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Astron. Astrophys. 320, 378-394 (1997)

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ROSAT observations of the galactic wind in M 82

D.K. Strickland , T.J. Ponman and I.R. Stevens

School of Physics and Space Research, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK

Received 5 March 1996 / Accepted 22 July 1996


We present ROSAT PSPC and HRI observations of the galactic wind from the starburst galaxy M 82. X-ray emission from the wind is detected to a distance of [FORMULA] from the plane of the galaxy. Making use of the PSPC's mixture of good spatial and spectral characteristics, we separate point source and diffuse emission, and investigate the spectral variation of the diffuse emission through the wind. The intrinsic X-ray luminosity of the wind in the [FORMULA] band is found to be approximately [FORMULA] outside the immediate vicinity of the nucleus. The temperature of the diffuse emission is found to decrease weakly from [FORMULA] to [FORMULA] along the minor axis, whilst the inferred gas density drops as [FORMULA] and [FORMULA] along the northern and southern minor axes respectively. We compare these results with those expected from two simple models for the emission: Chevalier & Clegg's adiabatically expanding free wind and emission from shocked clouds in a wind, and find that the emission cannot come from a free wind, but that shock heated clouds could be the source of the emission.

Key words: galaxies: individual: M 82 – galaxies: starburst – galaxies: ISM-galaxies: halos – X-rays: galaxies

Send offprint requests to: D.K. Strickland

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© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998