EDP Sciences
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Volume 396, Number 1, December II 2002
Page(s) 225 - 234
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20021365

A&A 396, 225-234 (2002)
DOI: 10.1051/0004-6361:20021365

New optical filamentary structures in Pegasus

P. Boumis1, F. Mavromatakis1, E. V. Paleologou1 and W. Becker2

1  University of Crete, Physics Department, PO Box 2208, 710 03 Heraklion, Crete, Greece
2  Max-Planck Institut für extraterrestrische Physik, Giessenbachstrasse, 85740 Garching, Germany

(Received 1 July 2002 / Accepted 10 September 2002 )

Deep H $\alpha$+[N II] CCD images have been obtained in the area of the Pegasus Constellation. The resulting mosaic covers an extent of ~ $7\fdg 5\times~8\fdg 5$ and filamentary and diffuse emission was discovered. Several long filaments (up to ~1°) are found within the field, while diffuse emission is present mainly in the central and northern areas. The filaments show variations in intensity along their extent suggesting inhomogeneous interstellar clouds. Faint soft X-ray emission was 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 were 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 H $\alpha$ emission lies in the range of $1.1 {-} 8.8 \times 10^{-17}$ erg s -1 cm -2 arcsec -2. The detected optical line emission could be part of a single or multiple supernova explosions.

Key words: ISM: general -- ISM: supernova remnants -- ISM: individual objects: Pegasus

Offprint request: P. Boumis, ptb@astro.noa.gr

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