The Atlas3D project - XIV. The extent and kinematics of molecular gas in
  early-type galaxies
  We use interferometric CO observations to compare the extent, surface
brightness profiles and kinematics of the molecular gas in CO-rich Atlas3D
early-type galaxies (ETGs) and spiral galaxies. We find that the molecular gas
extent is smaller in absolute terms in ETGs than in late-type galaxies, but
that the size distributions are similar once scaled by the galaxies
optical/stellar characteristic scale-lengths. Virgo cluster ETGs have less
extended molecular gas reservoirs than field counterparts. Approximately half
of ETGs have molecular gas surface brightness profiles that follow the stellar
light profile. These systems often have relaxed gas out to large radii,
suggesting they are unlikely to have had recent merger/accretion events. A
third of the sample galaxies show molecular gas surface brightness profiles
that fall off slower than the light, and sometimes show a truncation. We
suggest that ram pressure stripping and/or the presence of hot gas has
compressed/truncated the gas in these systems. The remaining galaxies have
rings, or composite profiles, that we argue can be caused by the effects of
bars. We investigated the kinematics of the molecular gas using
position-velocity diagrams, and compared the observed kinematics with dynamical
model predictions, and the observed stellar and ionised gas velocities. We
confirm that the molecular gas reaches beyond the turnover of the circular
velocity curve in ~70% of our CO-rich Atlas3D ETGs. In general we find that in
most galaxies the molecular gas is relaxed and dynamically cold. Molecular gas
is a better direct tracer of the circular velocity than the ionised gas,
justifying its use as a kinematic tracer for Tully-Fisher and similar analyses.
(abridged)
