We report the detection , using observations of the CO ( 2-1 ) line performed with the Atacama Pathfinder EXperiment ( APEX ) , of molecular gas in the region of the outer filament of Centaurus A , a complex region known to show various signatures of an interaction between the radio jet , an H i cloud , and ionised gas filaments .
We detect CO ( 2-1 ) at all observed locations , which were selected to represent regions with very different physical conditions .
The H _ { 2 } masses of the detections range between 0.2 \times 10 ^ { 6 } and 1.1 \times 10 ^ { 6 } M _ { \odot } , for conservative choices of the CO to H _ { 2 } conversion factor .
Surprisingly , the stronger detections are not coincident with the H i cloud , but instead are in the region of the ionised filaments .
We also find variations in the widths of the CO ( 2-1 ) lines throughout the region , with broader lines in the region of the ionised gas , i.e .
where the jet–cloud interaction is strongest , and with narrow profiles in the H i cloud .
This may indicate that the molecular gas in the region of the ionised gas has the momentum of the jet–cloud interaction encoded in it , in the same way as the ionised gas does .
These molecular clouds may therefore be the result of very efficient cooling of the down-stream gas photo- or shock-ionised by the interaction .
On the other hand , the molecular clouds with narrower profiles , which are closer to or inside the H i cloud , could be pre-existing cold H _ { 2 } cores which manage to survive the effects of the passing jet .