We present a detailed study of a statistically complete sample of highly
inclined disk galaxies in the near-infrared K' band. Since the K'-band light is
relatively insensitive to contamination by galactic dust, we have been able to
follow the vertical light distributions all the way down to the galaxy planes.
The mean levels for the sharpness of the K'-band luminosity peaks indicate that
the vertical luminosity distributions are more peaked than expected for the
intermediate sech(z) distribution, but rounder than exponential. Since
projection of not completely edge-on galaxies onto the plane of the sky causes
vertical luminosity profiles to become rounder, we have performed simulations
that show that it is possible that all our galaxies can have intrinsically
exponential vertical surface brightness distributions. We find that the profile
shape is independent of galaxy type, and varies little with position along the
major axis. The fact that we observe this in all our sample galaxies indicates
that the formation process of the galaxy disks perpendicular to the galaxy
planes is a process intrinsic to the disks themselves.Comment: 23 pages, LaTeX, includes 12 figures, accepted for publication in
Astronomy and Astrophysics. Fig. 1 will be sent on reques