Astron. Astrophys. 320, 731-745 (1997)

Evidence for a New "Superwind" Galaxy - NGC 4666

Michael Dahlem ^{* 1}, Monika G. Petr ², Matthew D. Lehnert ^{** 3, 4}, Timothy M. Heckman ⁵ and Matthias Ehle <sup>6

1</sup> Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
² Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
³ Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands
⁴ Institute for Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, P. O. Box 808, L-413, Livermore, CA 94551-9900, USA
⁵ Johns Hopkins University, Department of Physics and Astronomy, 3400 N. Charles Street, Baltimore, MD 21218-2695, USA
⁶ ATNF/CSIRO, P.O. Box 76, Epping, NSW 2121, Australia

Received 18 April 1996 / Accepted 5 September 1996

Abstract

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 6.5 kpc. The outflow is traced up to 7.5 kpc 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 6.5 kpc base (the extent of the central starburst) plus a cone with an opening angle of .

In the outer disk of NGC 4666 numerous luminous H II 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 1.43 GHz of kpc. NGC 4666 is in many respects very similar to NGC 4631, another edge-on galaxy with an extended gaseous halo.

Key words: galaxies: NGC 4666 galaxies: ISM galaxies: magnetic fields galaxies: starburst radio continuum: galaxies

* Affiliated with the Astrophysics Division in the Space Science Department of ESA; present address: ESTEC, Astrophysics Division, Postbus 299, 2200 AG Noordwijk, The Netherlands
** Visiting Astronomer, Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation

Send offprint requests to: MD, mdahlem@astro.estec.esa.nl

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998

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