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 10 ^ { 9 } M _ { \odot } , 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 polar-ring galaxies , test through numerical models their formation scenario , and deduce their dark matter content and 3D-shape .