  Using detailed Monte Carlo radiative transfer simulations in realistic models
for galactic nuclei, we investigate the influence of interstellar dust in
ionized gas discs on the rotation curves and the resulting black hole mass
measurements. We find that absorption and scattering by interstellar dust
leaves the shape of the rotation curves basically unaltered, but slightly
decreases the central slope of the rotation curves. As a result, the "observed"
black hole masses are systematically underestimated by some 10 to 20% for
realistic optical depths. We therefore argue that the systematic effect of dust
attenuation should be taken into account when estimating SMBH masses using
ionized gas kinematics.
