M. J. Stringer, R. G. Bower, S. Cole, C. S. Frenk, T. Theuns
The formation of galaxies is regulated by a balance between the supply of gas
and the rate at which it is ejected. Traditional analytical treatments of
galactic winds driven by supernovae assume that a fixed fraction of the
available energy is used to eject the gas. By a straightforward application of
this argument to galaxy formation in the cold dark matter cosmogony, we show
that the derived scaling of the wind with circular velocity leads to a
relationship between baryon content and galaxy circular velocity that matches
recent observational data remarkably well. We test this simple model on a set
of gasdynamical simulations of idealised galaxies in dark matter halos of
different mass. We find that although the mass outflow in the simulations
broadly follows the scaling implied by the model, the model is, in fact, quite
inadequate as a description of the overall behaviour of the simulations. By
isolating the dominant physical processes at work in limiting cases, we
motivate a more comprehensive model that incorporates both momentum-conserving
and energy-conserving constraints on the outflow. This formulation provides the
physical basis for a more realistic analytical model and can be used to
extrapolate simulation results beyond the highest achievable resolution.
View original:
http://arxiv.org/abs/1111.2529
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