The CO(1--0) and CO(2--1) lines were observed and detected out to a
radius of for an assumed distance of
. The line
width of the nuclear spectrum exceeds the global line width (
i.e. as determined by the rotation curve at
) by over
. No evidence for a compact nuclear source is seen in any
of these maps (roughly
resolution).
Assuming that the dust emission can be decomposed into
emission from dust in the atomic and in the molecular interstellar
medium, we derive the emissivity of the dust associated with the
relatively diffuse atomic gas. Based on this value, and taking the
emissivities for the diffuse atomic gas as lower limits
(cf. Hildebrandt 1983), we estimate
conversion factors of
in the disk and
in the nucleus, far below
standard estimates. The star formation efficiency must be very high
in the central region.
An interesting feature of our data is the variation of the CO(2--1)
line to continuum ratio, from 40% in the nuclear region
decreasing by a factor 10 with radius (see Fig. 1). We
interpret this as being largely due to a decrease in the gas
temperature and suggest that the CO(2--1) line to continuum ratio may
be a useful thermometer for studies of the ISM in galaxies.
Figure 1: CO(2--1) line to continuum ratio as a function of radial distance
in NGC 3079