Evidence for an Expanding Molecular

We present evidence for an expanding super-bubble in M 82 (diameter: 130 pc, expansion velocity: 45 km s ?1 , mass: 8 10 6 M). It is seen in the 12 CO (J = 1 ! 0), 12 CO(J = 2 ! 1), 13 CO(J = 1 ! 0) and C 18 O(J = 1 ! 0) lines. The superbubble is centred around the most powerful supernova remnant, 41.9+58. The CO observations show that the molecular superbub-ble already broke out of the disk. This scenario is supported by ROSAT HRI observations which suggest that hot coronal gas originating from inside the shell is the main contributor to the diiuse X{ray outtow in M 82. We brieey discuss observations of the same region at other wavelengths (radio continuum, optical, H I, X{rays, ionized gas). From our spectral line observations, we derive a kinematic age of about 10 6 years for the superbubble. Using simple theoretical models, the total energy needed for the creation of this superbubble is of order 2 10 54 ergs. The required energy input rate (0.001 SN yr ?1) is reasonable given the high supernova (SN) rate of 0:1 SN yr ?1 in the central part of M 82. As much as 10% of the energy needed to create the superbubble is still present in form of the kinetic energy of the expanding molecular shell. Of order 10% is conserved in the hot X{ray emitting gas emerging from the superbubble into the halo of M 82. This newly detected expanding molecular superbubble is believed to be powered by the same objects that also lie at the origin of the prominent X{ray outtow in M 82. It can therefore be used as an alternative tool to investigate the physical properties of these sources.