On the Origin of Interstellar Turbulence: Less SNe and More Galactic Dynamics

Abstract

Turbulence is ubiquitous in the ISM, from large (galactic) scales down to planet-sized eddies within pre-stellar accretion disks. The ISM turbulence is known to operate in the both ends of triggering star formation when occurring at molecular clouds, as well as quenching the process at HII regions. Its origin, however, is still controversial. Supernovae are generally accounted as the main source of the turbulent energy of the ISM. However, recent observations of stellar orbits and the gravitational potential of the Galaxy revealed a new possibility: ISM gas flows driven by the global galactic gravitational potential. In this work we provide the first numerical simulations of the dynamics of the diffuse and molecular ISM interacting with the gravitational potential wells of the Galaxy. These reveal the generation of arms and the triggering of turbulence at large scales ( > 100 pc). During the interactions, molecular clouds may be disrupted and dense cores be formed. We compare the statistics of the obtained turbulent media with the observations.