, M. Guélin 
, S. García-Burillo
,
R. Zylka
, R. Wielebinski
Institut de Radioastronomie Millimétrique, 300, rue de la
Piscine F-38406 St.Martin d'Hères, France 
Centro Astronómico de Yebes, IGN, E-19080 Guadalajara, Spain 
Max-Planck-Institut für Radioastronomie, Auf dem Hügel
69, D-53121 Bonn, Germany 
1.2 mm
continuum emission and the 
J= 1
0 and
2
1 line emissions in the edge-on spiral galaxy
NGC 4565. We selected NGC 4565 because it is strong in the HI
line, but weak in CO, contrary to the galaxies mapped so far at
1.2 mm.
Figure 9: The 
1.2mmcontinuum emission, smoothed to an angular
resolution of 20
and superimposed on a optical photograph of
NGC4565 (Lick Observatory). The contour levels are 3.0 (
),
6.0, 9.0,
21 mJy/
beam. The noise level increases by
about 
towards the outer parts of the map. Note the warp of the
continuum contours to the NW.
The CO emission in NGC 4565 resembles that in the Milky Way. It shows
a compact central source surrounded by a `molecular ring'. The
molecular ring peaks between 
and 
from the center (3-5
kpc) and has an outer radius of 
. It is twice smaller than
the broad `plateau' observed in HI and shows narrow structures which
could be spiral arms.
The 
1.2 mm continuum follows CO near the center and HI at
the periphery. It shows, like CO, a central peak and an inner ring
and, like HI, a weaker, extended plateau. This is the first time
that dust emission is unambiguously detected in extragalactic
HI clouds. Like HI, the 1.2 mm contours are warped near the NW
edge of the galaxy. The warp, already apparent at half the optical
radius, reaches a height of 50
(2.4 kpc) at the edge of the
optical disk (Fig. 9).
The average dust temperature is 18 K near the center and 15 K in the
HI plateau. From the 1.2 mm continuum intensity and the HI line
integrated intensity, we derive a dust absorption cross section per H
atom 
cm
in the plateau. This value is very close to that predicted by Draine
& Lee (1984) for the local diffuse clouds.
The velocity field derived from CO can be described by rotation (solid
body rotation between 0 and 4 kpc, constant velocity further out) plus
non-circular motions. The non-circular motions are observed mostly
near the `arms' and near the nucleus. They are are probably the
signature of a spiral density wave and/or of a central bar. The
presence of a bar could explain the boxy shape of the central bulge on
optical photographs.