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Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

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lack hole on these mass scales, but that the actual mass may vary considerably from<br />

any attempt to best fit the nuclear slope.<br />

The three rema<strong>in</strong><strong>in</strong>g galaxies are of some <strong>in</strong>terest, <strong>in</strong> NGC 4335 <strong>and</strong> NGC 5141 the<br />

gas is the more settled <strong>in</strong>to a smooth rotation curve than is the case for the majority<br />

of the galaxies (other than the very nearby M84 <strong>and</strong> M87), however <strong>in</strong> both of these<br />

cases we f<strong>in</strong>d that no black hole is necessary to expla<strong>in</strong> the observed k<strong>in</strong>ematics. In<br />

NGC 2329 the central slope of the rotation curve is very shallow compared even to<br />

the M• = 0 model. This suggests that either the gas <strong>in</strong> this galaxy is <strong>in</strong> a different<br />

plane to the one that we were expect<strong>in</strong>g or that there is significant <strong>in</strong>flow through<br />

the disk which is not supported by rotation <strong>in</strong> the gravitational potential.<br />

The M• −σc relation appears to be compatible with the observations that we have<br />

made here, other than for those three cases above. We are not satisfied, however, that<br />

we are able to put good limits on any of the black hole masses as various effects <strong>in</strong><br />

the gas reduces our ability to underst<strong>and</strong> the k<strong>in</strong>ematics of the central regions. The<br />

gas may not be settled <strong>in</strong>to a stable disk <strong>in</strong> the major plane of the galaxy, <strong>and</strong> the<br />

settl<strong>in</strong>g process may lead to <strong>in</strong>flow. In several nuclei we observe signs of k<strong>in</strong>ematic<br />

twists <strong>and</strong> warps <strong>and</strong> it is hard to accurately account for the consequences. Similar<br />

phenomena may go undetected <strong>in</strong> other nuclei. In four nuclei we observe (at very<br />

180

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