Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

NGC 5141: This S0 galaxy has a nuclear dust lane. The STIS slits were aligned
parallel to the galaxy major axis, 16 ◦ from the dust axis. The weighted mean obser-
vation - model residuals are plotted in Figure 4.14 and gives a minimum at an offset
of −50 km s −1 , equivalent to a galaxy recessional velocity of 5253 km s −1 . The model
velocity profiles for these observations are shown in Figure 4.37. The gas velocities
are very well settled into a smooth rotation curve, however no nuclear black hole is
necessary to explain the observed kinematics.
NGC 5490: This elliptical galaxy has a nuclear dust lane. The STIS slits were
aligned parallel to the galaxy major axis, 43 ◦ from the dust disk axis. The weighted
mean observation - model residuals are plotted in Figure 4.15 and gives a minimum
at an offset of −93 km s −1 , equivalent to a galaxy recessional velocity of 5697 km s −1 .
The model velocity profiles for these observations are shown in Figure 4.38. It is not
clear that the modeled velocity profiles match any of the observed kinematics in the
nuclear region. The fact that the dust disk and galaxy major axis are not coincident
by a sizeable angle also means that it is not clear what plane the gas will lie in, images
of the emission line disks (Verdoes Kleijn et al., 1999) do not make this any clearer.
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