Chemical Telemetry of OH Observed to Measure Interstellar Magnetic Fields |
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| Authors: | Dr Serena Viti PhD Thomas W Hartquist Philip C Myers |
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| Institution: | (1) Department of Physics and Astronomy, University College London, London, WC1E 6BT, UK;(2) School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK;(3) Harvard – Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA |
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| Abstract: | We present models for the chemistry in gas moving towards the ionization front of an HII region. When it is far from the ionization
front, the gas is highly depleted of elements more massive than helium. However, as it approaches the ionization front, ices
are destroyed and species formed on the grain surfaces are injected into the gas phase. Photodissociation removes gas phase
molecular species as the gas flows towards the ionization front. We identify models for which the OH column densities are
comparable to those measured in observations undertaken to study the magnetic fields in star forming regions and give results
for the column densities of other species that should be abundant if the observed OH arises through a combination of the liberation
of H2O from surfaces and photodissociation. They include CH3OH, H2CO, and H2S. Observations of these other species may help establish the nature of the OH spatial distribution in the clouds, which is
important for the interpretation of the magnetic field results. |
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| Keywords: | ISM: HII regions magnetic fields molecules– masers– stars: formation |
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