1997A&A...320..731D

Multi-wavelength observations of the edge-on galaxy NGC 4666 have led to the detection of an outflow cone associated with a galactic superwind, emanating from a central starburst with a radial diameter of about 6.5kpc. The outflow is traced up to 7.5kpc above the plane by optical emission line filaments, nonthermal radio continuum emission, associated magnetic fields perpendicular to the galactic plane, and soft X-ray emission from hot gas. Optical spectroscopy exhibits the kinematic signature of an outflow and the observed line ratios indicate that shock heating is the most likely excitation mechanism for the emission line gas. The outflow is well approximated by a 6.5kpc base (the extent of the central starburst) plus a cone with an opening angle of 30°±10°. In the outer disk of NGC 4666 numerous luminous HII regions were detected, which lead to additional outflows (galactic fountains or chimneys) of gas into the halo. Radially the radio halo is much more extended than the central outflow cone and it has an exponential z-scale height at 1.43GHz of 1.7±0.28kpc. NGC 4666 is in many respects very similar to NGC 4631, another edge-on galaxy with an extended gaseous halo.