  Edge-on spiral galaxies offer a unique perspective on disks. One can
accurately determine the height distribution of stars and ISM and the
line-of-sight integration allows for the study of faint structures. The Spitzer
IRAC camera is an ideal instrument to study both the ISM and stellar structure
in nearby galaxies; two of its channels trace the old stellar disk with little
extinction and the 8 micron channel is dominated by the smallest dust grains
(Polycyclic Aromatic Hydrocarbons, PAHs). Dalcanton et al. (2004) probed the
link between the appearance of dust lanes and the disk stability. In a sample
of bulge-less disks they show how in massive disks the ISM collapses into the
characteristic thin dust lane. Less massive disks are gravitationally stable
and their dust morphology is fractured. The transition occurs at 120 km/s for
bulgeless disks. Here we report on our results of our Spitzer/IRAC survey of
nearby edge-on spirals and its first results on the NIR Tully-Fischer relation,
and ISM disk stability.
