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: http://www.stsci.edu/~marel/abstracts/abs_R22.html
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To interpret the gas kinematics we construct axisymmetric models in which the gas and dust reside in a disk in the equatorial plane of the stellar body, and are viewed at an inclination of 70 degrees. It is assumed that the gas moves on circular orbits, with an intrinsic velocity dispersion due to turbulence (or otherwise non-gravitational motion). The latter is required to fit the observed increase in the line widths towards the nucleus, and must reach a value in excess of 500 km/s in the central 0.1 arcsec. The circular velocity is calculated from the combined gravitational potential of the stars and a possible nuclear black hole. Models without a black hole predict a rotation curve that is shallower than observed (V_pred = 92 km/s at r = 0.2 arcsec), and are ruled out at > 99% confidence. Models with a black hole of mass M_bh = 3.3^{+2.3}_{-1.3} x 10^8 solar masses provide an acceptable fit. The best-fitting model with a black hole adequately reproduces the observed emission line shapes on the nucleus, which have a narrower peak and broader wings than a Gaussian.
NGC 7052 can be added to the list of active galaxies for which HST
spectra of a nuclear gas disk provide evidence for the presence of a
central black hole. The black hole masses inferred for M87, M84, NGC
6251, NGC 4261 and NGC 7052 span a range of a factor 10, with NGC 7052
falling on the low end. By contrast, the luminosities of these
galaxies are identical to within 25%. Any relation between black hole
mass and luminosity, as suggested by independent arguments, must
therefore have a scatter of at least a factor 10.