New optical filamentary structures in Pegasus

Abstract

Deep Halpha+[N II] CCD images have been obtained in the area of the Pegasus Constellation. The resulting mosaic covers an extent of ~7.5 degr x ~8.5 degr and filamentary and diffuse emission is discovered. Several long filaments (up to ~1 degr) are found within the field, while diffuse emission is present mainly in the central and northern areas. The filaments show variations in the intensity along their extent suggesting inhomogeneous interstellar clouds. Faint soft X-ray emission is also detected in the ROSAT All-Sky Survey. It is mainly concentrated in the central areas of our field and overlaps the optical emission. The low ionization images of [S II] of selected areas mainly show faint diffuse emission, while in the medium ionization images of [O III] diffuse and faint filamentary structures are present. Spectrophotometric observations have been performed on the brightest filaments and indicate emission from photoionized or shock-heated gas. The sulfur line ratios indicate electron densities below ~600 cm^{-3}, while the absolute Halpha emission lies in the range of 1.1 - 8.8 x 10^{-17} erg s^{-1} cm^{-2} arcsec^{-2}. The detected optical line emission could be part of a single or multiple supernova explosions.