A quartet of black holes and a missing duo: probing the low-end of the
  Mbh - sigma relation with the adaptive optics assisted integral-field
  spectroscopy
  We present mass estimates of supermassive black holes in six nearby fast
rotating early-type galaxies (NGC4339, NGC4434, NGC4474, NGC4551, NGC4578 and
NGC4762) with effective stellar velocity dispersion around 100 km/s. We use
near-infrared laser-guide adaptive optics observations with the GEMINI/NIFS to
derive stellar kinematics in the galactic nuclei, and SAURON observations from
the ATLAS3D Survey for large-scale kinematics. We build axisymmetric Jeans
anisotropic models and axisymmetric Schwarzschild dynamical models. Both
modelling approaches recover consistent orbital anisotropies and black hole
masses within 1-2sigma confidence level, except for one galaxy for which the
difference is just above the 3sigma level. Two black holes (NGC4339 and
NGC4434) are amongst the largest outliers from the current black hole mass -
velocity dispersion relation, with masses of $(4.3^{+4.8}_{-2.3})\times10^7$
and $(7.0^{+2.0}_{-2.8})\times10^7$ M$_\odot$, respectively ($3\sigma$
confidence level). The black holes in NGC4578 and NGC4762 lie on the scaling
relation with masses of $(1.9^{+0.6}_{-1.4})\times10^7$ and
$(2.3^{+0.9}_{-0.6})\times10^7$ M$_\odot$, respectively (3sigma confidence
level). For two galaxies (NGC4474 and NGC4551) we are able to place upper
limits on their black holes masses ($<7\times10^6$ and $<5\times10^6$
M$_\odot$, respectively, $3\sigma$ confidence level). The kinematics for these
galaxies clearly indicate central velocity dispersion drops within a radius of
35 pc and 80 pc, respectively. These drops cannot be associated with cold
stellar structures and our data do not have the resolution to exclude black
holes with masses an order of magnitude smaller than the predictions.
Parametrizing the orbital distribution in spherical coordinates, the vicinity
of the black holes is characterized by isotropic or mildly tangential
anisotropy.
