Volume 431, Number 1, February III 2005
|Page(s)||65 - 72|
|Published online||02 February 2005|
Extra-planar H I in the starburst galaxy NGC 253
Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands e-mail: firstname.lastname@example.org
2 ASTRON, Dwingeloo, The Netherlands
3 Theoretical Physics, University of Oxford, UK
4 INAF - Osservatorio Astronomico di Bologna, Bologna, Italy
Accepted: 23 September 2004
Observations of the nearby starburst galaxy NGC 253 in the 21-cm line reveal the presence of neutral hydrogen in the halo, up to 12 kpc from the galactic plane. This extra-planar H i is found in only one half of the galaxy and is concentrated in a half-ring structure and plumes which are lagging in rotation with respect to the disk. The H i plumes are seen bordering the bright Hα and X-ray halo emission. It is likely that, as proposed earlier for the Hα and the X-rays, the origin of the extra-planar H i is also related to the central starburst and to the active star formation in the disk. A minor merger and gas accretion are also discussed as possible explanations. The H i disk is less extended than the stellar disk. This may be the result of ionization of its outer parts or, alternatively, of tidal or ram pressure stripping.
Key words: galaxies: individual: NGC 253 / galaxies: ISM / galaxies: halos / galaxies: structure
© ESO, 2005
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