Opening PANDORA's box: APEX observations of CO in PNe
  Context. Observations of molecular gas have played a key role in developing
the current understanding of the late stages of stellar evolution. Aims. The
survey Planetary nebulae AND their cO Reservoir with APEX (PANDORA) was
designed to study the circumstellar shells of evolved stars with the aim to
estimate their physical parameters. Methods. Millimetre carbon monoxide (CO)
emission is the most useful probe of the warm molecular component ejected by
low- to intermediate-mass stars. CO is the second-most abundant molecule in the
Universe, and the millimeter transitions are easily excited, thus making it
particularly useful to study the mass, structure, and kinematics of the
molecular gas. We present a large survey of the CO (J = 3 - 2) line using the
Atacama Pathfinder EXperiment (APEX) telescope in a sample of 93
proto-planetary nebulae and planetary nebulae. Results. CO (J = 3 - 2) was
detected in 21 of the 93 objects. Conclusions. CO (J = 3 - 2) was detected in
all 4 observed pPNe (100%), 15 of the 75 PNe (20%), one of the 4 wide binaries
(25%), and in 1 of the 10 close binaries (10%). Using the CO (J = 3 - 2) line,
we estimated the column density and mass of each source.
