Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

as face on disks are approached; the observed velocity difference is smaller, which is
as we would expect. The face on disks do not, however, sit at a value of ∆100 = 0,
indicating that there may be motions perpendicular to the plane of the disk across
the nuclei of these galaxies (for example precession of the disk), which may indicate
they are not settled into the major plane of the galaxy. However, we cannot rule
out the possibility that they are simply amongst the fastest rotators in the sample
– the small number statistics do not present strong constraints. Lines are indicated
where we approximately project the ‘intrinsic’ ∆int through inclination using the
relationship:
�
�
�
�
∆obs ≈ ∆int sin i ≈ ∆int × 1 −
239
� �2 b
, (5.7)
a
Two outliers are labeled in the figure: NGC 383 and UGC 7115 which, despite
being fairly face on, have large values of ∆100. In the case of NGC 383 it seems
that the observed rotation is compatible with the fastest rotating sample members
that are viewed edge on. Those fastest edge-on galaxies are NGC 4486 and M84,
which are both nearby so that ∆100 includes a great deal more of the resolved central
velocities, which makes comparisons with other galaxies less meaningful, and thus
leaves NGC 383 as an outlier. The large values of ∆100 may be an indicator that the
gas in these two galaxies is indeed rotating very fast, that there are gas systems present
that are very poorly described by the thin disk model, or that the dust distribution