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Uncertainties in Theoretical HeI Emissivities: HII Regions, Primordial Abundance, and Cosmological Recombination
R. L. Porter, G. J. Ferland, K. B. MacAdam +1
A number of recent works in astronomy and cosmology have relied upon theoretical He I emissivities, but we know of no effort to quantify the uncertainties in the atomic data. We an…
Fluorescent excitation of Balmer lines in gaseous nebulae: case D
V. Luridiana, S. Simon-Diaz, M. Cervino +3
(abridged) Non-ionizing stellar continua are a source of photons for continuum pumping in the hydrogen Lyman transitions. In the environments where these transitions are optically…
Collisional heating as the origin of filament emission in galaxy clusters
G. J. Ferland, A. C. Fabian, N. A. Hatch +4
[Abridged] Photoionization, whether by starlight or other sources, has difficulty in accounting for the observed spectra of the optical filaments that often surround central galaxi…
The origin of molecular hydrogen emission in cooling-flow filaments
G. J. Ferland, A. C. Fabian, N. A. Hatch +4
The optical filaments found in many cooling flows in galaxy clusters consist of low density ($\sim 10^3 \pcc$) cool ( K) gas surrounded by significant amounts of cosmic-…