Bringing Simulation and Observation Together to Better Understand the
  Intergalactic Medium
  The methods by which one characterizes the distribution of matter in
cosmological simulations is intrinsically different from how one performs the
same task observationally. In this paper, we make substantial steps towards
comparing simulations and observations of the intergalactic medium (IGM) in a
more sensible way. We present a pipeline that generates and fits synthetic QSO
absorption spectra using sight lines cast through a cosmological simulation,
and simultaneously identifies structure by directly analyzing the variations in
HI and OVI number density. We compare synthetic absorption spectra with a less
observationally motivated, but more straightforward density threshold-based
method for finding absorbers. Our efforts focus on HI and OVI to better
characterize the warm/hot intergalactic medium, a subset of the IGM that is
challenging to conclusively identify observationally. We find that the two
methods trace roughly the same quantities of HI and OVI above observable column
density limits, but the synthetic spectra typically identify more substructure
in absorbers. We use both methods to characterize HI and OVI absorber
properties. We find that both integrated and differential column density
distributions from both methods generally agree with observations. The
distribution of Doppler parameters between the two methods are similar for Lya
and compare reasonably with observational results, but while the two methods
agree with each other with OVI systems, they both are systematically different
from observations. We find a strong correlation between OVI baryon fraction and
OVI column density. We also discuss a possible bimodality in the temperature
distribution of the gas traced by OVI.
