AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 72. Shells in the Global ISM
Display, Wednesday, June 2, 1999, 10:00am-6:30pm, Southwest Exhibit Hall

## [72.11] Evidence for an Expanding Molecular Superbubble in M\,82

A. Weiss, F. Walter, N. Neininger, U. Klein (Radioastronomisches Institut der Univsit\"at Bonn)

We present evidence for an expanding superbubble in M\,82 (diameter: \approx\,130\,pc, expansion velocity: \approx\,45\,km\,s-1, mass: \approx\,8\cdot106\,M\odot) as traced by 12{\rm CO}(J\!=\!1\! \to \!0), 12{\rm CO}(J\!=\!2\! \to \!1), 13{\rm CO}(J\!=\!1\! \to \!0) and {\rm C}18{\rm O}(J\!=\!1\! \to \!0) observations. The superbubble is centred around the most powerful supernova remnant 41.9+58 in M\,82. The CO observations show that the molecular superbubble already broke out of M\,82's 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 diffuse X--ray outflow in M\,82. We briefly discuss observations of the same region at other wavelengths (radio continuum, optical, H{\small I}, X--rays, ionized gas). From our spectral line observations, we derive a kinematic age of about 106 years for the superbubble. Using simple theoretical models, the total energy needed for the creation of this superbubble is of order 2\times1054\,ergs (energy equivalent of 1000 'regular' type II supernova (SN) explosions and the strong stellar winds of their progenitors). The average energy input rate (0.001 SN\,yr-1) is reasonable given the high SN rate of \approx 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. This newly detected expanding molecular superbubble is believed to be powered by the same objects which also lie at origin of the prominent X--ray outflow in M\,82. It can therefore be used as an alternative tool to investigate the physical properties of these sources.\\ \\ acknowledgements:\\ A.W. and F.W. acknowledge the Deutsche Forschungsgemeinschaft for the award of a stipendium in the Graduate School  The Magellanic Clouds and Other Dwarf Galaxies''.

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