First optical detection of the supernova remnant G 15.1-1.6

Abstract

Deep optical CCD images of the supernova remnant G 15.1-1.6 were obtained where filamentary and diffuse emission was discovered. The images, taken in the emission lines of H, [S ii], and , reveal filamentary and diffuse structures all around the remnant. The radio emission at 4850 MHz in the same area is found to be strongly correlated with the brightest optical filaments. The IRAS 60 m emission may also be correlated with the optical emission but to a lesser extent. The flux-calibrated images suggest that the optical emission originates from shock-heated gas ([S ii]/Hα ∼ 0.4), while there is a possible region ([S ii]/Hα ∼ 0.3) contaminating the supernova remnant's emission to the east. Furthermore, deep long-slit spectra were taken at two bright filaments and also show that the emission originates from shock-heated gas. An filamentary structure is also detected farther to the west, but it lies outside the remnant's boundaries and may not be associated to it. The flux suggests shock velocities into the interstellar clouds" ~100 km s -1, while the [S II 6716/6731 ratio indicates electron densities up to ∼ 250 cm. Finally, the Hα emission is measured to be between 2 to s-1 cm-2 arcsec-2, while the lower limit to the distance is estimated at 2.2 kpc. © 2008 ESO.