A Model for Line Absorption and Emission from Turbulent Mixing Layers
  Turbulent mixing layers (TMLs) are ubiquitous in multiphase gas. They can
potentially explain observations of high ions such as O VI, which have
significant observed column densities despite short cooling times. Previously,
we showed that global mass, momentum and energy transfer between phases
mediated by TMLs is not sensitive to details of thermal conduction or numerical
resolution. By contrast, we show here that observables such as temperature
distributions, column densities and line ratios are sensitive to such
considerations. We explain the reason for this difference. We develop a
prescription for applying a simple 1D conductive-cooling front model which
quantitatively reproduces 3D hydrodynamic simulation results for column
densities and line ratios, even when the TML has a complex fractal structure.
This enables sub-grid absorption and emission line predictions in large scale
simulations. The predicted line ratios are in good agreement with observations,
while observed column densities require numerous mixing layers to be pierced
along a line of sight.
