Applying a one-dimensional PDR model to the Taurus molecular cloud and
  its atomic envelope
  In this contribution, we test our previously published one-dimensional PDR
model for deriving total hydrogen volume densities from HI column density
measurements in extragalactic regions by applying it to the Taurus molecular
cloud, where its predictions can be compared to available data. Also, we make
the first direct detailed comparison of our model to CO(1-0) and far-infrared
emission. Using an incident UV flux G0 of 4.25 ({\chi} = 5) throughout the main
body of the cloud, we derive total hydrogen volume densities of \approx 430
cm-3, consistent with the extensive literature available on Taurus. The
distribution of the volume densities shows a log-normal shape with a hint of a
power-law shape on the high density end. We convert our volume densities to H2
column densities assuming a cloud depth of 5 parsec and compare these column
densities to observed CO emission. We find a slope equivalent to a CO
conversion factor relation that is on the low end of reported values for this
factor in the literature (0.9 x 1020 cm-2 (K km s-1)-1), although this value is
directly proportional to our assumed value of G0 as well as the cloud depth. We
seem to under-predict the total hydrogen gas as compared to 100 {\mu}m dust
emission, which we speculate may be caused by a higher actual G0 incident on
the Taurus cloud than is generally assumed.
