We present deep CO ( 1-0 ) Â observations of NGC6240 performed with the IRAM Plateau de Bure Interferometer ( PdBI ) . NGC6240 is the prototypical example of a major galaxy merger in progress , caught at an early stage , with an extended , strongly-disturbed butterfly-like morphology and the presence of a heavily obscured active nucleus in the core of each progenitor galaxy .
The CO line shows a skewed profile with very broad and asymmetric wings detected out to velocities of -600 km/s and +800 km/s with respect to the systemic velocity .
The PdBI maps reveal the existence of two prominent structures of blueshifted CO emission .
One extends eastward , i.e .
approximately perpendicular to the line connecting the galactic nuclei , over scales of \sim 7 kpc and shows velocities up to - 400 km/s .
The other extends southwestward out to \sim 7 ~ { } kpc from the nuclear region , and has a velocity of - 100 km/s with respect to the systemic one .
Interestingly , redshifted emission with velocities 400 to 800 km/s is detected around the two nuclei , extending in the east-west direction , and partly overlapping with the eastern blue-shifted structure , although tracing a more compact region of size \sim 1.7 kpc .
The overlap between the southwestern CO blob and the dust lanes seen in HST images , which are interpreted as tidal tails , indicates that the molecular gas is deeply affected by galaxy interactions .
The eastern blueshifted CO emission is co-spatial with an H \alpha filament that is associated with strong H _ { 2 } and soft X-ray emission .
The analysis of Chandra X-ray data provides strong evidence for shocked gas at the position of the H \alpha emission .
Its association with outflowing molecular gas supports a scenario where the molecular gas is compressed into a shock wave that propagates eastward from the nuclei .
If this is an outflow , the AGN are likely the driving force .