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R. Boomsma, J.M. van der Hulst (Kapteyn Astronomical Institute, Groningen, NL), T.A. Oosterloo (N.F.R.A, Dwingeloo, NL), R. Sancisi (Osservatorio Astronomico, Bologna, It and Kapteyn Astr. Inst., Groningen, NL)
The last few years have brought new insight into the disk-halo connection in spiral galaxies. Chandra and H{\sc i} observations of nearly edge-on galaxies have shown that the halo is far from empty, but it contains, compared to the disk, a substantial amount of gas. It is still unclear how exactly this gas is brought into the halo. Studies on face-on galaxies have provided more information about the vertical motions of the gas, but lack of sensitivity has lead to an incomplete observational basis. We re-observed the nearby face-on spiral galaxy NGC 6946 in which widespread high velocity H{\sc i} has already been detected. We present the first results of recently obtained H{\sc i} data taken with the upgraded Westerbork Synthesis Radio Telescope. Although so far only a subset of the total observations requested has been analysed, these data already go twice as deep as the earlier observations of NGC 6946. H{\sc i} with vertical velocities as high as 100 km/s appear at radii within the bright optical disk. This gas shows a filamentary structure and could well be the extragalactic counterpart of our Galaxy's IVCs. The disk consists of many holes of which one, having a radius of about 1-2 kpc, appears to be empty also in the radio continuum, IR and H\alpha. At the location of the hole no source has been detected. We discuss all these features we have found and outline what we expect to learn from them.
The author(s) of this abstract have provided an email address for comments about the abstract: boomsma@astro.rug.nl
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.