Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

where the gas appears to be in a smooth, well ordered velocity profile. Considering
that we have found unsettled motions to play such a significant role in many nuclei,
we should probably question the safety of these assumptions. We may very well be
missing a lot of the unsettled motions in these galaxies, for example inflow or outflow
could produce effects resembling (or canceling out) rotation and, at a minimum, the
consequences of flow in model velocity profiles should be investigated.
The two galaxies in our own sample for which the gas appears to be well settled,
NGC 4335 and NGC 5141, appear to require ‘no black hole’ to explain the central
kinematics (no black hole here implies a M• < 1 × 10 8 M⊙). However, these galaxies
are not particularly unusual in their other properties, so how they would contrive to
have a smaller than usual black hole, yet still have nuclear and large scale properties
(e.g. the production of radio jets, typical velocity dispersions, etc...) comparable to
other radio galaxies is somewhat questionable. I feel that it is somewhat more likely
that the black hole is of a more typical size, and that we do not observe the full
kinematic signature as it is softened by the effects of flow in the gas. This conceivably
hints that if regular flow can be set up then other motions can be dissipated more
quickly resulting in velocity profiles that appear smother, though hydrodynamical
models would be required to test that possibility.
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