Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

We find that in 67% of the nuclei the gas appears to be rotating and, with one
exception, the cases where rotation is not seen are either face on or have complex
central morphologies. We find that in 62% of the nuclei the fit to the central spectrum
is improved by the inclusion of a broad component. 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 chapter is organized as follows. In section 2 we describe the sample and in
section 3 we describe the STIS spectroscopic observations and the data reduction. In
section 4 we describe our analysis procedures. We present our initial interpretations
in section 5 and draw conclusions in section 6. We use a Hubble constant of H0 =
50km s −1 Mpc −1 throughout.
3.2 STIS Observations
In program 8236 we used HST/STIS (see Kimble, et al., 1998) to take spectra of the
19 sample members not previously or concurrently observed by others. Observations
were carried out at both medium (for 19/19 galaxies) and low (for 4/19 galaxies) res-
olution, with the G750M and the G430L and G750L gratings respectively. Our medium
resolution observation log is shown in Table 3.1. We will present the low resolution
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