Wobbly discs -- corrugations seen in the dust lanes of edge-on galaxies
  We report the detection of small scale bending waves, also known as
corrugations, in the dust lanes of five nearby edge-on disc galaxies. This
phenomenon, where the disc mid-plane bends to become wavy, just as in warps but
on a smaller scale, is seen here for the first time, in the dust lanes running
across the discs. Because they are seen in absorption, this feature must be
present in the dust disc in the outskirts of these galaxies. We enhance the
visibility of these features using unsharp masking, trace the dust mid-plane
across the disc, measure the corrugation amplitude by eye and the corrugation
wavelength using Fourier analysis. The corrugation amplitude is found to be in
the range of 70 - 200 pc and the wavelengths lie between 1 - 5 kpc. In this
limited sample, we find that the amplitude of the corrugations tends to be
larger for lower mass galaxies, whereas the wavelength of corrugation does not
seem to depend on the mass of host galaxies. Linear stability analysis is
performed to find out the dynamical state of these dust discs. Based on WKB
analysis, we find that the dust corrugations in about half of our sample are
stable. Further analysis, on a larger sample would be useful to strengthen the
above results.
