The effect of nuclear gas distribution on the mass determination of
  supermassive black holes
  Supermassive black holes reside in the nuclei of most galaxies. Accurately
determining their mass is key to understand how the population evolves over
time and how the black holes relate to their host galaxies. Beyond the local
universe, the mass is commonly estimated assuming virialized motion of gas in
the close vicinity to the active black holes, traced through broad emission
lines. However, this procedure has uncertainties associated with the unknown
distribution of the gas clouds. Here we show that the comparison of black hole
masses derived from the properties of the central accretion disc with the
virial mass estimate provides a correcting factor, for the virial mass
estimations, that is inversely proportional to the observed width of the broad
emission lines. Our results suggest that line-of-sight inclination of gas in a
planar distribution can account for this effect. However, radiation pressure
effects on the distribution of gas can also reproduce our findings. Regardless
of the physical origin, our findings contribute to mitigate the uncertainties
in current black hole mass estimations and, in turn, will help to further
understand the evolution of distant supermassive black holes and their host
galaxies.
