, F. Wyrowski
, S.J.E. Radford
, C.
Henkel
, H. Lesch
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69,
D-53121 Bonn, Federal Republic of Germany 
Institut de Radioastronomie Millimétrique, 300, rue de la
Piscine F-38406 St. Martin d`Hères, France 
National Radio Astronomy Observatory, 949 N. Cherry Ave.,
Campus Building 65, Tucson, AZ 85721-0665, USA 
CO (J=1-0) interferometric observations are
presented of NGC 1275 (3C84, Perseus A), which is the dominant
galaxy of the Perseus cluster (Abell 426) and is believed to have a
strong cooling flow. No CO absorption was detected towards the
powerful point-like nucleus although CO emission may have been
detected in an area surrounding the nucleus.
The constraints placed by these observations and existing data on
the massive cooling flow scenario are examined. Contrary to some
claims, the covering fraction of neutral gas has been found to be
much less than unity in all cooling flows where the necessary data
are available. As the cooling gas presumably forms low-mass stars
or sub-stellar objects, the possibility of large masses of neutral
gas escaping detection is investigated in detail. The gas, with or
without dust, should not cool down to 
K as
has been claimed but should remain 
K through X-ray heating
at column densities up to 
. Greater
column densities may be physically reasonable if the magnetic field
is strong enough to support the cloud against fragmentation. In
this case, ambipolar diffusion or magnetic slip-ion heating becomes
important and should maintain the temperature 
. If the clouds contain dust, then although the dust radiates
away most of the energy, the absorbed starlight keeps the
temperature 
. Lack of CO or very broad lines
do not appear to be feasible means of reconciling large molecular
(or atomic) gas masses with the global lack of detections and tight
upper limits. The primary conclusion is that the real mass inflow
rates must be much lower that frequently claimed. It should then be
noted that present-day cooling flows, if not so massive, lose much
of their cosmological importance.
The FIR and CO emission from NGC 1275 correspond exactly to what is
found in gas-rich spirals. Rather than a massive cooling flow, the
gas may come from accretion of one or more gas-rich galaxies.
Since, however, at least 14 other central galaxies would have been
detected in CO if they contained similar quantities of gas, such
events must be quite rare, very roughly 
if
the time required for a large fraction of the gas to disappear is
yr. cm