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Full-Text Articles in Physical Sciences and Mathematics
Emission Line Ratios Of Fe Iii As Astrophysical Plasma Diagnostics, Sibasish Laha, Niall B. Tyndall, Francis P. Keenan, Connor P. Ballance, Catherine A. Ramsbottom, Gary J. Ferland, Alan Hibbert
Emission Line Ratios Of Fe Iii As Astrophysical Plasma Diagnostics, Sibasish Laha, Niall B. Tyndall, Francis P. Keenan, Connor P. Ballance, Catherine A. Ramsbottom, Gary J. Ferland, Alan Hibbert
Physics and Astronomy Faculty Publications
Recent, state-of-the-art calculations of A-values and electron impact excitation rates for Fe III are used in conjunction with the Cloudy modeling code to derive emission-line intensity ratios for optical transitions among the fine-structure levels of the 3d6 configuration. A comparison of these with high-resolution, high signal-to-noise spectra of gaseous nebulae reveals that previous discrepancies found between theory and observation are not fully resolved by the latest atomic data. Blending is ruled out as a likely cause of the discrepancies, because temperature- and density-independent ratios (arising from lines with common upper levels) match well with those predicted by theory. For …
Which Stars Are Ionizing The Orion Nebula?, C. R. O'Dell, W. Kollatschny, Gary J. Ferland
Which Stars Are Ionizing The Orion Nebula?, C. R. O'Dell, W. Kollatschny, Gary J. Ferland
Physics and Astronomy Faculty Publications
The common assumption that θ1 Ori C is the dominant ionizing source for the Orion Nebula is critically examined. This assumption underlies much of the existing analysis of the nebula. In this paper we establish through comparison of the relative strengths of emission lines with expectations from Cloudy models and through the direction of the bright edges of proplyds that θ2 Ori A, which lies beyond the Bright Bar, also plays an important role. θ1 Ori C does dominate ionization in the inner part of the Orion Nebula, but outside of the Bright Bar as far as …
Testing Atomic Collision Theory With The Two-Photon Continuum Of Astrophysical Nebulae, Francisco Guzmán, N. R. Badnell, Marios Chatzikos, P. A. M. Van Hoof, R. J. R. Williams, Gary J. Ferland
Testing Atomic Collision Theory With The Two-Photon Continuum Of Astrophysical Nebulae, Francisco Guzmán, N. R. Badnell, Marios Chatzikos, P. A. M. Van Hoof, R. J. R. Williams, Gary J. Ferland
Physics and Astronomy Faculty Publications
Accurate rates for energy-degenerate l-changing collisions are needed to determine cosmological abundances and recombination. There are now several competing theories for the treatment of this process, and it is not possible to test these experimentally. We show that the H i two-photon continuum produced by astrophysical nebulae is strongly affected by l-changing collisions. We perform an analysis of the different underlying atomic processes and simulate the recombination and two-photon spectrum of a nebula containing H and He. We provide an extended set of effective recombination coefficients and updated l-changing 2s − 2p transition rates using …