Column Density Profiles of Cold Clouds Driven by Galactic Outflows
  Absorption line studies are essential to understanding the origin, nature,
and impact of starburst-driven galactic outflows. Such studies have revealed a
multiphase medium with a number of poorly-understood features leading to a need
to study the ionization mechanism of this gas. To better interpret these
observations, we make use of a suite of adaptive mesh refinement hydrodynamic
simulations of cold, atomic clouds driven by hot, supersonic outflows,
including the effect of radiative cooling, thermal conduction, and an ionizing
background characteristic of a starbursting galaxy. Using a new analysis tool,
Trident, we estimate the equilibrium column density distributions for ten
different ions: H I, Mg II, C II, C III, C IV, Si III, Si IV, N V, O VI, and Ne
VIII. These are fit to model profiles with two parameters describing the
maximum column density and coverage, and for each ion we provide a table of
these fit parameters, along with average velocities and line widths. Our
results are most sensitive to Mach number and conduction efficiency, with
higher Mach numbers and more efficient conduction leading to more compact, high
column density clouds. We use our results to interpret down-the-barrel
observations of outflows and find that the adopted ionization equilibrium model
overpredicts column densities of ions such as Si IV and does not adequately
capture the observed trends for N V and O VI, implying the presence of strong
non equilibrium ionization effects.
