Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

velocity as given earlier in Table 2.1.
4.2.1 WFPC2 imaging: stars and dust
Each galaxy was observed during HST program GO-6673 using the Wide Field and
Planetary Camera - 2 (WFPC2) instrument (described in, e.g. Trauger, 1994; Biretta,
1996) on the Hubble Space Telescope. Observations and reduction are described by
Verdoes Kleijn et al. (1999) (and also in Appendix A of Verdoes Kleijn et al., 2002a,
for UGC 7115 and UGC 12064). Observations were obtained using wide band filters
approximating the V (F555W or F547M) and I (F814W or F791W) bands, along with
a narrow band image obtained using a linear ramp filter.
Verdoes Kleijn et al. (1999) fitted an elliptical contour to the outline of the dust
disk in each case to find the position angles of the dust disks, which were listed
earlier in Table 3.3. We assume that the gas and dust disks are coincident (this is
consistent with the observations of the dust and the narrow band Hα+ [N II]), and
that they coincide with the major axis of the galaxy and define the major plane. This
final assumption seems reasonable based on the position angles for the majority of
galaxies, however there are some cases where this may not be a fair assumption to
make about the disk as we see large differences in the dust and galaxy position angles
(e.g. NGC 3801, NGC 4374, NGC 5490 and UGC 7115). Inclinations for the dust
150