Co-author: Claudio Melioli (1) Anibale D'Ercole (2) Fabrizio Brighenti (2)

Co-authors' Institutions: (1) University of Bologna, Italy (2) Observatory of Bologna, Italy

Abstract:

Gemini-Keck-Chandra observations of the starburst galaxy M82 show some evidence that the wind of this galaxy is presently being fed mainly by SN explosions of two off-nuclear stellar associations. We present here three-dimensional large scale chemo-hydrodynamics simulations of the formation and evolution of superbubbles, chimneys, fountains and galactic winds which are driven by SNe explosions. Such simulations investigate the effects of isolated, randomly distributed and clustered supernovae in the structure and dynamics of the rotating disk and halo of normal galaxies, like the Milky Way, or starburst galaxies, like the prototype M82. Depending on the amount of energy that is injected by the SNe, the gas may evolve into a galactic wind or simply generate a galactic fountain. In a galactic fountain, the ejected gas is re-captured by the gravitational potential and falls back onto the galactic disk injecting turbulence, spreading heavy elements, and providing star formation feedback. From hydrodynamical simulations of the formation of SN-driven galactic fountains and high velocity clouds emerging from the disk of our Galaxy, we find that the ejected SN metals that fall back are not largely spread over the galactic disk, as invoked in previous models to explain metallicity gradient changes in the Galaxy. Instead, they fall nearby the region where they were injected. Also, we find that the emerging gas from the disk looses part of its angular momentum to the halo of the Galaxy, therefore increasing the halo rotational velocity as observed in several galaxies. We will also show 3-D numerical simulations of the SB M82 nuclear region where we investigate the possibility above suggested by the observations that off-nuclear stellar associations are presently the main driving sources of its wind. If confirmed, this evidence may shad new light on the comprehension of the global galactic wind driving-mechanism.

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