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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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4.5 Conclusions<br />

In this chapter we presented th<strong>in</strong> disk model velocity profiles of gas sitt<strong>in</strong>g <strong>in</strong> the<br />

stellar potential, <strong>and</strong> that potential <strong>in</strong>clud<strong>in</strong>g a 1 × 10 8 M⊙ <strong>and</strong> a 9 × 10 8 M⊙ black<br />

hole <strong>in</strong> our sample of 21 galaxies, apart from UGC 7115 (for which we have <strong>in</strong>sufficient<br />

reliable data, from only one observational slit) <strong>and</strong> NGC 3801 (where it is quite clear<br />

we are not observ<strong>in</strong>g the nucleus, which is highly dust obscured).<br />

In 6 of the 19 galaxies the modeled velocity profile gives no clear results as the<br />

non-rotational motions <strong>in</strong> the gas are too great. For 4 of the 13 rema<strong>in</strong><strong>in</strong>g galaxies<br />

we observe a signature compatible with a black hole <strong>in</strong> the range 1 × 10 8 M⊙ <<br />

M• < 9 × 10 8 M⊙, for 5 we observe k<strong>in</strong>ematic signatures that are compatible with<br />

M• ∼ > 9 × 108 M⊙. NGC 4261 has a profile compatible with an ∼ 1 × 10 8 M⊙ black<br />

hole, though this result is highly unreliable due to observational problems.<br />

Compatibility with these k<strong>in</strong>ematic signatures does not necessarily imply that we<br />

can state black hole masses for these galaxies. The scale of the r<strong>and</strong>om motions <strong>in</strong><br />

these galaxies is so great that we have no reason to believe that the gas <strong>in</strong> the center<br />

is only affected by the smooth gravitational potential of the stars <strong>and</strong> central black<br />

hole. More likely is that these profiles are <strong>in</strong>dicat<strong>in</strong>g the presence of a supermassive<br />

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