We have searched for CO lines in a sample of 21 new morphologically determined polar-ring galaxies (of which nine are kinematically confirmed);
obtained from a wide search in the Galaxy Zoo project by Moiseev and collaborators. Polar-ring galaxies (PRGs) are a unique class of objects;
tracing special episodes in the galaxy mass assembly: they can be formed through galaxy interaction and merging;
but also through accretion from cosmic filaments. Furthermore;
they enable the study of dark matter haloes in three dimensions. The polar ring itself is a sub-system rich in gas;
where molecular gas is expected;
and new stars are formed. Among the sample of 21 PRGs;
we have detected five CO-rich systems;
that can now be followed up with higher spatial resolution. Their average molecular mass is 9.4 × 109M;
and their average gas fraction is 27% of their baryonic mass;
with a range from 15 to 43%;
implying that they have just accreted a large amount of gas. The position of the detected objects in the velocity-magnitude diagram is offset from the Tully-Fisher relation of normal spirals;
as was already found for PRGs. This work is part of our multi-wavelength project to determine the detailed morphology and dynamics of PRGs;
test through numerical models their formation scenario;
and deduce their dark matter content and 3D-shape. © 2013 ESO;