The H II Region/PDR Connection: Self-consistent Calculations of Physical Conditions in Star-forming Regions
Abel N.P., Ferland G.J., Shaw G., van Hoof P.A.M.
published in: ApJS, 161, 65 (2005)
We have performed a series of calculations designed to reproduce infrared
diagnostics used to determine physical conditions in star-forming regions. We
self-consistently calculate the thermal and chemical structure of an H II
region and photodissociation region (PDR) that are in pressure equilibrium.
This differs from previous work, which used separate calculations for each gas
phase. Our calculations span a wide range of stellar temperatures, gas
densities, and ionization parameters. We describe improvements made to the
spectral synthesis code Cloudy that made these calculations possible. These
include the addition of a molecular network with approximately 1000 reactions
involving 68 molecular species and improved treatment of the grain physics.
Data from the Spitzer First Look Survey, along with other archives, are used
to derive important physical characteristics of the H II region and PDR. These
include stellar temperatures, electron densities, ionization parameters, UV
radiation flux (G0), and PDR density. Finally, we calculate the
contribution of the H II region to PDR emission line diagnostics, which
allows for a more accurate determination of physical conditions in the PDR.
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Peter van Hoof
Royal Observatory of Belgium
Ringlaan 3
1180 Brussel
Belgium
email: p DOT vanhoof AT oma DOT be
