HI Kinematics and Mass Distribution of Messier 33
  A new deep HI survey of the galaxy Messier 33 is presented, based on
observations obtained at the Dominion Radio Astrophysical Observatory. We
observe a perturbed outer gas distribution and kinematics in M33, and confirm
the disk warping as a significant kinematical twist of the major axis of the
velocity field, though no strong tilt is measured, in agreement with previous
work. Evidence for a new low brightness HI component with anomalous velocity is
reported. It harbours a large velocity scatter, as its kinematics both exceeds
and lags the rotation of the disk, and leaks in the forbidden velocity zone of
apparent counter-rotation. The observations also reveal wide and multiple peak
HI profiles which can be partly explained by crowded orbits in the framework of
the warp model. Asymmetric motions are identified in the velocity field, as
possible signatures of a lopsided potential and the warp. The mass distribution
modeling of the hybrid Halpha-HI rotation curve favours a cuspy dark matter
halo with a concentration in disagreement with the LambdaCDM dark halo
mass-concentration relationship. The total mass enclosed in 23 kpc is 8 10^10
Msol, of which 11% are stars and gas. At the virial radius of the cuspy halo,
the resulting total mass is 5 10^11 Msol, but with a baryonic mass fraction of
2% only. This strongly suggests a more realistic radius encompassing the total
mass of M33 well smaller than the virial radius of the halo, maybe comparable
to the size of the HI disk.
