Tuesday, July 23, 2013

1307.5639 (F. Renaud et al.)

A sub-parsec resolution simulation of the Milky Way: Global structure of the ISM and properties of molecular clouds    [PDF]

F. Renaud, F. Bournaud, E. Emsellem, B. Elmegreen, R. Teyssier, J. Alves, D. Chapon, F. Combes, A. Dekel, J. Gabor, P. Hennebelle, K. Kraljic
We present a hydrodynamical simulation of a Milky Way-like galaxy, reaching the resolution of 0.05 pc with a self-consistent description of the galaxy comprising live stellar and dark matter dynamics. The model includes star formation and a new implementation of stellar feedback through photo-ionization, radiative pressure and supernova blasts. The resolution of the simulation allows us to probe the structure of the interstellar medium down to the formation sites of individual stars, at subparsec resolution for a few cloud lifetimes, and at 0.05 pc for about a cloud crossing time. In the full galactic context, turbulence cascade and gravitation from the kpc scales are de facto included in smaller structures like molecular clouds, without having to add them artificially. In this first paper of a series, we present the global structures of the interstellar medium. In particular, the formation of a bar influences the dynamics of the central ~ 100 pc by creating resonances that regulate the fueling of the central black hole. At larger radii, the spiral arms host the formation of regularly spaced clouds: beads on a string and spurs form from gravitational and Kelvin-Helmholtz instabilities, respectively. These instabilities pump turbulent energy in the gas, generally in the supersonic regime. Because of asymmetric drift due to increased velocity dispersion of young stars compared to gas, and to galactic rotation, the supernovae explode outside of their dense gaseous nursery, which diminishes the effect of stellar feedback on the structure of clouds. The evolution of gas clouds is thus mostly due to fragmentation and gas consumption, regulated mainly by supersonic turbulence, while feedback plays a less important role. [abridged]
View original: http://arxiv.org/abs/1307.5639

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