identified optical filaments may eventually provide more detaile d information on the kinematics and distance to RCW 86, the distance c urrently remains uncertain. We argue that the shorter distance estimat es of similar to 1 kpc are still favored. (C) 1997 The American Astron omical Society.