Dust lanes causing structure in the extended narrow-line region of early-type Seyfert galaxies

We construct near-infrared to visible broadband NICMOS/WFPC color maps for four early-type Seyfert galaxies with S-shaped or one-sided ionization cones. We find that dust lanes are near or connected to many of the features seen in the [O III] and H alpha + [N III] line emission maps. This suggests that much of the structure of line emission in these ionization cones is determined by the distribution of ambient dense galactic gas. Spiral arms, dust lanes caused by bars, or gaseous warps provide dense gas, which when illuminated by a conical beam of ultraviolet photons can result in the complicated line emission morphologies observed.