Abstract
By means of analyzing the distribution of galaxy axial ratios we determine the shapes of spiral and elliptical galaxies in the Sloan Digital Sky Survey Data Release 3, taking into account the effects of dust extinction and reddening. In order to do this we assume the underlying shapes of spirals and ellipticals to be well approximated by ellipsoids parametrized by two axial ratios. We find that the distribution of projected axial ratios of elliptical galaxies are well fitted by oblate spheroids, which become closer to spherical for brighter ellipticals. Our analysis shows that ellipticals are consistent with a negligible dust optical depth, since there is no dependence of shape on galaxy color or size. Variations in the axial ratio distributions of spiral galaxies indicate a strong presence of dust in the galactic disks, consistent with an edge-on extinction of E_0 = 1.2 magnitudes. The intrinsic shapes of spiral galaxies are consistent with flat disks (with a thickness of 25% the diameter of the disk). We find that the dust optical depth in spiral galaxies is larger for faint galaxies (absolute r > -19), with E_0 = 1.7, than for bright galaxies (absolute r < -22.5) for which E_0 = 0.2.