, S.Garcıa-Burillo 
Departamento de Astronomıa y Geodesia,
Facultad de CC. Matemáticas,
Universidad Complutense de Madrid, 28040 Madrid, Spain
(aig@eucmos.sim.ucm.es) Observatorio Astronomico Nacional (IGN), Apartado 1143, E-28800 Madrid,
Spain (Burillo@oan.es) 
CO with the IRAM 30m telescope (HPBW 13'' and 21'' ).
CO emission is detected
within a galactocentric
radius, R 
100" (5.5 Kpc).
The radial molecular gas distribution consists of ring-like source (of radius
r 
1.5 kpc), and a fast rotating nuclear disk (of radius
r 
500 pc).
The CO velocity field, derived from the position-velocity diagram taken along
the galaxy major axis, reveals the existence of a compact nuclear disk rotating
at high velocities which has no HI counterpart. The derived rotation curve
reaches v 
130 kms 
in less than 
250 pc. This
high velocity regime for molecular gas is satisfactorily explained by an inner
bar scenario. The bulge of NGC4013 is box-shaped at optical wavelengths, which
suggests the existence of a non-axisymmetric potential in the inner disk.
The distribution of CO emissivity itself towards the center suggests that
the orbits of some molecular clouds are inclined with respect to
the plane of the galaxy.
NGC4013 presents a distorted vertical distribution of matter (stars and gas):
it has a box-shaped bulge, a thick optical disk with a warped plane,
and a spectacular HI
warp in the outer disk.
The molecular gas disk vertical structure is not resolved in the 2-1 line.
The slight inclination of the galaxy allows us detecting
non-axisymmetric structures that are probably spiral arms.
If so the estimated
inclination angle is i=86. 
5,
in excellent agreement with the derived by Guthrie (1992) from
optical data. We show that
the warp of the stellar disk reported from optical measurements
might be an
artifact due to
spiral arms seen in projection.
We have not detected a CO counterpart of the HI warp.
Figure 2: Position-velocity diagram, observed along the kinematical
major axis of NGC4013, in the CO(2-1) line (solid contours and
grey scale). The location of the nuclear disk (ND), the high
velocity gas (W 
and W 
) and the CO depleted regions
(H and H ) are indicated by the arrows. Countour
levels and gray scale are equally spaced from 10% to 90% by steps of
10% of the maximum value (0.075 K). The cross in the bottom left
quarter indicates the resolution in both axis (6.5 km s , 12")
