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Full-Text Articles in Physics
Atomic Data For S Ii—Toward Better Diagnostics Of Chemical Evolution In High-Redshift Galaxies, Romas Kisielius, Varsha P. Kulkarni, Gary J. Ferland, Pavel Bogdanovich, Matt L. Lykins
Atomic Data For S Ii—Toward Better Diagnostics Of Chemical Evolution In High-Redshift Galaxies, Romas Kisielius, Varsha P. Kulkarni, Gary J. Ferland, Pavel Bogdanovich, Matt L. Lykins
Physics and Astronomy Faculty Publications
Absorption-line spectroscopy is a powerful tool used to estimate element abundances in both the nearby and distant universe. The accuracy of the abundances thus derived is naturally limited by the accuracy of the atomic data assumed for the spectral lines. We have recently started a project to perform new extensive atomic data calculations used for optical/UV spectral lines in the plasma modeling code Cloudy using state of the art quantal calculations. Here, we demonstrate our approach by focussing on S II, an ion used to estimate metallicities for Milky Way interstellar clouds as well as distant damped Lyman-alpha (DLA) and …
Effects Of External Radiation Fields On Line Emission—Application To Star-Forming Regions, Marios Chatzikos, Gary J. Ferland, R. J. R. Williams, Ryan Porter, P. A. M. Vanhoof
Effects Of External Radiation Fields On Line Emission—Application To Star-Forming Regions, Marios Chatzikos, Gary J. Ferland, R. J. R. Williams, Ryan Porter, P. A. M. Vanhoof
Physics and Astronomy Faculty Publications
A variety of astronomical environments contain clouds irradiated by a combination of isotropic and beamed radiation fields. For example, molecular clouds may be irradiated by the isotropic cosmic microwave background, as well as by a nearby active galactic nucleus. These radiation fields excite atoms and molecules and produce emission in different ways. We revisit the escape probability theorem and derive a novel expression that accounts for the presence of external radiation fields. We show that when the field is isotropic the escape probability is reduced relative to that in the absence of external radiation. This is in agreement with previous …
Suppression Of Dielectronic Recombination Due To Finite Density Effects, D. Nikolić, T. W. Gorczyca, K. T. Korista, Gary J. Ferland, N. R. Badnell
Suppression Of Dielectronic Recombination Due To Finite Density Effects, D. Nikolić, T. W. Gorczyca, K. T. Korista, Gary J. Ferland, N. R. Badnell
Physics and Astronomy Faculty Publications
We have developed a general model for determining density-dependent effective dielectronic recombination (DR) rate coefficients in order to explore finite-density effects on the ionization balance of plasmas. Our model consists of multiplying by a suppression factor those highly-accurate total zero-density DR rate coefficients which have been produced from state-of-the-art theoretical calculations and which have been benchmarked by experiment. The suppression factor is based upon earlier detailed collision-radiative calculations which were made for a wide range of ions at various densities and temperatures, but used a simplified treatment of DR. A general suppression formula is then developed as a function of …