EDP Sciences
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Volume 426, Number 2, November I 2004
Page(s) 567 - 575
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20041176

A&A 426, 567-575 (2004)
DOI: 10.1051/0004-6361:20041176

The supernova remnant G 6.4-0.1 and its environment

F. Mavromatakis1, E. Xilouris2 and P. Boumis2

1  University of Crete, Physics Department, PO Box 2208, 71003 Heraklion, Crete, Greece
    e-mail: fotis@physics.uoc.gr
2  Institute of Astronomy & Astrophysics, National Observatory of Athens, I. Metaxa & V. Pavlou, P. Penteli, 15236 Athens, Greece

(Received 28 April 2004 / Accepted 12 July 2004)

Flux calibrated CCD images, in the H $\alpha+[$ $\ion{N}{ii}$ ], [ $\ion{S}{ii}$ ], and [ $\ion{O}{iii}$ ] emission lines, of a wide field around the supernova remnant G 6.4-0.1 are presented. The low ionization images identify a front of enhanced [ $\ion{S}{ii}$ ]/H $\alpha+[$ $\ion{N}{ii}$ ] ratio along the east-west direction. This front is very well correlated with the filamentary radio emission of the remnant as well as with molecular CO emission and may indicate the interaction of the primary blast wave with molecular clouds present in the vicinity of the remnant. We estimate a total H $\alpha$ flux, corrected for interstellar extinction, of 2 $\times$ 10 -8 erg s -1 cm -2, and a total [ $\ion{S}{ii}$ ] flux of 1.1 $\times$ 10 -8 erg s -1 cm -2. The H $\alpha+[$ $\ion{N}{ii}$ ] and [ $\ion{S}{ii}$ ] images provide evidence for the presence of emission from shock heated gas to the south-west and to the east of the bulk of the known optical emission, implying that the primary shock wave is able to drive radiative shocks into the interstellar clouds. The image in the medium ionization line of [ $\ion{O}{iii}$ ]5007 Å does not reveal any filamentary structures. On the contrary, the emission is diffuse and very weak, close to our detection limit of 5 $\times$ 10-17 erg s -1 cm -2 arcsec -2 (3 $\sigma$), and appears to be mainly present in the south-east to north-west areas of the remnant. The long-slit spectra indicate significant extinction in all positions observed, while the measured variations are within the 3 $\sigma$ error. The [ $\ion{O}{iii}$ ] emission in the spectra, whenever present, is weaker than the H $\beta$ flux suggesting shock velocities around 70 km s -1 or less all around the remnant in accordance with the [ $\ion{O}{iii}$ ] imagery. Thus, the low shock velocities are a common characteristic of G 6.4-0.1 and not just of the areas where the spectra were acquired. The average sulfur line ratio suggests postshock electron densities below 120 cm -3 at the 3 $\sigma$ limit.

Key words: ISM: general -- ISM: supernova remnants -- ISM: individual objects: G 6.4-0.1

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© ESO 2004