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S. Matsushita (Harvard-Smithsonian CfA), R. Kawabe (Nobeyama Radio Observatory), H. Matsumoto (Massachusetts Institute of Technology), T.G. Tsuru (Kyoto University)
We performed 12CO(1 - 0), 13CO(1 - 0), and HCN(1 - 0) interferometric observations of the central region (about 450 pc in radius) of M82 with the Nobeyama Millimeter Array. We have successfully imaged a molecular superbubble with a diameter of ~ 210 x 140 pc (~ 14'' x 9'') elongated perpendicular to the galactic disk. The kinetic energy of the superbubble is ~ (0.5-2) x 1055 erg, equivalent to the total energy of ~103-104 supernovae. The center of the superbubble is clearly shifted from the nucleus by 140 pc. This position is close to that of the massive black hole (BH) of > 460 Mo (Matsumoto et al. 2000; Matsumoto & Tsuru 1999; Ptak & Griffiths 1999) and the 2.2 micron secondary peak (a luminous supergiant dominated cluster; Joy et al. 1987), which strongly suggests that these objects may be related to the formation of the superbubble. Consideration of star formation in the cluster based on the infrared data indicates that (1) energy release from supernovae can account for the kinetic energy of the superbubble, (2) the total mass of stellar-mass BHs available for building-up the massive BH may be much higher than 460 Mo, and (3) it is possible to form the middle-mass BH of 102-103 Mo within the timescale of the superbubble. We suggest that the massive BH was produced and is growing in the intense starburst region. SM and HM are supported by the JSPS Postdoctoral Fellowship for Research Abroad.