The peculiar supernova remnant CTB 80

Deep CCD exposures of the peculiar supernova remnant CTB 80 in the light of the H +( Nii), (S ii), (O ii), and (O iii) lters have been obtained. These images reveal signicant shock heated emission in the area of the remnant. An extended bright diuse nebula in the south{east part of CTB 80 overlaps soft X-ray emission from ROSAT but it does not appear to be related to the remnant under study. New diuse and lamentary structures are detected to the south, south{east, and north of PSR 1951+32, most likely associated with CTB 80. Especially, the sulfur line image shows emission in the north along the outer boundary of the IRAS and HI shells. The (O iii) emission is lamentary, suggesting shock velocities greater than 100 km s 1 but its spatial extent is quite limited. Lower shock velocities are expected in the north and north{east areas of the remnant, since (O ii) emission is present, while (O iii) line emission is not detected. The comparison between the (O iii )a nd (Oii) line images further suggest the presence of signicant inhomogeneities in the interstellar medium. The flux{calibrated images do not indicate the presence of incomplete recombination zones, and we estimate that the densities of the preshock clouds should not exceed a few atoms per cm 3 . The typical projected angular widths of the observed laments are30 00 . Typical surface brightness values of the long (O iii) lament in the south are12 10 17 erg s 1 cm 2 arcsec 2 while the (O ii) image is characterized by fluxes of 10{20 10 17 erg s 1 cm 2 arcsec 2 . The area covered by the optical radiation along with the radio emission at 1410 MHz suggest that CTB 80 occupies a larger angular extent than was previously known.