The following document lists the file abstract/TBANIA_HII_S.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
We propose to use the LWS to obtain the complete FIR spectra of gas surrounding a sample of Southern Hemisphere Galactic HII regions. We shall examine in detail the effect of the ultraviolet radiation field strengths on the photodissociation regions (PDRs), the interfaces between the HII regions and the ambient molecular material. If these PDRs are to be understood, observations of many species in different states (ionized, atomic, and molecular) are needed in order to disentangle the competing effects of far ultraviolet (FUV) radiation field, source geometry, excitation, and chemistry. Our scientific goals are to observe a number of sources located throughout the Milky Way's disk in order to establish general trends, to observe regions spanning a wide range of UV field strengths, and, in particular, to compare for the first time global CO, [CII], [CI], and far infrared (FIR) continuum dust fluxes, which are some of the most important PDR diagnostics, for a statistically significant source sample. We have begun an observational program to study the [CI] line emission at 609 microns from Southern Hemisphere HII regions using the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO). AST/RO will also give us CO data using the 2->1 and 4->3 rotational transitions. The dust properties will be gotten using the FIR continuum derived from both ISO and IRAS measurements. These data will provide the stellar luminosities and extinctions which are both essential parameters in PDR models. The unsurpassed sensitivity of ISO will allow us to detect a number of FIR lines. The atomic fine structure lines are PDR diagnostics. The ionic lines provide a measure of the hardness of the UV field, HII region densities, and element abundances. The molecular lines available to the LWS (H20, CO, OH, and NH3) probe the warm, dense molecular gas associated with the PDRs. These data will therefore provide a complete census of the HII/PDR/GMC ISM in all of its phases which can be used to determine the effect of UV field strength on the ambient gas, to test the predictions of theoretical PDR models, and to establish whether PDR properties change systematically across the galactic disk.