Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

eminiscent of rotation in 67% of the nuclei, in the remainder the non-detection can be
accounted for as the systems are either face on, have complex central morphologies (as
judged from the nuclear dust distribution) or, in the case of NGC 5490, particularly
poor signal to noise.
We find that the inclusion of an additional fit component with unconstrained
parameters improves our fit to the nuclear spectrum in 62% of the galaxies, where
it fits in every case as a broad component in the vicinity of Hα and [N II]. The
detection of the broad component is related to the line flux (and therefore the signal
to noise). The broad components have a mean velocity dispersion of 1349±345 km s −1
and are redshifted from the narrow line components (assuming an origin in Hα) by
486 ± 443 km s −1 .
The broad component could be a consequence of non-Gaussian line profiles with
broad wings, which would be biased toward the brightest [N II] line (redwards of
Hα). However, our more detailed analysis of line shape shows that it is very hard
to reproduce this effect by including broad (even asymmetric) wings on each line,
suggesting the broad component may indeed have a physical origin.
The measured Hα to [N II] ratios for the narrow components in the central spectra
are consistent with standard photo-ionization or shock-ionization models (for example,
Doptia et al., 1997) other than two examples where the lines are highly blended
and may be leading us to misleading fits in the very center.
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