Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

Barth et al. (1999) found polarized Hα broad line emission in the nucleus of
NGC 315, and fit a profile of FWHM 3200 km s −1 in polarized light. This gives
σBL ∼ 1400 km s −1 which is certainly compatible with our earlier measurement of
1790 km s −1 where the errors were likely to be large. They also made observations
of NGC 4261, but were unable to readily separate a broad component; this matches
our findings shown in Table 3.27 that the broad line in NGC 4261 was a less strong
detection than the one in NGC 315.
Barth, et al.’s findings suggests that at least some of the broad emission we see
originates in physical broad-line regions. The broad emission comes from systems
closest to the central engine, as expected from the AGN unified model paradigm
(Urry & Padovani, 1995). The two primary sources to drive the broad line width are
therefore the gravitational potential in the central region (which is dominated by M•
in this regime) and the activity of the central engine (which is dominated by ˙ M). We
will revisit this issue later.
For the 11 galaxies where we were able to detect a broad component we measured
the kinematic properties of the Broad and Narrow lines, these were presented in
Table 3.28. Cross-correlating the velocity dispersions of these lines with the central
stellar velocity dispersion (σc) we find that neither the narrow nor broad component
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