Angular Momentum in Giant Molecular Clouds. II. M33
  We present an analysis comparing the properties of 45 giant molecular clouds
(GMCs) in M33 and the atomic hydrogen (HI) with which they are associated.
High-resolution VLA observations are used to measure the properties of HI in
the vicinity of GMCs and in regions where GMCs have not been detected. The
majority of molecular clouds coincide with a local peak in the surface density
of atomic gas, though 7% of GMCs in the sample are not associated with
high-surface density atomic gas. The mean HI surface density in the vicinity of
GMCs is 10 M_sol/pc^2 and tends to increase with GMC mass as Sigma_HI ~
M_GMC^0.27. 39 of the 45 HI regions surrounding GMCs have linear velocity
gradients of ~0.05 km/s/pc. If the linear gradients previously observed in the
GMCs result from rotation, then 53% are counterrotating with respect to the
local HI. If the linear gradients in these local HI regions are also from
rotation, 62% are counterrotating with respect to the galaxy. If magnetic
braking reduced the angular momentum of GMCs early in their evolution, the
angular velocity of GMCs would be roughly one order of magnitude lower than
what is observed. Based on our observations, we consider the possibility that
GMCs may not be rotating. Atomic gas not associated with GMCs has gradients
closer to 0.03 km/s/pc, suggesting that events occur during the course of GMC
evolution that may increase the shear in the atomic gas.
