Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 3 of 3
Full-Text Articles in Physics
The Abundance Discrepancy Factor And T2 In Nebulae: Are Non-Thermal Electrons The Culprits?, Gary J. Ferland, W. J. Henney, C. R. O'Dell, M. Peimbert
The Abundance Discrepancy Factor And T2 In Nebulae: Are Non-Thermal Electrons The Culprits?, Gary J. Ferland, W. J. Henney, C. R. O'Dell, M. Peimbert
Physics and Astronomy Faculty Publications
We discuss recent claims that the free electrons in ionized nebulae may not have a significantly Maxwellian velocity distribution. Supra-thermal electrons, electrons with much more energy than is encountered at electron temperatures found in nebulae, may solve the t2/ADF puzzle, the observations that abundances obtained from recombination and collisionally excited lines do not agree, and that different temperature indicators give different results. These non-Maxwellian electrons can be designated by the kappa formalism. We show that the distance over which heating rates change are much longer than the distance supra-thermal electrons can travel, and that the timescale to thermalize …
Rovibrationally Resolved Direct Photodissociation Through The Lyman And Werner Transitions Of H2 For Fuv/X-Ray-Irradiated Environments, C. D. Gay, N. P. Abel, R. L. Porter, P. C. Stancil, Gary J. Ferland, G. Shaw, P. A. M. Vanhoof, R. J. R. Williams
Rovibrationally Resolved Direct Photodissociation Through The Lyman And Werner Transitions Of H2 For Fuv/X-Ray-Irradiated Environments, C. D. Gay, N. P. Abel, R. L. Porter, P. C. Stancil, Gary J. Ferland, G. Shaw, P. A. M. Vanhoof, R. J. R. Williams
Physics and Astronomy Faculty Publications
Using ab initio potential curves and dipole transition moments, cross-section calculations were performed for the direct continuum photodissociation of H2 through the B1Σ+u ← X1Σ+g (Lyman) and C1Πu ← X1Σ+g (Werner) transitions. Partial cross-sections were obtained for wavelengths from 100 Å to the dissociation threshold between the upper electronic state and each of the 301 bound rovibrational levels v''J'' within the ground electronic state. The resulting cross-sections are incorporated into three representative classes of interstellar gas models: diffuse clouds, photon-dominated regions, and …
The Physical Conditions Within Dense Cold Clouds In Cooling Flows - Ii, Gary J. Ferland, A. C. Fabian, R. M. Johnstone
The Physical Conditions Within Dense Cold Clouds In Cooling Flows - Ii, Gary J. Ferland, A. C. Fabian, R. M. Johnstone
Physics and Astronomy Faculty Publications
This is a progress report on our numerical simulations of conditions in the cold cores of cooling flow condensations. The physical conditions in any non-equilibrium plasma are the result of a host of microphysical processes, many involving reactions that are research areas in themselves. We review the dominant physical processes in our previously published simulations, to clarify those issues that have caused confusion in the literature. We show that conditions in the core of an X-ray-illuminated cloud are very different from those found in molecular clouds, largely because carbon remains substantially atomic and provides powerful cooling through its far infrared …