Gas Streaming Motions towards the Nucleus of M81
  We present stellar and gaseous kinematics of the inner 120x250pc^2 of the
Liner/Seyfert 1 galaxy M81, from optical spectra obtained with the GMOS
integral field spectrograph on the Gemini North telescope at a spatial
resolution of 10pc. The stellar velocity field shows circular rotation but
deviations are observed close to the minor axis which can be attributed to
stellar motions possibly associated to a nuclear bar. The stellar velocity
dispersion of the bulge is 162km/s leading to a black hole mass of
M_BH=5.5x10^7M_sun based on the M_BH-sigma relationship. The gas kinematics is
dominated by non-circular motions and the subtraction of the stellar velocity
field reveals blueshifts of ~-100km/s on the far side of the galaxy and a few
redshifts on the near side. These characteristics can be interpreted in terms
of streaming towards the center if the gas is in the plane. On the basis of the
observed velocities and geometry of the flow, we estimate a mass inflow rate in
ionized gas of ~4.0x10^-3M_sun/year, which is of the order of the accretion
rate necessary to power the LINER nucleus of M81. We have also applied the
technique of Principal Component Analysis (PCA) to our data, which reveals the
presence of a rotating nuclear gas disk within ~50pc from the nucleus and a
compact outflow, approximately perpendicular to the disk. The PCA combined with
the observed gas velocity field shows that the nuclear disk is being fed by gas
circulating in the galaxy plane. The presence of the outflow is supported by a
compact jet seen in radio observations at a similar orientation, as well as by
an enhancement of the [OI]\Halpha line ratio, probably resulting from shock
excitation of the circumnuclear gas by the radio jet. With these observations
we are thus resolving both the feeding -- via the nuclear disk and observed gas
inflow, and the feedback -- via the outflow, around the nucleus of M81.
