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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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‘disorganized’ po<strong>in</strong>t-to-po<strong>in</strong>t motions. Aga<strong>in</strong>, the systems where we do not observe<br />

rotation (empty symbols) tend to lie towards the top of the envelope <strong>and</strong> <strong>in</strong>clude<br />

the face on disks. NGC 383, highlighted earlier, does not lie outside expectations -<br />

<strong>in</strong>dicat<strong>in</strong>g it is settl<strong>in</strong>g just as the other disks are but with considerably higher energy.<br />

From Figure 5.7 we can appreciate that the values of ɛ100 are consistently lower<br />

than the values of σ100 though these two parameters show no particular relationship<br />

beyond that. This <strong>in</strong>dicates to us that the small scale 3D r<strong>and</strong>om motions, as seen<br />

<strong>in</strong> the velocity dispersion, are a more significant k<strong>in</strong>ematic factor <strong>in</strong> the disks than<br />

larger scale po<strong>in</strong>t-to-po<strong>in</strong>t motions. This would be compatible with a picture where<br />

the gas is made up of turbulent cells, where the cells are settl<strong>in</strong>g <strong>in</strong>to a disk <strong>and</strong> los<strong>in</strong>g<br />

their r<strong>and</strong>om bulk motions to rotation, while ma<strong>in</strong>ta<strong>in</strong><strong>in</strong>g at least a large portion of<br />

their <strong>in</strong>tr<strong>in</strong>sic turbulence. Numerical simulations of the gas <strong>in</strong> the nuclei of galaxies<br />

suggest that clumpy turbulent structures may be a common feature of systems where<br />

active fuel<strong>in</strong>g of the central eng<strong>in</strong>e is tak<strong>in</strong>g place (see e.g. Wada, 2004, for a recent<br />

review).<br />

5.2.3 Relationships to the stellar k<strong>in</strong>ematics<br />

We described the central stellar velocity dispersion σc <strong>in</strong> Chapter 2, <strong>and</strong> values of that<br />

parameter were given <strong>in</strong> Table 2.3. We rem<strong>in</strong>d the reader here that σc is measured<br />

244

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