Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

weighted mean observation - model residuals are plotted in Figure 4.12 and gives
a minimum at an offset of 63 km s −1 , equivalent to a galaxy recessional velocity
of 1218 km s −1 . The model velocity profiles for these observations are shown in
Figure 4.35. In the observed velocity profile a central velocity gradient is observed
which seems as if it may correspond to gas rotating in the potential generated by
a M• > 9 × 10 8 M⊙ black hole. The proximity of this galaxy highlights many of
the problems in interpreting spectra from nearby sources where the steep flux profile
becomes more resolved and issues relating to the PSF and precise positioning of the
slits (which is not known) become important (see also Maciejewski & Binney, 2001).
NGC 5127: This elliptical peculiar galaxy has a nuclear dust lane. The STIS slits
were aligned parallel to the galaxy major axis, 20 ◦ from the dust axis. The weighted
mean observation - model residuals are plotted in Figure 4.13 and gives a minimum
at an offset of 7 km s −1 , equivalent to a galaxy recessional velocity of 4837 km s −1 .
The model velocity profiles for these observations are shown in Figure 4.36. In the
observed velocity profile a central velocity gradient is observed which seems as if it
may correspond to gas rotating in the potential generated by a 1 × 10 8 M⊙ < M• <
9 × 10 8 M⊙ black hole.
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