Faint [OIV] emission from starburst galaxies

D. Lutz, D. Kunze, H.W.W. Spoon, M.D. Thornley

Abstract:

We report the detection of faint emission in the high-excitation [OIV] 25.90um line in a number of starburst galaxies, from observations obtained with the Short Wavelength Spectrometer (SWS) on board ISO. Further observations of M82 spatially resolve the [OIV] emitting region. Detection of this line in starbursts is surprising since it is not produced in measurable quantities in HII regions around hot main-sequence stars, the dominant energy source of starburst galaxies. We discuss various models for the formation of this line. [OIV] that is spatially resolved by ISO cannot originate in a weak AGN and must be due to very hot stars or ionizing shocks related to the starburst activity. For low-excitation starbursts like M82, shocks are the most plausible source of [OIV] emission.

Keywords: Galaxies: ISM - Galaxies: starburst - Infrared: galaxies

Status: to appear in Astronomy and Astrophysics (accepted)

Address: mailto: lutz@mpe.mpg.de

Full text (PostScript file)

Figure: [OIV] towards the southwest starburst lobe of M82

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