The M_bh-sigma diagram, and the offset nature of barred active galaxies
  From a sample of 50 predominantly inactive galaxies with direct supermassive
black hole mass measurements, it has recently been established that barred
galaxies tend to reside rightward of the M_bh-sigma relation defined by
non-barred galaxies. Either black holes in barred galaxies tend to be anaemic
or the central velocity dispersions in these galaxies have a tendency to be
elevated by the presence of the bar. The latter option is in accord with
studies connecting larger velocity dispersions in galaxies with old bars, while
the former scenario is at odds with the observation that barred galaxies do not
deviate from the M_bh-luminosity relation. Using a sample of 88 galaxies with
active galactic nuclei, whose supermassive black hole masses have been
estimated from their associated emission lines, we reveal for the first time
that they also display this same general behavior in the M_bh-sigma diagram
depending on the presence of a bar or not. A new symmetrical and
non-symmetrical "barless" M_bh-sigma relation is derived using 82 non-barred
galaxies. The barred galaxies are shown to reside on or up to ~1 dex below this
relation. This may explain why narrow-line Seyfert 1 galaxies appear offset
from the "barless" M_bh-sigma relation, and has far reaching implications given
that over half of the disk galaxy population are barred.
