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Astrophysics and Astronomy

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Physics and Astronomy Faculty Publications

2006

ISM: H II Regions

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Full-Text Articles in Physical Sciences and Mathematics

Determining The H+ Region / Pdr Equation Of State In Star-Forming Regions, N. P. Abel, Gary J. Ferland Aug 2006

Determining The H+ Region / Pdr Equation Of State In Star-Forming Regions, N. P. Abel, Gary J. Ferland

Physics and Astronomy Faculty Publications

The emission-line regions of starburst galaxies and active nuclei reveal a wealth of spectroscopic information. A unified picture of the relationship among ionized, atomic, and molecular gas makes it possible to better understand these observations. We performed a series of calculations designed to determine the equation of state-the relationship among density, temperature, and pressure-through emission-line diagnostic ratios that form in the H+ region and the photodissociation region (PDR). We consider a wide range of physical conditions in the H+ region. We connect the H+ region to the PDR by considering two constant pressure cases: one with no …

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Physical Conditions In Orion's Veil. Ii. A Multicomponent Study Of The Line Of Sight Toward The Trapezium, N. P. Abel, Gary J. Ferland, C. R. O'Dell, G. Shaw, Thomas H. Troland Jun 2006

Physical Conditions In Orion's Veil. Ii. A Multicomponent Study Of The Line Of Sight Toward The Trapezium, N. P. Abel, Gary J. Ferland, C. R. O'Dell, G. Shaw, Thomas H. Troland

Physics and Astronomy Faculty Publications

Orion's Veil is an absorbing screen that lies along the line of sight to the Orion H II region. It consists of two or more layers of gas that must lie within a few parsecs of the Trapezium cluster. Our previous work considered the Veil as a whole and found that the magnetic field dominates the energetics of the gas in at least one component. Here we use high-resolution STIS UV spectra that resolve the two velocity components in absorption and determine the conditions in each. We derive a volume hydrogen density, 21 cm spin temperature, turbulent velocity, and kinetic …

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