Molecular Disks in Radio Galaxies: The pathway to ALMA
  Context. It has recently been proposed that the jets of low-luminosity radio
galaxies are powered by direct accretion of the hot phase of the IGM onto the
central black hole. Cold gas remains a plausible alternative fuel supply,
however. The most compelling evidence that cold gas plays a role in fueling
radio galaxies is that dust is detected more commonly and/or in larger
quantities in (elliptical) radio galaxies compared with radio-quiet elliptical
galaxies. On the other hand, only small numbers of radio galaxies have yet been
detected in CO (and even fewer imaged), and whether or not all radio galaxies
have enough cold gas to fuel their jets remains an open question. If so, then
the dynamics of the cold gas in the nuclei of radio galaxies may provide
important clues to the fuelling mechanism. Aims. The only instrument capable of
imaging the molecular component on scales relevant to the accretion process is
ALMA, but very little is yet known about CO in southern radio galaxies. Our aim
is to measure the CO content in a complete volume-limited sample of southern
radio galaxies, in order to create a well-defined list of nearby targets to be
imaged in the near future with ALMA. Methods. APEX has recently been equipped
with a receiver (APEX-1) able to observe the 230 GHz waveband. This allows us
to search for CO(2-1) line emission in our target galaxies. Results. Here we
present the results for our first three southern targets, proposed for APEX-1
spectroscopy during science verification: NGC3557, IC4296 and NGC1399. The
experiment was successful with two targets detected, and possible indications
for a double-horned CO line profile, consistent with ordered rotation. These
early results are encouraging, demonstrating that APEX can efficiently detect
CO in nearby radio galaxies. We therefore plan to use APEX to obtain CO
spectroscopy for all our southern targets.
