R.A. Jansen, J.H. Knapen, J.E. Beckman (I.A.C., La Laguna, Tenerife), R.F. Peletier and R. Hes have studied the extinction properties of dust in the well-defined dust lanes of four highly inclined galaxies using U, B, V, R and I band CCD and J and K' band Near-Infrared array images. For three of these galaxies, they have used the symmetry of the underlying light profile to obtain absolute extinction values in the dust lanes. Maximum values for the dust extinction near the centre of the galaxies range between 2 and 3 magnitudes in B.
They have studied the extinction law in these three galaxies by investigating the extinction ratios A / A_V . Assuming that the dust is uniformly mixed with the stars they find good agreement with the extinction law in our Galaxy and in the Sombrero galaxy (NGC 4594). They can discard a model of a screen of dust, thus eliminating the possibility that the scale-length of the dust is larger than that of the stellar population. The measured extinction values decrease rapidly with radius when going outward.